Lesson 5- Rationale for Food Preservation-23-2

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Lesson 5 Rationale for Food Preservation
Lesson Objective Describe the factors (chemical, enzymatic, microbiological) that commonly contribute to food deterioration and spoilage; Summarize possible mechanisms for inhibiting the factors that promote deterioration of quality in food systems
Required activity Watch the videos in lesson 5
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Food Deterioration Facts ❑ 10-20% preharvest deterioration ❑ 2.2 million tonnes ($17 billion) of food waste annually ❑ (National Zero Waste Council Canada)
Critical thinking: How does the food deteriorate ?
Critical thinking: How does the food deteriorate ?
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Physical causes Chemical cause Biochemical (enzymatic) causes Biological causes Critical thinking: How does the food deteriorate?
Food Deterioration- classification Perishable foods ◦ Not processed or are only minimally processed and have a shelf life of less than 60 days . Semi-Perishable ◦ Last between 2 to 6 months as a result of some form of preservation method . Shelf stable ◦ have a shelf life greater than 6 months .
Critical Thinking question Which one of the mentioned classifications needs date labelling as mandatory core labelling requirements?
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Microorganism-Classification Type Bacteria, Yeast, Mould,
Microorganism-Classification Function Good, bad, ugly Temperature Requirement Psychrophiles, Psychrotrophs, Mesophiles, Thermophiles Oxygen Requirement Aerobic, Anaerobic, Facultative anaerobe
Microorganism-Classification Side notes-Viruses ❑ Pseudo-organisms- (Not true organisms) ❑ Obligated parasites require living hosts to propagate ❑ Do not ferment or spoil food ❑ Can cause foodborne illnesses
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Bacteria – fast growth ◼ vegetative cells (active) or spores (dormant), germinating cells (transition from spores to vegetative) Yeasts – slower growth than bacteria but more tolerant ◼ Tolerate lower pH or water activity Moulds – even more tolerant of low pH and water activity Microorganisms- growth and tolerance Not all bacteria can form spores
Enzymatic Polyphenol + O 2 Brown pigments Polyphenol oxidase
Preservation Methods Old ◦ Dehydration ◦ Smoking ◦ Fermentation ◦ Salting ◦ Sweetening Modern ◦ Canning ◦ Freezing ◦ UHT ◦ Irradiation
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Preservation Methods- Comparison Old Method ◦ cause noticeable changes in the food (i.e. fresh salmon vs. smoked salmon, grapes vs. wine, milk vs. cheese); New Method ◦ cause little change (freezing, pasteurization) Without these "old" preservation methods we wouldn't have the variety of desirable food products such as cheese, bread, wine, smoked meats, etc
Preservation Methods- Side note ◦ Canned foods will not undergo microbial or enzymatic spoilage as long as the physical integrity of the can is maintained, but foods may spoil as a consequence of chemical reactions such as Maillard browning which can proceed slowly even at ambient temperature . No method can completely eliminate spoilage phenomena indefinitely.
Preservation Methods ❑ Dehydration ❑ Fermentation ❑ Low-temperature preservation ❑ Thermal processing ❑ Irradiation ❑ Addition of chemicals
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Preservation Methods - Dehydration Removal of water to control chemical , enzymatic and microbial activity ◦ Complete removal (Drying) ◦ Partial removal (Concentration )
Preservation Methods - Fermentation ❑ Use of the desired microorganism to delay the growth of non-desirable ones ❑ Production of acid ❑ Production of Antimicrobial ❑ Requires other forms of preservation (eg. vacuum or modified atmosphere packaging) This Photo by Unknown Author is licensed under CC BY-SA-NC
Preservation Methods – Low temperature ❑ Slowing down the rate of chemical, enzymatic and microbial activity ❑ Refrigeration ❑ Freezing: ❑ Should be blanched ❑ Freezer burn can occur ❑ Can be combined with other preservation methods to extend the shelf life This Photo by Unknown Author is licensed under CC BY-SA-NC
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Preservation Methods – Thermal processing Blanching ◦ Inactivate the enzymes Pasteurization ◦ Destroy the disease-causing microorganism ◦ Putrefaction microorganism survive Commercial sterilization (Botulinum cook) ◦ Destroys almost disease-causing and spoilage causing microorganisms This Photo by Unknown Author is licensed under CC BY-SA This Photo by Unknown Author is licensed under CC BY- ND
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Preservation Methods – Irradiation Using Ionization energy to inactivate microorganisms or biological systems ◦ General public concern ◦ Required dose is regulated This Photo by Unknown Author is licensed under CC BY
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Preservation Methods – Addition of Chemicals Acids ◦ pH 4.6 Sugar and Salt ◦ Lower water activity Antioxidants ◦ Vitamin C and E, Butylated hydroxyanisole (BHA) Preservatives ◦ Sodium propionate, Sodium benzoate
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Preservation Methods – video side notes Note that the video refers to milk, meat and poultry as " non-acidic " foods. However, as we learned in Lesson 2, these food items that have a pH > 4.6 , are actually classified as " low acid foods "
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Experiment Slice an apple and expose it to the air compare the rates of browning to those that: ❑ Have been dipped in boiling water for several minutes ❑ Stored underwater ❑ Treated with a commercial preparation of citric acid and ascorbic acid, or lemon juice This Photo by Unknown Author is licensed under CC BY-SA- NC
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In summary: Roles of preservation: 1. Eliminate any potential microbiological harm to the consumer 2. Maintain nutritional value within limits dictated by the production of a safe food product 3. Maintain quality of Food
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Terms to remember Bacteria, mould, yeast Psychrotrophs, mesophiles, thermophiles Spores Vegetative cells. Germinating cells Aerobic, anaerobic, facultative anaerobe Oxidative rancidity Hydrolytic or lipolytic rancidity Enzymatic browning Perishable, Semi perishable, Shelf stable
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