Food science

second midterm material

preservation

ensure safety and extend shelf-life by preventing decay, spoilage, and contamination

define food processing

convert agriculture commodities into desirable edible food products

define processed food

any foods other than raw agriculture commodities and can be categorized by the extent of changes occurring in foods as a result of processing

food preservation goals

minimize food spoilage, maximize food safety and stability, maintain nutritional value and acceptability

refrigeration

• 0-5 degree celsius

• - historically caves or holes in the ground worked. or ice boxes

  - first mechanical fridge 1875 (ammonia)

  - a gentle method of preservation (minimal effect on tase and nutritional value)

  - reduces the rate of food deterioration (chemical and enzymatic reactions are slowed, and only cold tolerant microbes can grow)

  - often combined with other preservation methods ( milk)

  - inhibits non-psychrophilic microbial growth

freezing

0 to -18

" unit operation in which the temperature of food is reduced below its freezing point and a proportion of water undergoes change in state to form ice crystals"

- proportion of water undergoes change in state to form ice crystals

- convient

- high shelf life

father of frozen foods

Clarance Birdseye

• opened a commercial freezing plant in 1920s

• conducted research

freezing as a preservation

• inhibit microbial growth (microbial are not destroyed by freezing)

• - reduces. the rate of food deterioration ( prior to freezing)

  - expected frozen shelf life will vary

how does a fridge work

when liquid evaporates it absorbs heat, when vapour condenses it releases heat.

Refrigerant: a liquid evaporating inside the fridge to create cold temperature

Hydrofluorocarbonds (HFCs) are common refrigerants

evaporated coils, condenser coils

what microbial growth does refrigeration inhibit

inhibits non- psychrophilic microbial growth

hydro cooling

spraying cold water on slaughtered meat to cool temps fast

vacuum cooling

reduce temperature of slaughtered meat

aging of cheddar cheese

4-6 degrees C then 8-10 degrees C

food quality challenges with refrigerated storage

1. spoilage

2. cross contamination

   3. temp management

   4. ours can transfer from food to food

foods do not freeze at 0

due to solvents present the conversion would be: change in temp = 1.885 x mol of solute

slow vs fast freezing

large ice crystals: lyse the cells and disrupt the cell wall.

leads to rupture of cell

nutritional value lost due to juices being release through thawing

loss of moisture

poor quality product (soft texture)

small ice crystals

result in better quality products. non uniform temperatures during freezing results in a variation of sizes of ice crystal

food quality challenges of freezing

1. fluctuation of temperature during storage (shorter shelf life)

2. - thaw - refreeze = large ice crystals = cell damage

   2. moisture loss (freezer burn - food is damaged by dehydration at the food surface)

   - prevent with use of moisture resistant airtight packaging

   3. chemical changes during freezing (rancidity)

   4. freeze concentrations

chemical changes during freezing

oxidative enzyme activity in vegetable.

- vegetables are blanched prior to freezing to inactive enzymes

activity in fruits:

- fruits are not blanched (too delicate) use citric acid instead

- addition of ascorbic acid

- prevent growing and vitamin C loss

Rancicity: more common in fatty products

freeze concentration:

intentional: freeze a certain product, then removing the water. leaving a concentrated solute behind.

commeical freezing methods

frozen by immersion: creates small ice crystals

cold plate freezing: large ice crystals

sharp freezing: lowest freezing rate due to lack of air movement

blast freezer: air moves by convection

fluidized bed freezer: cold air suspends the food

contact plate: direct contact with cold plate

immersion - cryogenic freezing: liquid nitrogen

ice crystal size with freezing

smallest: sharp freezing, blast freezing, fluidized, cryogenic

spiral freezer

space efficient, type of blast freezer

fluidized bed freezer

perforated tray (holes in the tray), cold air pushed through the holes. this causes individual freezing fastly

- minimal dehydration

- creates IQF

blast freezing

pushing cold air at high velocity across a food product in order to freeze. batch blast = trays stacked

continuous: product is frozen as it moves through a tunnel

contact plate freezing

plates are frozen, product comes in contact, refrigerant circulates throughout plate

value added raw

food to which values have been added through special growing processing or packaging techniques.

unit operations

every activity in the production process of food product is identified. heat exchange, evaportation, drying, forming, packaging.

order the freezing methods from slowest to fastest

sharp freeze, blast, fluidized bed freezer, cryogenic freeze

three main preservation principles:

low temperatures (fridge, freeze), drying (spray or sun), and thermal processing (sterilization or pasteurization)

preservation principle and process

drying - water removal

freezing - water unavailable

fridge- low temp

heat sterilization - viable microbes are inactivated

baking smoking pasteurizing - inactivation of pathogenic microorganisms

fermentation - acid producing microbes lower pH

pickling salting sugaring - add acid or salt or sugar to brine

additional preservation aids

removal of microbes from food prior to processing, good mandating practices, controlling surrounding atmosphere (removing O2 +- N or CO2, use chemical additives (BHA or sodium benzoate)

value added food products refer to

foods improved through special growing

advantages of dehydration and concentration

1. reduction of moisture content and water activity - concentrated products require additional preservative measures (freezing, pasteurization, sterilization, etc.)

