| Review Article (Open Access) |
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ABSTRACT- Fruits and vegetables are the important source in human life. It should be safe and consists of good shelf
life which can improve the level of consumption of fruits and vegetable among the society. The processing is such a great
parameter which analyses the quality of food. Today fruits and vegetables are susceptible to the growth of microorganism
which may be air borne, soil borne and water borne disease. Enzymes offer potential for many exciting applications for
the improvement of foods. There is still, however, a long way to go in realizing this potential. Economic factors i.e.
achievement of the optimum yields and efficient recovery of desired protein are the main deterrents in the use of enzymes.
Changing values in society with respect to recombinant DNA & protein engineering technologies and the growing need to
explore all alternative food sources may in time make enzyme applications more attractive to the food industry
Key-Words- Enzyme, immobilization, Screening, Food spoilage, Enzymes, Bacterial contamination, Food poisoning,
Perishable foods
INTRODUCTION-
Fruit and vegetables are an important source of health
benefits due to their content of fiber, vitamins and
antioxidant compounds. However, for the antioxidant
compounds many changes occur during harvesting,
preparation and storage of these fruits. During harvesting,
pronounced loss of the microbiological and antioxidant
qualities1. The preservation against oxidation in food
during processing and storage has become an increasing
priority in the food industry. The oxidation is the most
important cause of food deterioration after contamination.
The main reasons are enzymatic browning by the enzymes
such as oxidoreductases, polyphenoloxidase (PPO) and
peroxydase (POD). PPO catalyzes two reactions; the first, a
hydroxylation of monophenols to diphenols, which is
relatively slow and results in colourless products. The
another oxidation of diphenols to quinines, is rapid and
gives colored products2. Site of reactions are take place in the vacuoles and the
enzymes are present in the cytoplasm in the presence of
oxygen. Cutting, shock, loss of firmness lead to the starting
of browning reactions which induce losses or changes of
flavor, odor and nutritional value.3 The role of these
methods is either to inactivate polyphenol oxidase (PPO) or
to avoid contact between the enzyme and its substrate,
either by adding antioxidants or by maintaining the
structural integrity of the food. To prevent oxidation by
chemical controlled atmosphere and coating treatments.4
Food spoilage is a metabolic process that causes foods to be
undesirable or unacceptable for human consumption due to
changes in sensory characteristics. Spoiled foods may be
safe to eat, i.e. they may not cause illness because there are
no pathogens or a toxin present, but changes in texture,
smell, taste, or appearance cause them to be rejected. Some
ecologists have suggested these noxious smells are
produced by microbes to repulse large animals, thereby
keeping the food resource for themselves.5 Food loss, from
farm to fork, causes considerable environmental and
economic effects. Fresh produce and fluid milk each
accounted for nearly 20% of this loss while lower
percentages were accounted for by grain products (15.2%),
caloric sweeteners (12.4%), processed fruits and vegetables
(8.6%), meat, poultry and fish (8.5%), and fat and oils
(7.1%)6. Some of this food would have been considered
still edible but was discarded because it was perishable,
past its sell-by date, or in excess of needs. There are also environmental and resource costs associated with food
spoilage and loss. If 20% of a crop is lost, then 20% of the
fertilizer and irrigation water used to grow that crop was
also lost. Shelf life of a food is the time during which it
remains stable and retains its desired qualities. The wide
array of available dairy foods challenges the
microbiologist, engineer, and technologist to find the best
ways to prevent the entry of microorganisms, destroy those
that do get in along with their enzymes, and prevent the
growth and activities of those that escape processing
treatments. Troublesome spoilage microorganisms include
aerobic psychrotrophic Gram-negative bacteria, yeasts,
molds, heterofermentative lactobacilli, and spore-forming
bacteria. Psychrotrophic bacteria can produce large
amounts of extracellular hydrolytic enzymes, and the extent
of recontamination of pasteurized fluid milk products with
these bacteria is a major determinant of their shelf life.
Fungal spoilage of dairy foods is manifested by the
presence of a wide variety of metabolic by-products,
causing off-odors and flavors, in addition to visible changes
in color or texture5-6.
