The presentation highlights the factors and the causal organisms rresponsible for microbial contamination of cereals and its products

1. CEREAL AND
CEREAL
PRODUCTS
Presented by:-
Juhi
L-2019-Bs-307-M

2. CEREALS
• Cereals belong to the Gramineae or the grass family, are one
of the most important sources of carbohydrates in the human
diet.
• The seven principle cereals grown in the world are wheat,
maize, rice, barley, oats, rye and sorghum.
• Wheat, rice and maize are by far the most important cereal
crops on the basis of world-wide production.

3. Factors governing the
microbiology of cereals
• INTRINSIC PARAMETERS
• FACTORS LIKE ACIDITY, WATER ACTIVITY, REDOX
POTENTIAL AND AVAILABLE NUTRIENTS.
• INHERENT PROPERTIES OF FOOD ITSELF.
• EXTRINSIC PARAMETERS
• ENVIRONMENT WHERE THE FOOD IS STORED.
• TEMPERATURE, HUMIDITY AND ATMOSPHERIC
CONDITIONS.

4. microbiology
of cereals
• The microbial flora of wheat, rye, corn, and
related products may be expected to be that
of soil, storage environments, and those
picked up during the processing of these
commodities
• Water activity and temperature are the most
important environmental factors which
determine growth of microbes on cereals and
its products.
• Although these products are high in proteins

5. Microbiol
ogy of
cereals
Moisture content above 12-13 percent
may cause spoilage of cereals.
Little moisture causes mould growth and
high moisture may cause yeast and
bacterial growth.
Common moulds causing spoilage
includes-- Aspergillus, Penicillium,
Mucor, Rhizopus and Fusarium.
Common bacterial species causing
spoilage includes—acetobacter spp,
Micrococci, Bacillus and some coliforms.

6. Microbiol
ogy of
cereals
xerophilic moulds such as Eurotium spp. and
Aspergillus restrictus may grow very slowly at the lower limit
of their water activity range (14%) once they start growing
and metabolizing they will produce water of respiration and
the local water activity will steadily rise allowing more rapid
growth.
Indeed it will allow mesophilic mould spores to germinate
and grow. There is a sequence of observable consequences
of the process of mould growth on cereals starting with a
decrease in germinability of the grain. This is followed by
discolouration, the production of mould metabolites including
mycotoxins, demonstrable increase in temperature (self-
heating), the production of musty odours, caking and a rapid
increase in water activity leading finally to the complete
decay with the growth of a wide range of microorganisms
like bacteria and yeast.

7. Many aerobic spore formers are
capable of producing amylase, which
enables them to utilize flour and
related products as sources of
energy, provided that sufficient
moisture is present to allow growth to
occur. With less moisture, mould
growth occurs and may be seen as
typical mycelial growth and spore
formation. Members of the genus
Rhizopus are common and may be
recognized by their black spores.

8. Cereal
products
CEREAL GRAINS
• If the water activity increases above 0.6, some
of the species of fungi (Aspergillus, Penicillium
and Rhizopus) can grow and cause spoilage
• Yeasts are common on all cereals, although
they represent only a minority of microbial flora.
REFRIGERATED DOUGH (Biscuits,
rolls and pizza dough)
• Susceptible to spoilage (gas formation) from the
growth of psychrotrophic heterolactic species of
Lactobacillus and Leuconostoc which can blow
up the containers.

9. breads
• Commercially produced and properly handled bread
generally lacks sufficient amounts of moisture to allow for
the growth of any organisms except moulds. One of the
most common is Rhizopus stolonifer, often referred to as
the "bread mould." The "red bread mould," Neurospora
sitophila, may also be seen from time to time. Storage of
bread under conditions of low humidity retards mould
growth, and this type of spoilage is generally seen only
when bread is stored in high humidity or when wrapped
while still warm.
• Homemade breads may undergo a type of spoilage
known as ropiness, which is caused by the growth of
certain strains of Bacillus subtilis. The ropiness may be

10. CAKES
• Cakes of all types rarely undergo bacterial spoilage due to their
unusually high concentrations of sugars, which restrict the
availability of water. The most common form of spoilage
displayed by these products is mouldiness. Common sources of
spoilage moulds are any and all cake ingredients, especially
sugar, nuts, and spices.
• Although the baking process is generally sufficient to destroy
these organisms, many are added in icings, meringues,
toppings, and so forth. Also, moulds may enter baked cakes
from handling and from the air. Growth of moulds on the surface

11. Ways to prevent microbial
contamination of cereals
• Generally, this is achieved by
(a) restricting the access of the spoilage mould to the product,
(b) inactivating the fungal material
(c) inhibiting growth of the fungus.
• However, if the fungus gains access to the product the objective turns into controlling its
activity and growth on the food itself.
• The most common way to prevent or control mould growth in foodstuffs is by the use
of antifungal agents.
• At the present time mould spoilage of bread is generally prevented by the addition of
food grade preservatives such as propionic, sorbic and acetic acids and their salts.

12. This Photo by Unknown author is licensed under CC BY-NC-ND.