食品專業(yè)英語 LESSON 8 Principles Of Refrigerated Gas Storage

1、There are clear benefits from the cool temperature storage of foods. As this.thesis evolved there was another development which paralleled it. While slow.in maturing, it also had significant potential. The area dealt with the gas,storage of flesh foods. The matter had appeared in quite an unexpected

2、 systemrefrigerated dough. In this lesson we will explore the nature and direction. ofthe technology of gas storage as it is evolving. Gas Packed Refrigerated Dough Cooking is the art of preparing foods by heating until they have changed in flavor, appearance, tenderness and chemical composition. Ba

3、king is a form of cooking that is carried out in an oven. Baked bread is not only one of the most ancient foods manufactured by man, it is also the food most widely eaten in the world. The actual baking process is really the last and most important step in the production of bakery products. Through

4、the agency of heat, an unpalatable dough mass is transformed into a light, porous, easily digestible add appetizing product.Freshly baked products can be produced and distributed effectively However,the storage life of soft baked goods is generally less than a week. Duringthis time, products stale a

5、nd lost! desirable tastes and textures. The appealingaroma of baked goods is slowly lost after the products are removed from theovens. For best eating, baked products are generally soon after baking. An ingenious means of providing consumers with ready-td-bake dough products evolved in the past few

6、decades. This product line is called refrigerateddough. The essential technology involves the preparation of a dough, packagingit in a sealed container capab1e of holding about 5 atm of gas, and causing aninitial controlled release of carbon dioxide. Under refrigerated conditions, slightly above fre

7、ezing, such products can be effectively produced and distributed,and when baked yield excellent products. Matz(1968) reported that in such commercial refrigerated dough practices.there is ordinarily used, as the leavening agent or gas generating component a slowly rating sodium acid pyrophosphate ot

8、 the approximate formula Na2H2P2O7 in combination with sodium bicarbonate. All ingredients are mixed under very rigidly controlled temperature conditions. (Note: dough temperature out of mixer, 10 to 15) The resulting dough is rolled out and the dough is then sheeted and cut into banks, such as disc

9、s about 5 cm in diameter by l.2 cm thick. The cut-outs are dusted with rice flour or oiled to prevent sticking together. They are then stacked and packed in a suitable can. These cans are doughtight but not gas-tight. As a result, air and carbon dioxide may and do escape so that the dough reaches an

10、d blocks the gas outlets. Within about l.5 to 3 hr after the package is sealed, for instance, the biscuits will have so expanded as to fill the container and close the original vents for gas and the internal pressure of carbon dioxide gene ated by the leavening materials will have risen to around 1

11、atm. Pressure within the can will be maintained over a period of 8 weeks or so if the biscuit dough and cans are normal and the storage temperature is between 7 to 12. One of the difficulties in the manufacture of dough using phosphate leavening agents has been the formation of visible phosphate cry

12、stals (disodium phosphate dodecahydrate). This crystal formation occurs at storage temperatures below 10, and is frequently most abundant at about 7. This crystallization is prevalent in the canned refrigerated doughs because of their extended storage, including and normal period of transportation a

13、nd storage in the stores and homes. These visible crystals cause consumer rejection of the product because of their glass-like appearance and an uneven coloration of the baked goods which develops upon baking. It is found that phosphate leavened cereal doughs can be prepared. whichcan be kept at the

14、ir normal storage temperature (i.e., between about 7 and12) for periods up to 12 weeks or more, and which are free from visible phosphate crystal formation. Such a dough is made in the conventional manner, bymixing the ingredients such as flour, shortening, flavoring, water, the usualminor ingredien

15、ts, and the chemical leavening agent, and then allowing the doughto develop, and shaping the dough as desired. The dough is then Placed in the consumer container and sealed, then allowed to proof rapidly so that dough temperature teaches 14 to 20 as quicklyas possible. Proofing involves the reaction

