Food

1. T.Hepzibah
II-M.Sc.,Microbiology
Reg no : 20201232516104
Sri Paramakalyani College
Alwarkurichi
Food Microbiology
Dr.C.MARIAPPAN
Assistant Professor
Department of
Microbiology

2.  Microorganisms are widely used in the food industry to
produce various types of foods that are both nutritious and
preserved from spoilage because of their acid content.
 Microorganisms to carry out fermentation processes,
and for thousands of years mankind has used yeasts,
moulds and bacteria to make food products such as bread,
beer, wine, vinegar, yoghurt and cheese, as well as
fermented fish, meat and vegetables.
 Fermentation is one of the oldest transformation and
preservation techniques for food. This biological
process allows not only the preservation of food but
also improves its nutritional and organoleptic
qualities (relating to the senses ; taste, sight, smell,
touch). A well conducted fermentation will favour useful
flora, to the detriment of undesirable flora in order to
prevent spoilage and promote taste and texture.

3.  The first realisation that microorganisms were
involved in food production processes was in
1837, when scientists discovered the role of
yeast in an alcoholic fermentation.
 Later, when the world renowned French chemist
and biologist Louis Pasteur was trying to
explain what happened during the production
of beer and vinegar in the 1860es, he found
that microorganisms were responsible.
 However, it wasn’t until after the Second World
War that the food industry began to develop
the biotechnological techniques we rely on
today to produce a wide variety of better, safer
foods under controlled conditions

5.  Microbes used:
 Streptococcus lactis or S.cremoris
 Leuconostoc citrovorum or L.dextranicum
 General Points:
 The function of the lactic acid
streptococci is to produce lactic acid that
gives the sour taste and to curdle the
milk.
 The function of the Leuconostoc is to
produce volatile and neutral products
that impart a with characteristic
desirable odour, the starter culture must
contain vigorously growing bacteria,
incubation is performed at 21oC.

6.  Microbes used:
 Sterptococci
 Leuconostoc
 General Points:
 Not strictly a fermented milk but
manufacture resembles that of
cultured butter milk, cream is
inoculated and incubated until the
desired acidity develops.
 Flavour and aroma compounds are
also contributed by the starter
culture.

7.  Microbes used:
 Lactobacillus bulgaricus
 General Points:
 Incubation of inoculated milk at
37oC,but otherwise similar to
cultured butter milk.
 Product differs from commercial
butter milk in having higher acidity
and lacking aroma.

8.  Microbes used:
 L.acidophilus
 General Points:
 Milk for propagation of L.acidophilus
and the bulk milk to be fermented is
sterilized, since this organism is early
overgrown by contaminating
bacteria.
 Incubation is at 37oC.
 Acidity allowed to develop is 0.6-
0.7%

9.  Microbes used:
 Sterptococcus thermophilus
 L.bulgaricus
 General Points:
 Made from milk in which solids are
concentrated by evaporation of some
water and addition of skim milk solids.
 The product has consistency
resembling custard.

10.  Microbes used:
 Streptococcus lactis
 Lactobacillus bulgaricus
 General points:
 A mixed lactic acid and alcoholic
fermentation, bacteria produce acid(0.6
to 1.0% lactic acid) and yeasts produce
alcohol(0.5 to 1.0% ethanol)
 The organisms conglomerate to form
small granules called kefir grains, the
granules are used as starter culture.
 Kefir is made from cow, goat or sheep
milk.

11.  Microbes used:
 Streptococcus lactis
 Lactobacillus bulgaricus
 General Points:
 A mixed acid-alcoholic
fermentation product made from
mares milk in some parts of
Russia.

13.  Microbes involved in early stage:
 Enterobacter cloacae
 Erwinia herbicola
 Intermediate stage:
 Leuconostoc mesenteroides
 Final stage:
 Lactobacillus plantarum
 Starting product:
 Shredded cabbage
 General Points:
 Sauerkraut is a product of natural lactic acid
fermentation of fresh cabbage in the presence of
small amount of salt.
 Sauerkraut is rich in vitamin C and has a mild
laxative action due to dextran content of the
product.

14.  Microorganisms involved in early fermentation:
 L.mesenteroides
 Streptococcus faecalis
 Pediococcus cervisiae
 Later fermentation:
 Lactobacillus brevis
 L.plantarum
 Starting Product:
 Cucumbers
 General Points:
 Pickling is the process preserving food by
anaerobic fermentation in brine and vineger. The
resulting food is called a pickle. This procedure
gives the food a salt or sour taste.

15.  Microbes involved in early stage:
 L.mesenteroides
 Intermediate stage:
 L.plantarum
 L.brevis
 Final stage:
 L.plantarum
 Starting Product:
 Olives

16.  Microbes used:
 Pediococcus cerevisiae
 Micrococcus sp.
 Starting Product:
 Beef and pork
 General Points:
 Sausage define as a food prepared from
chopped and seasoned meats.
 During smoking the temperature of the
product is maintained at 32oC for 12 to16
hours during which time a lactic acid
fermentation develops within the
sausage.

17.  Microbial food cultures preserve food through
formation of inhibitory metabolites such
as organic acid (lactic acid, acetic acid, formic
acid, propionic acid), ethanol, bacteriocins,
etc., often in combination with decrease of
water activity (by drying or use of salt).
 Further, microbial food cultures help to improve
food safety through inhibition of pathogens or
removing of toxic compounds.
 Microbial food cultures also improve the
nutritional value and organoleptic quality of the
food.

18.  The microbial food cultures used in food
fermentation can be divided into three major
groups:
 Bacteria,
 Yeasts and
 Moulds.

19.  Bacterial food cultures can be divided into starter
cultures and probiotics.
 STARTER CULTURES:
 Starter cultures have mainly a technological function in
the food manufacturing. They are used as food ingredients
at one or more stages in the food manufacturing process
and develop the desired metabolic activity during the
fermentation or ripening process. They contribute to the
one or multiple unique properties of a foodstuff especially
in regard to taste, flavour, colour, texture, safety,
preservation, nutritional value, wholesomeness and/or
health benefits.
 PROBIOTICS:
 Probiotics have a functional role, which refers to the
ability of certain microbes to confer health benefits to the
consumer.

20.  The most familiar yeast in food
production, Saccharomyces cerevisiae, has been used
in brewing and baking for thousands of years.
 One of the most common is S. cerevisiae. The same
strain of S. cerevisiae which can also be used in
breadmaking is used to make ale-type beers. It is
known as a top-fermenting yeast because it creates
a foam on the top of the brew.
 Bottom fermenting yeasts, such as S.pastorianus ,
are more commonly used to make lagers. They
ferment more of the sugars in the mixture than top
fermenting yeasts, which gives a cleaner taste.
 Yeasts are also used to produce kefir products, semi-
soft ripened cheeses and fermented soy drinks.

21.  soy sauce has been made by mixing soybeans
and other grains with a mould (Aspergillus
oryzae or A. sojae) and yeast.
 Three main types of cheese rely on moulds
for their characteristic properties:
 Blue cheese,
 Soft ripened cheese and
 Rind-washed cheese.