Proteolysis development in enzyme-modified Cheddar cheese using natural and recombinant enzymes of Lactobacillus rhamnosus S93

Statistical improvement of protease production from a new isolate Bacillus thuringiensis strain-MA8 and its application in the production of enzyme-modified cheese

Enzyme-modified cheese (EMC) is a concentrated cheese flavor that is produced enzymatically from dairy substrates to provide an intense source of cheese flavor with broad applications. In this study, EMC was produced by enzymatic biotransformation from a new bacterial isolate described and molecularly identified as Bacillus thuringiensis strain-MA8. Optimization of protease production conditions using one-variable-at-a-time followed by multi-factorial (Plackett-Burman and Box-Behnken) designs increased production by 7-fold. Protease was used at different concentrations (300 and 900 U/100 g curd) as a cost-effective source of concentrated cheese flavor in the EMC preparation. Sensorial evaluation of EMC revealed that the overall acceptability, flavor, and texture were improved from the 2nd day compared to the control, and then decreased on the 4th day without any apparent bitterness. The chemical characteristics of EMC showed that the addition of protease extracts increased the total volatile fatty acids, water-soluble nitrogen, and acidity of EMC significantly (p≤0.05) compared to the control. The amino acids profile revealed that EMC1 which was treated with (300 U/100 g curd) protease had the highest essential amino acids (EAA) and EAA/total amino acids ratio. Nutritional parameters including protein efficiency ratio, biological value, and chemical score of EMC were higher than control based on Val, Met + Cys, Ile, Leu, and Phe + Tyr amino acids. Also, Scanning Electron Microscopy showed significant changes in EMC compared to the control. In conclusion, the addition of (300 U/100g curd) of protease revealed good EMC characteristics without any apparent defect.

Optimised production and spray drying of ACE-inhibitory enzyme-modified cheese

The proteolytic stage of the digestion process of white cheese curd was optimised to maximise the angiotensin I-converting enzyme (ACE)-inhibitory activity of the final enzyme-modified cheese (EMC) paste. It was found that bioactive peptides generation in EMC paste was of multi-variable dependent nature and could be optimised by targeted selection of specific component variables. Maximum ACE-inhibitory was obtained by proteolysis at 48 °C for 25 h with 1 g Flavourzyme/kg cheese curd. This bioactive EMC paste was subsequently spray-dried. The drying conditions were optimised to obtain a highly soluble powder to warrant quick and complete hydration, with the lowest water activity to maximise long term storage. The higher the inlet drying air temperature, the greater was the solubility of resultant EMC powder. Differential scanning calorimetry analysis revealed that the highest drying air temperature (200 °C) resulted in a lower glass transition temperature for the potentially bioactive EMC powder.