Chemical treatments will be presented by underlining the
main action of each molecule (antioxidants, acidifying,
agents of firmness or chelating Enzymes are proteins that
act as catalysts in all living organisms- microorganisms,
plants, animals, and humans. Catalysts are compounds that
increase the rate of chemical reactions in biological
systems. Very small quantities of enzymes can increase the
rate of reactions up to ten million times. Enzymes operate
within a narrow set of conditions, such as temperature and
pH (acidity), and are subject to inhibition by various
means.
Application of Enzyme in Food Production-
The main source of Enzymes which is obtained from edible
plants and the tissues of food animals, microorganisms,
have been used for centuries in food manufacturing. A
natural enzyme which is a mixture from the stomach of
calves or other domestic animals that has been used in
cheese making for centuries. Rennet contains a protease
enzyme that coagulates milk, causing it to separate into
solids (curds) and liquids (whey) and also wine enzyme.
Modern Production of Food Enzymes-
The microorganisms are the most chief source of
commercial enzymes. Although microorganisms do not
contain the same class of enzymes such as plants or
animals, a microorganism can usually be found that
produces a related enzyme that will catalyze the desired
reaction. For the enzyme production it has microorganisms
for the production of enzymes through natural selection and
classical breeding techniques.
The branch of science which provides the tools to have a
genetic sequence from a plant, animal, or a
micro-organism, from which commercial scale enzyme
production is not adequate, to be transferred to a
micro-organism that has a safe history of enzyme
production for food use. Although the production organism
is genetically modified (GM) the enzyme it produces is not.
Enzymes produced through biotechnology are identical to
those found in nature. In addition, enzymes produced by
micro-organisms are extracted and purified before they are
use in food manufacturing. Genetically modified (GM)
microorganisms are useful from a commercial standpoint
but would not survive in nature.
The safety of the source organism is the primary
consideration in assessing an enzyme product. Food
animals and edible plants have a history of safe use as
sources of enzymes for the food industry. A micro-organism
used for food enzyme production must be
well-characterized and not produce any toxins, pathogens
or antibiotics.
The safety assessment of an enzyme produced by a
genetically modified microorganism expands on the
approach above. In this case, Health Canada also reviews
the technique used to transfer the genetic material along
with the safety of the genetic material that has been
introduced and expressed in the production microorganism.
The genome of the production microorganism must be fully
characterized for a safety review to be completed.
Canning can be a safe and personally rewarding way to
preserve quality food at home. A Canning favorite and
special product to be enjoyed by family and friends often is
a fulfilling experience and a source of pride for many
people. Canning may not be the least expensive way of
obtaining every type of food and costs of equipment,
energy, and time must be considered.
However, the main objective of canning is to preserve the
food by the application of heat so that it can be safely eaten
at a later time. Safety of the consumer is the primary
concern when food is canned. It is also important to
achieve acceptable quality in the final product and to retain
as much of the nutritive value of the food as possible.
The potential advantages of home canning are lost:
1) When you start with poor quality fresh foods
2) When jars fail to seal properly
3) When food spoils
4) When flavors, texture, color, and nutrients deteriorate
during prolonged storage in warm, bright light conditions.
How Canning Preserves Foods
The high percentage of water in most fresh foods makes
them very perishable. They spoil or lose their quality for
several reasons:
* Growth of undesirable microorganisms, like:
Bacteria, molds, and yeasts
* Activity of food enzymes
* Reactions with oxygen
* Moisture loss
Microorganisms live and multiply quickly on the surfaces
of fresh food and on the inside of bruised, insect-damaged,
and diseased food. Oxygen (O2) and enzymes are present throughout fresh food tissues. Proper canning practices
minimize the effects of these microorganisms.
They include:
* Carefully selecting and washing fresh food
* Peeling some fresh foods
* Hot packing many foods
* Adding acids (lemon juice or vinegar) to some
foods
* Using acceptable jars and self-sealing lids
* Processing jars in a boiling-water or pressure
canner for the correct period of time
When these practices are followed along with
recommended methods, they control potential spoilage by
removing oxygen, destroying enzymes, destroying and/or
preventing the growth of undesirable bacteria, yeasts, and
molds, and by helping form a high vacuum in jars. Good
vacuums form tight seals which keep the food in the jars
and keep air and microorganisms from reentering.
