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 system─refrigerated dough In this lesson we will explore the nature and direction of
the 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 Baking 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 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 During
this time products stale and lost desirable tastes and textures The appealing
aroma of baked goods is slowly lost after the products are removed from the
ovens For best eating baked products are generally soon after baking
An ingenious means of providing consumers with readytdbake dough products evolved in the past few decades This product line is called refrigerated
dough The essential technology involves the preparation of a dough packaging
it in a sealed container capab1e of holding about 5 atm of gas and causing an
initial controlled release of carbon dioxide Under refrigerated conditions slightly above freezing 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 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 discs about 5 cm in diameter by l2 cm thick The cutouts 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 gastight As a result air and carbon dioxide may and do escape so that the dough reaches and blocks the gas outlets Within about l5 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 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 crystals (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 and storage in the stores and homes These visible crystals cause consumer rejection of the product because of their glasslike appearance and an uneven coloration of the baked goods which develops upon baking
It is found that phosphate leavened cereal doughs can be prepared which
can be kept at their normal storage temperature (ie between about 7℃ and
12℃) 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 by
mixing the ingredients such as flour shortening flavoring water the usual
minor ingredients and the chemical leavening agent and then allowing the dough
to 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 quickly
as possible Proofing involves the reaction of the chemical leaveners to provide
sufficient carbon dioxide to cause the dough to expand and fill the container so
as 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 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 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 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
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 the dough
After the canned dough has been conditioned the cans are removed from
the cooling area and transferred to the usual storage area where the temperature
is maintained at 4 to 10℃ The cans may then be transported and the dough
used in the ordinary manner
Gas Storage of Fruits And Vegetables
Controlled 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 andor CO2 The proportioas are controlled O2 usually is lower and CO2 [increased nitrogen acts as an inert filler other gases 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 andor 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 the spread of certain diseases and lower the incidence of some disorders This is usually not apparent when storage time is brief andor 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 misused 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 yellowing 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
Produce 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 through 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 thickness area temperature O2 and CO2 concentrations
It has been demonstrated that steady state conditions are established within
suck 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 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 consumer appeal Better use to regulate ripening and thus to prolong useful storage life is predicted by many people
