Effect of freeze tolerant baker‟s yeast on dough rising
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Date
2018
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Punjab Agricultural University, Ludhiana
Abstract
Among the sophisticated, ready to use frozen products, frozen dough is gaining considerable attention. So, attempt was made to improve freeze tolerance of baker‟s yeast strain by trehalose loading and cold acclimatization and to design its product formulations. Loading with 1.0M trehalose after 7 days of incubation led to increased intracellular trehalose content from 0.3% to 4.71%. Comparative freeze tolerance studies of parent and treated baker‟s yeast revealed that 14 day cold acclimatized culture exhibits maximum cell viability (193cfu/ml) under refrigerated conditions while further incubation for 21 day (167cfu/ml) and 28 day (165cfu/ml) lowered the cell viability. The 28 day cold acclimatized culture showed higher total sugar content of 36.29% followed by 1.0M trehalose loaded culture (29.44%). Maximum trehalose content (4.71%) was shown by 1.0M trehalose loaded culture. Minimum invertase (29.79 nmol/min/ml) and maximum maltase activity (627.99 nmol/min/ml) was shown by 1.0M trehalose loaded culture and 21 day cold acclimatized culture, respectively. Biomass production of baker‟s yeast was carried out at conditions pre-optimized in our laboratory:- pH-6.0, aeration-120 rpm and temperature-30⁰C using unclarified molasses as carbon source and corn steep liquor (CSL) as nitrogen source. Best dough rising ability was shown by 14 day cold acclimatized culture. Product formulation as cream yeast and dried (lyophilized and tray dried) yeast was prepared, out of which cream yeast was used in bread making while nutritional profiling of dried yeast formulations showed the presence of crude protein (23.39-28.98%), crude fat (2.14-2.73%), zinc (7.26-10.13mg/100g), iron (27.54-28.09mg/100g), phosphorus (463.9-593.44mg/100g), calcium (2913.7-5308.38mg/100g), tryptophan (0.71-1.09g/100g protein), methionine (0.73-0.83g/100g protein) and cysteine (0.38-0.4g/100g protein). The present study revealed that cold acclimatization of baker‟s yeast can improve its freeze tolerance. Among the two yeast formulations, cream yeast has been found to be suitable for use in dough rising for bread, while dried yeasts can be exploited as nutritional yeast by further testing for required parameters.
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