Physical & chemical changes

Physical changes, aerobic spoilage

bacteria, yeast, mold, surface spoilage (unless prod w/ pockets of air), color change, taints, modification, texture issues, slime

Physical changes, anaerobic spoilage

interior of product or within container, packaged meat spoilage

chemical changes are the result of...

enzyme action, breakdown of sugars, fats, & carbs

hydrolytic enzymes

Sources/ types of hydrolytic enzymes

1. Endogenous

2. Microbial enzymes

Endogenous

Initially responsible for breaking down complex molecules or macros, enzymes that are already present within a food ex. pectic enzymes in an apple

Microbial enzymes

enzymes that come from outside (MOs)

Food prod, enzyme breakdown order

1. Apple: Endogenous then Microbial enzymes

2. Muscle tissue + non-tissues: Microbial then endogenous

3. Pasteurized milk: microbial then endogenous (pseudomonas protease breaks down protein to produce bitter flavor)

4. raw milk: endogenous then microbial

O2 availability and enzyme action

1. Aerobic conditions favor hydrolysis of proteins into peptides and AA

2. Anaerobic conditions favor degradation of proteins into sulfur containing compounds, ammonia (N source)