The most critical step in ensuring safety in canning is
processing in a boiling-water bath or pressure canner. This
is what destroys microorganisms and creates the desired
vacuum for a good seal. Both a high temperature and
sufficient time is required to be certain of adequate heat
processing. This ensures that all parts of the food being
canned have received enough heat to reduce the number of
microorganisms to an extremely small level. A safe food
with a long storage life is produced. The complete
destruction of every microorganism would result in a
product with unacceptable quality and little nutritional
value. A best process is that which has a maximum effect
on spoilage organisms and minimal effect on quality.
Fruits and vegetables are very important food commodities
not only in India but all over the world. India, which is the
second most populated country of the world, is still
struggling to achieve self-sufficiency to feed about 800
million people. For this purpose, fruits and vegetables have
got their specific importance to provide a balance and
healthy diet to the people. India is the second largest
producer of vegetables and fourth largest producer of fruits
in the world. Though India is producing adequate quantities
of fruits and vegetables, yet on account of losses in the field
as well as in storage, they become inadequate.
Fresh fruits and vegetables are perishable and highly prone
to these losses because they are composed of living tissues.
These tissues must be kept alive and health throughout the
process of marketing. These are composed of thousands of
living cells which require care and maintenance. Therefore,
the reduction of post-harvest loss of fruit and vegetables is
a complementary means for increasing production. It may
not be necessary to considerably step up the production of
fruits and vegetables with the growing demand if the
post-harvest loss is reduced to a great extent. The cost of
preventing losses after harvest in general is less than
preventing a similar additional amount of fruit and
vegetable crop of the same quality7-8. Products range from
those that are readily spoiled by microorganisms to those
that are shelf stable for many months, and the spoilage rate
can be influenced by factors such as moisture content, pH,
processing parameters, and temperature of storage.
Food, fruits and vegetables are also prone to microbial
spoilage caused by fungi, bacteria, yeast and moulds. A
significant portion of losses of fruits and vegetables during
post-harvest period is attributed to diseases caused by fungi
and bacteria. The succulent nature of fruits and vegetables
makes them easily invaded by these organisms. Besides
attacking fresh fruits and vegetables, these organisms also
cause damage to canned and processed products. Many
serious post-harvest diseases occur rapidly and cause
extensive break down of the commodity, sometimes
spoiling the entire package. It is estimated that 36 % of the
vegetable decay is caused by soft rot bacteria. Similarly
fruit rot in aonla and other soft fruits caused by fungi is also
very destructive. As far as vegetables are concerned,
naturally the source of infection is from the field, water
used for cleaning the surface, contact with equipment and
storage environment. The most common pathogens causing
rots in vegetables and fruits are fungi such as Alternaria,
Botrytis, Diplodia, Monilinia, Phomopsis, Rhizopus,
Pencillium, Fusarium, etc. Among bacteria Ervinia,
Pseudomonas, etc. cause extensive damage. High
temperature and relative humidity favour the development
of post-harvest decay organisms. More acidic tissue is
generally attacked by fungi, while fruits and vegetables
having pH above 4.5 are more commonly attacked by
bacteria, ego bacterial soft rot of potato caused by
Ceratocystis, fimbriation, water soft rot of carrot by
Sclerotinia sclerotiorum etc. In India, there is a vast scope
for growing fruit and vegetable throughout the year in one
or other part of the country because the climatic conditions
are highly suitable for growing various types of fruits and
vegetables. Fruit and vegetable is highly perishable but
most important commodity for human diet due to their high
nutritional value. They are the cheapest and other source of
protective food supplied in fresh or processed or preserved
form throughout the year for human consumption. Hence
the national picture will improve significantly. Fruit and
vegetable are available in surplus only in certain seasons
and availability in different regions. In peak season due to
improper handling practices, marketing, storage problems
around 20-25% fruit and vegetable are spoilt in various
stages. Fruit and vegetable are living commodities as they
respire. Hence, proper post harvest management handling
and processing is required in horticulture crops. A variety
of fresh fruit and vegetable in India can be made available
in plenty due to favorable agro-climatic situations. Hence
there is no derth for raw material processing. Product
profile being developed in India at present is limited to few
fruit and vegetable like mango, pineapple, grapes etc. But
there is a wider potentiality for processing of papaya,
banana, jack, guava, aonla, carambola and other minor
fruits. Similarly there is a greater scope for processing
cauliflower, carrot, bitter-gourd onion, garlic, watermelon,
muskmelon etc. Proper handling, packaging, transportation and storage reduce the post-harvest losses of fruit and
vegetables. For every one percent reduction in loss will
save 5 million tons of fruit and vegetable per year.
