LOSSES OF VITAMINS IN FOOD

KIMIA HASIL PERTANIAN

P E N DA H U LU A N Vitamins adalah zat gizi mikro essensial yang diperlukan untuk pertumbuhan normal, pemeliharaan, dan fungsi tubuh manusia.

VITAMIN

Vitamins function in vivo:" (a) Co-enzim dan prekusor enzim (niacin, thiamin, riboflavin,

biotin, pantothenic acid, vitamin B6, vitamin B12, folate); !

(b) Antioksidan (ascorbic acid, carotenoid tertentu, vitamin E); ! Recommended Textbook:! Damo daran, S., Parkin, K.L., Fennema, O.R. Fennema’s Foo d Chemistry 4th Ed. CRC Press.!

2007.

Belitz, H.D., Grosch, W., Schieberle, P. 2009. Chemsitry 4th Ed. Springer.

Foo d

(c) Terlibat dalam regulasi genetik (vitamins A dan D); ! (d) Fungsi khusus, seperti vit. A untuk vision, vit. C membantu r e a k s i h i d r o x y lat i o n , v it. K m e m b a n t u k r e a k s i carboxylation.

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Jurusan Teknologi Hasil Pertanian " Fakultas Pertanian Universitas Lampung

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Vitamin Deficiency:" • Keku ran gan vitam in disebut hyp o vitam in o sis an d

PERANAN: Food Chemist, Food Technologists, Food Scientists:"

avitaminosis. !

✦ Memahami bagaimana vitamin rusak dan hilang, serta mampu mengontrolnya.!

• Disebabkan oleh konsu msi ti dak cukup, gangguan

✦ Memahami: !

• Effek kekurangan:!

serapan karena penyakit atau stress.

a) konsep perubahan kimia proses degradasi vitamin dalam bahan pangan.!

✴ Vitamin A ==> xerophthalmia or buta malam.!

b) mekanisme reaksi, kinetika, dan termodinamika vitamin dalam berbagai keadaan.!

✴ Niacin ==> pellagra!

✦ Menentukan kondisi dan metode pengolahan makanan, penyimpanan, dan penanganan untuk mengoptimalkan ketahanan vitamin.

✴ Thiamine ==> beriberi! ✴ Vitamin B12 ==> anemia! ✴ Vitamin C ==> scurvy! ✴ Vitamin K ==> coagulation darah terganggu


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4

Vitamin Stability: Nutrients

Neutral

Acid

Alkali

O2

Light

Heat

Cooking

Vitamin A Ascorbic Acid Biotin Carotenes Choline Vitamin B12 Vitamin D Folate Vitamin K Pantothenic Acid Vitamin B6 Riboflavin Thiamin Tocopherol

S U S S S S S U S S S S U S

U S S U S S S U U U S S S S

S U S S S S U U U U S U U S

U U S U U U U U S S S S U U

U U S U S U U U U S U U S U

U U U U S S U U S S U U U U

40 100 60 30 5 10 40 100 5 75 40 75 80 55

5 5


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3


VARIATION/LOSSES OF VITAMINS IN FOOD 1) Inherent Variation:" ✴ Varietas,

tahap kematangan, lokasi tumbuh, iklim, metode pertanian, dan kondisi lingkungan.!

✴ Tabel hubungan tingkat kematangan tomat dan kadar

vitamin C.

Weeks from Anthesis

Weight (g)

Color

2

33.4

green

3

57.2

green

7.6

4

102

green-yellow

10.9

5

146

yellow-red

20.7

6

160

red

14.6

7

168

red 6 6

Ascorbic Acid ! (mg/100g) 107

10.1


Vitamin variation . . .


3) Preliminary Treatments:"

2) Postharvest Handling:"

• Selama penanganan pascapanen, kerusakan sel dan

kantung-kantung enzim menyebabkan pelepasan enzim oksidasi dan hidrolisis, menyebabkan perubahan struktur kimia dan aktivitas vitamin.

• Contohnya: ! ✴ Dephosphorilasi vit. B6, thiamin, atau co-enzyme

✴ Peeling dan trimming menyebabkan kehilangan vitamin, terutama pada vitamin yang tersimpan di bawah kulit.! ✴ Penambahan Alkali untuk mempermudah peeling dapat meningkatkan kehilangan vitamin, seperti folate, ascorbic acid, dan thiamin. ✴ Penggilingan biji-bijian, meliputi grinding dan fraksinasi untuk membuang bran (kulit ari/dedak) dan embrio menyebabkan kehilangan vitamin. Karena banyak vitamin tersimpan dalam embrio dan bran (dedak).!

flavin.!

✴ Deglycosylasi vitamin B6.! ✴ Enzim lipoxygenase mengurangi konsentrasi berbagai

✴ Adanya kontak (exposure) antara jaringan bahan pangan yang terpotong atau rusak dengan air menyebabkan hilangnya vitamin yang larut air akibat pencucian (ekstraksi/leaching).

vitamin.!

✴ Ascorbic acid oxidase dapat mengurangi konsentrasi as. askorbat


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FIGURE 1 Retention of selected nutrients as a function of deg ree of refining in production of wheat flour. Extraction rate refers to the percentag e recovery of flour from whole g rain during milling (redrawn by Ref. 98). Pag e 542


4) Blanching and Thermal Processing:" • Selama blanching, kehilangan vitamin disebabkan oleh:!

1. Leaching (wet blanching, dengan air panas atau steam).! 2. Oxidation (dry blanching, dengan udara panas atau mikrowave).! • Peningkatan

vitamin.

suhu meningkatkan reaksi deg ra dasi Pag e 543

study and thorough review [61,vitamin 62, 72, 113]. akibat The elevated penamanasan temperature of thermal processing accelerates reactions that would • Kerusakan tergantung otherwisepada:! occur more slowly at ambient temperature. Thermally induced losses of vitamins depend on the chemical nature of the food, its chemical environment (pH, relative humidity, transition metals, other reactive compounds, concentration of dissolved 1. the Komposisi kimia bahan ! and the opportunity for leaching. The nutritional oxygen, etc.), stabilities of the individual forms ofpangan. vitamins present, Gb. 1. Effek Fderajat refining IGURE 1 significance such losses depends on the lingkungan degree of loss and the importance of the food as a source of the vitamin in typical Retention nutrients terhadap as a function of 2.ofKomposis kimia bahan pangan (pH, RH, tepungof selected gandum diets. Although subject to considerable variation, representative data for losses of vitamins during the canning of vegetables are deg ree of refining in production of wheat flour. retensi beberapa zat gizi logam, O 2 terlarut, dan komponen aktif lainnya). ! Extraction rate refers to the percentag e recovery of shown in Table 6.

Gb. 2. RetensiFIGURE asam askorbat 2 Retention of ascorbic acid in peas during dalam kacang polong pada experimental water blanching for 10 min at various p etemperatures r c o b a(redrawn a n from b la ching Ref.n118.) selama 10 menit pada berbagai suhu.

yang dikandungnya.

3. Stabilitas masing-masing vitamin. !

flour from whole g rain during milling (redrawn by Ref. 98).

8.6.5 Losses of Vitamins Following Processing

4. Kemungkinan leaching.

Jurusan Teknologi Hasil Pertanian "

Fakultas Pertanian Universitas Lampung 9 subsequent storage Compared to loss of vitamins during thermal processing, often has a small but significant effect on vitamin 9 content. Several factors contribute to small postprocessing losses: (a) reaction rates are relatively slow at ambient or reduced temperature, (b) dissolved oxygen may be depleted, and (c) pH may change during processing (pH usually declines) because of thermal effects or concentrative effects (drying or freezing), and this can have a favorable effect on the stability of vitamins such as thiamin and ascorbic acid. For example, Figure 3 illustrates how vitamin C retention in potatoes can be affected by thermal processing. The relative importance of leaching, chemical degradation, and the type of container (cans or pouches) is apparent from these data.

