Cereal crops can be defined as any plants cultivated for seed as human food, although they tend to include only crops closely related to grass.

1. Mr. Taj Mohammad
Assistant professor
Department of home science
Indian Institute of Food Science & Technology
Aurangabad
Contamination and spoilage of cereals,
grains and cereal products.

2. Microbial spoilage and preservation of cereal
and cereal products
 Cereal grains, such as wheat, corn, rye, oat, rice, etc., are
important nutrients and energy sources for humans.
 Cereal grains are the most commonly consumed food
group worldwide and they are grown on about 60% of the
cultivated land in the world.
 Cereals are consumed in various forms in the food
industry.
 Cooked cereals are eaten directly after cooking (rice,
maize).

3. Cont….
 Bread is usually made from flours of wheat and rye
by yeast fermentation.
 Manufactured dried cereal products produced from
wheat, maize, oats, and rice.
 However, cereals are also used to produce dough,
batter, pasta, noodles, pastries, cake, etc.
 These products are subject to physical, chemical,
and microbiological spoilage that affects the taste,
aroma, leavening, appearance, and overall quality of
the end consumer product.

5. Contamination source of cereal
products
 Air and dust
 Soil
 Water
 Insects
 Rodents
 Birds
 Animals
 Humans
 environmental conditions (such as drought, rainfall,
temperature, and sunlight)
 harvesting and processing equipment
 Contaminated equipment and unsanitary handling.
 Storage condition and storage temperature
 Shipping containers

6. Spoilage of cereal
 Cereals usually contain 70–75% carbohydrates, 8–15% protein,
fat, fiber, vitamins, and minerals with near-neutral pH and hence
are susceptible to microbial growth leading to spoilage.
 Microbial growth is normally prevented due to sufficiently low
water activity (i.e. below 0.70).
 Mold is considered the primary organism for causing spoilage in
cereal.
 Bacteria can also cause spoilage of cereals, but yeasts cause few
spoilage problems.
 The most commonly associated bacterial families with cereals are
Bacillaceae, Micrococcaceae, Lactobacillaceae, and
Pseudomonadaceae.
 Yeast that is found in cereal includes Candida, Cryptococcus,
Pichia, Sporobolomyces, Rhodotorula, Trichosporon
 Mold spores in cereals and flour are chiefly Aspergillus,
Penicillium, Alternaria, Mucor, Cladosporium, Fusarium,
Helminthosporium, Cladosporium, and Rhizopus.
 Mycotoxins are the toxic secondary metabolites produced by mold
that is found in cereal crops under favorable growth conditions.

7. Some examples of mycotoxin and the mold that produce them
are:

8. Some of the microorganisms and the defects caused by them in
cereals are

9. Preservation of
cereal

10. Pesticides
 The chemicals used to prevent and control the
occurrence of pests causing harm to crops that
includes including fungicides, herbicides, and
insecticides.
 The pesticides provide crop protection from the
damaging influences of pests, higher yields, and
better quality of cereals.

11. Drying
 Grains are dried to a low moisture content until
the moisture content level guaranteeing safe
storage conditions( i.e. equivalent to <0.70 aw)
 Drying helps to create unfavorable conditions for
mold growth and the proliferation of insects.

12. Debranning
 Debranning is a process during which the bran
layers are removed.
 This technique is found to improve the yield and
degree of refinement of flour, as well as allowing
the production of good quality grains.
 After debranning, grains are found to be
microbiologically purer as the total microbial
contamination was reduced up to 87%.

13. Chlorine and hypochlorite
 The chlorine-based methods are widely used in
cereal for microbial control.
 Sodium hypochlorite has also been used
frequently.

14. Irradiation
 It is a process that involves exposing cereal food
to a certain amount of ionizing radiation.
 Irradiation has been successfully used for the
control of microorganisms on cereals and flours.

15. Ozone
 Ozone (O3) is the triatomic oxygen formed by the
addition of a free radical of oxygen to molecular
oxygen.
 The use of ozone as a fungicide for
decontamination of cereal grains has been
investigated in several studies.

16. Microwave (MW) treatment
 Microwaves are electromagnetic waves with
frequencies within 300 MHz to 300 GHz.
 It is widely used for the inactivation of
microorganisms associated with cereal grains.
 Microwave energy can also be used for the
control of stored grain insects.

17. Pulsed ultraviolet (UV) light
treatment
 Pulsed UV light treatment is a non-thermal
technology that can be used both for
decontamination of foods and food contact
surfaces.
 Pulsed UV light is considered to be more efficient
in microbial inactivation than UV light, offering
safer and faster decontamination.
 The antimicrobial efficacy of this technology
against microorganisms occurring on stored
cereal grains has been studied.

