processing methods

Question 1

water is key to:

Answer 1

lipid oxidation, degradation of nutrients, colour, change in flavour, and growth of microbes

Question 2

water activity tool

Answer 2

Aw = P/Po - the ratio of the vapour pressure of water in a food to the saturated vapour pressure of pure water at the same temperature (Aw of pure water = 1)

Question 3

water activity can representing different types of water interaction w/. food - high/intermediary/low

Answer 3

• At higher water activity we can see more changes driven by microbial growth in enzymatic reactions, foods that are perishable and often require chilled storage
• intermediary water activities we see browning reactions, driven by yeast, mould and oxidation reactions, Aw often controlled by sugar and salt
• Lower water activities we see oxidation and based reactions occurring in food systems, highly processed foods with low levels of water

Question 4

what controls Aw

Answer 4

reduction of water content - drying
water binding ingredients - salts, carbohydrates, proteins
temp. - lowering of temp, changing of phase (freezing)

Question 5

food processing unit of operations (series of steps)

Answer 5

material handling, cleaning, serperating, size reduction, fluid flow, mixing, heat transfer, concentration, drying, forming, packing
(MCSS, FMHC, DFP)

Question 6

‘fresh’ fruits unit operations

Answer 6

harvest, transportation, cleaning, sorting, (additional processing), sale of fresh produce

Question 7

how is fresh produce transfered and what are the high risks involved

Answer 7

trucking from the farm to factory, transfer from one storage area to another, transfer to the point of sale.
high risk = physical damage, contamination

Question 8

cleaning aspects of fresh produce

Answer 8

washing - removal of dirt, physical contaminations, microbial and chemical contaminations - use clean water and can combine with chemical cleaning agents: sodium hypochlorite (bleach)
brushes, air, magnets - remove physical contaminants.

Question 9

what does Sorting involve + methods

Answer 9

separating produce by set characteristics - weight, size, shape, colour
used to - remove defective produce, ensure the product is suitable to meet quality expectations for sale
methods done by - hand, optical sorting, weight/size

Question 10

size reduction physical equipment

Answer 10

grate/mince, cut, slice, peel

Question 11

definition of peeling

Answer 11

the process of separating out the undesirable outside and desirable inside of a food product

Question 12

size reduction in fluid foods + example

Answer 12

F.F products contain a range of insoluble material (
homogenisation - reduction in partial size of material suspended in liquid

Question 13

effects on size reduction on food

Answer 13

surface area and volume - increases flavour release, heat transfer rates, diffusion rates
break down tissue structure - loss of compartmentalisation and textural changes - loss of macro-structure

Question 14

definition of mixing and its role

Answer 14

the formation of a semi-uniform combination of two or more components
role in facilitating chemical reactions
development and break down of physical structures

Question 15

changes that can occur during drying

Answer 15

shrinkage, browning, change in voltile flavours/odours, loss of nutrients, lipid oxidation

Question 16

types of drying methods and how they are conducted

Answer 16

sun drying - energy source: solar radiation, vapour removal: the atmosphere
air drying - energy source: hot air, removing the vapour through changing the air, can use tray drying, bed dryers, spray drying
freeze drying (needs pre-freezing) - 1. sublimation of water in food - energy is needed to reduce pressure, driven by drop in pressure
2. removal of the water vapour from desorption from the air

Question 17

benefits of freeze drying

Answer 17

very high retention of texture, colour, and flavour - expensive process

Question 18

cooking food vs drying (what happens to both)

Answer 18

cooking - microbial inactivation due to heat, denaturation of proteins, starch gelatinisation, removal of surface water
drying - collapse of physical structure, removal of water from all proportions of the food
both - colour changes, flavour changes

Question 18

cooking food vs drying (what happens to both)

Answer 18

cooking - microbial inactivation due to heat, denaturation of proteins, starch gelatinisation, removal of surface water
drying - collapse of physical structure, removal of water from all proportions of the food
both - colour changes, flavour changes

Question 19

freezings role in food preservation

Answer 19

reduction in the amount of free water by converting water from its solid state to liquid state

