Enzymes Flashcards
why are enzymes important in the food industry?
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
enzyme functionality depends on
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 nature of the enzyme is dependent on
the identity of the a.a. that set up the active site
what is the main function of enzymes?
to decrease activation energy and through that catalyze (accelerate) a process that would have occured normally but at a much slower rate
what environmental properties can affect enzyme activity?
pH, water activity, temperature
changes in pH may affect the enzymatic reactions by changing
enzyme activity, enzyme stability, interaction and change in reaction equilibrium
most enzymes exhibit optima near what pH
neutral (7)
why is water activity important for enzymes?
it serves as a co-substrate in enzymes activity
how can water activity be changed to affect enzymes?
dehydration and freezing are used to preserve foods by the removal or immobilization of water. altered enzyme activity.
what enzymes can be used to test for proper heat treatment?
alkaline phosphatase activity can be used to see if dairy has been pasteurized - peroxidase can be used to insure the adequate blanching of vegetables
what are beneficial advantages of using enzymes over conventional chemical catalysts?
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
what are potential undesirable effects of enzymes in food?
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
milk enzymes can come from several sources, which?
native milk, somatic cells present in milk, airborne bacterial contamination, intentionally added bacteria
lipases like lipoprotein lipase can cause defects in milk, explain
associates with casein micelle but when milk is agitated enzyme comes into contact with fat and degrades fat to produce off flavours
what function does plasmin serve in cheese maturation?
it breaks down proteins
how can alkaline phosphatase be used as an indicator of pasteurization completeness?
if it shows activity, temperatures have not been high enough to pasteurize the milk
catalase activity in milk indicates
elevated leukocyte levels, characteristic for mastitis milk
why is lactase sometimes added to milk in processing?
for lactose removal to increase sweetness, prevent crystallization in ice cream or reduce lactose levels for intolerant
what can transglutaminase be used for?
cross-linking of protein molecules to improve texture in meat/seafood products or to give better texture to structured meat products.
what endogenous grape enzymes are very important in wine making?
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.
why are proteases important in wine making?
degrade proteins forming haze and degrade enzymes forming C6 alcohols that could give grassy taste
why do we want to inactivate polyphenol oxidases in wine making?
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
why are amylases important in breadmaking?
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
