9. Food preservation

9. Food preservation Food starts to deteriorate or spoil from the time it is harvested or slaughtered. Preserving food to slow down the spoilage processes, extend the shelf life and to ensure the safety and quality is one of the essential focuses of the food industry. Although no preservation methods can completely eliminate dangerous microbes, the effort is to eradicate potential microbiological risk to the consumer, and maintenance of food quality and nutritional value within limits stated by the safe food production. Many preservation methods have been known since the ancient time and are nowadays considered traditional. However, together with the development of technologies and new discoveries a steady stream of new preservation techniques has been appearing. Each foodstuff has a specific period after which it begins to spoil. This period is called “shelf life”. A term used in the context of food that goes bad is “perishable”. According to its perishability the foodstuff can be classified as perishable and non-perishable (shelf-stable) foods. Perishable foods usually refer to items that are likely to rot, spoil, deteriorate or go bad quickly with the shelf life of about 1 or 2 days. A good example is fruit and vegetables, fresh meat, fish, milk and other “fresh” food. Non-perishable foods normally do not decay or spoil and do not require refrigeration and include canned fruits and vegetables, cereals, pulses or spices. It is also possible to convert a perishable foodstuff into a semi-perishable or non-perishable by some treating. For instance, if the fresh milk is boiled and refrigerated it can be stored for a few days. Food preservation methods can be divided into three main groups: physical, chemical and biological. Physical methods involve techniques of heat treatment, cold processing, control of water content, irradiation and preservation by controlled modified atmosphere. Chemical methods comprise salting, curing, smoking and use of preservatives. Biological methods are mainly represented by fermentation. Commonly more than one method is employed to achieve a more durable product with better taste, smell, appearance or nutritional value. The most efficient technique of killing the microbes and inactivating the tissue enzymes is the heat treatment. Although viruses and parasites can be destroyed by heat treatment employed in the food industry, thermophile bacteria and spores are able to survive. According to the objective, there are several techniques heat treatment such as thermization, pasteurization, sterilization, blanching, ultra-heat treatment, cooking and canning. Thermization can be described as a weakened form of pasteurization used for sterilization of raw milk. Pasteurization is mainly applied on dairy and egg products and canned food, non-alcoholic and low-alcoholic beverages. Although it can destroy most of spoilage organisms and pathogens as mycobacteria, brucella, salmonella, Campylobacter, thermoduric bacteria (e.g. Enterococcus and Micrococcus) and spores (e.g. Cl. botulinum) can survive. Sterilization helps inactivate all forms of microorganisms and the aim is to make storage of foodstuff long-term without chilling. Frequently sterilized products are milk, fruit juices or canned foods. The type of heat treatment often used in home preservation is blanching. The food (usually vegetable or fruit) is plunged into boiling water, removed after a short time interval and finally chilled in ice water to stop the cooking process. Blanching stops enzyme actions, rids the surface of dirt and organisms, brightens the colour and helps retard loss of vitamins. Ultra-heat treatment (UHT) helps destroy microorganisms without significant change to flavour, relying upon high temperature for a very short time. Canning does not include only heat treatment but also removing oxygen and hermetic sealing of containers to prevent post-process contamination. Cold processing is another food preservation techniques using temperature but working on the opposite principle then the previous ones. By chilling the food is cooled to a temperature approximately between zero degree and seven degree Celsius (depending on a type of foodstuff) which retards bacterial growth, biochemical activities, an thus prevents spoilage and lengthens the shelf-life. However, this treatment can never produce sterility and although parasites can be destroyed, typical surviving microbes are psychrophilic bacteria and psychrotrophs. Commonly refrigerated foods are milk products, meat products, ready meals, or desserts and all other that says 'keep refrigerated' on the label. By freezing the food is cooled to a temperature below zero degrees

