Tika Bahadur Karki

Flocculation properties of several microalgae and a cyanobacterium species during ferric chloride, chitosan and alkaline flocculation

Flocculation holds great potential as a low-cost harvesting method for microalgae biomass production. Three flocculation methods (ferric chloride, chitosan, and alkaline flocculation) were compared in this study for the harvesting of 9 different freshwater and marine microalgae and one cyanobacterium species. Ferric chloride resulted in a separation efficiency greater than 90% with a concentration factor (CF) higher than 10 for all species. Chitosan flocculation worked generally very well for freshwater microalgae, but not for marine species. Alkaline flocculation was most efficient for harvesting of Nannochloropsis, Chlamydomonas and Chlorella sp. The concentration factor was highly variable between microalgae species. Generally, minimum flocculant dosages were highly variable across species, which shows that flocculation may be a good harvesting method for some species but not for others. This study shows that microalgae and cyanobacteria species should not be selected solely based on their productivity but also on their potential for low-cost separation.

Malting and fermentation effects on antinutritional components and functional characteristics of sorghum flour

Abstract The research was aimed to observe the effect of malting and fermentation on antinutritional component and functional characteristics of sorghum flour. For whole sorghum flour, cleaned sorghum grain was milled to pass through 40 mesh sieve. For malting, cleaned sorghum grain was steeped in 0.2% calcium hydroxide solution for 24 hr and then germinated for 48 hr at 90% RH and 27 ± 2°C. Sprout was removed, dried in hot air oven at 50 ± 2°C for 24 hr and milled to pass through 40 mesh sieve. For fermented sorghum flour, 13.3 mg% diastase and 2 mg % pepsin (on the basis of whole sorghum flour weight) was added to cooked (88 ± 2°C) sorghum flour and left for 1 hr. Lactobacillus plantarum (107 cfu/g) was inoculated and incubated at temperature 30 ± 2°C for 48 hr. The fermented slurry was dried at 50 ± 2°C in hot air oven for 24 hr and milled to pass through 40 mesh sieve. The lower yield of sorghum flour was obtained compared to whole and malted sorghum flour. Germination of sorghum reduced phytate, tannin, and oxalate by 40%, 16.12% and 49.1%, respectively, whereas fermentation of sorghum flour reduced above by 77%, 96.7% and 67.85%, respectively. There was no significant change in hydrogen cyanide in malted sorghum flour compared to whole sorghum flour, but fermentation of sorghum flour reduced hydrogen cyanide by 52.3%. Bulk density and viscosity was significantly reduced by the malting and fermentation, whereas water absorption capacity and oil absorption capacity was markedly increased by the malting and fermentation. Fermented flour was good due to reduced ANF and improved functional property despite of lower yield.

Phytochemicals and syneresis of osmo-dried mulberry incorporated yoghurt

Abstract The research was aimed to study the effect of the addition of Osmo‐air‐dried mulberry (TSS 29.33%) in yoghurt on syneresis and a bioactive component of yoghurt. Two types of yoghurts, with or without Osmo‐dried mulberry, were developed using standard culture (Streptococcus thermophilus and Lactobacillus bulgaricus), and changes at refrigerated temperature (<5°C) were studied. Fruit yoghurt showed high total soluble solids (TSSs) and low‐fat content (dry basis) (17.67% and 11.84%) compared with normal yoghurt (9.5% and 17.21%). The addition of fruits increased the ascorbic acid (0.77 to 5.96 mg/100 g yoghurt), anthocyanins content (0 to 7.9 mg/100 g yoghurt), total phenol content (TPC) (6.63 to 68.03 mg GAE/100 g yoghurt), and antioxidant activity (20.73% to 47.6% radical scavenging activity) in yoghurt. During 18 days of storage at refrigerated condition (<5°C), the acidity of all samples increased, while pH decreased. Syneresis increased with a storage period in control samples while fruit incorporated yoghurt showed decreased syneresis with time. The viability of lactic acid bacteria (LAB) count went on decreasing at similar rates for both with and without the Osmo‐dried mulberry incorporated yoghurt. There is an ample opportunity for utilization of Osmo‐air‐dried mulberry in yoghurt to prevent syneresis during storage with increased bioactive components.

Selection and Characterization of Potential Baker’s Yeast from Indigenous Resources of Nepal

The study aims to isolate the yeast strains that could be used effectively as bakers yeast and compare them with the commercial bakers yeast available in the market of Nepal. A total of 10 samples including locally available sources like fruits, Murcha, and a local tree “Dar” were collected from different localities of Bhaktapur, Kavre, and Syangja districts of Nepal, respectively. Following enrichment and fermentation of the samples, 26 yeast strains were isolated using selective medium Wallerstein Laboratory Nutrient Agar. From the differential tests which included morphological and microscopic observation and physiological and biochemical characterization such as nitrate reduction and lactose utilization tests, 8 strains were selected as possible Saccharomyces strain. The selected strains were further assessed for their efficient leavening ability by tests such as ethanol tolerance, osmotolerance, invertase test, and stress exclusion test. The three most potent strains ENG, MUR3B, and SUG1 isolated from grape, Murcha, and sugarcane, respectively, were used in the fermentation and baking of dough. These strains also carried a possibility of being used as industrial bakers yeast.

Ethnic Fermented Foods of Nepal

The topographical and ecological niche variations of Nepal have been blessed with diverse microbial community and variations in preparation methodology and use of substrates which have eventually resulted in a wide range of sensory attributes. Ethnic communities of Nepal have their own diverse culture and cultural heritage resulting into various types of fermented foods. Gundruk, mesu, sinki, and khalpi are the fermented vegetables produced by lactics from Brassica leafy vegetables, tender bamboo shoot, radish, and ripened cucumber, respectively, which are consumed as a soup, curry, and pickles and preferred by all indigenous groups of Nepal. Similarly kinema is a non-salted fermented soybean product by Bacillus sp. with an ammoniacal odor. However murcha is a traditional starter culture for producing alcoholic beverages from starchy substrates which consists of saccharifying molds, liquifying yeasts, and lactics. Jaanr, raksi, and hyaun thon are the resultant fermented alcoholic beverages of Nepal prepared by using murcha starter and cereal as base ingredients which are consumed only by a certain ethnic group. These indigenous fermented foods are highly acclaimed products and have been consumed since time immemorial. These are spontaneously fermented products by natural flora. Improvement and standardization of the traditional process may be considered as an essential element in the protection, conservation, and exploration of our indigenous resources for industrialization and sustainable development.