Physicochemical changes of Citrullus lanatus (watermelon) seeds during Bacillus species mediated fermentation and sensory Evaluation of condiment produced
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Date
2019
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Journal ISSN
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Publisher
Centrepoint Journal (Science Edition)
Abstract
Watermelon (Citrullus lanatus), a drought tolerant and ubiquitous fruit, contains a lot of seeds that are generally discarded after consumption of the juicy portion. This study was designed to assess changes in proximate, amino acid, mineral and phytochemical compostions of watermelon seeds during a 72 hr fermentation period with mixed inocular of Bacillus subtilis and Bacillus licheniformis in the production of a local condiment similar to ogiri (a condiment produced from Citrullus vulgaris porpularly consumed in Nigeria). The sensory quality was also evaluated for the resulting watermelon condiment. Proximate analysis revealed significant (p < 0.05) with an increase in crude protein (14.00-21.10 %), and ash (1.90-2.55%) at the end of fermentation. Some of the essential amino acids obtained include: threonine, valine, isoleucine, tryptophan and leucine, all of which increased with days of fermentation. Similar trend was observed
in the mineral components: magnesium (41.02-45.06 mg/100 g), zinc (5.05-7.15 mg/100 g), phosphorus (14.52-17.00 mg/100 g), potassium (22.03-33.02 mg/100 g), calcium (13.45-16.03 mg/100 g), sodium (5.40-7.14 mg/100 g), and manganese (1.10-2.53 mg/100 g). Results showed that pH of the condiment ranged from 5.6 to 8.6 over 72 hrs of
fermentation. Length of fermentation caused a steady decrease in hydrocyanic acid (1.57-0.03 mg/100 g), tannin (22.05-16.00 mg/100 g) and phytate (7.05-3.52 mg/100 g) but an increase in flavonoids (1.58-2.30
mg/100 g) and phenol (0.11-1.41 mg/100 g). Sensory evaluation showed that ogiri produced from C. vulgaris was more generally accepted but that produced from C. lanatus was more preferred in taste with a score of 6.20.
Increased days of fermentation with B. subtilis and B. licheniformis in consortium had varying effects on the nutritional and phytochemical compositions of watermelon condiment
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Keywords
Watermelon seed, Bacillus species, Condiment, Fermentation, Physicochemical