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In reduced-moisture foods, vitamin stability is strongly influenced by water activity in addition to the other factors to be discussed. In the absence of oxidizing lipids, water-soluble vitamins generally exhibit little degradation at water activity less than or equal to monolayer hydration (~0.2–0.3 aw). Degradation rates increase in proportion to water activity in regions of multilayer hydration, which reflects greater solubility of the vitamin, potential reactants and catalysts. In contrast, the influence of water Vitamin variation . . .of fat-soluble vitamins and carotenoids parallels the pattern for unsaturated fats, that is, a minimum Vitamin activity on the stability rate at variation . . . monolayer hydration and increased rates above or below this value (see Chap. 2). Substantial losses of oxidation-sensitive vitamins can occur if foods are overdried. TABLE 6 Typical Losses of Vitamins during canning Product

5) Chemical and Other Food Components:"

a

Biotin

Folate

B6

Pantothenic acid

A

Thiamin

Riboflavin

Niacin

C

0

75

64

-

43

67

55

47

54

Asparag us Lima beans

-

62

47

72

55

83

67

64

76

Green beans

-

57

50

60

52

62

64

40

79

Beets

-

80

9

33

50

67

60

75

70

Carrots

40

59

80

54

9

67

60

33

75

Corn

63

72

0

59

32

80

58

47

58

Mushrooms

54

84

-

54

-

80

46

52

33

Green peas

78

59

69

80

30

74

64

69

67

Spinach

67

35

75

78

32

80

50

50

72

Tomatoes

55

54

-

30

0

17

25

0

26

aIncludes

blanching .

Source: From various sources, compiled by Lund [87].

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✴ Koposisi kimia bahan pangan sangat mempengaruhi 2 stabilitasFIGURE vitamin. ! Retention of ascorbic acid in peas during ✴ Oxidizing agents merusak ascorbic acid, vitamin A, carotenoids, dan vitamin E.

experimental water blanching for 10 min at various temperatures (redrawn from Ref. 118.)

✴ Reducing agents seperti ascorbic dan isoascorbic acids, serta thiol dan tetrahydrofolates meningkatkan stabilitas vitamins, berfungsi sebagai pengikat oxygen and free radical.! ✴ Sulfite (SO2, bisulfite, metabisulfite), digunakan untuk anti mikroba dan menghambat enzymatic browning, melindungi ascorbic acid. 12 12



BIOAVAILABILITY OF VITAMINS

Chemical and other . . ." ✴ Ion Sulfite bereaksi dengan thiamin, menyebabkan thiamin inaktif. Sulfite juga bereaksi dengan carbonyl groups pada vitamin B6, menyebabkan vit. B6 inaktif.! ✴ K o m p o s i s i b a h a n p a n g a n ya n g m e n ye b a b ka n p e r u b a h a n p H ( d a r i n et ra l m e n j a d i a s a m ) , mempengaruhi stabilitas thiamin dan ascorbic acid. ! ✴ Acidulation meningkatkan stabilitas asam askorbat dan thiamin. Sebaliknya, senyawa alkali mengurangi stabilitas asam askorbat, thiamin, asam pantotenat, dan folates.

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Terminologi yang merujuk pada sejauh mana nutrisi yang dikonsumsi diserap oleh usus, berfungsi dalam metabolisme, atau pemanfaatannya dalam tubuh.

Factors yang mempengaruhi bioavailability of vitamins:" (a) Komposisi bahan pangan (viscosity, sifat emulsi, dan pH) dapat mempengaruhi waktu bahan pangan di usus.! (b) Bentuk vitamin (misal: coenzim), mempengaruhi bentuk aktifnya atau fungsi metabolisme.! (c) Interaksi antara vitamin dan komponen bahan pangan (proteins, starches, dietary fiber, lipids) yang proses penyerapan vitamin oleh usus.


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ADDITION OF NUTRIENTS TO FOODS

CLASSIFICATION OF VITAMIN:

a) Restoration: Penambahan nutrisi pada bahan pangan untuk mengembalikan ke kondisi (konsentrasi) awal.!

b) Fortification: Penambahan nutrisi dalam jumlah yang cukup signifikan untuk membuat makanan menjadi sumber nutrisi yang ditambahkan.

c) Enrichment: Penambahan nutrisi tertentu dalam jumlah

sesuai dengan standar identitas seperti yang didefinisikan oleh US Food and Drug Administration (FDA).!

d) N ut r if icat i o n : Ist i la h g e n e r i k d i m ak s u d ka n u nt u k mencakup setiap penambahan nutrisi makanan.

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A. Fat Soluble Vitamins;" A (Retinol), D (Calciferol), E (Tocopherol), dan K (Phytomenadione).!

B. Water Soluble Vitamins:" C ( Ascorbic acid) dan B [B1 (Thiamin), B2 (Ribiflavin), B3 (Niacin), B5 (Pantothenic acid), B6 (Pyr i doxin e), B7 (Biotin), dan B12 (Cuanocobalamine)].


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2) Structure of Vit. A

VITAMIN A (RETINOL)

Pag e 546

Pag e 54

1) Vit. A: Structure and General Properties:"

• Vitamin A mengacu pada sekelompok hidrokarbon tak jenuh yang aktif, termasuk retinol dan senyawa terkait, serta karotenoid tertentu.!

• Vitamin A di jaringan hewan didominasi dalam bentuk retinol atau esternya, retinal, dan asam retinoat.!

• Karotenoid merupakan jenis vitamin A dalam makanan yang berasal dari tanaman dan hewan.

FIGURE 5 Structures and provitamin A activities of selected carotenoids.

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FIGURE 4 in foods (Table 7 and 8). Conversion to cis isomers, which can occur during thermal processing, causes a" loss of vitamin A Jurusan Teknologi Hasil Pertanian Structures of common retinoids. Fakultas Pertanian Universitas Lampung

activity.

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bond in the intestinal mucosa to release two molecules of active Among the carotenoids, -carotene exhibits the greatest 8.7.1.2retinal. Stability and Modes of Degradation pro-vitamin A activity. Carotenoids with ring hydroxylation or the presence of carbonyl group exhibit less pro-vitamin A activity The degradation of vitamin A (retinoids and vitamin cartenoids) generally parallels the oxidative degradation of than -carotene if only one ring is affected, and have no activity if both rings are oxygenated. Although twoA-active molecules of vitamin Factors that promote oxidation of unsaturated A are potentially producted from each molecule of dietary unsaturated -carotene,lipids. the inefficiency of the process accounts for thelipids factenhance that degradation of vitamin A, either by direct oxidation or by indirect effects of free radicals. Changes in the -carotene content of cooked dehydrated carrots illustrate typica -carotene exhibits only ~50% of the vitamin A activity exhibited by retinol, on a mass basis. Considerable variation exists extents of degradation during processing and typical exposure to oxygen during associated handling (Table 9). It should be among various animal species and humans with respect to the efficiency utilization carotenoids andAthe extent of as absorption noted, however,ofthat extendedof storage of vitamin in foods such fortified breakfast cereal products, infant formulas, fluid of carotenoid molecules in intact form. The in vivo antioxidative function attributed to dietary is carotenoids absorption of retention of added vitamin A. milk, fortified sucrose, and condiments usually not requires highly detrimental to the the intact molecule [18]. Losses of vitamin A activity of retinoids and carotenoids in foods occur mainly through reactions involving the unsaturated

3) VIT. A: Sources:"

✴ Vitamin A hanya terdapat pada jaringan hewan, minyak

hati ikan, di hati mamalia, lemak susu dan kuning telur. Karotenoid pada hewan berasal dari tumbuhan yang dimakan oleh hewan.!

