Use of Agglutination-Sensitive Bulk Starters in the Manufacture of Stirred Curd Cheese

Abstract

The effect of agglutinated bulk cultures on the manufacture of experimental stirred curd cheese was observed. To prepare three bulk starters, three aliquots of bulk medium were inoculated with cultures differing in agglutination sensitivity. Each bulk starter was divided into two portions, one of which was homogenized at 17.2 MPa (13.8 MPa, first stage; 3.4 MPa, second stage) pressure. Seventy grams (1%) of each starter were inoculated into 7000 g of milk, and stirred curd cheese was manufactured. The experiment was replicated three times. Cell chain length and clump size were markedly reduced in starters that were homogenized. No differences were observed in culture activity (acid production) during cheese manufacture between homogenized and unhomogenized cultures. Acid production was uniform throughout the vat of milk for both homogenized and unhomogenized cultures. The pH at the bottom of the vat was slightly lower when unhomogenized culture CH970 (a clump former) was used as the bulk starter. Large agglutinated complexes of bacteria and protein may have been physically buoyed up by the fat globules based upon photomicrographs of the cheese coagulum.