Celsius which turns residual moisture into ice and thus inhibits the growth of most bacterial species. This method has been used since early times by fishermen, farmers and trappers who preserved their game and produce in unheated buildings during the winter. Drying is a method of food preservation in which the water in the food is removed resulting into bacteria, yeasts and moulds growth inhibition. It belongs to the oldest preservation techniques as food has been dehydrated since ancient times. Water is usually removed physically by evaporation, hot air drying (sun-drying – fruits and vegetables), spray drying (vegetables, egg and dairy products) or freeze drying (food is first frozen and then the water is removed by sublimation – meat and fish). Nonetheless, xerophiles (spore formers, some moulds, etc.) are more resistant to this method and may form a typical residual flora of dehydrated products. Food irradiation is a treatment of food with ionizing radiation belonging to the newest food preservation techniques. It dates back to the beginning of the 20th century when the scientists received patents to use ionizing radiation to kill bacteria in food. Since 2006 food irradiation has been approved by more than 50 countries either for specific or unlimited applications and it has been applied for several foods in more than 30 countries with successes. This method provides energy that destroys cell structures including DNA in bacteria, parasites, insects and moulds. However some spores and viruses may be highly resistant to ionizing energy. Food irradiation is sometimes referred to as "cold pasteurization” because the treatment by ionizing radiation can provide an effect similar to heat pasteurization not heating the food to high temperatures during the process, as in heatpasteurization. In modified atmosphere packaging the air around the product has a decreased O2 content and increased level of N and CO2 which retards growth of many pathogens; in vacuum packing the O2 is removed so that aerobic bacteria cannot grow but it does not prevent anaerobes from thriving. There are a wide range of chemical additives used for food preservation which influence the growth of micro-organisms in different ways and their usage is the issue of specific regulations which control the types and quantity of chemicals approved in the food industry. Frequently the additives have also other effect as for instance flavouring and colouration. The most common chemical compounds are salt in salting (meat and meat products, fish and cheese), salt and nitrates in curing (meat and meat products and fish), phenols and acids in smoking (meat and meat products, fish and cheese). Moreover, other preservatives as acetic acids and lactic acids, benzoic acids or sorbic acids are employed for preservation of e.g. cheese, bread or jam. Typical biological method of food preservation is fermentation, a process in which a starter culture (typically bacteria and yeast but also mould or enzyme) causes an organic substance to break down into simpler substances; especially, the anaerobic breakdown of sugar into alcohol that prevents the growth of undesirable microorganisms. The process is used to produce alcoholic beverages such as wine, beer, and cider but it can be also used in the leavening of bread, and for preservation techniques to create lactic acid in sour foods such as sauerkraut, dry sausages, and yogurt, or vinegar (acetic acid) for use in pickling foods. Combination of different preservation factors or techniques ('hurdles') in order to achieve multi-target, mild but reliable preservation effects is called hurdle technology. The hurdles keep spoilage or pathogenic organisms under control because these microorganisms cannot overcome all of the hurdles present. Theoretically, there can be application of high temperature during processing, low temperature during storage, low water activity, acidity (pH), as well as preservatives in the product.

Phrases and expressions Food spoilage spoil/perish/go off/deteriorate decay/fester/putrefy curdle (milk) sour (milk)

Kažení potravin kazit se, zkazit se hnít, rozkládat se srazit se (mléko) zkysnout

Food additives acids acidity regulators anticaking agents antifoaming agents antioxidants bulking agents food colouring colour retention agents emulsifiers flavours flavour enhancers glazing agents humectants preservatives stabilizers sweeteners thickeners

Potravinářské přísady kyseliny regulátory kyselosti protispékavé látky činidla proti pěnění antioxidanty plnidla potravinářské barvivo látky zachovávající barvu emulgátory aromata látky zvýrazňující chuť lešticí látky zvlhčovadla konzervační látky stabilizátory sladidla zahušťovadla

Food preservation methods drying pasteurization refrigeration/cooling freezing pickling canning thermization blanching sterilization pasteurization UHT (ultra-heat treatment) vacuum packing salting

Metody konzervace potravin sušení pasterizace chlazení mražení nakládání do láku konzervace v plechovkách termizace blanšírování sterilace pasterizace vysokoteplotní úprava vakuové balení nasolování

drying

sušení

freeze drying spray drying hot air drying fermentation hurdle technology Curing irradiation modified atmosphere packaging smoking

sublimační sušení sprejové sušení horkovzdušené sušení fermentace, kvašení technologie překážek nakládání (masa, zeleniny) ozařování balení v modifikované atmosféře uzení