✴ Ta n a m a n t i n d a k m e m p u n ya i v ita m i n A , teta p i

mengandung karotenoid yang berfungsi sebagai provitamin A. !

✴ Karotenoid banyak terdapat dalam sayuran warna hijau

dan kuning (wortel, bayam, selada, kangkung, paprika, dan tomat) dan dalam buah-buahan (labu, aprikot, jeruk dan dan minyak sawit)

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KHP: Vitamin

4) VIT. A: Requirement and Bioavailability:" • Kebutuhan harian vitamin A berasal dari:! ✴ 75% retinol (seperti ester asam lemak, terutama palmitat retinil),! ✴ 25% β-karoten dan karotenoid lainnya (provitamin A). 6 gr β-karoten diperlukan untuk menghasilkan 1 gr retinol. • Retinoid, retinyl acetate, dan retinyl palmitate diserap secara efektif kecuali dalam kondisi di mana mal-absorpsi lemak terjadi. Diet yang mengandung bahan hidrofobik non-absorable seperti pengganti lemak tertentu dapat berkontribusi untuk mal-absorpsi vitamin A. ! • Penye rapan karoten o i d mu n gkin te rgan g gu karena terjadinya ikatan caroteno-protein atau terperangkap dalam matriks sayuran yang sulit dicerna. 21


Pag e 551

21

presumably other carotenoids, causes a reduction or total loss of vitamin A activity regardless of the mechanisms by which free radical initiation occurs. For retinol and retinyl esters, however, the attack of free radicals occurs at the C14 and C15 positions.

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Oxidation of -carotene involves the formation of the 5,6-epoxide, which may isomerize to the 5,8-epoxide (mutachrome). Photochemically induced oxidation yields mutachrome as the primary degradation product. Fragmentation of -carotene to many lower molecular weight compounds can occur especially during high-temperature treatments. Resulting volatiles can have a significant effect on flavor. Such fragementation also occurs during oxidation of retinoids. An overview of these reactions and other aspects of the chemical behavior of vitamin A is shown in Figure 8. 8.7.1.3 Bioavailability Retinoids are absorbed effectively except under conditions in which malabsorption of fat occurs. Retinyl acetate and palmitate are as effectively utilized as nonesterified retinol. Diets containing nonabsorable hydrophobic materials such as certain fat substitutes may contribute to malab-

VITAMIN D (CALCIFEROL)

5) Vit. A: " !

1) Vit. D: Structure and General Properties:"

Stability and Degradation:

✴ Vitamin D adalah beberapa jenis sterol yang larut dalam

lipid, termasuk cholecalciferol (vitamin D3) dari sumber hewan dan ergocalciferol (vitamin D2) diproduksi secara sintetisis

✴ Cholecalciferol (vitamin D3) terbentuk dari kolesterol

dalam ku lit m elalui fotolisis 7- dehydro chole ste rol (provitamin D3) oleh sinar ultra violet pada kulit manusia setelah terpapar sinar matahari. Karena dalam sintesis vivo, kebutuhan vitamin D untuk diet tergantung pada sejauh mana paparan terhadap sinar matahari.!

✴ Ergocalciferol (Vitamin D2) adalah bentuk sintetis dari Jurusan Teknologi Hasil Pertanian " FIGURE 8 Fakultas Pertanian Universitas Lampung 23 Overview of vitamin A deg radation. 23

vitamin D yang dibentuk dari radiasi fitosterol (sterol Jurusan Teknologi Hasil Pertanian " tanaman) dengan sinar UV. 24 Fakultas Pertanian Universitas Lampung 24

he requirement for dietary vitamin D will depend on the extent of exposure to sunlight. Ergocalciferol is an exclusively rm of vitamin D that, is formed by commercial irradiation of phytosterol (a plant sterol) with UV light. Several ed metabolites of vitamin D2 and D3 form in vivo. The 1,25-dihydroxy derivative of cholecalciferol is the main ally active form, and it is involved in the regulation of calcium absorption and metabolism. 25-Hydroxycholecalciferol, to cholecalciferol, 3) Vit. D: Sources:"

✴ Hampir semua bahan pangan mengandung vitamin D. " ✴ Pro-vitamin D (ergosterol dan 7-dehydrocholesterol), terdapat pada hewan dan tanaman. "

✴ Yeast, jamur, kol, bayam, dan minyak gan du m mengadung provitamin D2.

FIGURE 9 Structure of erg ocalciferol (vitamin D2) and cholecalciferol (Vitamin D3).

telur, mentega, susu sapi, hati, kerang, lemak hewan, dan kulit babi. "

✴ Sumber utama vitamin D adalah minyak ikan."

2) Vit. D: Stability and Degradation:"

Vitamin D rentan terhadap degradasi oleh oksigen dan cahaya. Sekitar 50% dari cholecalciferol ditambahkan ke susu skim akan rusak bila terkena paparan lampu neon terus-menerus pada suhu 4°C selama 12 hari. 25

✴ Vitamin D3 dan provitaminnya terdapat pada kuning

✴ Fortifikasi vitamin D produk susu cair menggunakan ergocalciferol atau cholecalciferol D.


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25


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VITAMIN E (TOCOPHEROL) 1) Vit E: Structure and General Properties:"

• Vitamin E adalah nama generik untuk tokoferol, yang

merupakan turunan dari tocol yang memiliki satu atau lebih gugus metil pada posisi 5, 7, atau 8 pada struktur cincin (chromanol ring).

• Bersifat antioksidan, yang memperlambat atau mencegah oksidasi lipid. Dengan demikian, ini memberikan kontribusi Pag e(misalnya; 554 untuk stabilisasi bahan aktif lainnya vitamin A, ubiquinone, hormon, dan enzim) terhadap oksidasi. !

• Vitamin E berperan dalam konversi asam arakidonat

menjadi prostaglandin dan memperlambat agregasi sel darah.

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2) Structure of Vitamin E: Pag e 554

FIGURE 10 Structures of tocopherols. The structures of tocotrienols are identical to the corresponding tocopherols, except for the presence of double bonds at positions 3', 7', and 11'.

dants; they quench free radicals by donating the phenolic H and an electron. Tocopherols are a natural constituent of all 29 30 occurring biological membranes and are thought to contribute to membrane stability through their antioxidant activity. Naturally tocopherols and tocotrienols also contribute to the stability of highly unsaturated vegetable oils through this antioxidant action. In contrast, -tocopheryl acetate added in food fortification has no antioxidant activity because the acetate ester has replaced the phenolic hydrogen atom. -Tocopheryl acetate does exhibit vitamin E activity and in vivo antioxidant effects as a result of FIGURE 10 Structures of tocopherols. The of structures of tocotrienols enzymatic cleavage the ester. Theareconcentration of dietary vitamin E in animals has been shown to influence the oxidative identical to the corresponding tocopherols, except for the presence of double bonds at positions 3', 7', and 11'. example, it has been shown that the susceptibility of pork muscle products to oxidation of stability of meats after slaughter. For



29

30

3) Vit. E: Stability and Degradation" • Vitamin E menunjukkan stabilitas yang cukup baik dalam ketiadaan oksigen dan pengoksidasi lipid.! • Aplha-toco phe rol dapat be reaksi dengan ra dikal peroxyl (atau radikal bebas lainnya) untuk membentuk hidroperoksida dan radikal alpha-tokoferil

408

• Reaksi pemutusan (terminasi) radikal menhasilkan dimer tokoferil yang terikat secara kovalen membentuk dimer dan trimer. Adanya oksidasi lanjutan dan penataan ulang d i m e r t e r s e b ut m e n g h a s i l k a n t o c o p h e r o x i d e , hydroquinone tokoferil, dan kuinon tokoferil.