16、 of the chemical leaveners to providesufficient carbon dioxide to cause the dough to expand and fill the container soas to close the gas vents. The canned dough is cooled in a conditioning area, such as controlled temperature room, at a temperature above its freezing point but below O. Normally the

17、freezing point of such doughs is about -6. The time and temperature required to condition the dough will vary dependent upon can dimensions, net weight of the dough, formation of the dough, and refrigeration conditions used. However, it is important that the temperature of the conditioning room not

18、be below the freezing point of the dough. The necessary time and temperature can be determined by withdrawing sample cans at intervals. opening them, and noting the temperature and condition of the dough. When microscopic crystals of disodium phosphate phosphate dodecahydrate are observed dispersed

19、substantially uniformly throughout the dough, the dough is conditioned and will not exhibit visible phosphate crystals even after 12 weeks of storage. Once the time has been obtained for a given product under given cooling conditions, the same time of treatment can be used for subsequent production.

20、 Conventional refigerated doughs can be conditioned by being held at about-7 to -5 for about 48 hr. With a higher temperature it is recommended that the bolding time be increased to 4 days. At temperatures of about -1 a longer holding time of about 3 days is required to obtain proper conditioning of

21、 the dough. After the canned dough has been conditioned, the cans are removed fromthe cooling area and transferred to the usual storage area where the temperatureis maintained at 4 to 10. The cans may then be transported and the doughused in the ordinary manner. Gas Storage of Fruits And VegetablesC

22、ontrolled atmosphere (CA) storage Controlled atmosphere (CA) storage refers to the composition of the atmosphere altered from that of air in respect to the proportions of O2 and/or CO2. The proportioas are controlled; O2 usually is lower and CO2 increased; nitrogen acts as an inert “filler,” other g

23、ases may be added in low concentrations. Modified atmosphere (MA) storage is similar in principle to CA storage. except control of gas concentrations is less precise. Respiratory CO2 or CO2 derived from dry ice accumulates and Oz decreases. Lipton (1975) believes that the modification of the O2 and/

24、or CO2 concentration in the atmosphere surrounding fresh produce is justified if the vegetable or fruit will be more valuable after CA storage than after a similar storage period in the air. CA is used most commonly to slow ripening of fruits, but appropriate mixtures of O2 and CO2 also can retard t

25、he spread of certain diseases and lower the incidence of some disorders. This is usually not apparent when storage time is brief and/or when storage temperature is optimal. The use of CA can also prevent desirable ripening. induce severe physiological disorders and cause an increases in decay when m

26、isused. Each kind of vegetable and fruit has its own specific, unpredictable tolerance for atmosphere modification . Controlled atmosphere storage bas been commonly used to delay ripening of fruits, retard the spread of disease, lower the incidence of storage disorders and inhibit toughening and yel

27、lowing. An extension of this technique is the use of packaging films to develop a microcontrolled environment in retail packages. Modification of the storage environment by suitable packaging can provide storage benefits which exceed those observed with refrigeration and controlled atmosphere.Produc

28、e Package System A package of apples can be a dynamic s)-stem in which two processes, respiration and permeation, occur simultaneously. There is an uptake of O2 by the apples and evolution of CO2, C2H4, H20 and other volatiles, and, at the same time. specific restricted exchange of these gases throu

29、gh the packaging film. Variables that affect respiration are: weight of apples, stage of maturity, membrane permeability, temperature, 02 and CO2 partial pressures, ethylene concentration, light, etc. Variables affecting gas exchanges into and out of the package are; structure of the packaging film,

30、 thickness, area, temperature, O2, and CO2 concentrations . It has been demonstrated that steady state conditions are established withinsuck an intact packaging system; equilibrium concentrations of 02 and CO2 prevail, and the respiration rate is equal to the rate of gas exchange. Any change in the

31、system variables will affect the equilibrium or the time to establish steady state conditions. The packaging of fresh food in polymeric films is now frequently used in retail stores and about 40% of the produce is now distributed to retail stores in consumer packages. This packaging is designed for