Common food borne pathogens (Enteric) viruses Protozoan parasites mycotoxins bacteria enterotoxins parasites

Běžné choroboplodné bakterie v potravinách (střevní) viry parazitičtí prvoci mykotoxiny bakterie enterotoxiny paraziti

perishable foods non-perishable foods

potraviny podléhající rychlé zkáze trvanlivé potraviny

Vocabulary part 1. Answer the following questions. 1. Why is food preservation important? ___________________________________________________________________________ 2. What food preservation methods belong to the oldest and to the newest ones? ___________________________________________________________________________ 3. What food preservation techniques are commonly applied at home? ___________________________________________________________________________ 4. What types of food drying do you know? ___________________________________________________________________________ 5. What is the difference between hot pasteurization and cold pasteurization? ___________________________________________________________________________ 6. What food borne pathogens do you know? ___________________________________________________________________________ 7. How can we classify foods according to perishability? ___________________________________________________________________________ 8. What preservation methods connected to packaging do you know? ___________________________________________________________________________ 2. Discussion. Work with your partner. Decide whether the following foods are perishable, semi-perishable or non-perishable and what is the common applied food preservation. Food P/SP/NP Food preservation methods eggs seafood spices pasta dried plums potatoes sour cream rice pork liver almonds 3. Translate the following phrases into English.  různé formy tepelné úpravy syrového mléka  doba, po které dojde ke kažení  potraviny, které nepotřebují skladovat v chladu  krátké ponoření do horké vody a zchlazení  spory přežívající v extrémních podmínkách  zlepšení chuti, vůně a vzhledu výrobku

……………………………………………………. ……………………………………………………. ……………………………………………………. ……………………………………………………. ……………………………………………………. …………………………………………………….

    

zpomalit růst bakterií a zastavit jejich množení trvanlivé a rychle se kazící potraviny prodloužit skladovací lhůtu velká řada chemických přísad schválené a doporučené konzervanty

……………………………………………………. ……………………………………………………. ……………………………………………………. ……………………………………………………. …………………………………………………….

4. Explain the following term in English. thermophile ………………………………………………………………………………………………………………………… thermoduric ………………………………………………………………………………………………………………………… psychrophilic ………………………………………………………………………………………………………………………… fermentation ………………………………………………………………………………………………………………………… moisture ………………………………………………………………………………………………………………………… sublimation ………………………………………………………………………………………………………………………… undesirable ………………………………………………………………………………………………………………………… hurdle ………………………………………………………………………………………………………………………… 5. Fill in the gaps with the words from the table. consumed sun salted shelf-life sterilized hot fermentation fresh growth The hind legs are washed in ………………………….. water and wiped dry and prepared for drying. With technological improvements, hot air drying is gradually taking over from the traditional process of ………………………….. drying. Food additives are substances that are not normally ………………………….. as food. The testing is not compulsory for ………………………….. milk and milk-based products. The meat is ………………………….. in meat salting tubs or on salting racks. The producer should also specify the expected ………………………….. of the product. Spoilage in transit must be avoided, e.g. ………………………….. samples should be kept cool and frozen samples must remain frozen. If bacterial ………………………….. inhibitors are detected, the Salmonella infection shall be considered as confirmed. The temperature during ………………………….. must be carefully monitored.

Grammar part – Countable and uncountable nouns Key points: Countable nouns  have a singular and a plural form (we can count them). We can use a singular or plural verb with them. We can use numbers with them. Uncountable nouns  have only one form (we cannot count them). The plural number doesn’t exist. We can only use a singular verb with them. We cannot use numbers with them. However, we can count an uncountable noun indirectly by using a phrase like a piece of, a bit of.  Typical uncountable nouns are substances: (water, air, coffee, plastic, iron, paper), abstract ideas (life, fun, freedom, health, time, progress), activities (work, travel, sleep, football, help, research), human feelings (happiness, anger, honesty, hope, respect, courage) or groups of items (furniture, luggage).  Some uncountable nouns can be used in a countable way when they describe a category: e.g. All the food (jídlo) is cooked and served immediately after. Many foods (potraviny) are very spicy.  Some words have different meanings in countable and uncountable forms: U - paper (papír obecně) U - hair (vlasy) U - chocolate (čokoláda) U - beer (pivo - obecně nápoj) U - coffee (káva - obecně nápoj) U - room (prostor) U - experience (zkušenosti) U - chicken (kuřecí maso) U - lamb (jehněčí) U - cake (koláč, dort) U - pepper (pepř)

