HNSC unit 6

food processing

food processing

operation carried out on raw food, results in process food product

reasons for food processing

• preservation - extending the shelf life of the food

• make food edible

• enhance nutritional quality

• convenient to consume

• price reduction by reduction in wastage

principles of food preservation - aspesis

keeping out the microorganisms

principles of food preservation - slowing the growth of microbes

• to multiply microbes require water activity, pH, temp, substrate

• if conditions are changed = microbial growth declines = extend shelf-life

principles of food preservation - inhibit growth of microbes

certain conditions are required for their growth, conditions can be modified to inhibit certain microbes

principles of food preservation - killing microorganisms

• heat treatment

• UV treatment

• chemical preservatives

principles of food preservation - controlling chemical reactions

• colour, texture or flavour can change over time due to chemical reactions

  • reaction can be controlled by removing one of the reactants

controlling chemical reactions examples

• unsaturated fatty acids react with oxygen leading to oxidative rancidity of the oil. if the oxygen can be kept away from the oil, the oxidation of the oil would not take place

• fruits and vegetables contain enzymes. food can be preserved by inactivating such enzymes

how to inactivate enzymes

• heat treatment

• pH conditions

• enzyme inhibitors

pasteurization

• application of heat in order to

  • destroy pathogenic microorganisms

  •  inactivate spoilage-causing enzymes

  • reduce or destroy spoilage microorganisms

• higher temp = shorter time period for destruction

• goal to destroy microbes without causing changes to the food

pasteurization in milk example

• can be achieved low temperature long time at 63C for 30 mins

• or by high temperature short time (HTST) treatment at 73 °C for 15 sec 

• or even higher temperature treatment at 94 °C for 0.1 sec

sterilization

• killing all the microorganisms

• commercial sterilization - aims to reduce microbial population to 10-6

  cells/spores per ml (or just one cell/spore in million millilitres)

commercial sterilization example

• ultra high temp. milk

  • treatment at temperatures higher than 138 °C for a few seconds

    can destroy most of the bacterial population without changing the nutritional properties of milk

  • packaged in aseptically which are hermetically sealed (doesn’t allow the microbes to enter)

canning

• goal is to destroy almost all the microbes such that only 1 in a million cans have microbial cell/spore

  • correct and time and temp is determined experimentally and dependent on several factors (type of food, pH, size of can, material of the can, viscosity)

• no microbes can enter, aerobic microbes cannot grow, most microbes are destroyed by heat, sealed can stored at room temp = extend shelf life

commercial canning basic steps

• cleaning the food and filling the food in the can

• exhausting and sealing the can

• cooking food in the can

• cool the cans to room temp.

how to do home canning

• be cautious of the artificial additives and high sodium

• pressuring canning is necessary because higher temps are required to kill bacteria

• boiling water canning is suitable for high acid foods because the acidity combined with heat is sufficient to kill bacteria

• removing rings from cans

blanching

• dipping the food in boiling water then cooling under cold water to stop cooking

• purpose is to inactivate enzymes because it would deteriorate the quality

dehydration (removal of water) - sun drying

• least controlled method (sun light and air cannot be controlled)

• method takes the longest time of all the methods

• care is required to ensure that the food is kept free from insects, dusts, etc

sun dried tomato

• multiple washing and sorting steps to ensure quality and remove any discoloured or field debris

• mechanically slicing, washing, and sorting by size helps prepare for the drying process

• laid out to dry in a specific section of the drying yard for 9-14 days

• packing line involves agitating, scraping, and sorting before they are transported back to storage

• two shaking steps are conducted to remove skins, seeds, and any leftover debris while also sorting by size

• stored until orders arrive since the harvesting season is limited to a few months

dehydration - plate drying

• food placed on trays then heated in a hot chamber

• chamber has a exhaust to let the moist air out

• dehydrators have vacuum pump

• another variation of the plate/cabinet drying is

  conveyor belt drying

dehydration - drum drying

• dehydrating viscous fluids to make powder

  • soup powder → prepped soup then thickened by heating or reverse osmosis → put in troughs → coated as a thin film on the drum → gets dried into thin sheet → sheet is scrapped off to form powder

dehydration - spray drying

• atomizing the milk into droplets using atomizer in a hot chamber

• droplets enter the chamber → get dried → vacuum pump removes moist air

dehydration - freeze drying

• known lyophilization (sublimation)

• doesn’t need to be heated (causing little damage)

• absence of water = loss nutrients and flavour compounds and minimal loss of the texture

• 99% of water is removed = better quality dehydrated product

refrigeration

• cooling the food (above 0°C to 4°C to slow down the microbial growth)

• prevents spoilage

• 45% of veggies and fruits are wasted (58% from Canada)

• modern fridges reduce wastage

• underdeveloped countries, more food is wasted at production level due to the lack of infrastructure and advanced technology

freezing

• temperatures below 0 °C to freeze the water in the food

• freezing halts microbial growth

• faster freezing = smaller ice crystals = better texture, colour and flavour

individually quick frozen tech

• food is immersed in a cryogenic fluid such that the food freezes very quickly, and the individual pieces do not stick together

• liquid nitrogen (boiling point -196 °C) and liquid carbon dioxide (boiling point -79 °C)

IQF cauliflower

• before freezing - blanching

• after freezing - spray cold water

• shake to separate

changing the pH of food (directly or indirectly)

• direct addition of acids such as acetic acid, vinegar, citric acid, tartaric acid: pickles

• indirectly lowering the pH by fermenting bacteria that produce acid in the food

