Preparation and quality comparision of perry from nepali pears using different isolated yeasts

Abstract

Local starter murcha, ghanti phool (Argyreia nervose) and fruits such as raisin, grape, apricot were selected for the isolating wine yeast capable of efficient fermentation. The murcha were collected from places like Jorpati, Palpa, Lubhu, Sunsari, Bhojpur, ghanti phool was obtained from Kritipur and fruits were purchased from local market. Yeast extract peptone dextrose (YPD) agar medium with 50 ppm chloramphenicol was used as a substrate to isolate yeast strains. The nine yeast strains isolated were screened for their tolerance in sugar, sulphur dioxide, alcohol and checked for their alcohol production capacity. All isolated strains exhibited growth in YPD broth containing 20% dextrose, 14% alcohol and 75 ppm Sulphur dioxide. However, yeast from murcha (Palpa murcha), and ghanti phool flower exhibited the best result and these two isolates were selected for fermenting pear juice. Extracted juice from pear fruit was ameliorated to 20° Brix. The ameliorated juice was pasteurized (65ᵒC for 5min), inoculated with yeast and held at room temperature for 20 days. Addition of pectinase solution at the concentration of 5 ppm showed the best result as compared 600 ppm bentonite, 6% dry gelatin, 0.15% egg white. Soluble solids, pH decreased while titratable acidity increased with increasing length of time. The highest alcohol production was shown by wine produced using flower yeast (W-YFW) 10.5% compared to the wine produced using commercial yeast (W-SN9) 9.17%)and wine produced using Palpa yeast (W-YPM) 9.84%. Result of sensory evaluation conducted by the untrained panelist showed that there was similar character in context of flavor, taste, and clarity but had some difference in color and aroma between the labs prepared pear wine and reference wine. The overall acceptability of the pear wine prepared in the lab was similar with the reference wine. Three lab wine prepared W-YPM, W-YFW AND W-SN9 and four commercial wines C.W-1, C.W-2, C.W-3 and C.W-4 were subjected to quantitative chemical analysis for the presence of the titratable acidity, volatile acidity, esters, total phenol, alcohol percentage, SO₂ free and total. pH, ᵒBrix, titratable acidity (%MA), volatile acidity (g/L), ester (mg/L), total phenol (mg/L), free SO₂ (mg/L) and total SO₂ (mg/L) of all wines ranged from 3.34 to 3.72, 5.8 to 13.8, 0.29 to 0.48, 0.111 to 70 to 281, 53 to 110, 2.30 to 5.12, 2.30 to 32.64 respectively. Gas Chromatography Qualitative analysis of the lab prepared wine using yeast isolated from Palpa murcha, flower and commercial wine samples against control showed the presence of the acetaldehydes, acetone, ethylacetate, ethanol, methanol, propanol-2 and propanol-1. The methanol limit on usage is often set at 250 mg/L with an alcoholic strength by volume of less than 15% by International Organization for Vine and Wine (OIV), however presence of in the commercial wine did not exceeded the limit and was found to be 130mg/L. Quantitative analysis of three wine samples showed the percentage of acetaldehydes, acetone, ethanol, methanol and propanol-2 between 0.004 to 0.041, 0.003, 9.3 to 12.3, 0.013, and 0.003 to 0.0019 respectively. Keywords; Marcha, Pear, Yeast, Fermentation and Clarification.