6 Vitamins


31

(6.3)

31

6.2.3.3 Stability, Degradation Losses occur in vegetable oil processing into margarine and shortening. Losses are also encountered in intensive lipid autoxidation, particularly in dehydrated or deep fried foods (Table 6.6). Table 6.6. Tocopherol stability during deep frying Tocopherol total (mg/ 100 g) Oil before deep frying after deep frying Oil extracted from potato chips immediately after production after 2 weeks storage at room temperature after 1 month storage at room temperature after 2 months storage at room temperature after 1 month kept at −12 ◦ C after 2 months kept at −12 ◦ C Oil extracted from French fries immediately after production after 1 month kept at −12 ◦ C after 2 months kept at −12 ◦ C

32


32

82 73

Loss (%)

11

75 39

48

22

71

17 28 24

77 63 68

78 25 20 33 33

6.2.4 Phytomenadione (Vitamin K1 Phylloquinone) 6.2.4.1 Biological Role

7′ and 11′ is R and corresponds to that of natural phytol. Racemic vitamin K1 synthesized from optically inactive isophytol has the same biological activity as the natural product. Vitamin K is involved in the post-translational synthesis of γ -carboxyglutamic acid (Gla) in vitamin K-dependent proteins. It is reduced to the hydroquinone form (Formula 6.4) which acts as a cofactor in the carboxylation of glutamic acid. Oxidative degradation of Vit. E In this process, it is converted to the4) epoxide from which vitamin K is regenerated. Blood clotting factors (prothrombin, proconvertin, Christmas and Stuart factor) as well as proteins which perform other functions belong to the group of vitamin K-dependent proteins which bind Ca2+ ions at Gla. Deficiency of this vitamin causes reduced prothrombin activity, hypothrombinemia and hemorrhage.

Pag e 557

6.2.4.2 Requirement, Occurrence

The activity is given in vitamin equivalents (VE): 1 VE = 1 µg phylloquinone. The daily requirement of vitamin K1 is shown in Table 6.3. It is covered by food (cf. Table 6.7). The bacteria present in the large intestine form relatively high 68 amounts of K2 . However, it is uncertain whether 74 Jurusan they appreciably to covering the reTeknologi Hasil Pertanian contribute " Jurusan Teknologi Hasil Pertanian " Fakultas Pertanian Universitas Lampung Fakultas Pertanian Universitas Lampung FIGURE34 11 Pag e 558 quirement. Overview of the oxidative deg radation 34 of vitamin E. In addition to the initial Vitamin K1 occurs primarily in green leafy veoxidation products shown, many other compounds are formed as a result getables (spinach, cabbage, cauliflower), but liver of further oxidation and rearrang ement. (veal or pork) is also an excellent source (Taspecific forms of vitamin E (e.g., -, -, -, -tocopherols and tocotrienols) and, thus, estimation of total vitamin E activity in a ble 6.7).

product based on relative potencies of the specific compounds [26]. Detection can be accomplished using either ultraviolet (UV) absorbance of fluorescence. When saponification is used to aid in the separation of lipids from vitamin E, any vitamin E ester will be hydrolyzed to free -tocopherol. Care must be taken to prevent oxidation during extraction, saponification, and other 6.2.4.3 Stability, Degradation preliminary treatments.

Vitamin K The K-group vitamins are naphthoquinone Little is known about8.7.4 the reactions of vitamin K1 derivatives which differ in their side chains. in foods. The vitamin8.7.4.1 K compounds Structureare anddestroyed General Properties The structure of vitamin K1 is shown in For- by light and alkali. They are relatively stable to Vitamin K consists of a mula 6.4. The configuration at carbon atoms atmospheric oxygen and exposure to heat.group of naphthoquinones that exist with or without a terpenoid side chain in the 3-position (Fig. 13). VITAMIN K (PHYTOMENADIONE)

3) Vit. K Classification:"

1) Vit K, Structure and Propersties:" Vitamin K adalah kelompok vitamin yang terdiri dari struktur cincin methil naphthoquinone (menadione) dan FIGURE 12 rantai alifatik yang terikat pada 3.and-tocopherol. Reaction ofposisi sing let oxyg en

2) Structure of Vit. K

The unsubstituted form of vitamin K is menadione, and it is of primary significance as a synthetic form of the vitamin that is used in vitamin supplements and food fortification. Phylloquinone (vitamin K1) is a product of plant origin, while menaquinones 1.Phylloquinone (vitamin K1); Berjumlah yang relatif (vitmain K2) of varying chain length are products of bacterial synthesis, mainly by intestinal microflora. Phylloquinones occur in dalamincluding sayu ran kale, becauliflower, rdau n andsecabbage, p e rtiand they bayam, relatively large quantitiesbe in sar leafy vegetables spinach, are present, but less abundant, in tomatoes and certain vegetable oils. Vitaminkol, K deficiency is rare in tetapi healthy individuals of the widespread kangkung, kembang dan kubis, sedikitbecause dalam presence of phylloquinones in the diet and because microbial menoquinones are absorbed from the lower intestine. Vitamin K tomat with danmalabsorpminyak nabati tertentu. Hati (sapi atau deficiency is ordinarily associated

babi) juga merupakan sumber vit. K1 yang penting!

2.Menaquinones (vitmain K2); Disintesis oleh bakteri, terutama oleh mikroflora dalam usus.! 3. Terdapat 3 vitamin K sintetis, yaitu vitamin K3, K4, dan K5, yang digunakan di berbagai bidang termasuk industri makanan hewan (vitamin K3) dan untuk menghambat pertumbuhan jamur (vitamin K5). 35 35


FIGURE 13 Structure of various forms of vitamin K.

36 36


4) Vit. K, Source:

THIAMIN (VIT. B1) 1) Vit. B1, Structure and Properties:"

✴ Thiamin (Vit. B1) adalah kombinasi pyrimidine dan thiazole yang dihubungkan dengan jembatan methylene (-CH2-).!

✴ Secara alami, thiamin dalam bentuk thiamin pyrophosphate, thiamin monophosphate, and thiamin triphosphate.

Pag e 568

✴ Thiamin secara komersial dalam bentuk garam hydrochloride

ment of L-ascorbic acid and DHAA. The coupling of chromatographic separation with spectro-photometric, fluorometric, or electrochemical detection makes HPLC analysis far more specific than traditional redox methods. HPLC methods have been reported that permit the simultaneous determination of ascorbic and isoascorbic acids as well as their dehydro forms [134]. A ✴ method based on gas chromatography-mass spectrometry has been reported, but extensive sample preparation is a disadvantage of the procedure [33].

dan mononitrate, digunakan sebagai fortifikasi pangan.!

Thiamin pyrophosphate berfungsi sebagai coenzyme berbagai enzim alpha-keto acid dehydrogenases, alpha-keto acid decarboxylases, phosphoketolases, and transketolases. !