C- a paper (noviny, esej) C - a hair (jeden vlas, jeden chlup) C- a chocolate (čokoládový bonbon) C - a beer ('jedno' pivo v hospodě) C - a coffee (jeden šálek, např. v kavárně) C - a room (místnost, pokoj) C - an experience (jeden zážitek) C - a chicken (jedno kuře) C - a lamb (jehně) C - a cake (jeden celý koláč či dort) C - a pepper (paprika)

U – meat (maso) U – sugar (cukr)

C – a meat (maso – konkrétní druh) C – a sugar (cukr – konkrétní množství na oslazení např. kávy)



Some names of animals spell their singular and plural exactly alike: deer, moose, sheep, bison, salmon, pike, trout, fish, swine

Grammatical aspects Plural: C – have a plural (2 eggs) U – do not have a plural (flour, knowledge) Articles: C – definite or indefinite article should be always used in singular U – indefinite article cannot be used, some substitutes the indefinite article Quantity: C – a lot of (positive statements), many (negative statements and questions), few/a few U – a lot of (positive statements), much (negative statements and questions), little/a little !!! If on doubts you should always check in a dictionary to see if a noun is countable (C) or uncountable (U). The meaning of a noun may change depending on whether it is used in a countable or uncountable sense. !!! Some nouns ending in -s take a singular verb: The news is good today. !!! Some nouns only have a plural form: The police are investigating the new case. !!! There are many words uncountable in English but countable in Czech language: e.g. information, advice, news, knowledge, homework.

1. Underline the most suitable word in each sentence. Efforts in food/foods safety continue. Dairies purchase sheep's/sheeps’ and cow's/cows’ milk in the regions surrounding them. The government doesn’t/don’t want to support our project. We will need more animal brush-making bristle/bristles or hair/hairs. The traditional slaughter gave rise to sausage/sausages of various shapes, different ingredients and different colours and flavour. Still, there is no decrease in price for fresh fish/fishes for end consumer/consumers. All this item/these items can be eaten without heat treatment/treatments before consumption. 2. Fill in the gaps with the proper quantifier (a lot of, many, much, few, a few, little, a little). She knows exactly how ……………………. milk each cow yields and how ……………………. cows there are on the farm. The new project contains …………………….new improvements both for consumers and producers. The new diet is based …………………… more on milk, milk products and lean meat. Too …………………… unintelligible information will lead to consumers ignoring the essential information and paying attention to information which has no real value. Is there …………………… milk left in the fridge? The beverage should be cooled for only …………………… seconds. This method requires …………………… time and material and is particularly suitable for nonspecialist laboratories. If necessary moisten the sample with …………………… water.

Vocabulary acetic acid (n) anaerobic (adj) approved (adj) benzoic acid (n) blanching (n) break down (v) canned (adj) chill (v) cider (n) cool (v) cure (v) decay (v) deteriorate (v) dirt (n) dry sausage (n) durable (adj) employ (v) enzyme (n) eradicate (v) fermentation (n) food (n) foodstuff (n) go bad (phr.) harvest (v) heat (v) hurdle (n) inhibit (v) ionize (v) irradiation (n) lactic acid (n) leavening (n) maintenance (n) moisture (n) mould (n) nitrite (n) nonetheless (adv) objective (n) overcome (v) package (v)

