Lec 6-Preservation

what are some changes that lead to food spoilage? (3) what causes them?

biological: caused by microorganisms i.e. bacteria yeast mold

chemical: usually caused by enzymes like proteases lipases carbohydrases

physical: *don’t result in formation of new compounds in the food *: evaporation, drip loss, separation

the most common preservation techniques used for more then xxxx years include:

the most common preservation techniques used for more then 5000 years include:

drying

salting

fermenting

what triggered increase in food preservation techniques

food spoilage vs food contamination . also perishable foods will often have higher concentrations of xxx

food spoilage—> obvious & detectable

food contamination—> often undetectable 

• perishable foods will often have higher concentrations of protein and/or water! ex:Fish, seafood, meat, eggs, dairy

Watery fruits and vegetables

what types of foods are required to have best before date?

Foods with a shelf life of 90 days or less, except for fresh fruit and

vegetables and certain other products, are required to have either a

best-before date or packaged on date, depending on where they are

packaged and sold.

best before date vs expiration date

what types of environment do bacteria live in?

bacteria live well in potentially hazardous foods

because these foods are often warm, moist, carbohydrate or protein-rich, and neutral or low in acid.

he FAT TOM acronym stands for Food, Acidity, Time, Temperature, Oxygen, and Moisture

F in FAT TOM

FOOD

•Bacteria needs

nutrient-rich foods

like carbohydrates

and proteins to

survive and grow.

•Bacteria grow more

easily and quickly on

moist food such as

meats, poultry,

cooked rice and

vegetables

A in FAT TOM

•Bacteria do not

survive and grow in

food that is very acid

or alkaline.

•Most potentially

hazardous foods

have a pH level

between 4.6 and 7.5. -clos-ish to neutral 

T in FAT TOM

•At room temperature,

bacteria can double

in number every 10

to 20 minutes

• 4 hrs rule: Food

must not spend more

than a maximum

total of four hours in

the Temperature

Danger zone

T (2nd) in FAT TOM

TEMPERATURE

The Temperature

Danger Zone for

potentially hazardous

foods is 4⁰C to 60⁰C

(40⁰F to 140⁰F).

• Foodborne

microorganisms grow

best in the

Temperature Danger

Zone

• Exposing bacteria to

temperatures outside

the Temperature

Danger Zone doesn’t

always kill them.

• Refrigeration for

example, is not total

protection against

bacterial growth as it

may only slow it dow

O in FAT TOM

OXYGEN

Microorganisms have

different oxygen

needs for growth:

→Aerobic bacteria

need oxygen to grow

→ Anaerobic bacteria

grow only when

oxygen is

absent (Example:

Clostridium

botulinum)

•Most microorganisms

that cause foodborne

illness can grow with

or without oxygen

(Facultative)

M in FAT TOM

MOISTURE

•Available water is

measured on a scale

ranging from 0 to 1.0.

•Food with an aw level

of 0.85 or lower is

not considered

potentially

hazardous.

•Most potentially

hazardous food

have aw values of

0.97-0.99, which is

ideal for bacterial

growth.

Chemical vs biological vs physical protection methods for food preservation

chem→ Prevents changes from exposure to

gases, moisture, or light. Glass and metal = barriers from those factors , Plastic is impermeable and only provides partial protection

biolo—> Prevents contact with microorganisms, rodents, insects, and other animals

physi→precebts mechanical damage

what moisture content do bacteria+mold vs yeast need to survive

Bacteria and molds need approximately a 15% moisture level to survive, whereas yeast needs at least a 20% moisture content.

how does Drying work on food preservation? what are some different types? (8)

why is sulfur compounds used ? what vitamins are involved? 

what is curing? how does it work and what is the historical +cultural use? 

what is smoking used for?

Smoking is sometimes used as an optional step in

curing meats to enhance flavor.

During the process, meats are placed in smokers

and exposed to the smoke from burning wood.

The type of wood used (such as sawdust, mesquite,

hickory, oak, or a combination) greatly influences

the flavor profile of the final product.

However, there are some health concerns with

smoked foods as they have been linked to cancer in

laboratory animals and possibly humans.

what is fermentation definition?what is it used for and why?

“Fermentation is the cellular metabolic process that breaks down organic matter (often carbohydrates) into alcohol, lactic acid, gasses,

and various other acids.

Fermentation has been used for thousands of years to both produce and preserve food.It makes food easier to digest

• Ex: Soybeans are indigestible unless fermented

• Ex: Bacteria in yogurt remove lactose

✓To enhance flavor

• Think of the umami taste from cured meats and cheeses!

what does fermentation rely on?

on microorganisms (bacteria, yeast,

and molds) to transform the food into an easily preserved form while

simultaneously creating desired changes in flavor, color, and texture.

what is responsible for fermentation, and what do they produce?

Two of the most common and well-known fermenters=yeast and lactobacillus bacteria

• Yeast consumes sugar and produces alcohol and CO2

• Most lactobacillus produce lactic acid but Some also produce alcohol and CO2

The chemical and biochemical changes that occur during fermentation primarily depend on the

1. Raw material

2. Selected microorganisms or ones naturally present

3. Various processing steps

For example, using different grains or starter cultures will result in entirely different types of alcoholic beverages.

what does lactic acid do and why is it used?

One of the most common types of bacteria used in fermentation, especially of dairy products, is the species that produces lactic acid. The lactic acid lowers the food’s pH, alters the flavor, and inhibits microorganisms that are pathogenic or that might cause spoilage.

how are salt-resistant bacteria used in cured meats? 

Various salt-resistant bacteria are used to create dried sausages. Dry-curing of minced meats occurs when very small pieces of meat and fat are mixed with flavorings (salt, nitrates and/or nitrites, sugar, and spices), stuffed into casings,

fermented, dried, and possibly smoked. The longer the fermentation period is, the drier the sausage.

what yeast is commonly used in bread and beer making? what does it do?