✴ Kekurangan thiamin (Vitamin B1) menyebabkan enzim di atas

8.8.2 Thiamin 8.8.2.1 Structure and General Properties Jurusan Teknologi Hasil Pertanian " Thiamin is a substituted pyrimidine linked through a methylene bridge (-CH2-) to Fakultas a substituted 20). Thiamin is Pertanian thiazole Universitas (Fig. Lampung 37 widely distributed in plant and animal tissues. Most naturally occurring thiamin exists as thiamin pyrophosphate (Fig. 20), with 37 lesser amounts of nonphosphorylated thiamin, thiamin monophosphate, and thiamin triphosphate. Thiamin pyrophosphate functions as a coenzyme of various -keto acid dehydrogenases, -keto acid decarboxylases, phosphoketolases, and transketolases. Thiamin is commercially available as the hydrochloride and mononitrate salts, and these forms are widely used for food fortification and as nutritional supplements (Fig. 20).

tidak berfungsi. Kekurangan yang parah menyebabkan beriberi. 38


38

The thiamin molecule exhibits unusual acid-base behavior. The first pKa (~4.8) involves dissociation of the protonated pyrimidine N1 to yield the uncharged pyrimidyl moiety of thiamin free base (Fig. 21). In the alkaline pH range another transition is observed (apparent pKa 9.2) that corresponds to the uptake of two equivalents of base to yield the thiamin pseudobase. The pseudobase can undergo opening of the thiazol ring to yield the thiol form of thaimin, accompanied by dissociation of a single proton. Another characteristic of thiamin is the quaternary N of the thiazole ring, which remains cationic at all pH values. The marked pH dependence of thiamin degradation corresponds to the pH-dependent changes in ionic form. Protonated thiamin is far more 2) stable than free base, pseudobase, and thiol forms, which accounts for the greater stability observed in acidic media (Table 15). Although thiamin Thiamin is relatively stable oxidation and light, it is among the least stable of the vitamins when in solution at neutral or ✴ (vit.to B1) Structures: alkaline pH.

Thiamin (Vit. B1), Sources:" Terdapat pada biji-bijian, seralia, umbi-umbian, ragi, dan beberapa jenis buah-buahan.!

✴ Terdapat pula pada daging, ikan, telur, susu, dan organ dalam hewan seperti hati, ginjal, jantung, dan otak.

FIGURE 20 Structures of various forms of thiamin. All have thiamin (vitamin B1) activity.

39


40

39


40

412

6 Vitamins Pag e 572

3) Thiamin (Vit. B1), Stability and Degradation:"

• Stabiltas Thiamin dalam air sangat rendah (mudah

larut). Stabilitasnya dipengaruhi oleh pH, suhu, kekuatan ion, dan ion metal. !

• Thiamin yang terikat oleh enzim kurang stabil dibandingkan dengan Thiamin bebas.!

• Thiamine menjadi inaktif dengan adanya nitrites and sulfite, Kemungkiana disebabkan oleh reaksi antara group amino dengan cincin pyridine.

41

drate metabolism, the requirement increases in a carbohydrate-enriched diet. The assay of transketolase activity in red blood cells or the extent of transketolase reactivation on addition of thiamine pyrophosphate can be used as indicators for sufficient vitamin intake in the diet. Vitamin B1 is found in many plants. It is present in the pericarp and germ of cereals, in yeast, vegetables (potatoes) and shelled fruit. It is abundant in pork, beef, fish, eggs and in animal organs such as liver, kidney, brain and heart. Human milk and cow’s milk contain vitamin B1 . Whole grain bread and potatoes are important dietary sources. Since vitamin B1 is localized in Fig. 6.2. Inactivation rate of thiamine as affected by pH pengaruh pH terhadap IGURE 22 pengaruh suhu dan Aw aGambar the outer part Gambar of cereal grain Fhulls, flour milling Thiamine in phosphate buffer, b thiamine in wheat or Influence of water activity and temperature on the inaktivasi Thiamin. a) Thiamin dalam oat flour, c thiamine pyrophosphate in flour terhadap thiamin. with a low extraction grade orin tahan rice polishing retention of daya thiamin a dehydrated model foodrebuffer phospat, b) Thiamin dalam system simulating a breakfast cereal product. move most of the vitamin in the bran (cf. 15.3.1.3 Percentag e retention values apply to an 8-month t e p u n g o a t, c ) T h i a m i n storag e period. (From Ref.the 32.) occurand 15.3.2.2.1). Table 6.7 lists data on phyrophospate terigu. Table 6.8. Thiaminedalam losses in food during storage (12 rence of thiamine. months)


42


42 Food

41

6.3.1.3 Stability, Degradation Thiamine stability in aqueous solution is relatively low. It is influenced by pH (Fig. 6.2), temperature (Table 6.8), ionic strength and metal

Apricots Orange juice Peas Green beans Tomato juice

Thiamine loss, % 1.5 ◦ C

38 ◦ C

28 0 0 24 0

65 22 32 92 40

spectrum from 420–560 nm, photolytically cleaves ribitol from the vitamin, converting it to lumiflavin:

6.3.2 Riboflavin (Vitamin B2 ) 6.3.2.1 Biological Role

Riboflavin (Formula 6.9) is the prosthetic group of flavine enzymes, which are of great importance in general metabolism and particularly in 2. Ribiflavin (Vit. B2), Sources:" RIBOFLAVIN (VIT. B2) of protein. metabolism (6.10) sayuran, ✴ Sumber utama adalah susu dan produk susu, telur, 1. Riboflavin, Structure an d ragi, organPagdalam hewan, seperti jantung, hati dan ginjal, dan e 577 Properties:" hati ikan dan telur ikan.! TABLE 19 Distribution of Riboflavin Compounds in Fresh Human and

✴Riboflavin, sebelumnya dikenal Cow's Milk

sebagai vitamin B2, adalah istilah Compound Human milk (%) generik untuk kelompok senyawa ya n g m e n u n j u k ka n a k38–62 t i v ita s FA D biologis riboflavin. Semua turunan Riboflavin 31–51 riboflavin diberi nama generik flavin.! 10-Hydroxyethylflavin 2–10

Trace ✴R10-Formylmethyflavin i b o fl a v i n a d a la h k e lo mpok

prostetik enzim flavinTrace–0.4 e yan g 7 -Hydroxyriboflavin penting dalam metabolisme protein.

✴ Kandungan6.3.3 riboflavin dalam urin merupakan indikator tingkat Pyridoxine (Pyridoxal, Vitamin B )

23–46a 35–59

(Formula 6.11) or pyridoxol (R = CH2 OH),

11–19

= CHO) pyridoxamine (R = vitamin ✴ Terdapat pyridoxal dua jenis(RFlavin yang and menghambat aktivitas

Trace

B2,(6.9) yaitu:!CH2 NH2 ).

0.1–0.7

8 -Hydroxyriboflavin Trace Trace–0.4 ✴ Kekurangan riboflavin akan menyebabkan akumulasi asam amino

aFollowing pasteurization, FAD in bulk raw milk decreases from 26 to yang menyebabkan penurunan aktivitas reduktase glutathione 13%, withsel a corresponding increase in the percentag e of riboflavin. dalam darah merah. Jurusan Teknologi Hasil Pertanian "

Source:Adapted from Refs. 111 and 112.

43

6 pasokan riboflavin. Kadar riboflavin normal bila mengandung lebih dari 80μg riboflavin/gr kreatinin, kadar rendah bila 6.3.3.1 Biological Role mengandung 27-79 μg/gr, sedangkan bila nilainya kurang dari dari 27 μg/gr individu tersebut disarankan untuk mengkonsumsi B6 activity is exhibited by pyridoxine suplemen Vitamin riboflavin.

