Part #2 Flashcards
(54 cards)
What is food processing vs food preservation?
Food processing
- Conversion of raw animal and plant tissue into forms that are convenient and practical to consume
- All the operations from field and farm to consumer
Food Preservation
- Use of specific thermal and non-thermal techniques to minimize the number of spoilage and pathogenic microorganisms in foods, making them safe and extending the shelf life.
How many unit operations are there in food processing?
12
What are the 12 unit operations?
- Materials and handling
- Separating
- Cleaning
- Disintegrating
- Pumping
- Mixing
- Heat exchange
- Evaporation
- Drying
- Forming
- Packing
- Non-thermal methods
What are the three types of food deterioration?
- Physical - Handling
- Chemical - Enzymatic reactions
- Biological - Microbial growth
What are the three types of food deterioration?
- Physical - Handling
- Chemical - Enzymatic reactions
- Biological - Microbial growth
What are the major causes of food deterioration?
- Growth and activity of microorganisms
- Activity of endogenous food enzymes and other chemical reactions
- Infestation by insects, parasites and rodents
- Inappropriate temperatures
- Gain or loss of moisture
- Oxidation
- Exposure to light
- Physical stress
- Time
What are the major causes of food deterioration?
- Growth and activity of microorganisms
- Activity of endogenous food enzymes and other chemical reactions
- Infestation by insects, parasites and rodents
- Inappropriate temperatures
- Gain or loss of moisture
- Oxidation
- Exposure to light
- Physical stress
- Time
What is fermentation in food preservation?
Desirable microbial growth in food lead to certain chemical and physical changes so that the food can be stored for a longer period of time without deterioration
What are the two new food processing technologies we covered?
- Non-thermal: Irradiation, high-pressure, pulse electric field, ultrasonic waves
- Novel thermal process: microwave and ohmic heating
What are the three basic mechanisms by which heat is transferred?
- Conduction: Solid-Solid
- Convection: Fluid-Fluid
- Radiation:
What is lost during cooking?
- Lysine bioavailability reduced
- Heat sensitive vitamins (A and D)
- Water soluble vitamins (Thiamine, niacin, folate)
What is the primary objective of blanching?
- Inactivating deteriorative enzymes
- (minor) kills some spoilage bacteria
What deteriorative enzymes are inactivated in blanching?
- Lipoxygenase (LOX): Catalyze peroxidation of unsaturated fatty acids
- Polyphenol oxidase (PPO): Responsible for enzymatic browning
- Pectinase: Breaks down pectin. Tomato past would loose its thickness if not head treated immediately. (Hot Break process)
What nutrients are lost during blanching?
- Ascorbic acid
What are the two pasteurization processes?
- LTH (low temp, hold) 63C for 30min. This is more detrimental to nutritional and sensory properties.
- HTST (high temp, short time or flash) 72C for 15sec
What pH does Clostridium botulinum grow at?
4.6 or greater
What is the D value?
The number of minutes required at a particular temperature and in a particular medium to destroy 90% of the microorganisms in the population.
- Or to decrease the population by one log cycle.
What are the bulk effects of thermal processing on food constituents?
- Acid and salter accelerated destruction of microorganisms
- Protein denaturation
- Generation of cooked flavor due to reaction of sulfur from amino acid cysteine
- Maillard Browning reaction between reducing sugars and proteins (loss of nutrients)
- Loss of heat sensitive vitamins
What temperature is considered to be freezing storage?
-18C to -30C
What are the three distinct stages of a freezing process?
- Removal of sensible heat until freezing temperature
- Removal of latent heat of fusion leading to ice formation
- Further removal of sensible heat towards storage temperature
What is the continual decline of freeing point in foods?
However, as the solution freezes, pure water freezes
out preferentially. Therefore, the unfrozen region becomes more and
more concentrated with solute and exhibits further
depression in the freezing point – leading to a
continual decline in freezing point
What determines the size of ice crystal?
Rate of freezing (slow freezing leads to the formation of a limited number of ice crystals meaning large crystals but few)
- In frozen vegetables, ice crystals first form between the cells as they have lower concentration of solutes there.
What are the effects of slow freezing?
- Large ice crystals damage cellular structure of
frozen vegetables and lead to loss of structural
integrity - Formation of large crystals in inter-cellular
region of vegetables pulls water out of the cell
(due to osmotic equilibrium) - results in cellular dehydration - On thawing the cells unable to maintain rigidity
due to dehydration and disruption of cell wall by
ice crystals – leading to soft, flaccid texture and
loss of water
What are the effects of rapid freezing?
• Rapid freezing results in higher ice crystal
nucleation rate which lead to formation of
numerous small ice crystals both outside and
inside the cells of frozen vegetables
• Cells maintain their rigidity and minimizes drip
loss of water during thawing of frozen vegetables
• However, disruptive effect of size of ice crystals is
minimum in fish or meat (muscle food) due to the
elasticity of the cellular structure in muscles
– The mechanism of loss of quality due to slow freezing
of muscle foods is different than fruits and vegetables
