Enzymes

they are naturally present and we may want to inactivate them or insure that they do act. they can be used as indicators of proper processing or to create other desirable compounds

a.a. sequence, folding of polypeptides, interactions of a.a. side chains by electrostatic and hydrophobic forces and disulfide bridges, assemblage with protein subunits

the identity of the a.a. that set up the active site

to decrease activation energy and through that catalyze (accelerate) a process that would have occured normally but at a much slower rate

pH, water activity, temperature

enzyme activity, enzyme stability, interaction and change in reaction equilibrium

neutral (7)

it serves as a co-substrate in enzymes activity

dehydration and freezing are used to preserve foods by the removal or immobilization of water. altered enzyme activity.

alkaline phosphatase activity can be used to see if dairy has been pasteurized - peroxidase can be used to insure the adequate blanching of vegetables

active in low concentrations - high specificity, can ex differentiate between stereoisomers - low reactivity with other substances - more environmentally friendly - can work under mild temp, pressure and pH conditions preserving integrity of heat-labile essential nutrients - activity can be stopped ex by drying or heat treatment

autolytic changes such as proteolysis in cheese or canned tuna, may cause off flavouring - proteases lipases and carbohydrases break down biological molecules which may impact quality negatively - decarboxylases and deaminases degrade biomolecules like free a.a. to form undesirable and/or toxic components - polyphenol oxidases and lipoxygenases promote oxidations and undesirable discolorations and/or color loss in fresh vegetables and fruits - ascorbic acid oxidase destroys vit C

native milk, somatic cells present in milk, airborne bacterial contamination, intentionally added bacteria

associates with casein micelle but when milk is agitated enzyme comes into contact with fat and degrades fat to produce off flavours

it breaks down proteins

if it shows activity, temperatures have not been high enough to pasteurize the milk

elevated leukocyte levels, characteristic for mastitis milk

for lactose removal to increase sweetness, prevent crystallization in ice cream or reduce lactose levels for intolerant

cross-linking of protein molecules to improve texture in meat/seafood products or to give better texture to structured meat products.

pectolytic enzymes which hydrolyzes pectin chains into small fragments. reduces viscosity and allows sedimentation of clouding particles, and is thus beneficial for faster and more complete juice clarification and easier wine filtration.

degrade proteins forming haze and degrade enzymes forming C6 alcohols that could give grassy taste

they oxidate phenolic compounds and cause loss of color and formation of brown color. the enzyme can be removed by clarification (sedimentation or centrifugation) or inactivated by heat treatment and/or sulfur dioxide addition

they break down starch into smaller sugars, making it easier for yeast to act. also improves taste, crust color and toasting qualities of the bread