Cow's milk (%)

The metabolically active form,

1.10-Hydroxyethylflavin, produk metabolisme bakteri flavin, dapat menghambat penyerapan riboflavin ke dalam jaringan.! 2.Lumiflavin, juga dapat bertindak sebagai penghambat.

Fakultas Pertanian Universitas Lampung

44

43


44

to very good during conventional thermal processing, handling, and preparation. Losses during storage of riboflavin in various dehydrated food systems (breakfast cereals and model systems) are usually negligible. Rates of degradation increase measurably at aw above the monolayer value when temperatures are above ambient [32]. The typical mechanism of degradation of riboflavin is photochemical, which yields two biologically inactive products, lumiflavin and lumichrome (Fig. 26), and an array of free radicals [142]. Exposure of solutions of riboflavin to visible light has been used for many years as an experimental technique to generate free radicals. Photolysis of riboflavin yields superoxide and riboflavin radicals (R. ), and the reaction of O2 with R. provides peroxy radicals and a wide range of other products. The extent to which photochemical degradation of riboflavin is responsible for photosensitized oxidation reactions in food has not been quantitatively NIACIN (NICOTINAMIDE, VIT. B3) this process contributes significantly. Sunlight-induced off flavor in milk, which is no longer 3.determined, Vit. B2,although Stability andassuredly Degradation:" common, is a riboflavin-mediated photochemical process. Although the mechanism of off-flavor formation has not been fully Structure and Properties:" ✴determined, Riboflavin relatif(probably stabilradical-mediated) pada proses penangan normal.of methionine 1. light-induced decarboxylation and deamination to form methional (CH 3S-CH 2-CH2=O is pada at least partially mild oxidation of milk lipids also occurs. Changes in packaging and Penyusutan proses responsible. tersebutConcurrent sekitar 10︲15%. • Niacin adalah nama generik untuk pyridine 3-carboxylic acid commercial distribution have minimized this problem. (nicotinic acid) dan turunannya yang mempunyai sifat yang

sama.!

✴ Kerusakan riboflavin

disebabkan oleh adanya Photokimia.!

• Nicotinic acid amide (I), dalam bentuk nicotinamide adenine dinucleotide (NAD+), atau dalam bentuk phosphorylated (NADP +), berfungsi sebagai coenzymes pada reaksi dehydrogenase.

✴ Terekspos reboflavin

oleh cahaya dengan panjang gelombang 420︲560 nm, menghasilkan lumiflavin dan lumichrome, yang bersifat tidak aktif.

2. Niacin, Resources:"

• 60︲70% kebutuhan Vit. B3 berasal dari konsumsi tryptophan, dimana 60 mg L-tryptophan sama dengan 1 mg nicotinamide.!

• Vit. B3 baik dalam bentuk nicotinic acid berasal dari daging, hati, serealia, dan jamur.

FIGURE 26 Jurusan Teknologi Hasil Pertanian " Fakultas Pertanian Universitas Lampung 45 Photochemical conversion of riboflavin 45 to lumichrome and lumiflavin.

46

Pag e 579

PANTOTHENIC ACID (VIT. B5) 1. Structure and Properties:"

• Pantothenic acid adalah vitamin yang terdiri dari beta-alanine

berikatan dengan 2,4- dihydroxy-3,3- dimethyl-butyric (pantoic) acid.!

• Fungsi Pantothenic acid: ! 1. Sebagai komponen coenzyme A.! 2. Sebagai prosthetic group pada sintesis asam lemak..!

• Pantothenic acid didalam darah dalam bentuk molekul bebas, sedangkan dalam organ tubuh berbentuk coenzym A.!

FIGURE 27 Structures of nicotinic acid, nicotinamide, and nicotinamide adenine dinucleotide (phosphate).

• Pantothenic acid is sangat stabil. Sekitar 10% hilang pada pengolahan susu, sedangkan pada pemasakan sayuran sekitar 10-30% hilang karena leaching.


FakultasisPertanian Universitas Lampung e mildly acidic conditions that prevail during roasting of 47 coffee, trigonelline demethylated to form nicotinic acid, 47 30-fold increase in the niacin concentration and activity of coffee.

also changes the relative concentration of certain niacin compounds through interconversion reactions [137, 138]. For heating releases free nicotinamide from NAD and NADP during the boiling of corn. In addition, the distribution of mpounds within a product varies as a function of variety (e.g., sweet corn vs. field corn) and stage of maturity.

ioavailability


46

48 48


component of a coenzyme A (Fig. 42) and as a covalently bound prosthetic group (without the adenosyl moiety of coenzyme A) of acyl carrier proteins in fatty acid synthesis. Formation of a thioester derivative of coenzyme A (CoA) with organic acids facilitates a wide variety of metabolic processes, mainly involving addition or removal of acyl groups, in an array of biosynthetic and catabolic reactions. Pantothenic acid is essential for all living things and is distributed widely among meats, cereal grains, eggs, milk, and many fresh vegetables. Pantothenic acid in many foods and most biological materials is mainly in the form of coenzyme A, the majority of which exists as thioester derivatives of a wide variety of organic acids. Although analytical data are quite limited with respect to the free and coenzyme A forms of pantothenic acid in foods, free pantothenic acid has been found to account for only half of the total of this vitamin in beef muscle and peas [58]. Coenzyme A is fully available as a source of pantothenic acid because it is converted to free pantothenic acid in the small intestine by the action of alkaline phosphatase and an amidase. Intestinal absorption occurs through a carrier-mediated absorption process.

2. Pantothenic Acid, Function:

Synthetic pantothenic acid is used in food fortification and in vitamin supplements in the

✴Kebutuhan 6︲8 mg/hari.

1. VIT. B6, Structure and Properties:"

✴ Vitamin B6 adalah nama generik untuk jenis vitamin

Konsentrasi pada darah 10︲40 μg/100 ml and 2︲7 mg/hari dibuang lewat urin!

mempunyai aktivitas seperti pyridoxine.

✴ Bebagai jenis Vit. B6

d i b e d a k a n b e r d a s a ka n p a d a komponen pada karbon posisi ke 4. !

✴Synthetic pantothenic

acid digunakan untuk fortifikasi pangan dan dalam bentuk calcium pantothenate.!

✴ Pyr i doxine (PN) = alkohol, !

✴Panthen ol, digu nakan

✴ P y r i d oxal ( P L) =

sebagai suplemen pangan ternak.

aldehid,!

FIGURE 42 Structure of various forms of pantothenic acid.


49 49

FIGURE 28 Structures of vitamin B6 compounds.

✴ Pyridoxamine (PM) = amine. of the 3-OH (pK

Jurusan Teknologi Pertanian " a 3.5–5.0), the pyridine system of vitamin B6 molecules mainlyHasil exists in Zwitterionic form at ne Fakultas Pertanian Universitas Lampung 50markedly as a function net charge on vitamin B6 compounds varies of pH. The 4'-amino group of PM and PMP (p 50 and the 5'-phosphate ester of PLP and PMP (pKa <2.5, ~6, and ~12) also contribute to the charge of these forms vitamin.

