Date post: | 24-Oct-2014 |
Category: |
Documents |
Upload: | vithyia-murugiah |
View: | 53 times |
Download: | 4 times |
fermentation
THOSAI ??
What Is
• Fermented crepe or pancake
• Made from rice and urad dhal
• Usually taken during breakfast
• Healthy food : no sugar or trans fat
• Prepared by fermentation process
• Served with chutney or dhal curry
• Contains carbohydrate, protein and vitamins
Rice, ural dhal and fenugreek is soaked
in water for about 6 hours
The soaked mixture will be grind with adequate water to produce a smooth and fluffy paste
Salt can be added to make it tastier
The batter is set aside for approximately 12 hours to ferment
• Thosai is a products of natural lactic acid fermentation
• Natural microflora of the ingredient act as the starter
• Bacteria & yeasts are contributed by rice & urad dhal
• Prevalence of bacteria & yeasts affected by seasonal variations
• Starch digesting enzyme > amylase contribute in initial stage of fermentation
• Fermentation improves flavor, texture & enhance bioavailability of nutrients
Predominant bacteria responsible for souring and leavening of Thosai batter
From Rice :
Leuconostoc mesenteroides
Streptococcus faecalis
Lactobacillus fermentum
Bacillus amyloliquefaciens
Bacteria always dominate the overall microbial load
• Yeasts if present, belonged to :
Saccharomyces cerevisiae Debaryomyces hansenii Trichosporon beigelli.
• It produce flavor, enzymes and help in saccharification of starch
• During soaking, Leuconostoc and Streptococcus develops and continue multiplying
• Each eventually reaches more than 1 × 109 cells per gram after 11 to 13 hours
• Heterofermentative Leuconostoc mesenteroides produces CO2 in addition to lactic acid
• Streptococcus faecalis responsible for acid production
• After 23 hours, if batter is further incubated : Lactobacilli and streptococci decrease in numbers but Pediococcus cerevisiae develops
Biochemical changes : After 15 - 20 hours , 1: 2 ratio of Black Gram : Rice
• Increase in microbial load after fermentation at 30°C
• Increase in batter volume about 113 %
• Increase in total acidity to 2.2 %
• Increase in total nitrogen and soluble proteins
• Increase in vitamin B1 & B2 content lead to improved nutritional quality
• Increased activity of amylases but gradually decline with the progress
• Decrease in pH to less than 4.5
• Glucose ( reducing sugar ), decrease steadily from 3.3 ml/g to 0.8 ml/g which reflects utilization for acid and gas production..
• Fermented batter of Thosai shows 80% destruction of aflatoxin
• This may be due to the microorganisms involved in fermenting the batter
• Lactic acid causes degradation of aflatoxin B1 to B2a
• Fermentation process breakdown the bonding between protein and aflatoxin B1 molecule.
• Further destruction may be due to critical moisture and temperature of heat processing
• Fermenting finger millet with horse gram increases soluble proteins concentration in Thosai.
• A 4:1 ratio of finger millet : horse gram increases essential amino acid concentration
• This formulation produces a high protein food that could overcome malnutrition problem
• Zinc & iron concentration can be increased by 50 % & 127 % respectively
• Do not use air tight lid when batter is fermenting
• The fermentation can be retarded by Yogurt, Baking yeast, Baking soda or Baking powder.
• The best ambient temperature for fermentation is 30°C to 32.2°C
• If the temperature is below 30°C, it will take longer to achieve acceptable level of fermentation.
• If the temperature is higher than 32.2°C, the batter may become sour
• Chlorinated tap water can inhibit fermentation.
• Thosai is fried on pan with little oil while Idli is steamed in mould with water
• Thosai batter is thinner and finely grinded than Idli batter
• Thosai is crusty and crisp while Idli are soft and fluffy
• There is less Amylopectin in Thosai than Idli