A Study On Fermentation And Nutritional Evaluation Of Masyaura-A Legume-based Traditional Fermented Food Of Nepal

Traditional foods have been a very important part of lives of people all over the world including Nepal. Masyaura is a traditional legume based protein rich fermented food of Nepal. Masyaura was prepared using blackgram dhal and colocosia tuber by traditional sun-drying and alternate controlled fermentation and mechanical drying technique in the present study. Masyaura was also prepared using pure dominant lactic acid bacteria culture of Pediococcus pentaseceous yeast Saccharomyces cerevisiae and mold Aspergillus niger. Biochemical, microbiological and physicochemical properties were evaluated during the course of fermentation. Masyaura prepared by different fermentation methods was also evaluated for sensory, nutritional and antinutritional characteristics. Organic acid, volatile components, polyphenol and antioxidant characteristics of Masyaura was also studied. A basic study on the fractionation of blackgram and Masyaura protein and the nutritional evaluation of their major fraction was also carried out.The biochemical parameters such as acidity, soluble protein, amino nitrogen, free sugar and reducing sugar were increased while pH was decreased during soaking of the blackgram dhal. During fermentation, acidity, soluble protein and amino nitrogen were increased while pH, free sugar and reducing sugar decreased significantly. Longer fermentation resulted decrease in acidity and increase in pH which could be due to activity of mold. The microbial load especially dominating lactics was increased during processing.Controlled fermentation and mechanical drying method resulted Masyaura sensorily superior and nutritionally comparable to sun-dried Masyaura. Fermentation at 30℃/24h at 80-90% relative humidity seemed better fermentation condition before drying at 50℃ for 12-16h while preparing Masyaura. Texture and bulk density of sun-dried Masyaura was higher as compared to controlled fermented Masyaura.Inoculation of Saccharomyces cerevisiae during fermentation improved sensory quality of Masyaura as compared to controlled fermented Masyaura. Pediococcus pentosaceous inoculation has no influence on sensory quality. Aspergillus niger inoculation resulted sensorily unacceptable Masyaura. Inoculation of single culture of Saccharomyces cerevisiae and single culture of Pediococcus pentaseous in separate batches of sterilized substrate couldn't improve sensory characteristics of Masyaura. Mixed culture of lactic acid bacteria and yeast seemed as the desirable microorganism in Masyaura fermentation.Masyaura was good source of protein (21.4-22.4%) comparable to animal protein, carbohydrates (60.6-64.7 %) and minerals (4.9-5.2 %) especially of potassium, calcium, phosphorous and magnesium. Thiamine, riboflavin, pyridoxine, niacin and Vitamin B-12 are the major B-Complex vitamins in Masyaura. Overall quality of B-complex vitamins was found to be higher as compared to its raw ingredients. Starch was the major carbohydrate component accounting 46.5 to 56.1 % followed free sugar content (5.3 to 6.8) and reducing sugar (0.8 to 1.9).The result of organic acid indicated that acetic acid was the major organic acid in Masyaura prepared by sundrying technique. The proportion of acetic acid was low in controlled fermented and mechanical dried Masyaura with concomitant increase in the lactic and citric acid. Large number (31-55) and amount (23.4-65.3% of total volatiles) of hydrocarbons were detected inMasyaura samples prepared by different methods. Aldehydes (0.9-4.9%), esters (2.1-2.3%), acids (3.4-20.1%), alcohols (1.1-6.1%) and pyrazine (0.3-10.2%) were detected in Masyaura.Total essential amino acid in Masyaura was found in the range of 31.7 to 38.3 % of total amino acid. Sulphur containing amino acids were the limiting amino acids in Masyaura. Total free amino acid in Masyaura ranged from 5.1 to 13.1 %. Heat stable antinutrients oxalate and phytate were reduced during the course of fermentation. Bioavailability of calcium and zinc were better in Masyaura samples as compared to its raw ingredients. Nutritional quality of Masyaura was improved with respect to protein and starch digestibility compared to raw ingredients.Total polyphenol content of Masyaura samples ranged 235.2 to 351.9 mg/lOOg, which was the lower value to its raw ingredients. Colocosia tuber showed higher antioxidant activity. Masyaura also exerted antioxidant property. Fat uptake and reconstitution property of controlled fermented Masyaura was higher as compared to sun-dried Masyaura. Frying of Masyaura lowered the reconstitution capacity.Globulin and albumin were the major protein fractions in Masyaura protein as well as to its raw ingredients. Nutritional quality of albumin fraction in Masyaura protein is superior as compared to globulin fraction. SDS-PAGE study of Masyaura albumin and globulin showed major protein fraction of its raw ingredients degraded to lower molecular weight protein fractions which also reflected on the improvement in protein digestibility of Masyaura. This could be due to enzymatic hydrolysis during fermentation.Overall, Controlled fermented and Mechanical dried Masyaura is physically and sensorily superior with better hygienic and keeping quality than sun-dried Masyaura. Nutritionally they are comparable to sun-dried Masyaura. Lactic acid bacteria and yeasts are desirable microflora for Masyaura fermentation. Nutritional quality, mineral bioavailability and nutrient digestibility characteristics of Masyaura were superior to its raw ingredients. Controlled fermentation and mechanical drying method can be used commercially. Further investigation on the influence of mixed culture on sensory, biochemical and nutritional characteristics of Masyaura are recommended.