32、consumer appeal. Better use to regulate ripening and, thus, to prolong useful storage life is predicted by many people.第八課 食品冷氣保藏原理食品低溫貯藏有明顯的好處。以往，隨著這一課題展開，就出現(xiàn)與之相平行的另外新的發(fā)展。新的課題雖然尚處在緩慢成熟的過程中)、卻同樣有很大的潛力。這一領(lǐng)域的研究內(nèi)容是生鮮食品的氣體保藏法。此事首、先出現(xiàn)在一個(gè)完全沒有意料。到的食物體系冷藏生面團(tuán)之中。本課我們將探討當(dāng)前在發(fā)展中的氣體保藏技術(shù)的特點(diǎn)和趨勢。充氣包裝冷藏面團(tuán) 烹任是利用加熱方法使食

33、物的風(fēng)味、外觀、嫩度和化學(xué)組成發(fā)生變化的食物制作技藝。焙烤是一種在烤爐中進(jìn)行的烹證形式。烤制的面包不僅是人類制作的最古老食品之，而且也是世界上食用最廣泛的食品。真正的焙烤過程其實(shí)是焙烤制品生產(chǎn)中最后、也是最重要的一步，通過加熱的作用，一塊食而無味的面團(tuán)就轉(zhuǎn)變成了疏松多孔、易于消化的美食制品。 新烤制產(chǎn)品的生產(chǎn)效率和銷售效果都可以很好。但松軟的焙烤制品的貯藏期一般不超過一周。在貯藏期內(nèi)，制品變硬并失去美味和質(zhì)構(gòu)。焙烤制品在移出烤爐之后，誘人的香氣便慢慢消失。通常，焙烤制品剛烤好就消費(fèi)是最適宜的。 最近幾十年里發(fā)展了一種巧妙的方法，向消費(fèi)者提供便于焙烤的現(xiàn)成面團(tuán)產(chǎn)品。這種產(chǎn)品的生產(chǎn)線稱為冷藏面團(tuán)生

34、產(chǎn)線。其基本的工藝包括面團(tuán)的制備、面團(tuán)包封在能夠保持氣體壓力為5atm的密封容器中、以及CO2最初有控制地促使釋放。在冷藏(略高于冰點(diǎn))溫度條件下，這種產(chǎn)品可以有效地進(jìn)行了生產(chǎn)和銷售，且在焙烤后可以獲得優(yōu)質(zhì)的產(chǎn)品。 馬茨(1968年)曾報(bào)道，在這種商業(yè)化冷藏面團(tuán)的生產(chǎn)作業(yè)中，通常使甩一種作用緩慢、分子式大體為Na2H2P2O7的焦磷酸氫鈉與小蘇打的混合物作為膨松劑(產(chǎn)氣成分)。所有的配料要在非常嚴(yán)格控制的溫度下混合(注：從混合器出來的面團(tuán)溫度在1015)。調(diào)好的面團(tuán)通過軋輥送出，壓成面片,再切割成面坯，如切成直徑約；5cm、厚1.2cm的圓形面坯。將這些切出來的面坯，撒上米粉或涂上油，以免粘在

35、一起。然后把它們壘起來，裝入適當(dāng)?shù)慕饘俟?。金屬罐對面團(tuán)不透漏，但不是氣密性的。因此空氣和二氧化碳可以逸出，使面團(tuán)有可能到達(dá)并堵住氣體逸出口。例如，罐裝容器在密封后1.53h內(nèi)；餅干面坯會(huì)膨脹充滿整個(gè)容器，并堵住原有的泄氣口。由膨松材料產(chǎn)生的內(nèi)部二氧化碳壓力將升到1atm左右。只要餅干面坯和罐子正常，且貯藏溫度在712之間，那么罐內(nèi)的壓力將維持約8周以上。 面團(tuán)生產(chǎn)中使用膨松劑磷酸鹽的困難之一是生成肉眼看得見的磷酸鹽晶體(十二水磷酸氫二鈉)。這種晶體在貯藏溫度低于10時(shí)形成，而在7左右時(shí)常常大量產(chǎn)生。罐裝冷藏面團(tuán)中這種結(jié)晶現(xiàn)象很普遍，其原因是它的貯藏期長(包括正常的運(yùn)輸時(shí)間和在：商店及家庭中的存