Processing and preservation technology helps. There are
about 4000 small and large scale processing units in the
country which process only about 2.5% of the total fruit
and vegetable as against 40-85% in developed countries.
Food spoilage microorganisms Chemical reactions that
cause offensive sensory changes in foods are mediated by a
variety of microbes that use food as a carbon and energy
source. These organisms include prokaryotes (bacteria),
single-celled organisms lacking defined nuclei and other
organelles, and eukaryotes, single-celled (yeasts) and
multicellular (molds) organisms with nuclei and other
organelles. Some microbes are commonly found in many
types of spoiled foods while others are more selective in the
foods they consume; multiple species are often identified in
a single spoiled food item but there may be one species (a
specific spoilage organism, SSO) primarily responsible for
production of the compounds causing off odors and flavors.
Within a spoiling food, there is often a succession of
different populations that rise and fall as different nutrients
become available or are exhausted. Some microbes, such as
lactic acid bacteria and molds, secrete compounds that
inhibit competitors.9
Spoilage microbes are often common inhabitants of soil,
water, or the intestinal tracts of animals and may be
dispersed through the air and water and by the activities of
small animals, particularly insects. It should be noted that
with the development of new molecular typing methods,
the scientific names of some spoilage organisms,
particularly the bacteria, have changed in recent years and
some older names are no longer in use. Many insects and
small mammals also cause deterioration of food but these
will not be considered here.
Yeasts are a subset of a large group of organisms called
fungi that also includes molds and mushrooms. They are
generally single-celled organisms that are adapted for life
in specialized, usually liquid, environments and, unlike
some molds and mushrooms, do not produce toxic
secondary metabolites. Yeasts can grow with or without
oxygen (facultative) and are well known for their beneficial
fermentations that produce bread and alcoholic drinks.
They often colonize foods with a high sugar or salt content
and contribute to spoilage of maple syrup, pickles, and
sauerkraut. Fruits and juices with a low pH are another
target, and there are some yeast that grows on the surfaces
of meat and cheese.
Yeasts spoilage Species-
Zygosaccharomyces and related genera tolerate high sugar
and high salt concentrations and are the usual spoilage
organisms in foods such as honey, dried fruit, jams and soy
sauce. They usually grow slowly, producing off-odors and
flavors and carbon dioxide that may cause food containers
to swell and burst.
Hansenii can grow at salt concentrations upto 24%,
accounting for its frequent isolation from salt brines used
for cured meats, cheeses, and olives example in salad
dressings.
Saccharomyces spp. a are used for their role in production
of bread and wine which spoil wines and other alcoholic
beverages by producing gassiness, turbidity and associated
with hydrogen sulfide and acetic acid. Some species grow
on fruits, including yogurt containing fruit, and some are
resistant to heat processing.
Dekkera/Brettanomyces are mostly involved in spoilage of
fermented foods, including alcoholic beverages and some
dairy products. They can produce volatile phenolic
compounds responsible for off-flavors.
Molds are filamentous shape fungi that do not produce
large number of fruiting bodies like mushrooms. Molds are
very important for recycling dead plant and animal remains
in nature but also attack a wide variety of foods and other
materials useful to humans. They are well adapted for
growth on and through solid substrates, generally produce
airborne spores, and require oxygen for their metabolic
processes.10 Most molds grow at a pH range of 3 to 8 and
some can grow at very low water activity levels (0.7–0.8)
on dried foods. Spores can tolerate harsh environmental
conditions but most are sensitive to heat treatment. An
exception is Byssochlammys, whose spores have a D value
of 1–12 minutes at 90ºC. Different mold species have
different optimal growth temperatures, with some able to
grow in refrigerators. They have a diverse secondary
metabolism producing a number of toxic and carcinogenic
mycotoxins. Some spoilage molds are toxigenic while
others are not. Spoilage molds can be categorized into four
main groups: Zygomycetes are considered relatively
primitive fungi but are widespread in nature, growing
rapidly on simple carbon sources in soil and plant debris,
and their spores are commonly present in indoor air.