   2. reduction of product weight and volume

   - reduced packaging, and transportation cost

sun drying:

slow rate of drying, low cost, poor completeness of drying

• weather dependant based on conditions

case hardening

when large pieces are used for drying "case hardening" results

• case hardening prevents moisture loss from the food piece

• the use of small pieces for drying reduces case hardening and increases the drying rate uniformity snd completeness of drying

Case hardening may be observed in the unit operation of dehydration. It can be avoided by which of the following?

decrease the size of the product to increase the surface area for drying. ex: cutting, grinding

spray drying:

concentrated liquid is atomized, small droplets are sprayed into hot air for rapid drying, spray drying creates food or beverage powders ex: milks, pharmaceuticals

phase graph of water: list properties

pressure and temp are directly proportional

vacuum drying

remove water form a paste or liquid food product at a lower temperature under partial vacuum

drying method considerations

rate of drying, uniformity of drying, completeness, characteristic of food, cost

Vacuum dehydration of food products is more efficient than dehydration at atmospheric pressure for what reason?

Under vacuum, the boiling point of water is decreased, making water more easily removed from the food product.

freeze drying

the product is frozen (-18 usually), then use vacuum chamber, under vacuum condition ice turns into gas (sublimation),

• high salt = high solute concentration = freezing point depression

Order the freezing methods from slowest to most rapid.

sharp freezing, blast freezing, cryogenic freezing

how does sugar influence jams shelf life

high sugar content = lower water activity = longer shelf life

selected food concentrations methods

open kettle (evaporation), vacuum evaporators, reverse osmosis

open kettle method

steam is driven form the product using an open heated kettle

ex - jam, maple syrup

vacuum evaporators

a vacuum is used to remove water at a lower T. avoids heat damage to the product ex - evaporated milk, tomato paste

reverse osmosis method:

a semipermeable membrane allows water to pass through and concentration solutes. x - maple syrup concentrate

osmosis - the movement of water through cells in semi permeable membrane ( moving from low to high solute concentrations)

reverse osmosis - the movement of water between cells in high concentration to low concentration, due to applied energy

who is Nicolas Appert

established industrial thermal processing foods 1750-1841

who is Louis Pasteur

developed pasteurization, microbes spoil in wine beer and milk

thermal processing heat sterilization

bacteria are susceptible to heat, enzymes and oxidative changes are also inhibited. enzymes are proteins, which can be mediated with heat

why were dehydration and freezing effective preservation processes

freezing - altering the alignment, reducing water activty

heat - targeting organism

A canned low-acid food processed at 121°C achieves commercial sterility. what could we say about the microorganisms?

Surviving microorganisms cannot grow under normal storage conditions

canning

• a 2 year shelf life is achieved

• pressurized chamber, and high temp, then cook (110-121 degrees for 15 min)

food preservation goals

minimize food spoilage, max safety and stability, optimize nutritional value and acceptability

define commercial sterility

severe heat treatment. destruction of all pathogens and gear resistant microbes that could grow in the can under normal storage conditions.

• destroying all microorganisms that could survive under normal conditions, able to destroy most spores and pathogens

do any microbes remain in commercially sterile food products

there are certain spores (thermoderic) that can withstand high temps.

what factors do we consider for how much heat is required for thermal processing?

1. type (can, glass) and size of container, heat transfer ability of the food, and microbial heat resistance.

2. pH of the food. ex: acidic food don't have to go as high

   3. proximate composition of food

   4. specific organism present

   5. number of organism present

conduction

molecule to molecule in straight line. from external to internal. usually used with dry solid foods

convection

fluid motion, heat circulates. usually used with liquids

In a conduction-heated canned food, microbial survival risk is highest at:

cold spot (the last area to achieve the processing temperature)

thermal death time curve

low temp - long time

high temp- short time

D value

used to describe heat resistance of microbes. D values represent the time to destroy the 1 log (90%) of the bacteria present

- D value represents process time in the food industry (decimal reduction time)

- D100 = 2min (100 = temp in celsius)

12 D concept

12 log cycle reductions of heat are applied to canned foods, the probability that one in 10^12 cans would have a botulinum spore ( lethal)survive

• this treatment creates a commercially sterile product

pH processing

low acid (basic): pH-7 high temp (116-121), olives, sardines, beef, oyster

Acid: boiling water process pH-4, tomatoes, pears peaches

high acid - lemon juice, pickles

Which process primarily targets enzyme inactivation rather than pathogen destruction?

