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Table 3 Traditional processing steps during the Himalayan fermented soybean food production with scientific explanation for noteworthy ethno-microbiological knowledge of the Himalayan people

From: Dietary culture and antiquity of the Himalayan fermented foods and alcoholic fermented beverages

Flow sheet Details of production steps Scientific explanation
Soybean
      ↓
Cleaned and washed
      ↓
Soaked in water 8–10 h; drained off excess water
      ↓
      ← Added clean water
      ↓
Cooked in an open cooker
      ↓
Drained off
      ↓
Cracked in a wooden mortar lightly by a wooden pestle
      ↓
Kept in a bamboo basket lined with jute bag and wrapped by fern leaves
      ↓
Fermented (25–40 °C, 1–3 d)
      ↓
Sticky fermented soybeans
Soaking of soybeans in water for overnight Soaking of soybeans will make the seeds soften and also helps to develop some flavour properties [25]
Soaked soybean seeds are boiled till it becomes soft Boiling of soybean reduces the opportunistic and pathogenic microorganisms except heat-tolerant bacteria, and also allergenicity of soybeans [26]
Wrapped in fresh leaves (fern fronds, banana, paddy straw) Since the dominant fermentative bacterium is Bacillus which is aerobic to semi-anaerobic, loosely pack leaves or ferns will create the semi-anaerobic condition to facilitate the growth of Bacillus on the surface of fermenting soybeans. [18, 27]
Naturally fermented at warm place Bacillus is heat resistant and can grow up to 45 °C [27]
Fermented beans are covered with whitish mass, mucilaginous materials if touch appears sticky with umami favour Whitish mass is the spores of Bacillus with PGA production which appears as mucilaginous and sticky materials on the surface of soybeans with umami flavour. Flavour is generated during proteolysis (breaking down of protein to amino acids by proteolytic enzymes synthesized by Bacillus spp. during fermentation) [22]