Chemical : browning/flavour changes (eg. maillard), denaturation of proteins and polysaccharides, loss of water sol compounds, loss of volatiles (flavour). For better DH quality : smaller surface area of food, higher temp, higher air velocity, less humidity in air, less pressure. Methods : Sun drying, Spray drying-droplets of food sprayed into stream of heated air (eg. poweder milk, instant coffee), tray/tunnel- heated air with trays or racks (eg. pasta, spices), drum-rotating heated drum, rapid (eg. food paste, baby cereal, purees), freeze drying-vacuum chamber, sublime (solid water vapour), vacuum microwave-vacuum low temp, rapid energy transfer, deep fat frying,-hot oil evaporation of water (eg. snack foods), vacuum extrusion drying-slurry of food with steam heating, under pressure, release pressure stean increase (puffing) gelatinization. Packaging requirements : protect against moisture absorption (hygroscopic), physical protection, protection from O2 and light (photo oxidation)
(9) Biotechnology =application of science and engineering in direct/indirect use of living organisms in their natural or modified terms. Fermentation ((an) aerobic breakdown of carbs ), plant and animal breeding, cell and tissue culture, genetic engineering. foods : fermented beverages (wine, beer), dairy (salami), traditional (soy sauce, miso). additives : amino acids (methionine, glutamic acid), biopolymers (xanthan gum, alginates), enzymes (rennin), vits (B). Biotechnology=fermentation : biotech also use of probiotics, genetically modifies organisms for prod of ingreds. Metabolites : ends products of fermentation – antimicrobial cmpnds (acids,alcohols)/acids (situ) to lower pH. Microbial antagonism : suppress growth and metabolic activities of spoilage causing microflora. (but still need additional pres). Benefits : nutritional value/availability (mold-vit B), make nutrients from plants digestible, microbial hydrolysis of cellulose, variety. Factors affecting fermentation 1. Starter culture – microbial culture, metabolism, pure (yeast), from prev batch of fermented food (yogurt), normal microflora. 2. Temp – optimum temp. 3. Oxygen – diff O2 reqs (eg. bakers yeast=aerobic, yeast ferments sugar=anaerobic). 4. Salt – for growth of lactic acid producing bacteria, inhitbits bad MOs. Cheese 1. Setting milk – lactic acid-producing culture added to pasteurized milk, starter culture is present in larger #s than other MOs, rennet added so caseins coagulate, form gel 2. Curd cutting –cut into cubes to remove whey from curd 3. Cooking –curd is cooked for further expansion of whey from curd 4. Draining whey and curd matting –whey is drained from the cheese vat, matting of curd = rubbery slab 5. Salting/cutting –salt draws out whey, flavors the cheese 6. Pressing –curd knits together 7. Curing and ripening –placed in a cool room for 3-4 days, prevent growth of mold cheese is vacuum packed. Cheese : 1. Swiss (hard) –extra bac culture, Propionibacterium shermanii is added to milk with starter culture, produces propionic acid and carbon dioxide which is formation of the holes in cheese 2. Blue-veined (semi- soft) –curd is injected with a mold grows within the hooped curd 3. Camembert
You've reached the end of your free preview.
Want to read both pages?
- Spring '12
- Food processing, Food technology=using info, food prior packaging