food micro spoilage

what is spoilage

The deterioration or decay of food, materials, or products, rendering them unsafe or unsuitable for consumption or use.

what does spoilage involve?

flavor change, texture change, and odors

approximately what percent of the food supply in the US goes to waste

30-40%

the cost of food waste in the us is estimated to be approx

400 billion annually

estimated that what percent of food purchased is wasted due to spoilage?

25-30%

us food industry loses approximately how much due to food spoilage?

160 billion

environmental impacts of spoilage

food waste and spoilage contribute to greenhouse emissions

food waste accounts for about 8-10% of us methane emissions

what causes spoilage

biological- bacteria, yeasts, molds

chemical- oxidation, rancidity, enzymatic browning

physical- moisture loss, freezer burn, texture degradation

spoilage cycle

1. initial microbal contamination

2. microbial growth and metabolism

3. chemical changes

4. sensory changes

5. microbial overgrowth and competition

who can remind me about the ecology of food

intrinsic and extrinsic factors

intrinsic factors

ph, water activity, nutrients, antimicrobial compounds, structure

extrinsic factors

temp, oxygen, humidity, packaging

oxidation

chemical reaction where molecules lose electrons through interaction with oxygen or other oxidizing agents. can cause off flavors, discoloration, nutrient degration, etc. while oxidation can occur independently, microbial activty can accelerate oxidative changed by damaging tissues or producing compounds that promote oxidation

oxidation

a chain reaction that starts with a free radical formation, propagates by radical transfer, and ends when radicals combine and stabilize

rancidity

deterioration of fats and oils caused by oxidation or hydolysis of lipids, producing off flavors, off odors, and oxidation products. while rancidity can occur through purely chemical reaction, microbial lipases can accelerate hydrolytic rancidity, linking biological spoilage to chemical deterioration

oxidative randicity

occurs when fats and oils react with oxygen, usually initiated by heat, light or metal ions, requires oxygen

hydrolytic rancidity

occurs when lipase enzymes or moisture break triglycerides into free fatty acids, does not require oxygen

enzymatic browning

chemical reaction where polyphenol oxidase reacts with oxygen to convert phenolic compounds into brown pigments, not caused by microorganisms

sensory changes

apperance, odor, flavor, texture, sound

sour smell

organic acids

rotten egg odor

sulfur compounds

slime

EPS production

gas package

co2 production

mold growth

fungal growth

ropy texture

expolysaccharides

microbial overgrowth

occurs when microorganisms multiply to high numbers causing undesirable sensory changes and reduced food quilty

microbial overgrowth occurs due to

competition for resources

succession and community shifts

time

bread

mold

milk

LAB

ground beef

Pseudomonas

vacuum packaged steak

LAB

fresh produce

yeasts and molds

seafood

Shewanella, Photobacterium

spoilage yeasts

Saccharomyces species- known for fermenting sugars

Candida species: spoils fruit juices and other sugary products

spoilage bacteria

Pseudomonas species

Lactobacillus

Clostridiums

pseudomanas

gram negative rod

motile

strictly aerobic

Psychrotrophic

common in soil, water, and processing environments

Psychrotrophic

thrives in cold temperatures

pseudomonas produce extracellular enzymes that break down

proteins, lipids, surface biofilms

shewanella

gram negative, short rod

motile

facultatively anaerobic

Psychrotrophic

found in cold water, sediments, and seafood

how shewanella spoil foods

protein breakdown, lipid breakdown, gas production, slime formation, discoloration

lactic acid bacteria

gram postive

non motile

facultatively anaerobic

fermentative metabolism

many are tolerant to acid, low oxygen, and some salt

common in raw materials, envionments and on equipment

when is lactic acid bacteria bad instead of good?

causes off flavors, souring, gas, and texture defects, reduce shelf life and product quailty

how lactic acid bacteria spoil foods

over acidification, gas production, slime or ropiness, color changes

clostridium species

gram postive, rod shaped

spore forming

obligately anaerobic

fermentative metabolism

psychrotopic to mesophilic

common in soil, sediments, animal intestines, and processing environments

spores allow survival in harsh condisions and germinate when conditions become favorable

saccharomyces species

gram postive, oval

non motile

facultatively anaerobic

fermentative metabolicm produce ethanol and co2 from sugars

psychrophic

common in fruits, vegtables, sugary foods, and processing environments

candida species

eukaryotic yeasts- single cells, oval

reproduces by budding, some from pseudohyphae

facultatively anaerobic

fermentative metabolism- produces ethanol, co2, and organic acids

psychrotopic

common in fruits, vegtables, dairy, meats,beverages, and food processing environments

tolerant to low water activity, acidic pH, and high sugar concentrations

spoilage molds

multicellular filamentous fungi

produce spores

grow on the surface of foods

visible as fuzzy cottony, powdery or slimy growth

wide range of colors