food technology

2.  Of, or relating to, both physical and chemical
properties, including changes and reactions.
(https://en.oxforddictionaries.com/definition/us/physicochemical
)
 why is it important : the physical and chemical
characteristics of plant and animal food
materials affect how they are to be processed,
handled, stored, and consumed, knowledge of
these characteristics are important to engineers,
processors and food scientists, plant and animal
breeders, and other scientists.

3.  Initial quality
- perfectly fresh or not
- injured
- methods of cultivation and harvesting
- pre-storage treatment, if any or processing
 Cooling down time after harvesting
 Storage temperature
 Relative humidity
 Condensation : happens when the dew point of the air is higher than
the surface temperature of produce.
- stimulates the growth of micro organisms
- cartons, will also suffer in rigidity
 Ventilation
 Packaging and stacking
 Hygiene conditions while storing period
 Expected or practical storage life : the produce may be stored either
with maximum commercially acceptable loss of quality and nutritive
value or with maximum acceptable wastage by spoilage

4. PHYSICAL CHARACTERISTICS
 Shape
 Surface area
 Appearance
 Size
 Density
 Drag coefficient
 Weight
 Porosity
 Center of gravity
 Volume
 Color
CHEMICAL CHARACTERISTICS
 Water
 Saccharides
 Proteins
 Lipids
 Minerals
 Colorants
 Enzymes
 Vitamins
 Fats

5.  FnV are in a living state after harvest
 Continued respiration gives off carbon dioxide, moisture, and heat
which influences storage
 changes in carbohydrates, pectins, organic acids, and the effects
these have on various quality attributes of the products.
 Unripe fruit is high in starch and low in sugars, Continued ripening
after harvest generally results in a decrease in starch and a
increase in sugars. E.g. apples and pears.
- this courses of change in starch and sugars are markedly
influenced by postharvest storage temperatures.
- e.g. potatoes stored below about 10 C° (50 F°) continue to build up
high levels of sugars, while the same potatoes stored above 10 C°
do not.
- used to help the dehydration process in potato storage, low
reducing sugar content so as to minimise Maillard browning
reactions

6.  Pectin
- decrease in water-insoluble pectin substance
- increase in water soluble pectin
- Further breakdown of water-soluble pectin by pectin methyl
esterase.
- contributes to the gradual softening of FnV during storage and
ripening.
 Organic acids
- decreases during storage and ripening
- e.g. apples, pears and oranges
- influences : tartness ( decreases), colour, viscosity of pectin
gel ( decreases).

7. wound/pests/pathogens
produces
H2C=CH2
(ethylene)
induces/turns on
genes
temperature increase
(for enzyme synthesis)
produce
degrade
fruit tissues
results in
increases
(chlorophyll, acids, starches,
pectin, proteins, etc.)
enzymes
oxygen
reacts with
methionine
to be
converted to
inhibits growth of/diffuses into
catalyze
biochemical reactions
Amylase: starch --> sugar
Pectinase: pectin --> less pectin
Kinase: acids --> neutral
Protease: proteins --> amino acids

8. Factors type Changes
Enzymes : endogenous to
plant tissues can have
undesirable or desirable
consequences.
The major factors useful in
controlling enzyme activity
are: temperature, water
activity, pH, chemicals
which can inhibit enzyme
action, alteration of
substrates, alteration of
products and pre-
processing control.
a. Pectinase
b. Phenolase
c. Amylases
• post-harvest
senescence and
spoilage
• oxidation of phenolic
substances, leading to
browning.
• sugar - starch
conversion
• post-harvest
demethylation of pectic
substances, leading to
softening of plant
tissues during ripening.

10. Factors Change
Chemical :
1. lipid oxidation
2. non-enzymatic browning.
3. Colour changes
- Chlorophylls
- Anthocyanins
- Carotenoids (lipid soluble
compounds )
4. Flavour changes
1. Loss in firmness
2. the formation of volatile or soluble substances and leading to
insoluble brown polymers.
- Phenophytinisation (with consequent formation of a dull
olivebrown phenophytin) is the major change and photo-
oxidation.
- form complexes with metals such as Al, Fe, Cu and Sn ( packaging
material if used to store ), e.g. red sour cherries react with tin to
form a purple complex
- Oxidation
- Enzyme-induced oxidative breakdown of unsaturated fatty acids
and associated with some ripening fruits and disrupted tissues.