第八课 食品冷气保藏原理
食品低温贮藏明显处着课题展开出现相行外新发展新课题然尚处缓慢成熟程中).样潜力领域研究容生鲜食品气体保藏法事首先出现完全没意料食物体系——冷藏生面团中课探讨前发展中气体保藏技术特点趋势
充气包装冷藏面团
烹利加热方法食物风味外观.嫩度化学组成发生变化食物制作技艺焙烤种烤炉中进行烹证形式烤制面包仅类制作古老食品世界食广泛食品真正焙烤程实焙烤制品生产中重步通加热作块食味面团转变成疏松孔易消化美食制品
新烤制产品生产效率销售效果松软焙烤制品贮藏期般超周贮藏期制品变硬失美味质构焙烤制品移出烤炉诱香气便慢慢消失通常焙烤制品刚烤消费适宜
十年里发展种巧妙方法消费者提供便焙烤现成面团产品种产品生产线称冷藏面团生产线基工艺包括面团制备面团包封够保持气体压力5atm密封容器中CO2初控制促释放冷藏(略高冰点)温度条件种产品效进行生产销售焙烤获优质产品
马茨(1968年)报道种商业化冷藏面团生产作业中通常甩种作缓慢分子式体Na2H2P2O7焦磷酸氢钠苏混合物作膨松剂(产气成分)配料非常严格控制温度混合(注:混合器出面团温度10~15℃)调面团通轧辊送出压成面片切割成面坯切成直径约5cm厚12cm圆形面坯切出面坯撒米粉涂油免粘起然垒起装入适金属罐金属罐面团透漏气密性空气二氧化碳逸出面团达堵住气体逸出口例罐装容器密封15~3h饼干面坯会膨胀充满整容器堵住原泄气口膨松材料产生部二氧化碳压力升1atm左右饼干面坯罐子正常贮藏温度7~12℃间罐压力维持约8周
面团生产中膨松剂磷酸盐困难生成肉眼见磷酸盐晶体(十二水磷酸氢二钠)种晶体贮藏温度低10℃时形成7℃左右时常常量产生罐装冷藏面团中种结晶现象普遍原贮藏期长(包括正常运输时间:商店家庭中存放时间)肉眼见晶体致产品难消费者接受晶体外观象玻璃焙烤时会焙烤制品形成均匀颜色
发现磷酸盐作膨松剂制成谷物面团正常贮藏温度(7~12℃)存放12周更长时间明显磷酸盐晶体形成种面团传统方法制造先种配料面粉起酥油调味料水常微量配料化学膨松剂混合起然面团展开求形状成型
接着面团装入包装容器密封迅速醒发面团温度快达14~20℃醒发程涉化学膨松剂反应产生足够二氧化碳面团膨发充满容器封住泄气口
然罐装面团放温控室类调理场中高面团冰点低0℃温度进行冷类面团冰点通常6℃左右面团调理求时间温度金属罐尺寸面团净重面团成形制冷条件异重调理室温度低面团冰点面团调理必需时间温度通定期取样开罐观测面团温度状态确定观察显微镜见十二水焦磷酸二钠微晶体明显均匀分散整面团中时时面团已处正常良状态便会甚贮存12周出现肉眼见磷酸盐晶体定产品定冷条件调理时间旦确定便样时间应生产中
传统冷藏面团调理约7~5℃保持约48时采更高温度建议保持时间延长4天1℃左右温度面团获适调理求保持时间延长3天左右
罐装面团调理冷场移温度保持4~10℃普通贮藏场时便常规方式运送罐装面团面团
水果蔬菜气体保藏法
气调贮藏(CA贮藏)
气调(CA)贮藏指贮藏环境气组成02C02(两者)含率改变空气组成贮藏方法气体含率受控制通常做法O2含率降低CO2含率提高氮气起着惰性填充剂作加入低浓度气体变气(MA)贮藏气调(CA)贮藏原理相似气体浓度控制没精
确已呼吸作产生CO2干冰C02累积起降低O2含量李卜顿(1975)认:果蔬菜水果CA贮藏空气中贮藏相时间更高价值改变新鲜农产品周围气体中02C02 (两者)浓度合理CA水果缓慢熟普遍混合适02C02减少某植物病害蔓延降低腐坏事出现机会贮藏时间短贮藏温度适宜时通常易见种良事
果CA会妨碍正熟诱发严重生理紊乱造成腐烂率增加种蔬菜水果特殊难预测气体调整承受限度
气调贮藏已波普遍减慢水果熟减少病害传播降低贮藏腐坏事防止变老变韧变黄种技术种推广应零售包装中包装薄膜形成范围控制环境适包装改变贮藏环境贮藏带胜致冷气调贮藏中见处
农产品包装系统
包苹果动态体系该体系中时进行着呼吸渗透两种程苹果吸取02放出C02乙烯水份挥发性物质时气体透包装薄膜进行着特节制交换影响呼吸作变量:苹果重量成熟期薄膜渗透性温度O2C02分压乙烯浓度光等影响进出苹果包气体交换变量:包装薄膜构造b厚度面积温度O2C02浓度
已实验证明:样完整损包装体系部稳定状态条件已建立
Lesson 8
doMgh ①(揉生)面团 ② 团
tendemess 柔软性嫩度
oy7en ①炉 干燥炉 面包烤炉 ②烘箱烤箱
poyous 孔 疏松
aroma ①香气 香味 ②果香
sodium acid pyrophosphate 焦磷酸氢钠
sodium bic3rbonate 碳酸氢钠苏
ingredient 成份 拼分 拼料
Vent ①(通气)孔 通气口 ②出口 ②排出 泄放 排久 放气
sheet ①薄板 薄片 ②面片 压面片 ②张数
disodium Phosphatedodecahydrate 十二水磷酸氢二钠
PreValent 流行 盛行 普遍[罕]优势
Proof (面团)醒发成形
1eaVen ①膨松剂 ②(加膨松剂)膨松
盛mension a①尺寸尺度线度②[复]面积容积②范围 方
四
micNscopic 显微镜 象显微镜显微镜 见 微观N 微
细微
naInlc a①动力 动力学 ②生气 动 力 n.
①动力 原动力 ②动态
v01atile 挥发 易挥发
ethylene 乙烯
P01ym棚c 聚合
permeation n. 渗入 通 弥漫 充满
Englishbug
1 The importance of sanitation practices is to combat the proliferation and activity of food spoilage and food poisoning microorganisms(…进行斗争)
2 These microbes are also characterized by their display of a variety of colors and generally recognized by their mildewy or fuzzy cotton like appearance(呈现…颜色)
3 Although mold growth is optimal at a water activity (Aw) of approximately 085growth can and does occur below 080 (…适条件)
4 Like molds yeasts can be spread through the air or other means and alights on the surface of foodstuffs(通…传播)
5 Certain spores are resistant of heat chemicals and other adverse environmental conditions(利环境条件)
6 Most methods used to kill microorganisms may be applied in a milder treatment to inhibit microbial growth
1) 句中this thesis 指课文中句中提 the cool temperature storage of foods Thesis 作题课题解Another development 应引伸作新发展起食品低温储藏解Which 引导句作定语修饰another development 中it指this thesis
2)while slow in maturing 省略语动词步状语句语句相完整形式应while it was slow in maturing 句语it指句中提another development
3)句中that in such commercial…in combination with sodium bicarbonate 宾语句该句there be 句型语a slowly acting sodium acid pyrophosphate…with sodium bicarbonateOf the approximate formula Na2H2P2O7 介词短语作定语 修饰pyrophosphate in combination with sodium bicarbonate 介词短语作定语修饰pyrophosphate ordinarily used as…component 分词短语作定语修饰pyrophosphate
4)句动句语Better use to…life 谓语is predicted语中介词短语to regulate ripeningto prolong useful storage life列作定语修饰Better
文档香网(httpswwwxiangdangnet)户传
《香当网》用户分享的内容,不代表《香当网》观点或立场,请自行判断内容的真实性和可靠性!
该内容是文档的文本内容,更好的格式请下载文档