Generally they require high water activities for growth and
are notorious for causing rots in a variety of stored fruits
and vegetables, including strawberries and sweet potatoes.
Some common bread molds also are zygomycetes. Some
zygomycetes are also utilized for production of fermented
soy products, enzymes, and organic chemicals. The most
common spoilage species are Mucor and Rhizopus.
Zygomycetes are not known for producing mycotoxins but
there are some reports of toxic compounds produced by a
few species. Penicillium and related genera are present in
soils and plant debris from both tropical and Antarctic
conditions but tend to dominate spoilage in temperate
regions. They are distinguished by their reproductive
structures that produce chains of conidia. Although they
can be useful to humans in producing antibiotics and blue
cheese, many species are important spoilage organisms,
and some produce potent mycotoxins (patulin, ochratoxin,
citreoviridin, penitrem). Penicillium spp. cause visible rots
on citrus, pear, and apple fruits and cause enormous losses
in these crops. They also spoil other fruits and vegetables,
including cereals. Some species can attack refrigerated and processed foods such as jams and margarine. A related
genus, Byssochlamys, is the most important organism
causing spoilage of pasteurized juices because of the high
heat resistance of its spores. Aspergillus and related molds
generally grow faster and are more resistant to high
temperatures and low water activity than Penicillium spp.
and tend to dominate spoilage in warmer climates. Many
aspergilla produce mycotoxins: aflatoxins, ochratoxin,
territrems, cyclopiazonic acid. Aspergilli spoil a wide
variety of food and nonfood items (paper, leather, etc.) but
are probably best known for spoilage of grains, dried beans,
peanuts, tree nuts, and some spices. Other molds, belonging
to several genera, have been isolated from spoiled food.
These generally are not major causes of spoilage but can be
a problem for some foods. Fusarium spp. cause plant
diseases and produce several important mycotoxins but are
not important spoilage organisms. However, their
mycotoxins may be present in harvested grains and pose a
health risk. Bacteria Spore-forming bacteria are usually
associated with spoilage of heat-treated foods because their
spores can survive high processing temperatures. These
Gram-positive bacteria may be strict anaerobes or
facultative (capable of growth with or without oxygen).
Some spore-formers are thermophilic, preferring growth at
high temperatures (as high as 55ºC). Some anaerobic
thermophiles produce hydrogen sulphide
(Desulfotomaculum) and others produce hydrogen and
carbon dioxide (Thermoanaerobacterium) during growth on
canned/ hermetically sealed foods kept at high
temperatures, for example, soups sold in vending machines.
Other thermophiles (Bacillus and Geobacillus spp.) causes
a flat sour spoilage of high or low pH canned foods with
little or no gas production, and one species causes ropiness
in bread held at high ambient temperatures. Mesophilic
anaerobic bacteria, growing at ambient temperatures, cause
several types of spoilage of vegetables (Bacillus spp.);
putrefaction of canned products, early blowing of cheeses,
and butyric acid production in canned vegetables and fruits
(Clostridium spp.); and "medicinal" flavors in canned
low-acid foods (Alicyclobacillus)11. Psychrotolerant spore
formers produce sickly and gas odors in chilled meats and
brine-cured hams (Clostridium spp.) while others produce
off-odors and gas in vacuum-packed, chilled foods and
milk (Bacillus spp.). Lactic acid bacteria (LAB) are a group
of Gram-positive bacteria, including species of
Lactobacillus, Pediococcus, Leuconostoc and Oenococcus,
some of which are useful in producing fermented foods
such as yogurt and pickles. However, under low oxygen,
low temperature, and acidic conditions, these bacteria
become the predominant spoilage organisms on a variety of
foods. Undesirable changes caused by LAB include
greening of meat and gas formation in cheeses (blowing),
pickles (bloater damage), and canned or packaged meat and
vegetables. Off-flavors described as mousy, cheesy, malty,
acidic, buttery or liver-like may be detected in wine, meats,
milk, or juices spoiled by these bacteria. LAB may also
produce large amounts of an exo-polysaccharide that causes
slime on meats and ropy spoilage in some beverages.