11.  artificial ripening of Red banana
using ethylene was studied for nine
days of storage
 temperature : 22 degree celsius
 relative humidity : 85-88%
Moisture content :
- continued to increase during ripening
- reveals that within fruit, moisture have
been migrated from peel to pulp and
due to increase in sugar content in the
pulp as a result of starch hydrolysis to
sugar
- Hence, moisture content has a
significant influence on theTSS content

12.  Total soluble solids
- post-harvest causes sugar
formation as a result of
starch hydrolysis.
- increase inTSS was 5 to
23.41
 Pulp to peel ratio
- elevated with consequent
increase
- related to accumulation of
moisture in the pulp
derived from carbohydrate
breakdown and osmotic
transfer from peel to pulp

13.  Peel thickness
- decrease from 4.20±0.28 to
2.52±0.24
- modification of cell wall of
peel which may affect
firmness loss and ultimately
lead in vanishing void space
and hence reduction in peel
thickness
 Firmness
- loss in firmness
- thickness,TSS and moisture
content are the main cause
of alteration

14.  Titrable acidity
- total amount of acid
(malic, citric and oxalic
acid), first increases and
then decreases
Asutosh Mohapatra, BhosaleYuvraj K. and S. Shanmugasundaram
Indian Institute of Crop ProcessingTechnology,Thanjavur, Tamilnadu, 613005, India

15.  The glycogen content of animal muscles is reduced when the animal is
exposed to pre-slaughter stress which changes the pH of the meat, to
higher or lower levels.
 Lactic acid is produced due to the breakdown of glycogen content of
animal muscles via an anaerobic glycolytic pathway.
 Higher levels of pH (6.4-6.8) result in Dark, Firm and Dry
 pH lower than normal ultimate value of 6.2 which is responsible for the
breakdown of proteins, providing a favorable medium for the growth of
bacteria
 Factors that causes change could be due to lipid oxidation and autolytic
enzymatic spoilage.

16.  Natural processes which affect fatty acids
and lead to oxidative deterioration of
meat and off-flavours development
 depends : fatty acid composition, the level
of the antioxidant vitamin E ( tocopherol)
and pro oxidants such as the free iron
presence in muscles.
 Hydroperoxides are produced due to the
lipid oxidation of highly unsaturated fatty
acid fractions of membrane
phospholipids, which are susceptible to
further oxidation/ decomposition
 breakage causes secondary reaction
products such as pentanal, hexanal, 4-
hydroxynonenal and malondialdehyde
(MDA) as well as other oxygenated
compounds such as aldehydes, acids and
ketones
loss of colour and nutritive
value are directly related to
carcinogenic and
mutagenic processes
causes

17. ENZYMATICALLY
 termed lipolysis
 by specific enzymes such as
lipases, estarases and
phospholipase (present in the
skin, blood and tissue of
animals)
- lipases split the glycerides
forming free fatty acids which
are responsible for common
off-flavour, frequently
referred to as rancidity
 Occurs in 3 stages
1. cleavage of triacylglycerol:
pancreatic lipase hydrolyses the
1(3) positions of the
triacylglycerols and resulted in
formation of 2 monoacylglycerols
and fatty acids.

18. 2. Acyl migration
3. Cleavage of 1-monoacyl-sn-
glycerol
caused by heme proteins such as
hemoglobin, myoglobin and cytochrome
which are susceptible to oxidation and
produce hydroperoxides
ascorbic acid is the main initiator
of lipid peroxidation in fresh muscle foods
 Non-enzymatically

19.  breakdown of polypeptides are the result
of tissue proteases and is responsible for
flavour and is textural changes in meat
- Proteolytic enzymes are active at low
temperatures (5°C) which lead to
deterioration of meat quality due to
growth of microbes and biogenic amines
production
 The enzymes calpains, cathepsins and
aminopeptidases are found to be
responsible for the post mortem autolysis
of meat through digestion of the z- line
proteins of the myofibril

20.  CANTWELL, M., 2002. Storing fresh fruit and vegetables
,http://postharvest.ucdavis.edu/Produce/Storage/index.html#properties
 Chemical and Functional Properties of Food Components, Third Edition,
Zdzislaw E. Sikorsk
 PHYSICOCHEMICAL CHANGES DURING RIPENING OF RED BANANA,
Asutosh Mohapatra, BhosaleYuvraj K. and S. Shanmugasundaram,Indian
Institute of Crop ProcessingTechnology,Thanjavur, Tamilnadu, 613005, India
 Meat Spoilage Mechanisms and PreservationTechniques: A Critical Review D.
Dave and A.E. Ghaly Department of Process Engineering and Applied Science
Dalhousie University, Halifax, Nova Scotia, Canada
 http://www.fao.org/docrep/v5030e/v5030e07.htm