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Transcript of Food Preservation
Food Service Sanitation and Safety
Delay autolysis ( how? ->destroying enzymes/preventing enzymatic action)
Minimize damage caused by insects, rodents, physical trauma
Low- temperature food preservation
High- temperature food preservation
Food preservation by dehydration
Chemical food preservation
Food preservation by radiation
Slow the growth of spoilage organisms
Decrease the rate of microbial reproduction and eventually stops altogether
Decrease the rate of chemical reactions and enzyme activity.
There are two main types of low-temperature food preservation: refrigerated storage and freezer storage
Temperatures -> from 0°C (32°F) to 5°C (41°F).
Mostly for perishables (meat, poultry, fish, dairy, fruits and vegetables)
Slows the growth rate of spoilage mo and most pathogenic bacteria
Temperature : -18°C (0°F)
Reduce the growth of microorganisms even further than refrigeration
Freezing also reduces the Aw (water activity) of food products(water is converted from liquid to solid) and microbes can no longer use it.
Quick Freezing reduces the temperature in less time (e.g: -20°C in 30 minutes instead of 3-72 hours) It also preserves better food quality
IQF / Individually Quick Frozen
Are effective because it control the growth of microorganisms
When microbial cells are heated they are damaged, deactivated or destroyed
There are two methods of high-temperature food preservation: pasteurization and sterilization
Used to extend shelf life of food by reducing spoilage organisms or to destroy all pathogenic microorganisms present in the food.
Pasteurization typically uses T°s below boiling
The normal process of pasteurization involves heating the product to 63°C (145°F) for 30 minutes.
In the High-temperature short time (HTST) method product is heated to 72°C (161°F) for 15 seconds (E.g milk)
Both methods require the heated food to be immediately cooled to 10°C (50°F) or less.
Products that are commonly pasteurized: dairy products (ice cream, cheese, butter) , canned food, juices, vinegar, syrups.
Destroys almost all microorganisms and their spores (T°s > 100°C)
Once the food is sterilized, must be stored in a hermetically sealed container (can, glass bottle or jar, or flexible plastic containers)
Food products dont need to be refrigerated until the containers are open.
Autoclaves commonly use steam heated to 121–134 °C (250–273 °F).
Examples: 15 minutes at 121 °C (250 °F) at 100 kPa (15 psi), or 3 minutes at 134 °C (273 °F) at 100 kPa (15 psi)
Prolong the lag phase of bacterial growth
Prevention of microbiological breakdown of food
Low - Temperature
Dehydration reduces the Aw of the food and therefore inhibits microbial activity.
There are four methods of drying food:
drying by smoking.
Sun drying (areas w/low humidity and high T°)
Mechanical drying (heat + moving air)
Freeze – drying (sublimation: conversion of solid water to water vapor) product must be frozen
Drying during smoking: quite slow. Alters the odor, color, appearance, texture, flavor, etc
Chemical food additives have been approved for food preservation applications.
They inhibit the activity of selected pathogens and spoilage organisms
Nitrites and nitrates (in meat products),
Sugar (syrups for canned food)
Salt (brine for canned food)
Nitrites and nitrates
Sugar and Salt
Sulfur dioxides and sulfites (retard oxidative or enzymatic browning of fruits and vegetables and control gray mold on table grapes)
Ethanol (ethyl alcohol) is produced by fermentation in wine, beer and spirits
Sulfur dioxides and sulfites
Also called Irradiation.
Involves exposing food to ultraviolet light, gamma rays, or X-rays to destroy harmful organisms
Irradiation can keep grains from sprouting, deactivate mold and kill bacteria
Food preservation by Radiation
Food irradiated is exposed to the gamma rays of a radioisotope -- one that is widely used is cobalt-60
The energy from the gamma ray destroy the bacteria
The effect is not strong enough to change the quality, flavor or texture of the food
The food never comes in contact with the radioisotope and is never at risk of becoming radioactive
The FDA has approved the irradiation of several food categories and is most widely used on spices, herbs and dehydrated vegetables
Although the FDA has approved the irradiation, the industry hesitates to adopt the process because they are afraid of a negative response from consumers.
Thank you for attention!