Spoilage of dairy products-
Milk is an excellent medium for growth for a variety of
bacteria. Spoilage bacteria may originate on the farm from
the environment or milking equipment or in processing
plants from equipment, employees, or the air. LABS are
usually the predominant microbes in raw milk and
proliferate if milk is’nt cooled adequately. When
populations number reach about 106 cfu/ml, off-flavors
develop in milk due to production of lactic acid and other
compounds. Refrigeration suppresses growth of LAB
media and within 1 day psychrophilic bacteria (Enterobacter,
Alcaligenes, Pseudomonas, and some spore-formers)
grow and can eventually produce rancid odors through the
action of lipases and bitter peptides from protease action.
Pasteurization kills the psychrophiles and mesophilic
bacteria (LAB), but heat-tolerant species (Alcaligenes,
Microbacterium, and the sporeformers Bacillus and
Clostridium) survive and may later cause spoilage in milk
or other dairy products12. Immediately following
pasteurization, bacterial counts are usually pH of 5.0–6.5
and a moisture content of 50–80% may be spoiled by
Pseudomonas, Alcaligenes, and Flavobacterium.
Clostridium sporogenes has been found in spoiled
processed cheese, where it produces gas holes and
off-flavors.Yeasts and molds are the main spoilage
organisms found in cultured milks (yogurt, sour cream and
buttermilk) because the higher acidity in these products
inhibits many bacteria. Pseudomonas, yeasts and molds can
spoil butter and “light” butters. Since the light butters have
higher moisture content than butter, they can support more
microbial growth. Cream may become rancid when
populations of Pseudomonas and Enterobacter
proliferate15-16.
Prevention from food spoilage microorganism-
Many food products are perishable by nature and require
protection from spoilage during their preparation, storage
and distribution to give them desired shelf-life. Because
food products are now often sold in areas of the world far
distant from their production sites, the need for extended
safe shelf-life for these products has also expanded. The
development of food preservation processes has been
driven by the need to extend the shelf-life of foods. Food
preservation is a continuous fight against microorganisms
spoiling the food or making it unsafe. Several food
preservation systems such as heating, refrigeration and
addition of antimicrobial compounds can be used to reduce
the risk of outbreaks of food poisoning; however, these
techniques frequently have associated adverse changes in
organoleptic characteristics and loss of nutrients13. Within
the disposable arsenal of preservation techniques, the food
industry investigates more and more the replacement of
traditional food preservation techniques by new
preservation techniques due to the increased consumer
demand for natural, tasty, nutritious, and easy-to-handle food products. Improvements in the cold distribution chain
have made international trade of perishable foods possible,
but refrigeration alone cannot assure the quality and safety
of all perishable foods. The most common classical
preservative agents are the weak organic acids, for example
acetic, lactic, benzoic and sorbic acid. These molecules
inhibit the outgrowth of both fungal and bacterial cells and
sorbic acid is also reported to inhibit the outgrowth and
germination of bacterial spores. In the production of food
it’s crucial that proper measures are taken to
ensure the safety and stability of the product
during its whole shelf-life. In particular, modern consumer
trends and food legislation have made the successful
attainment of this objective much more of a challenge to
the food industry. Firstly, consumers require more high
quality, preservative-free, safe but mildly processed foods
with extended shelf-life. For example, this may mean that
foods have to be preserved at higher pH values and have to
be treated at mild-pasteurization rather than sterilization
temperatures. As acidity and sterilization treatments are
two crucial factors in the control of outgrowth of
pathogenic spore-forming bacteria, such as C. botulinum,
addressing this consumer need calls for innovative
approaches to ensure maintenance of products. Secondly,
legislation has restricted the use and permitted levels of
some currently accepted preservatives in different foods.