Saccharomyces cerevisiae used in bread and beer production to metabolize carbohydrates into carbon dioxide gas (CO2) and ethanol (which evaporates during baking).

yeast are fungi, T Or F

T

what is the end product of glycolysis?

Pyruvate

what does aspergillum produce vs lactobacillus vs saccharomyces produce? 

lactobacillus form, use, and ‘survivability’

Rod shaped bacteria

• Used in production of

fermented milk products

• Are resilient and can survive in

pH as low as 4

what yeasts are common in sourdough?

Before the widespread availability of baker’s yeast, pieces of fermented dough were kept to leaven the next batch

• These leftovers contained mixtures of

Saccharomyces and Lactobacillus

• This mixture gave the bread a characteristic sour flavor, hence the name sourdough bread

how are cocoa beans fermented?

Precursor to chocolate

• Ripe seeds are removed from the fruit and

fermented for 9-12 days

• Fermentation will digest the pulp, intensify the

color, and add aroma and flavor

• Fermented seeds are then dried, roasted, and

ground

how are fermented sausage made?

• Some producers use bacterial cultures to:

o Quickly initiate fermentation

o Increase the acidity – and hence food safety

o Counter rancidity of fat

• Salt and nitrates are also added to inhibit the growth of

disease-causing bacteria

• Once fermented, they are essentially shelf-stable!

how is yogurt made? what is added ?

Lactobacillus bulgaricus and Streptococcus

thermophiles are added to pasteurized milk

• Left to ferment at 42°C

• Bacteria consume lactose and produce

lactic acid which denatures the milk

protein causing the mixture to thicken

how is vinegar made? what bacteria are present?

“Vin” “aigre” literally means wine sour.

• Produced by converting alcohol into acetic acid

• Bacteria: Acetobacter and Gluconobacter

• Vinegars are distinguished by their source of alcohol

oEx: Wine, rice, apple cider, grain

• Vinegar is used in cooking to add sharpness and brightness

Pickling preserves food through xxx which may involve…

Pickling preserves food through acidification, which may involve:

• Directly adding acid (usually vinegar)

• Fermentation that naturally produces acid→ Lactic acid is the main acid formed during the fermentation

of natural sugars in many pickled foods.

• These foods are typically preserved using vinegar and salt, often with added spices for flavor

why is vinagre commonly used in pickling?

Vinegar is commonly used because:

• Its acidity inhibits the growth of many microorganisms

• It has been used since at least 1000 BC in the Middle East to preserve items like fruits, onions, and walnuts

• Traditional method: Food is covered with vinegar, boiled, sealed in a container, and left to sit for at least 3 weeks for full acid infusion/absorption

what is clostridium botulinum, how can it be inhibited? 

Clostridium botulinum, a dangerous

foodborne pathogen, is inhibited by pickling:

• It cannot grow in environments with a pH

below 4.6

fermenting vs pickling : liquid, environment , probiotic?, speed, flavour, shelf stable?

what are 4 main purposed of edible coatings?

1. Increase shelf life by acting as a barrier to moisture, oxygen, carbon

dioxide, volatile aromas, and other compounds.

2. Impart improved handling characteristics, such as the ability to bend more

easily without breaking.

3. Improve appearance through increased gloss and color.

4. Serve as a vehicle for added ingredients such as flavors, antioxidants,

antimicrobials, and so on

what are edible coatings produced from?

Edible coatings can be produced from carbohydrate, protein, or lipid materials.

• most common edible coatings are lipid-based (beeswax, candelilla wax, carnaub, rice bran wax); oils (paraffin oil, mineral oil, vegetable oils); and petroleum-basedwaxes (paraffin, polyethylene wax)

Carbohydrate coatings include starches, cellulose, seaweed extracts (carrageenan,

alginates), pectinates, and chitosan.

Previously, sugar was used to coat foods to prevent decay and moisture loss (e.g., sugar -

coated nuts).

Protein films can be made from foods through the use of gelatin, collagen, whey protein,

corn zein, soy protein, and wheat gluten

what is the process of food canning?

Canning is a two-step process.

1. 2. The food is prepared by being packed into containers, which are then sealed.

The containers are canned or heated to ensure that all microorganisms are destroyed.

▪ As previously mentioned, during the Napoleonic wars, Napoleon was having difficulty feeding

his troops. He offered a prize to the person who could discover a new method of preserving

food.

▪ The winner was Nicolas Appert, who invented the canning process in the late 1790s.

▪ Food was placed in glass jars or canisters (cans), boiled, and then sealed shut.

▪ The jars were then boiled a final time, creating a vacuum.

▪ Many people believed that lack of oxygen in the cans preserved the foods. Almost a hundred

years later, Louis Pasteur discovered that the real reason canning was successful was because

the high boiling temperatures destroyed harmful bacteria.

▪ The heat processing also destroyed the enzymes responsible for the deterioration of foods,

thereby protecting canned food from both harmful microorganisms and natural spoilage!

what are 4 problems w freezing foods?

- Freezer burn

- Cell rupturing

- Fluid loss

- Recrystallization

what are three main heat preservation methods?

what is irridiation & what are some approved irradiated foods in canada?

Irradiated foods are foods that have been treated with ionizing radiation (like X-rays or gamma rays) to kill bacteria, insects, and other microorganisms

Canada approved the irradiation and sale of:

- Onions

- Potatoes

- Wheat

- Flour

- Whole wheat flour

- Whole or ground spices

- Dehydrated seasonings

Health Canada has authorized the use of ionizing

radiation to treat fresh and frozen raw ground beef

nutrient retention- what is lost vs maintained during cooking and storing?