Abstract
The beneficial properties of overripe tempeh as a functional ingredient protein isolate are overlooked by most food manufacturers. The present study aims to optimise the enzymatic hydrolysis conditions to obtain tempeh protein hydrolysate (PH) that can be used as potential functional foods. The enzymatic hydrolysis (using Flavourzyme) conditions, namely, temperature (°C), enzyme to substrate concentration (%) and hydrolysis time (min) on both total flavonoid content (TFC) and glutamic acid content (GAC), as responses, were optimised using response surface methodology (RSM) by employing three factors, 3-level, and central composite rotatable design (CCRD). Enzyme inactivation was successfully performed by keeping the hydrolysate at 85°C in a water bath for 10 min. Based on the results, the optimum conditions for the hydrolysis of 6.0 g of soy protein isolate (SPI) from soybean tempeh were at temperature 55°C with 2.6% enzyme to substrate concentration heated for 128 min which resulted in 8.93 g QE/100 g DEW of TFC and 12.96 g/100 g DEW of GAC. The results also showed that TFC and GAC were significantly influenced by all the factors studied. Therefore, the results suggested that soybean by-product such as overripe tempeh can be converted into hydrolysate which is a good source of protein fortification of various food products as well as a potential functional food ingredient.
Highlights
Tempeh, an indigenous fermented food from Indonesia, was known since several centuries ago
The objective of the study was to optimise the enzymatic hydrolysis condition of protein hydrolysate derived from soy protein isolate (SPI) of tempeh by using Flavourzyme
The analysis indicated that maximum total flavonoid content (TFC) and glutamic acid content (GAC) for hydrolysis of SPI by enzymatic hydrolysis can be achieved by using a 2.6% enzyme/substrate ratio at a temperature of 55°C and hydrolysis time of 128 min
Summary
Tempeh ( spelt as tempe), an indigenous fermented food from Indonesia, was known since several centuries ago. It is well known that proteins are important in food processing and food product development, as they are responsible for various functional properties that influence consumers’ acceptability. Both animal and plant proteins are commercially used as functional ingredients. Enzymatic hydrolysis is influenced by several factors such as pH, temperature, time and enzyme concentration that cooperatively influence the enzyme activity thereby making the process more controllable [11]. The objective of the study was to optimise the enzymatic hydrolysis condition of protein hydrolysate derived from soy protein isolate (SPI) of tempeh by using Flavourzyme
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