This has created problems for the industry because the
susceptibility of some microorganisms to most currently
used preservatives is falling. An increasing the numbers of
consumers prefer minimally processed foods, prepared
without chemical preservatives. Many of these ready-to-eat
and novel food types represent new food systems with
respect to health risks and spoilage association. Against this
background, and relying on improved understanding and
knowledge of the complexity of microbial interactions,
recent approaches are increasingly directed towards
possibilities offered by biological preservation. The high
salt concentration in the serum-in-lipid emulsion of butter
limits the growth of contaminating bacteria to the small
amount of nutrients trapped within the droplets that contain
the microbes. However, psychrotrophic bacteria can grow
and produce lipases in refrigerated salted butter if the
moisture and salt are not evenly distributed. When used in
the bulk form, concentrated (condensed) milk must be kept
refrigerated until used. It can be preserved by addition of
about 44% sucrose and/or glucose to lower the water
activity below that at which viable spores will germinate
(aw 0.95). Lactose, which constitutes about 53% of the non
fat milk solids, contributes to the lowered water activity.
When canned as evaporated milk or sweetened condensed
milk, these products are commercially sterilized in the cans,
and spoilage seldom occurs. Microbial growth and enzyme
activity are prevented by freezing. Therefore, microbial
degradation of frozen desserts occurs only in the
ingredients used or in the mixes prior to freezing. Chemical
preservatives Chemical preservatives are substances which
are added to food just to retard inhibit or arrest the activity of microorganisms such as fermentation, putrefaction and
decomposition of the food14-15. Commonly used
preservatives include, common salt, sugar, dextrose, spices,
vinegar, ascorbic acid, benzoic acid and its salt, SO2 and
the salts of sulphuric acid, nitrates, sorbic acid and its salts,
propionic acid and its salts, lactic acid and its salts.
Features of Potassium metabisulphate-
It releases the SO2 and it is unstable and it’s used for the
fruit which have non water solvent pigment, it is used in
naturally coloured juices such as jamun, phalsa because
they have the anthocynin pigment. Hydrogen Sulphide has
an unpleasant smell and also forms a black compound with
the base plate of containers. The requirement of 350 ppm
KMS is mostly use in fruit juice products.
Features of Sodium benzoate-
A mixture of benzoic acid which is added in water which
delays the fermentation in the juices, commonly it is used
in the anthocynin pigment. It is used in 750 ppm Sodium
benzoate is mostly used in fruit juices, squashes and
cordials.
CONCLUSION-
The microorganisms like fungi and bacteria which spoil
food by growing in it and producing substances that change
the colour, texture and odour of the food. Eventually the
food will be not beneficial for human consumption. When
food is kept with a furry growth and becomes pulpy to
produce bad smells which cause the spoilage by growth of
moulds and yeasts. Spoilage due to moulds and yeasts such
as souring taste of milk, growth of mould on bread and
rotting of fruit and vegetables. These organisms are rarely
harmful to humans, but bacterial contamination is often
more severe because the food does not always look bad,
even if it is severely infected. When microorganisms get
present in food, they use the nutrients which are present in
it and their numbers rapidly increase. They change the
food’s smell and prepare new compounds that can be
harmful to humans. Food spoilage directly affects the
colour, taste, odour and consistency or texture of food, and
it may become dangerous to eat. The bad odour or smell
coming from food is an indication that it may be unsafe.
The chief factor for food security is reduction in food
spoilage. Through spoilage the food become deteriorates
and it is not edible to humans or its quality of edibility
becomes reduced.
REFERENCES
| International Journal of Life-Sciences Scientific Research (IJLSSR) Open Access Policy Authors/Contributors are responsible for originality, contents, correct references, and ethical issues. IJLSSR publishes all articles under Creative Commons Attribution- Non-Commercial 4.0 International License (CC BY-NC). https://creativecommons.org/licenses/by-nc/4.0/legalcode |
| How to cite this article: SahuM, Bala S: Food Processing, Food Spoilage and their Prevention: An Overview. Int. J. Life. Sci. Scienti. Res., 2017; 3(1): 753-759. DOI:10.21276/ijlssr.2017.3.1.1 Source of Financial Support: Nil, Conflict of interest: Nil |