食品工程學品質(zhì)變化速度課件

1、食品工程學品質(zhì)變化速度1tel: fax: e-mail: 食品工程學品質(zhì)變化速度2科學回答：是什么？為什么？技術回答：做什么？怎么做？科學是發(fā)現(xiàn)，技術是發(fā)明?？茖W是創(chuàng)造知識的研究技術是綜合利用知識于需要的研究工程：依靠、使用復雜的系統(tǒng)、工具、設備或裝備來完成的工作。食品工程學品質(zhì)變化速度3食品工程學品質(zhì)變化速度4多組分，不均質(zhì)，多樣性生物材料；物理的，化學的，生化的及其綜合變化； -品質(zhì)變化速度論 食品工程學品質(zhì)變化速度5食品工程學品質(zhì)變化速度6品質(zhì)變化速度式設定;感官性狀的變化（味道、氣味、色澤、質(zhì)地）；營養(yǎng)成分的變化（碳水化合物、蛋白質(zhì)、脂質(zhì)、維生素等）；氧化（酶促和非酶促；油脂氧化、維

2、生素氧化、血紅蛋白氧化等）；著色（酶促著色、非酶促著色）；漂洗；糊化（糊化與老化）；蛋白質(zhì)變性（加熱、凍結、其他）；其他品質(zhì)變化（鹽漬、糖漬、醋漬、薰蒸等）食品工程學品質(zhì)變化速度7 食品工程學品質(zhì)變化速度8a. enzymatic changesa. enzymatic changes- enzymes are complex, globular proteins that have 3 important characteristics:(1) act as catalysts, accelerate the rate of chemical reactions by factors of

3、1012 1020 over uncatalyzed reaction.(2) highly specific, enable the food processors to selectively modify particular food components.(3) have a regulatory role, control the biochemical processes.types of enzymes:exogenous addition of enzyme (from microorganism) in the milk during manufacturing certa

4、in cheeses, intentional fermentation (desirable), spoilage (undesirable).endogenous involving autolysis of fish postharvest (off-flavor), the senescence and spoilage of fruits and vegetables postharvest, glycolysis in postmortem, prerigor muscle and suberization (wound healing) of plant tissues post

5、harvest, oxidation of lipids by lipase and lipoxygenase 食品工程學品質(zhì)變化速度9b. chemical changesb. chemical changeschemical reactions lead to deterioration of food quality or impairment of safety- non-enzymatic browning (maillard reaction = reducing sugar + amino acid)- lipid hydrolysis / oxidation- protein

6、denaturation- protein cross-linking- protein hydrolysis- oligo- and polysaccharide hydrolysis- polysaccharide synthesis- degradation of specific natural pigment- glycolytic changes食品工程學品質(zhì)變化速度10a. lipid oxidation- development of off-flavor.- react with protein and result in extensive cross-linking.b.

7、 non-enzymatic browning、- one of the major deteriorative chemical reactions occurs during storage of dried and concentrated foods.- leads to formation of insoluble brown polymers (mw 1000).c. color change- change in structure or content of chlorophyll, hem pigment, anthocyanins, carotenoids.d. flavo

8、r changes- flavor has evolved to a usage that implies and overall integrated perception of the contributing senses of smell and taste at the time of food consumption.-the permeability of packaging materials is of importance in retaining desirable volatile components within package, or in permitting

9、undesirable components to permeate through package from the ambient to.four major factors which impact on nutrient degradation and can be controlled to varyingextents by packaging are light, o2 concentration, to and aw食品工程學品質(zhì)變化速度11c. physical changesc. physical changesphysical properties include geo

10、metrical (size, shape, volume, density and surface area as related to homogeneous food units, as well as geometrical textural characteristics such as referring to particle size and shape; referring to particle shape and orientation), thermal, optical, mechanical, rheological, electrical, and hydrody

11、namic properties- for foods containing solid carbohydrates, the largest effect in physical properties results from sorption of water, especially for the recrystallization of amorphous carbohydrate, e.g. in boiled sweets leading to stickiness and graining, in milk powders leading to caking and lumpin

12、ess食品工程學品質(zhì)變化速度12d. biological changed. biological change- major groups of microorganisms found in foods are bacteria and fungi (yeasts and molds)- foods are frequently classified on the basis of their stability as non-perishable,semi-perishable, perishable factors affecting microbial growth1. intrin

13、sic parameters: moisture, ph2. extrinsic parameters: temperature (e.g. 30 40oc referred to mesophiles), rh%, gases in environment.-flies and cockroaches, moth, beetles- proper sanitation (all packaging material apart from metal and glass can be attacked by rats and mice)食品工程學品質(zhì)變化速度13案例案例食品工程學品質(zhì)變化速度1

14、4* * one-step heating ( one-step heating (60c kamaboko gel) )* * two-step heating ( two-step heating (cooking at 85c/30min after one-step setting) )measure indices:measure indices: 食品工程學品質(zhì)變化速度1501002003004005000min10min30min1hour2hour3hour5hour10hourheating timebreaking force (g)304050607085heating

15、heating temperaturtemperature e食品工程學品質(zhì)變化速度16three-dimensional configuration of three-dimensional configuration of breaking force of walleye pollack breaking force of walleye pollack surimi gels surimi gels surimisurimi食品工程學品質(zhì)變化速度17 silver carp big-head carp chinese snake-silver carp big-head carp ch

16、inese snake-head blunt snout breamhead blunt snout bream tilapia grass carp mud carp tilapia grass carp mud carp common carpcommon carp食品工程學品質(zhì)變化速度18 320g (fmax)0501001502002503003500100200300400500600incubation time (min)breaking force (g)t1/2(1500sec)(1500sec)160160g (0.5fmax)g (0.5fmax)a ab bc c食品

17、工程學品質(zhì)變化速度19arrhenius plots for gelation rates of freshwater fish and walleye pollack protein10.00100.001000.003.33.23.13.02.92.81/t103 (k-1)gelation rate k105 (s-1)walleye pollacksilver carp big-head carp grass carp 85 70 60 50 40 30 (c)* * heat-induced gelation of surimi occurs due to different heat-induced gelation of surimi occurs due to different mechanism mechanism at the upper and lower temperature sides of a boundary of at the upper and lower t