blanching

mild heat treatments: pasteurization and blanching

aims: kill pathogens (Pasteur only), reduce bacterial count, inactive enzymes. food is NOT sterilized

advantages: minimal nutritional and palatability changes

disadvantages: some spores survive, short shelf life, additional processing method is requires (fridge and freezer)

mild heat treatments

blanching and pasteurization:

aims: kill pathogens (pasture only), reduce bacteria count, inactivate enzymes

advantages: minimal nutrital changes

disadvantages: shorter shelf life

lower temp process acid foods

acid foods = pH less than 4.6

bacteria are moe easily destroyed by moist heat

blanching:

goal: inactivate enzymes that would cause off odours and off colours during frozen storage

• vegetables are immerse in boiling water

• - reduces the microbial load

  - does not create commercially sterile product

microwave heating

polar molecules in food generate heat by molecular friction

- the food is heated while the surroundings are not

- need water molecules

- heat the first 5cm of the food, then what is transferred by conduction

It is illegal to sell irradiated food products in Canada.

false

irradiation

ionizing radiation, cold process, limited to foods and specific purposes

• reduces micbrial load, spoilage inhibition microbes insects, longer shelf life, 2017 regulatory amendment - Canada

Ohmic Heating

an electric current passes through foods to heat them at a rapid rate. foods must have sufficient water and electrolyse to allow the current to pass through. destroys microbial and spores

• potential to replace evaporation dehydration and pasteurization

• liquid eggs, meals in space missions, military food rations

Ohmic heating differs from microwave heating because heat is generated by:

the passage of an electrical current directly through a conductive food material

high pressure processing

cold pasteurization, alternate to thermal pasteurization

0 high physical pressure for 5-20 min

- destroys microbes but not spores

- product motional and sensory properties are preserved

- works best on high moisture products

- fresh juices, meat

go through the process of high pressure processing

product loaded in carrier - carrier filled with water - high pressure treatment - water drained from carrier - shipped to store

why does high pressure processing perform poorly in dry foods

Air pockets resist pressure transmission

true or false "May contain" statements on food labels are mandatory in Canada and are used to indicate the possibility of cross-contamination with allergens during production.

false

Case hardening may be observed in the unit operation of dehydration. It can be avoided by doing what?

Decreasing the size of the product to increase the surface area for drying.

true or false: The 'Best Before' date on a food package indicates the date after which the food product will likely become unsafe to consume.

false. best before is about freshness and quality, not safety.

Which of the following statements is true regarding food preservation methods?

Ohmic heating uses an electric current to rapidly heat food, effectively destroying microbes and spores.

high pressure processing and irradiation have what in common

no heating involved

fast freeze of a fruit product is desirable for what reason?

Ice crystals are small and do not disrupt plant cell membranes, maintaining tissue integrity when thawed.

Which of the following food fraud techniques is considered to pose an indirect risk of allergen exposure to consumers if the product is being exported to the US from Canada?

Substituting coconut in place of peanuts in a snack bar.

The D value of S. aureus is D71.7 = 4.1 s. What proportion of bacteria are destroyed by this D value?

90%

Stimulation of the trigeminal sense is characteristic of which set of foods?12/29

Hot wasabi, cool chewing gum

name examples of Canada food safety systems

health Canada, public health agency of Canada, Canada food and drug act/ regulation, Canadian food inspection agency

can you talk about food quality separate from food safety

no, food safety plays an important role in food quality

can you talk about food safety seperate from food quality

yes

CFIA

Canadian food inspection agency

develops and enforced food safety inspections policy and programs: investigates and recalls foods

PHAC

public health agency of Canada

• surveillance and human health investigation for food borne outbreaks; public education/communication

FSQA in the food industry

codex alimentarius - international food standard

corporate quality assurance- SOP, PRPs, HACCP

industry/commodity trade standards- members of an industry

federal provincial local regulations- SFCR (safe food for Canadians)

why is traceability important

• the ability to trace where the product came from, where the product went to, and what happened to the product during processing can help ensure the safety of consumers

history of Canadian food and drug act

1876- the inland revenue act ( liquor regulation)

1884- the adulteration act (drugs included)

1913- many legal standards for food were written

post WWI - food production became industrialized

1920- food and drug act replaces AA (adulteration act)

- sanitary practices, inspection, grading

food labelling requirements

by weight in descending order, ingredients, best before, allergy, common name, etc.

best before date:

the freshness of the product. "packaged on" date on pre packaged foods with a durable life of 90 days or less

expiration date

safety can be comprised if consumed after this date. only on foods that would not have the same nutrient content after the expiration date

food grading

grades describe the quality parameter son a food products. grades are associate with specific "products quality requirements"

- flavour, aroma, texture, colour, size, etc.

- used to describe the product quality and facilitate trade

ex: maple syrup, steak