All chemical forms of vitamin B6 exist in foods, although the distribution varies markedly. PN glucoside exists only products, although most plant products also contain all other forms of the vitamin. Vitamin B6 in muscle and organ predominantly (>80%) PLP and PMP, with minor amounts of the nonphosphorylated species. Disruption of raw pl freeze-thaw cycling or homogenization releases phosphatases and -glucosidases that can alter the forms of vitamin compounds by catalyzing dephosphorylation and deglycosylation reactions. Similarly, disruption of animal tissues p cooking can cause extensive dephosphorylation of PLP and PMP. PNP is a transient intermediate in vitamin B6 me is usually a negligible component of the total vitamin B6 content. Pyridoxine (as the HCI salt) is the form of vitamin food fortification and in nutritional supplements because of its good stability. TABLE 21 pK a Values of Vitamin B6 Compounds

BIOTIN (VITAMIN B7 ATAU H)

2. Vit. B6, Sources:"

• Vitamin B6 yang mengandung glycosida, seperti pyridoxal atau pyridoxamine, merupakan bentuk Vit. B6 dalam buah, sayuran, dan serealia.! Pag e 600

• Pyridoxine glucoside menjadi tersedia setelah dihidrolisis oleh beta-glucosidases di dalam usus halus.!

•

neral Properties Pyridoxal

phosphate, berfungsi sebagai coenzyme untuk asam amino.! oluble vitamin that enzyme functions coenzymatically in carboxylation and transcarboxylation reactions. The

N-biotinyl-L-lysine) ms are free D-biotin and biocytin ( -Pyridoxine (Fig. 41). Biocytin functions as the menyebabkan:! • Kekurangan y consists of a biotinylated lysyl residue covalently incorporated in a protein chain of various 1. inMetabolisme protein terganggu, seperti sistesis em of biotin can exist eight possible stereoisomers, only one of which (D-biotin) is the hemoglobin.! natural, oth free biotin and protein-bound biocytin exhibit activity when consumed in the diet. Biotin is widely 2. Koversi tryptophan menjadi nicotinic acid terhenti, mal products, and biotin deficiency is rare in normal humans.

n

PYRIDOXINE (PYRIDOXAL, VIT. B6)

menyebabkan terakumulasainya xanthurenic acid

Hydroxykynurenine dan

t, light, and oxygen. Extremes of high or low pH can cause degradation, possibly Jurusan because they Teknologi Hasil Pertanian " Pertanian Universitas Lampung N-C=O (amide) bond of the biotin ring system. Oxidizing conditions such as Fakultas exposure to hydrogen 51 51 lfur to form biologically inactive biotin sulfoxide or sulfone. Reaction of the biotin ring carbonyl with hough this has not been examined. Losses of biotin during food processing and subsequent storage d summarized [12, 67, 86]. Such losses may occur by chemical degradation processes as mentioned ree biotin. Little degradation of biotin occurs during low-moisture storage of fortified cereal products. retained in foods.

1. Biotin, Structure and Properties:"

pK a

PM PLP PMP • Biotin adalah bicyclic, vitamin larut dalam air yang berfungsi Ionization

PN

PL

5.00 s e b a g3–OH ai co n e zim p a d a 4.20–4.23 r e a k s i c3.31–3.54 a r b o x y4.14 lat i3.25–3.69 on an d Pyridinium N 8.96–8.97 8.66–8.70 7.90–8.21 8.69 8.61 transcarboxylation.!

4'-Amino g roup 10.4–10.63 ND biotin yaitu D-biotin bebas dan biocytin (e-N• Dua jenis

biotinyl-L-lysine).! 5'-Phosphate ester

<2.5 terhadap panas dan oksigen, tetapi:! <2.5 pK • Biotin stabil 6.20 5.76 pK ✴ pH terlalu tinggi dan rendah menyebabkan kerusakan a1

a2

karenapKmenyebabkan hidrolisis ikatan -N-C=O (amide). ! ND ND a3

✴ Terekspos oleh hydrogen peroxide mengoksidasi sulfur Note: PN, pyridixine; PL, pyridoxal; PM, pyridoxamine; PLP, pyridoxal 5' -phosphate; PMP, pyridoxamine 5' -phosphate. ND, not determined. membentuk biotin sulfoxide atau sulfone yang tidak aktif.!

Source: Ref. 123. • Kebutuhan Biotin adalah 30-60μg/hari. Kekurangan biotin

ditunjukan oleh kadar biotin dalam urin kurang dari 5 μg (normal: 30︲ 50μg). Jurusan Teknologi Hasil Pertanian " 52

Fakultas Pertanian Universitas Lampung

52

ng storage of human milk also has been examined [174]. The biotin concentration of the milk samples k at ambient temperature, 1 month at 5°C, or at -20°C or lower for 1.5 years.

ods

plantarum oods is performed by microbiological assay (usually with Lactobacillus ) or bydan varioushewan ✴ Bahan pangan Biotin nvolving avidin2. as the bindingAvailability: mengandung biotin. Dalam

tubuh manusia, dihasilkan oleh bakteri dalam usus halus!

✴ Pen ye ra p an biotin terhambat oleh konsumsi telur mentah, terbentuk ikatan biotin-protein avidin. Avidin adalah tetrameric glycoprotein pada albumin (putih telur). ! ✴ Ke k u ra n g a n b iot in m e n ye b a b ka n : A lo p e c i a (ra m b ut rontok), conjunctivities (pink eye), dermatitis (kulit),

FIGURE 41 Structures of biotin and biocytin.

53 53


CYANOCOBALAMIN (VIT. B12) 1. Vit B12, Structure and Properties:" • Vitamin B12 merupakan nama untuk komponen yang mempunyai sifat seperti cyanocobalamin.! • These compounds are:! ✴ Corrinoids, struktur tetrapyrrole (empat pyrrrole nitrogen) dengan ion kobal (Co) sebagai inti struktur. ! ✴ Koordinat ke lima pada ion Kobal mengikat atom nitrogen dari dimethylbenzimidazole moiety, ! ✴ Position ke enam pada ion Kobal dapat mengikat 5' deoxyadenosyl group, methyl group, water, hydroxyl ion, nitrite, ammonia atau sulfite! • Vitamin B12 stabil pada pH 4︲6. Pada media basa atau mengandung reducing agents, seperti ascorbic acid or SO2, vit. Jurusan Teknologi Hasil Pertanian " B12 cepat rusak. Fakultas Pertanian Universitas Lampung 54 54

2.

Pag e 604 R = 5' -deoxyadenosyl group, a methyl group, water, a hydroxyl ion, or other ligands such as nitrite, ammonia or sulfite

Vit. B12, Source and Availability:"

• Sekitar 20 vitamin B12 analog ditemukan di bahan pangan.

Pyrolle2

Tetapi sebagian tidak mempunyai aktivitas seperti vit. B12 dan beberapa lainnya bersifat sama dengan vit. 12, tetapi tidak dapat diserap.!

Pyrolle1

• Vit. B12 disintesis oleh mikroba, kemudian diserap oleh tanaman, terutama tanaman legumes (kacang-kacangan). !

Pyrolle3 Pyrolle4

• Vitam in B12 dar i hewan dalam bentuk coenzym e,

m et h y lco ba la m i n, 5 ' - d e ox ya d e n o s y lco ba la m i n, d a n Pag e 559 aquocobalamin. Dan disimpan dalam hati, ginjal, limpa, dan FIGURE 43 tion syndromes or the use of pharmacological anticoagulants. Although the use of certain fat substitutes has beenjaringan reported to otot. Structure of various forms of dimethylbenzimidazole

impair vitamin K absorption, moderate intakes vitamin B12. of these substitutes have no significant effect on vitamin K utilization.

quinone of vitamin compounds can be reduced to theinhydroquinone form by certain functions coenzymatically The in the transferstructure of a methyl groupK(from 5-methyltetrahydrofolate) methionine synthetase, whilereducing 5' - agents, but vitamin Jurusan Teknologi Hasil Pertanian " Fakultas Pertanian Universitas Lampung K activity is retained. Photochemical degradation can occur, but thecatalyzed vitamin isby quite stable to heat. 55 deoxyadenosylcobalamin serves as the coenzyme in an enzymatic rearrangement reaction methylmalonyl-CoA 55 mutase. Little or no naturally occurring cyanocobalamin 8.7.4.2 Analytical Methods exists in foods; in fact, the original identification of vitamin B12 as cyanocobalamin involved its formation as an artifact of the isolation procedure. Cyanocobalamin has a reddish color in the Spectrophotometric chemical based of oxidation-reduction properties of vitamin crystalline state and in solution. This colorationand may pose a assays limitation in on themeasurement possible addition of cyanocobalamin to certain foods, K lack the specificity required food analysis. Various HPLC methods exist that provide satisfactory specificity and permit individual especially light colored products (e.g., white for bread).


