Production of Fermented foods and Beverages

Biotechnology

Food BiotechnologyFermented food productsAlcoholic beveragesProduction of organic acidsProduction of amino acidsFood flavorsSingle 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 bacteriaCommon genera include

Lactobacillus Leuconostoc Pediococcus Lactococcus Streptococcus Aerococcus Carnobacterium Enterococcus Oenococcus Sporolactobacillus Tetragenococcus Vagococcus Weisella

Fermented food productsMilk Products

Fermented milk products have longer shelf life as compared to raw milk

Curd, buttermilk, yogurt and cheese require lactic bacteria

1. Butter and buttermilkMade from cream/curdFrom cream: soured by using Streptococcus cremoris or

S. lactis for the production of lactic acidLeuconostoc cremoris imparts characteristic flavor.By churning of cream/curd, butter is produced, leaving

buttermilk (liquid portion).

YogurtFermentation 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 proteinCheese 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 fermentationCoagulated 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 VarietiesRipening of the cheese by

BacteriaMold

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

roguefortiiSalting cheese with sodium chloride

Fermented MeatsA 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 fermentationGives flavourPreserves food

Leavening breadThe 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 yeastNormally grown at 30◦C on molasses which is

Having low conc. of sugar (0.5-1.5%)Rich in mineral saltspH 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 BeveragesVinegar 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 malt1. S. cerevisiae anerobically converts carbs to alcohol 2. Oxidative transformation of alcohol to acetic acid by

Acetobacter and Gluconobacter. Starting material includes

Citrus fruitsApple PearVegetables like potatoesMalted cerealsSugary syrups such as molasses, honey etc.

Production of organic acidsAcetic acidCitric acidGluconic acidLactic acidGibberallic 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 CleaningCitric 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 AcidUsed as a preservative and also in leather and textile

industriesMicrobes involved in lactic acid production are

Lactobacillus delbrueckiiStreptococcus and Leuconostoc species.

Typical fermentation medium containsGluscose 10-15%Calciun carbonate 10%Ammonium phosphateTrace 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 FlavoursAll 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 sourcesEconomical 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 BacteriaCheap SCP is obtained from bacteria growing on cheap

agricultural and mineral wastesCellulomonas and Alcaligenes are mostly used

Fungi as source of SCPSaccharomyces, Candida utilis and Torulopsis can be grown

on wastes from paper industry and forestryRhodosporium 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.

DisadvantagesPossibility 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

thanSCP for animal feed.