Question 20

explain different parts of foods that are affected by freezing

Answer 20

flavour - prevents loss of volatiles, can drive lipid oxidation over long storage times
colour - Millard browning reaction can occur, degradation due to enzymatic reactions, retention of heat liable compounds
texture - direct damage from ice crystal formation, the smaller crystal the better and determined by freezing rate (faster rate = smaller crystal size)
nutrients - no substantive change to most micro-nutrients, some changes to macro-nutrient digestibility
Freezing food is safe- doesn’t kill microbes or allow pathogens to grow, will inactivate some parasites

Question 21

definition of blanching and why it is applied

Answer 21

short heat treatment specifically designed to inactivate endogenous enzymes
applied to veggies prior to further storage or processing

Question 22

blanching effects on food

Answer 22

flavour - loss of volatiles, destruction of heat liable compounds
nutrients - leaching of water soluble compounds (minerals)
colour - removal of oxygen in tissue structures
texture - degradation of cell wall and cell membrane

Question 23

the use of chilling food

Answer 23

reduce rate of chemical reactions, growth of microbes

Question 24

irradiation mean

Answer 24

food preservation method that involves exposing food to ionizing radiation, such as gamma rays or electron beams
used to kill or reduce harmful bacteria, parasites, insects, and other microorganisms
can extend the shelf life of food by slowing down spoilage and inhibiting sprouting or ripening

Question 25

Microfiltration

Answer 25

technique that uses micro-sized pores to separate particles and microorganisms from a liquid.
used in the food industry to remove bacteria, yeast, molds, and other contaminants from liquids, such as milk, juices, and beer
can help extend the shelf life of products, improve clarity, and enhance safety by reducing microbial load

Question 26

Size Reduction

Answer 26

refers to the process of reducing the particle size of solid food materials through mechanical means
achieved through techniques such as grinding, milling, cutting, or crushing
Size reduction enhances the functionality and digestibility of food ingredients and aids in various food processing steps, such as mixing, extraction, and cooking
Size reduction is used in the production of flours, powders, pastes, and various processed foods.

Question 27

High-Pressure Processing (HPP)

Answer 27

involves subjecting food products to elevated pressures, typically between 100 to 1000 MPa (megapascals)
HPP is a non-thermal pasteurization method that inactivates microorganisms, including bacteria, viruses, yeasts, and molds, without the use of heat
helps extend the shelf life of food while preserving its nutritional quality and sensory attributes
HPP is commonly used for products such as juices, meats, seafood, salsas, and guacamole
It is an effective alternative to traditional heat pasteurization methods, as it minimizes the loss of flavor, color, and nutrients

Question 28

Spray Drying

Answer 28

Spray drying is a technique used to convert liquid or semi-liquid food into dry powder form
The process involves atomizing the liquid into small droplets, which are then rapidly dried using hot air or gas
used in the food industry to produce powdered ingredients, such as milk powder, coffee powder, instant soup mixes, and powdered flavors
advantages like extended shelf life, improved handling and storage, easy reconstitution, and enhanced solubility of the final product
requires careful control of temperature, air flow, and droplet size to maintain the desired quality attributes of the powdered product.

Question 29

freeze drying methods - why can it be left at room temp. for months

Answer 29

Freezing: The product to be freeze dried is first frozen to a very low temperature. helps preserve structure and integrity of the product during the subsequent drying process.
Vacuum Chamber: Chamber is sealed, and the pressure inside is reduced to create a vacuum environment.
Sublimation: the direct transition of a solid (ice) to a gas In the vacuum environment, the frozen water in the product bypasses the liquid phase and goes from solid to vapor.
Heat Application: heat causes the ice in the product to sublime, turning it into water vapor.
Desorption: The vapor is condensed and collected by vacuum pump leaving the product dry.
Sealing and Packaging: packaging helps to protect the product from moisture and other environmental factors.

Freeze drying preserves the product by removing moisture, which inhibits the growth of microorganisms and enzymatic reactions that can cause spoilage.