18. Non-thermal (cold) plasma
 Cold plasma can be generated at atmospheric as
well as low pressure and consists of UV photons,
neutral or excited atoms and molecules, negative
and positive ions, free radicals, and free
electrons.
 As a non-thermal process, cold plasma does not
cause damage to the food product after
treatment.
 This process has shown the inactivation of two
pathogenic fungi, Aspergillus spp. and Penicillium
spp. in cereals.
 This process has also shown the inactivation of
Geobacillus stearothermophilus and Bacillus

19. Organic acid
 Organic acids are used as food additives and
preservatives and can also be used for grain
preservation.
 Adding organic acids (acetic, citric, lactic, or
propionic) or a combination of organic acids and
NaCl added to tempering water is found to reduce
microbial contamination in cereal.
 It was reported that the combination of lactic acid
(5.0%) and NaCl (52%) was the most effective
against aerobic plate count and

20. Spoilage of cereal
products

21. Flour spoilage
 The moisture content of the flour is less than 13% that
prevents the growth of microorganisms.
 However, the addition of water to flour tends to make it
susceptible to microbial growth in flour.
 The molds found in flours are mostly Eurotium species
and Aspergillus candidus. The molds produce typical
mycelium in flour.
 The spoilage flour contains many psychrotrophs, flat
sour bacteria, and thermophilic spore-forming bacteria
such as Acetobacter spp, Bacillus spp, Lactic acid
bacteria.
 If acid-forming bacteria are present in flour, acid
fermentation occurs followed by alcoholic fermentation
by yeasts and then acetic acid by Acetobacter spp.
 Bacillus spp is known for producing lactic acid, gas, and

22. Preservation of flour
 Flour can be preserved in an air-tight container
for 6-10 months and a vacuum-packed container
for 1-2 years.
 It can also be preserved in the freezer.
 It can also be preserved by filling it in oxygen
absorbers containers for a long shelf-life of flour.

23. Bakery product
 There are a wide variety of bakery products including leavened and
unleavened bread, rolls, buns, croissants, muffins, cakes, doughnuts,
pastries, pancakes, waffles, biscuits, cupcakes, and sweet rolls.
 The nutrient content of bakery products includes carbohydrates,
proteins, lipids, vitamins, and minerals.
 Therefore, bakery products are susceptible to microbial growth due to
their high nutrient content and also because the most common factor of
these products is water.
 The most famous bakery product that is consumed worldwide for a very
long period is bread.
 The ambient temperatures, product pH levels between 5.4 and 7.5, and
water activity in the range of 0.75–0.98 promote spoilage of baked
cereal foods with mold, yeast, and rope bacteria.
 The most common source of microbial spoilage of bread is mold growth.
The bacterial spoilage condition is known as ‘rope’ caused by the growth
of the Bacillus species. The least common of all types of microbial
spoilage in bread is that caused by certain types of yeast.
 Typical genera of mold involved in spoilage are Penicillium, Aspergillus,
Cladosporium, Fusarium, Monilia, Endomyces, Rhizopus, and Mucor.
 Yeasts that can cause surface spoilage of bakery products include
Saccharomyces, Debaryomyces, Kluyveromyces, Pichia, Candida, and
Zygosaccharomyces.

24. Some defects observed on bread due to microbial spoilage are

25. Cont….
 Pastry spoilage is similar to bread, but the pastry
filling or topping is more susceptible to microbial
growth.
 Pastries include cakes and baked shells filled
with cream, or sauces that contain egg or milk
products that support the growth of spoilage-
causing bacteria.
 However, due to high sugar concentration,
pastries are rarely spoiled by bacteria.
 The most common spoilage is caused by mold.
They cause sugar fermentation and make them
sour in taste with an alcoholic odor.

26. Preservation of bakery products
 Several methods have been used to control mold growth on
bakery products that include reformulation, freezing, and the
use of preservatives.
 Reformulation involves a reduction of available water in
bakery products. Reduction in product aw can be achieved by
dehydration, either through evaporation or freeze-drying or by
high osmotically active additives e.g., sugars and salts,
incorporated directly into the food.
 Freezing has been used for the long-term preservation of
bakery products particularly, cream-filled products.
 Cakes, cookies, shortcakes, and pancakes are commonly
frozen and marketed in frozen form.
 Preservatives are most commonly used to control mold growth
in baked goods.
 Chemical and natural permitted chemical preservatives which
act as mold inhibitors in bread include acetic, sorbic, propionic
acids and their salts. Natural food preservatives, such as

27. Pasta and noodle spoilage
 Both pasta and noodle manufacture includes no
cooking step, microbial contamination may occur
during the mixing and drying process.
 They are stored and distributed in dry form so
spoilage is rare.
 During the manufacturing process, it may spoil
from bacterial or fungal growth.
 For example, Enterobacter (Aerobacter) cloacae
have been found in pasta and noodle that causes
gas production.

28. Preservation of pasta and noodle
 Pasta and noodles are produced by mixing milled
wheat flour and water to form an unleavened
dough, followed by kneading and shaping.
 Pasta and noodle are packed in sealed plastic to
extend their shelf-life.
 Pasta should be dried or refrigerated promptly
after manufacture.
 Some of the chemical additives used to inhibit
microbial growth are Potassium bromate, benzoyl
peroxide, calcium propionate, sodium benzoate,
sodium dehydroacetate, sodium polyacrylate,
phosphate salts BHA, BHT.

29. THANKS