  • ex. yogurt adding Lactobacillus bulgaricus and Streptococcus thermophilus → bacteria would multiply in milk using up the lactose and producing lactic acid → lactic acid lowers the milk pH

why does yogurt sometimes have mold growth

yogurt has a acidic pH (prevent bacteria growth and bacteria is sensitive to pH), though fungi can grow between levels of 2-11, yogurt can have a pH tolerant mold grow in it

preservation by reducing water activity of the food

• sugar’s hygroscopic property is used in jam/jelly making

• salt’s hygroscopic and osmotic properties are used to reduce water activity

dehydrated fish

lowering the water activity and minimize microbial load (killing some microbes by dehydration) by salt, and sun drying

table salt and hypertension

• table salt contains 40% sodium by weight (If you take 1 g salt; 400 mg of sodium)

• sodium recommendation: 1500 mg/day (3.75 g of salt will give this amount)

• tolerable Upper Intake level: 2300 mg/day (<6 g of salt)

• average intake in Canada: 2760 mg/day (2017), was 3400 mg/day in 2004.

• goal of below 2300 mg/day by 2016 was established by Canadian Government

why is too much salt bad for you?

• cause water retention, leading to increased blood pressure and strain on blood vessels

• high blood pressure = thickened blood vessel walls, reducing blood flow to organs and increasing the risk of heart attacks, strokes, and other health issues.

• limiting salt intake can help prevent or manage high blood pressure and reduce the risks

• food labels and color-coded systems can help

• seasonings like black pepper, herbs, spices, and lemon juice can enhance flavor without relying on excessive salt

• it's important to be aware of hidden sources of salt in ready-made foods

table salt and hypertension cont.

• reported that 58% of canadians (1 year and older) and 72% of children (4 and 13 years) exceed limits of sodium intake

• 77% of sodium comes processed food

irradiation

• cold pasteurization

• exposing food to ionizing radiation (gamma rays, electron beams, X-rays etc)

  •  high speed and/or high energy waves that destroy any biomolecules

  • proper dose they are effective in destroying the biomolecules

  •  gamma rays can penetrate the food deeper than the electron beams

  • rays are produced by radioactive material but the radioactive material doesn’t touch the food

packaging

• several reasons for packaging

  • including branding, putting mandatory and optional labeling information, preventing physical damage to the food,

    enabling shipping, preventing chemical deterioration, biological spoilage and pathogenic contamination,

glass

• takes long time to decompose naturally, however they are infinitely recyclable

• odorless and chemically inert with virtually all food products

• impermeable to gases and vapors, can withstand high processing temperatures

• provides good insulation

• heavier and poor durabilty

metals

• highly malleable and very durable even when sheeting thin

• much lighter than glass containers

• impermeable to water, air/gases, microbes but some may react with the food contents

• coated inside

paper

• light weight, cheap and biodegradable, but is permeable to gases, moisture and fat, and has poor strength

• cardboards are a stronger form of paper but they are still very permeable

tetra packaging

• combination of plastic, paper, metal

• long shelf life due to the special layers

• light weight and eco-friendly

plastic

• synthetically produced by polymerization and condensation of monomers

• advantages

  • Fluid and moldable, made into sheets, shapes, and structures, offering considerable design flexibility

  • chemically resistant, inexpensive and lightweight with a wide range of physical and optical properties

• disadvantage

  • plastic bags are not accepted in your recycling bin

  • reduce your use of plastic bags, reuse “single use” bags for hold household garbage, pet waste and other items and finally, recycle the

    ones already in your home

concern for plastic

• leaching out of the chemical components the plastic

• bisphenol A (BPA) has been banned to be used in infant products

  • canada has ALARA (As low as reasonably achievable) principle for BPA

  • provides strength and clarity to the plastic

controlled or modified atmospheric packaging (CAP or MAP)

• the concentration of gases in the package are controlled or modified

  • oxygen absorbent patches can be used to minimize the availability of oxygen during transport

  • bananas ripen very fast mainly because they continue to produce high levels of ethylene gas even after their harvest

  • fruits continued to ripen are called climacteric fruits

bananas cont.

• picked green and are stored and transported in chambers that are kept cool at about 13 °C to slowdown their post-harvest respiration → ethylene production stops

• tissue gets damaged below 10 °C and they turn brown and fail to ripen at such low temperatures → ripen quickly and unevenly at temperatures above 17 °C

• the retail stores a modified atmosphere chamber is used to evenly ripen the bananas → chamber is flushed with ethylene gas = speeds up the ripening of bananas

another ex. of MAP - chips

• nitrogen packaging of chips → potato chips fried in oil are packaged in bags filled with nitrogen gas to prevent rancidity

• gas flushed meat packaging: a combination of oxygen and carbon dioxide prevents growth of both aerobic and anaerobic microbes

chemical methods - CFIA

allows the use of certain chemicals that can act as preservatives. these are classified as below:

Class 1 - curing preservatives

Class 2 - antibacterial;

Class 3 - antifungal and antimycotic;

Class 4 – antioxidants

GRAS meaning

generally recognized as safe

synthetic preservatives - natural preservatives (class 1)

• table salt, sugars and acids are in food preservation

• other natural preservatives include nitrates and nitrites: These have long been used in curing meats

• long history of use

nitrates and nitrites

• killing pathogenic microbes, maintaining the red color of meat, and preventing the rancidity

• can form nitrosamines when they react with amino acids. nitrosamines are carcinogenic

• declared that highly processed meat consumption is linked with certain types of cancers

carcinogenic

causes/producing cancer

synthetic preservatives - antibacterial (class 2)

sodium benzoates, sulphates

synthetic preservatives - antifungal (class 3)

propionates and sorbates

synthetic preservatives - antioxidants (class 4)

Ascrobic acid, Butylated hydroxytoulene (BHT) and Butylated hydroxyanisole (BHA)