Immobilized rennin in TC/SG composite in cheese production

• Repeated coagulation batches using rennin immobilized on TC/SG composite.
• Continuous coagulation of milk using TC/SG – rennin biocatalyst.
• TC/SG composite becomes a suitable material for rennin enzyme immobilization for dairy application.
• Optimum conditions of enzyme concentration and immobilization were determined.
• Physicochemical characteristics and volatile compounds were similar to commercial products.

The object of the current study was to develop a new process for continuous Feta-type cheese production using a biocatalyst consisting of immobilized rennin on a tubular cellulose/starch gel (TC/SG) composite, which has been proven to be an appropriate carrier for enzyme immobilization. Different methodologies were used in order to prepare four biocatalysts. The most effective was selected for cheese production in a 1 L continuous system, providing two economically useful results for the dairy industries: (i) increase of productivity by the continuous coagulation of milk, and (ii) saving of the rennin enzyme expenses of the batch coagulation of milk. The criteria used to choose the appropriate biocatalyst was based on the time of coagulation in successive batches, the concentration of immobilized rennin combined with the filter efficiency and its application in the continuous system. Physicochemical analyses of the cheeses at various stages of the ripening were performed. No significant differences compared to cheeses prepared with the traditional method were found. Aroma compounds were determined by SPME GC–MS.