Preparation, properties and preservation of lactic acid fermented shrimp heads

Abstract

Raw heads of the African river prawn ( Macrobrachium vollenhovenii) were fermented with 5% ( w w ) Lactobacillus plantarum as inoculum at 30 °C using 15% ( w w ) cane molasses as a carbohydrate source. After incubation for 7 days, a desirable and stable pH, < 4.5, was attained in the anaerobic treatments which lasted until 30 days after the start of fermentation. Addition of trona at 5% ( w w ) prior to fermentation restricted protein hydrolysis by inhibiting the activity of endogenous autolytic enzymes. Addition of onion extract at 5 ml kg −1 proved effective as an antioxidant as the thiobarbituric acid reactive substances value remained low after 30 days' fermentation. In a storage experiment, fermented shrimp heads were stored at 30 °C for 180 days and analyzed at intervals. The non-protein nitrogen increased and attained a maximum of 50.1% of total nitrogen content after 180 days. Proximate composition varied slightly during storage and there was a > 12% loss of tryptophan.