Transcript Citric acid - Lectures For UG-5

Production of
Fermented
foods and
Beverages
Food Biotechnology
 Fermented food products
 Alcoholic beverages
 Production of organic acids
 Production of amino acids
 Food flavors
 Single cell protein
Lactic acid bacteria (LAB)
 A clade of Gram-positive, acid-tolerant, generally non-sporulating
rods or cocci
 Usually found in decomposing plants and lactic products, produce
lactic acid as the major metabolic end-product of carbohydrate
fermentation.
 This trait has, links LAB with food fermentations, as acidification
inhibits the growth of spoilage agents.
 Bacteriocins are produced by several LAB strains and provide an
additional hurdle for spoilage and pathogenic microorganisms.
 Generally recognized as safe (GRAS) status, due to their ubiquitous
appearance in food and their contribution to the healthy microflora
of human mucosal surfaces.
Lactic acid bacteria
 Common genera include
 Lactobacillus
 Leuconostoc
 Pediococcus
 Lactococcus
 Streptococcus
 Aerococcus
 Carnobacterium
 Enterococcus
 Oenococcus
 Sporolactobacillus
 Tetragenococcus
 Vagococcus
 Weisella
Fermented food products
 Milk Products
 Fermented milk products have longer shelf life as compared to
raw milk
 Curd, buttermilk, yogurt and cheese require lactic bacteria
1. Butter and buttermilk
 Made from cream/curd
 From cream: soured by using Streptococcus cremoris or S. lactis for
the production of lactic acid
 Leuconostoc cremoris imparts characteristic flavor.
 By churning of cream/curd, butter is produced, leaving
buttermilk (liquid portion).
Yogurt
 Fermentation of milk by
 Lactobacillus bulgaricus and Streptococcus thermophilus at 40-45 ◦C.
 After 4 hrs, sufficient acidity is generated, good to enhance shelf life.
 Flavour is imparted by accumulation of lactic acid and acetaldehyde
produced by L. bulgaricus.
 Commercially produced from pasteurized skimmed milk with added
milk powder.
Cheese, the milk protein
 Cheese is a generic term for a diverse group of milk-based food




products.
Cheese is produced throughout the world in wide-ranging flavors,
textures, and forms.
Obtained by milk fermentation
Coagulated mixture of proteins including casein
Enzymetic process (rennin)
 Cheese
 Whey
 Lactic bacteria are used
 Renin may be obtained
 From the calf stomach or
 Produced by microorganisms
Cheese Varieties
 Ripening of the cheese by
 Bacteria
 Mold
 Soft cheese water content 50-80 %
 Ripened by surface growth
 Semi-hard
40-45%
 Briefly cooked to lower the curd content
 Hard cheese
<40%
 Ripened with inoculation of spores of mold Penicillium roguefortii
 Salting cheese with sodium chloride
Fermented Meats
 A delicacy in some middle-east countries.
 Fermentation of meat is carried out during curing by lactic
bacteria and Pedicoccus cerevisiae.
 Several types of salamis and sausages are produced by
fermentation
 Gives flavour
 Preserves food
Leavening bread
 The dough is fermented in the presence of sugar and yeast.
 Saccharomyces cerevisiae, the Baker’s yeast is mostly used in leavening
process.
 Production of Baker’s yeast
 Normally grown at 30◦C on molasses which is
 Having low conc. of sugar (0.5-1.5%)
 Rich in mineral salts
 pH about 4.5
 During fermentation, sugar content of molasses is meticulously
controlled as higher conc. is deterrent to respiratory enzymes.
 Yeast is collected through centrifugation.
Alcoholic Beverages
 Vinegar is an alcoholic liquid that has been allowed to sour.
 Used to flavor and preserve foods.
 Ingredient in salad dressings and marinades.
 Used as a cleaning agent.
 Two successive fermentations of grape juice, raisins or malt
1.
2.