/əˌsiːtɪk ˈæsɪd/ /ˌænəˈrəʊbɪk/ /əˈpruːvd/ /bɛnˈzəʊɪkˈæsɪd / /blɑːntʃɪŋ/ /breɪk daʊn/ /kænd/ /ˈtʃɪl/ /ˈsaɪdə(r)/ /kuːl/ /kjʊə(r)/ /dɪˈkeɪ/ /dɪˈtɪəriəreɪt/ /dɜː(r)t/ /draɪ ˈsɒsɪdʒ/ /ˈdjʊərəb(ə)l/ /ˈdjʊərəb(ə)l/ /ˈenzaɪm/ /ɪˈrædɪkeɪt/ /ˌfɜː(r)menˈteɪʃ(ə)n/ /fuːd/ /ˈfuːdˌstʌf/ /ɡəʊ bæd/ /ˈhɑː(r)vɪst/ /hiːt/ /ˈhɜː(r)d(ə)l/ /ɪnˈhɪbɪt/ /ˈaɪənaɪz/ /ɪˌreɪdiˈeɪʃ(ə)n/ /ˌlæktɪk ˈæsɪd/ /ˈlev(ə)nɪŋ/ /ˈmeɪntənəns/ /ˈmɔɪstʃə(r)/ /məʊld/ /ˈnaɪtreɪt/ /ˌnʌnðəˈles/ /əbˈdʒektɪv/ /ˌəʊvə(r)ˈkʌm/ /ˈpækɪdʒ/

kyselina octová anaerobní schválený kyselina benzoová blanšírování rozložit v plechovce, v konzervě chladit, mrazit jablečné víno, mošt ochladit, zchladit nakládat do láku hnít, tlít zkazit se špína, nečistota trvanlivý slam trvanlivý, odolný použít, využít enzym vymýtit, vyhubit fermentace potravina potraviny zkazit se sklízet, sklidit ohřát překážka zabránit, znemožnit ionizovat ozáření, ozařování kyselina mléčná kynutí zachování, udržení vlhkost plíseň dusičnan, nitrát nicméně záměr překonat zabalit, balit

packing (n) pasteurization (n) perishability (n) phenol (n) pickle (v) plunge (n) preservative (n) produce (n) pulses (n, pl.) residual (adj) retard (v) rid of (v) rot (v) salt (v) sauerkraut (n) seal (v) shelf life (n) smoke (v) sorbic acid (n) stream (n) sublimation (n) thermization (n) thermoduric (adj) thermophile (n) thrive (v) trapper (n) treatment (n) vinegar (n) xerophile (n) yeast (n) yogurt or yoghurt (n)

/ˈpækɪŋ/ /ˌpɑːstʃəraɪˈzeɪʃ(ə)n/ /perɪʃəˈb(ə)ləti/ /ˈfiːnɒl/ /ˈpɪk(ə)l/ /plʌndʒ/ /prɪˈzɜː(r)vətɪv/ /ˈprɒdjuːs/ /ˈpʌlsɪz/ /rɪˈzɪdjuəl/ /rɪˈtɑː(r)d/ /rɪd əv/ /rɒt/ /sɔːlt/ /ˈsaʊə(r)ˌkraʊt/ /siːl/ /ʃelf laɪf/ /sməʊk/ /sɔːbɪkˈæsɪd/ /striːm/ /ˌsʌblɪˈmeɪʃ(ə)n/ /θɜː(r)miˈzeɪʃ(ə)n/ /θɜː(r)mʊə ˈdjʊərɪk/ /ˈθɜːməʊˌfaɪl/ /θraɪv/ /ˈtræpə(r)/ /ˈtriːtmənt/ /ˈvɪnɪɡə(r)/ /ˈzɪərəfaɪl/ /jiːst/ /ˈjɒɡə(r)t/

balení pasterizace zkazitelnost fenol naložit, sterilovat (v nálevu) ponořit konzervant zemědělská produkce, plodiny luštěniny zbylý, zbytkový zpomalit zbavit se zkazit se, shnít nasolit, solit kyselé zelí neprodyšně uzavřít, utěsnit skladovatelnost udit kyselina sorbová tok sublimace termizace snášející vysoké teploty termofil, termofilní mikrob prospívat, růst lovec kožešin ošetření, úprava ocet xerofyt, suchomylný mikrob kvasinky jogurt