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.
An angiotensin-I converting enzyme (ACE)-inhibitory enzyme-modified cheese (EMC) was spray-dried at different inlet drying air temperatures, feeding pump rates and spraying air flow rates. Powder moisture content, bulk density, porosity, production yield and particles size were responses of interest measured. Response surface optimisation determined that if the cheese paste is pumped at feeding pump rate of 5%, sprayed with the compressed air at rate of 400 L h À1 and dried by an air at temperature of 154°C, minimum moisture content is achieved for the produced powder. Spray drying decreased the ACE-inhibitory of EMC significantly, but the powder was still extremely bioactive. Scanning electron microscopy (SEM) images revealed that inlet drying air temperature of 150°C yielded a powder with relatively well-separated particles. Higher drying air temperatures resulted in lower browning indices for the EMC powder. References Aghbashlo, M., Mobli, H., Rafiee, S. & Madadlou, A. (2012).Energy and exergy analyses of the spray drying process of fish oil microencapsulation. Biosystems Engineering, 111, 229-241.
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