36、放時(shí)間)。這些肉眼可見的晶體致使產(chǎn)品難以為消費(fèi)者所接受，因?yàn)榫w外觀象玻璃，并且焙烤時(shí)會(huì)在焙烤制品上形成不均勻的顏色。 有人發(fā)現(xiàn)，用磷酸鹽作膨松劑制成的谷物面團(tuán)可在正常的貯藏溫度(即在712)下存放12周或更長的時(shí)間，并且無明顯磷酸鹽晶體形成。這種面團(tuán)用傳統(tǒng)方法制造，先把各種配料如面粉、起酥油、調(diào)味料、水、常用的微量配料以及化學(xué)膨松劑混合在一起，然后讓面團(tuán)展開，并按所要求的形狀成型。 接著將面團(tuán)裝入小包裝容器并密封，讓其迅速醒發(fā)，使面團(tuán)的溫度盡快達(dá)到1420。醒發(fā)過程涉及到化學(xué)膨松劑的反應(yīng)，產(chǎn)生足夠的二氧化碳，使面團(tuán)膨發(fā)充滿容器，從而封住泄氣口。 然后將罐裝面團(tuán)放在溫控室之類的調(diào)理場所中，在高

37、于面團(tuán)冰點(diǎn)但低于0的溫度下進(jìn)行冷卻。這類面團(tuán)的冰點(diǎn)通常在-6左右。面團(tuán)調(diào)理所要求的時(shí)間和溫度隨金屬罐尺寸、面團(tuán)凈重、面團(tuán)成形及所用制冷條件的不同而異。但是，重要的是調(diào)理室的溫度不得低于面團(tuán)的冰點(diǎn)。面團(tuán)調(diào)理所必需的時(shí)間和溫度可以通過定期取樣開罐、觀測面團(tuán)的溫度和狀態(tài)來確定。當(dāng)觀察到有顯微鏡可見的十二水焦磷酸二鈉微晶體明顯均勻地分散在整個(gè)面團(tuán)中時(shí)，那么此時(shí)面團(tuán)已處于正常良好狀態(tài)，便不會(huì)在甚至貯存12周以后出現(xiàn)肉眼可見的磷酸鹽晶體。給定產(chǎn)品在給定冷卻條件下的調(diào)理時(shí)間一旦確定，便可將同樣的時(shí)間應(yīng)用于隨后的生產(chǎn)中。 傳統(tǒng)冷藏面團(tuán)的調(diào)理可在約-7-5下保持約48小時(shí)。若采用更高的溫度，則建議將保持時(shí)間延長

38、到4天。在-1左右的溫度下，為使面團(tuán)獲得適當(dāng)?shù)恼{(diào)理，要求將保持時(shí)間再延長3天左右。罐裝面團(tuán)經(jīng)調(diào)理后，可從冷卻場所移到溫度保持在410的普通貯藏場所，這時(shí)便可按常規(guī)方式運(yùn)送罐裝面團(tuán)和使用面團(tuán)。水果和蔬菜的氣體保藏法氣調(diào)貯藏(CA貯藏) 氣調(diào)(CA)貯藏是指貯藏環(huán)境大氣的組成在02或C02(或兩者)的含率上是由改變空氣組成而來的貯藏方法。各氣體的含率受到控制，通常做法將O2的含率降低，將CO2的含率提高，而氮?dú)馄鹬栊浴疤畛鋭钡淖饔?，還可以加入一些低濃度的其它氣體。變氣(MA)貯藏與氣調(diào)(CA)貯藏的原理相似，只是對氣體濃度的控制沒那么精確而已。由呼吸作用產(chǎn)生的CO2和來自干冰的C02累積起來，