56 56

forms of vitamin K to be measured [135].

Unlike other vitamins that are synthesized primarily in plants, cobalamins are produced only by microbial biosynthesis. Certain 8.8toWater-Soluble Vitaminsof vitamin B12 produced by bacteria associated with root nodules, but legumes have been reported absorb small amounts little enters the seeds [99] Most 8.8.1 plant-derived Ascorbic Acidfoods are devoid of vitamin B12 unless contaminated by fecal material, such as from fertilizer [64, 65]. The vitamin B12 in most animal tissues consists mainly of the coenzyme forms, methylcobalamin and 5' Structure and GeneralHerbert Properties deoxyadenosylcobalamin, 8.8.1.1 in addition to aquocobalamin. [65] has classified foods according to their vitamin B12 content, as shown in Table 29.

L-Ascorbic acid (AA) (Fig. 14) is a carbohydrate-like compound whose acidic and reducing properties are contributed by the

ASCORBIC ACID (VIT. C) compound ishave highly polar; thus, it is readilyofsoluble in aqueous solution activity and insoluble Approximately 20 naturally2,3-enediol occurringmoiety. analogsThis of vitamin B12 been identified. Some these have no biological in in less nonpolar solvents. AApartial is acidic in character as but a result of ionization the C-3 hydroxyl group (pKa1 = 4.04 at 25°C). A second mammals, while others exhibit at least vitamin activity are often poorly of absorbed.

Vit. C, Source and Availability:"

ionization, dissociation of the C-2 hydroxyl, is much less favorable (pKa2=11.4). Two-electron oxidation and hydrogen

1. Structure andconvert Properties:" dissociation L-ascorbic acid to L-dehydroascorbic acid (DHAA). 8.8.9.2 Stability and Modes of Degradation

Ascorbic acid ( AA) adalah Under most✴ conditions of food processing, preservation, and storage, there is little nutritionally significant loss of vitamin B12. Cyanocobalaminkadded o m to p breakfast o n e ncereal sproducts e p e has r tbeen i reported to undergo an average loss of 17% during processing, with an additional 17% loss during storage for 12 months at ambient temperature [125]. In studies of the processing of fluid karbohi drat dimana sifat milk, 96% mean retention has been observed during high-temperature, short-time (HTST) pasteurization, and similar retention asam reduksi berasal (>90%) was found in milk dan processed using various modes of ultra-high-temperature (UHT) processing [45]. Although dari 2,3-enediol.! refrigerated storage of milk has little impact on vitamin B12 retention, storage of UHT-processed milk at ambient temperature for up to 90 days causes progressive losses that can approach 50% of the initial vitamin B12

✴ AA sangat polar sehingga

• Vitamin C terdapat pada sel tumbuhan dan hewan, dalam bentuk molekul bebas dan berikatan dengan protein.!

• Vitamin C banyak terdapat pada strawberries, parsley,

oranges, peterseli, jeruk, lemon (di kulit lebih banyak dari pada dalam pulp), berbagai kubis, dan kentang.!

• Kebutuhan harian adalah 60-150 ug/hari. Indikator

mudah larut dalam air dan tidak larut dalam pelarut non polar.!

kekurangan vit. C adalah bila kadar AA dalam plasma darah kurang dari 0,65 mg AA/100 ml plasma.

✴ O k s i d a s i m e n g u b a h Lascorbic acid menjadi Ldehydroascorbic acid (DHAA).

57 57


FIGURE 14 Universitas Lampung Fakultas Pertanian Structures of L-ascorbic acid and L-dehydroascorbic acid and their isomeric forms. (Asterisk indicates vitamin C activity.)


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Pag e 566

6.3 Water-Soluble Vitamins

Vit. C, Function:" • AA digunakan sebagai bahan makanan/aditif karena sebagai pereduksi dan antioksidan.! • AA efektif menghambat browning enzimatis mengurangi produk ortho-quinone.!

Diketogulonic acid degradation products, xy- juices and dried fruits. The intermediates that losone and 4-deoxypentosone (Formula 6.21), are have been identified are scorbamic acid (I in FIGURE 18 then converted into ethylglyoxal, various reduc- Formula 6.22), which is produced by Strecker Participation of dehydroascorbic acid in the Strecker deg radation tonesVit. (cf. 4.2.4.3.1), furfural furancarboxylic degradation with an amino acid, and a red C, Stability and Dengadation:" reaction. and acid. pigment (II). A wealth of data is available on water to act as a solvent for reactants and catalysts. The presence of certain sugars (ketoses) can increase the rate of anaerobic ascorbic acidsome losses during preservation, storage cincin Lactone menyebabkan kerusakan Vit. C.! degradation. Sucrose has a similar effectPembukaan at low pH, consistent with its pH-dependent generation of fructose. In contrast, bersifat sugars and sugar alcohols exert a protective effect against the oxidative degradation of AA, possibly byand binding metal ions andof food. Tables 6.1 and 6.2 and processing reducing their catalytic potency. The significance of these observations to actual foods remains to be determined. and Polimerisasi 6.4 present severaldan examples. Degradasi AA disebabkan Figs. oleh:6.3(a) (b) Ascorbic lurus acid degradation is oftendengan used as 8.8.1.3 Functions of Ascorbic Acid in Foods fragmentasi menghasilkan rantai atau ring a general indicator of changes occurring in food. dengan In addition to its function as an essential nutrient, AA is widely used as a food ingredient/additive because of its reducing and

• •

panjang rantai kurang dari 6 karbon.

antioxidative properties. As discussed elsewhere in this book, AA effectively inhibits enzymatic browning by reducing orthoquinone products. Other functions include (a) reductive action in dough conditioners, (b) protection of certain oxidizable com-

• Fungsi AA lainnya adalah (a) melindungi komponen yang mudah teroksidasi (misalnya, folates), dengan cara mengikat radikal bebas dan oksigen, (b) pelembut adonan, (c) penghambat pembentukan nitrosamine dalam daging, dan (d) mengikat ion logam.! • Kekurangan Vit. C menyebabkan Scurvy (gusi membusuk).

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419


(6.21) In the presence of amino acids, ascorbic acid, dehydroascorbic acid and their degradation products might be changed further by entering into Maillard-type browning reactions (cf. 4.2.4.4). An example is the reaction of dehydroascorbic acid with amino compounds to give pigments, FIGURE 19 Deg radation acid as a browning function of storagin e which can causeof ascorbic unwanted citrus temperature and water activity in dehydrated model food systems simulating breakfast cereal products. Data (means ±SD) are expressed as apparent first-order rate constants for the loss of total ascorbic acid (AA + DHAA). (Data from Ref. 77).


Fig. 6.3. Ascorbic acid lossesPertanian as a result of cooking of Fakultas Universitas Lampung 60 cabbage (according to Plank, 1966)

60

LOSSES OF VITAMINS IN FOOD

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