S. cerevisiae anerobically converts carbs to alcohol
Oxidative transformation of alcohol to acetic acid by Acetobacter
and Gluconobacter.
Starting material includes
Citrus fruits
Apple
Pear
Vegetables like potatoes
Malted cereals
Sugary syrups such as molasses, honey etc.
Production of organic acids
 Acetic acid
 Citric acid
 Gluconic acid
 Lactic acid
 Gibberallic acid
Citric acid production
 Citric acid is a weak organic acid.
 It is a natural preservative/conservative and is also used to add an
acidic, or sour, taste to foods and soft drinks.
 Aspergillus niger is used for commercial production
 Various strains of A. niger are used in the industrial preparation of
citric acid and gluconic acid and have been assessed as acceptable
for daily intake by the World Health Organisation.
Citric acid Uses
 Cleaning
 Citric acid's ability to chelate metals makes it useful in soaps and
laundry detergents.
 By chelating the metals in hard water, it lets these cleaners produce foam
and work better without need for water softening.
 Citric acid is the active ingredient in some bathroom and kitchen
cleaning solutions.
 A solution with a 6% concentration of citric acid will remove hard water
stains from glass without scrubbing. In industry, it is used to dissolve
rust from steel.
 Citric acid can be used in shampoo to wash out wax and coloring
from the hair.
Cosmetics and pharmaceuticals
 Citric acid is commonly used as a buffer to increase the solubility of brown
heroin.
 Single-use citric acid sachets have been used as an inducement to get heroin users
to exchange their dirty needles for clean needles in an attempt to decrease the
spread of AIDS and hepatitis.
 Citric acid is used as one of the active ingredients in production of antivirals.
Dyeing
 Citric acid can be used in food coloring to balance the pH level of a normally
basic dye.
 Citric acid is used as an odorless alternative to white vinegar for home dyeing
with acid dyes.
Foods, beverages, and personal care
 As a food additive, citric acid is used as a flavoring and preservative in food and
beverages, especially soft drinks.
 Citric acid can be added to e.g. ice cream as an emulsifying agent to keep fats
from separating, to caramels to prevent sucrose crystallization, or to recipes in
place of fresh lemon juice.
 Citric acid is used with sodium bicarbonate in a wide range of effervescent
formulae, both for ingestion (e.g., powders and tablets) and for personal care.
Lactic Acid
 Used as a preservative and also in leather and textile
industries
 Microbes involved in lactic acid production are
 Lactobacillus delbrueckii
 Streptococcus and Leuconostoc species.
 Typical fermentation medium contains
 Gluscose
10-15%
 Calciun carbonate
10%
 Ammonium phosphate
 Trace elemnets
 Fermentation at 40-50 ◦C, pH 5.5-6.5 for 5-7 days
Production of Amino Acids
 Amino acids are consumed in a variety of markets.
 The largest by volume is the food flavoring industry.
 Monosodium Glutamate, alanine, aspartate, arginine are all used to improve
the flavor of food.
 L-lysine is directly produced from carbs by using Corynebacterium
glutamcum, an auxotroph
 MSG is produced by Arthrobacter, Corynebacterium and Brevibacterium
Food Flavours
 All kinds of preserved foods, such as soft drinks, milk
products and beverages are flavoured suitably.
 The flavouring compounds are mostly purine nucleotides,
including inosinic acid (IMP), and GMP.
 Yeast is commercial source of flavouring compounds
 Bacillus subtilis also enzymetically produces purine nucleotides
through fermentation
Single-cell protein (SCP)
 SCP refers to the dried microbial cells or total protein extracted from
pure microbial cell culture (monoculture – Algae, bacteria,
filamentous fungi, yeasts, etc…), which can be used as food
supplement to humans (Food Grade) or animals (Feed grade).
 SCP contains high protein content (60 – 80% of dry cell weight), fats,
carbohydrates, nucleic acids, vitamins, and minerals.
 It is also rich in essential amino acids such as Lys and Met.
SCP from Algal sources
 Economical as algae utilize solar energy for growth.
 Chlorella and Spirulina (blue-green algae).
 Food from these sources contain 65% protein, 20% carbohydrates
and remaining 15% include lipids, fibre, pigments etc.
SCP from Bacteria
 Cheap SCP is obtained from bacteria growing on cheap agricultural
and mineral wastes
 Cellulomonas and Alcaligenes are mostly used
Fungi as source of SCP
 Saccharomyces, Candida utilis and Torulopsis can be grown on wastes
from paper industry and forestry
 Rhodosporium sphaeroides produce a cell mass that contains more than
50% lipids.
Advantages of using microorganisms for SCP
production
 Protein synthesis is much more rapid than higher living systems.
 Microbes have short generation time.
 Easily modifiable genetically for determining the amino acid
composition.
 Microbes have high protein content (7.12g protein Nitrogen/100g dry
weight).
 Microbes can be grown on media containing cheap sources of C and
N.
 Easy regulation of environmental factors for efficient yield.
Disadvantages
 Possibility of contamination with pathological organisms in SCP.
 Association of carcinogenic and other toxic substances with SCP is
often observed.
 Digestion of microbial cells is rather slow, and is frequently
associated with indigestion and allergy reactions.
 Food grade production of SCP is more expensive than other
sources of proteins, as it depends on the raw materials.
 SCP for human consumption is 10-12 times more expensive than
SCP for animal feed.