39、降低了O2的含量。李卜頓(1975)認(rèn)為：如果蔬菜或水果經(jīng)CA貯藏后比在空氣中貯藏相同時(shí)間后有更高的價(jià)值，那么改變新鮮農(nóng)產(chǎn)品周圍氣體中02或C02 (或兩者)的濃度是合理的。CA用于水果的緩慢后熟最為普遍，但混合適當(dāng)?shù)?2和C02也能減少某些植物病害的蔓延，從而降低腐壞事故出現(xiàn)的機(jī)會(huì)。當(dāng)貯藏時(shí)間很短或貯藏溫度適宜時(shí)，通常不易見到這種不良的事故。 如果使用不當(dāng)，CA也會(huì)妨礙正當(dāng)?shù)暮笫?，誘發(fā)嚴(yán)重的生理紊亂和造成腐爛率的增加。每一種蔬菜和水果都有它自己特殊的難以預(yù)測的對氣體調(diào)整的承受限度。 氣調(diào)貯藏已波普遍地用于減慢水果后熟，減少病害傳播，降低貯藏腐壞事故和防止變老、變韌、變黃，這種技術(shù)的一種推廣應(yīng)

40、用是零售包裝中使用包裝薄膜；以形成小范圍的控制環(huán)境。因適當(dāng)包裝而改變的貯藏環(huán)境可以給貯藏帶來勝過在致冷氣調(diào)貯藏中能見到的好處。農(nóng)產(chǎn)品包裝系統(tǒng) 一包蘋果可以是一個(gè)動(dòng)態(tài)體系，在該體系中，同時(shí)進(jìn)行著呼吸和滲透這兩種過程；蘋果吸取02，放出C02、乙烯、水份和其它揮發(fā)性物質(zhì)，與此同時(shí),這些氣體透過包裝薄膜進(jìn)行著特別有節(jié)制的交換。影響呼吸作用的變量有：蘋果重量、成熟期、薄膜的可滲透性、溫度、O2和C02的分壓、乙烯濃度、光照等。影響進(jìn)出蘋果包氣體交換的變量有：包裝薄膜的構(gòu)造b厚度、面積、溫度、O2和C02的濃度。 已經(jīng)由實(shí)驗(yàn)證明：在這樣完整無損的包裝體系內(nèi)部，穩(wěn)定狀態(tài)的條件已建立。 Lesson 8do

41、Mgh (揉好的生)面團(tuán)， 一團(tuán)tendemess 柔軟性，嫩度oy7en 爐、 干燥爐， 面包烤爐 烘箱，烤箱poyous 孔的， 疏松的aroma 香氣， 香味 果香sodium acid pyrophosphate 焦磷酸氫鈉sodium bic3rbonate 碳酸氫鈉，小蘇打ingredient 成份， 拼分， 拼料Vent (通氣)孔， 通氣口 出口 排出， 泄放， 排久 放氣sheet 薄板， 薄片 面片， 壓面片 張數(shù)disodium Phosphatedodecahydrate 十二水磷酸氫二鈉PreValent 流行的， 盛行的， 普遍的，罕優(yōu)勢的Proof (面團(tuán))醒發(fā)成

42、形1eaVen 膨松劑 (加膨松劑)使膨松盛mension a。尺寸，尺度，線度復(fù)面積，容積，大小范圍， 方四micNscopic 顯微鏡的， 象顯微鏡的，用顯微鏡， 可見的， 微觀N， 微小的， 細(xì)微的卻naInlc a，動(dòng)力的， 動(dòng)力學(xué)的 有生氣的， 能動(dòng)的。 有力的 n動(dòng)力， 原動(dòng)力 動(dòng)態(tài)v01atile 揮發(fā)的， 易揮發(fā)的ethylene 乙烯P01ym棚c 聚合的permeation n 滲入。 通過， 彌漫， 充滿English-bug 1. The importance of sanitation practices is to combat the proliferation and activity of food spoilage and food poisoning micro