EFFECT OF VARIOUS CUTTING AND STIRRING CONDITIONS ON CURD PARTICLE-SIZE AND LOSSES OF FAT TO THE WHEY DURING CHEDDAR CHEESE MANUFACTURE IN OST VATS

Nine combinations of speed and duration of cutting the coagulum were v aried during the commercial manufacture of Cheddar cheese in 27 Ost IV cheese vats. The effects of cut speed ramp-up rate, vat overfilling a nd stirring rate after cutting were also evaluated. The effects of the variations were assessed by determining the curd particle size distri bution and fat losses to the whey at draining. The results of varying the speed and duration of cutting were compared with the results of a similar investigation carried out using vertical, double O, Damrow vat s. Although the results showed similar trends, compared with the Damro w vat at the same speed the Ost vat's cutting system reduces curd part icles to a constant size more rapidly, thereby avoiding excessive curd shattering and high whey fat losses during subsequent stirring. Based on these results and comparisons with the results from the Damrow tri al, a model is proposed. It explains how variation in speed and durati on of continuous cutting, followed by a constant stirring speed, deter mines curd particle size distribution in an Ost IV cheese vat. The mod el can be used to maximise moisture retention and minimise whey fat lo sses. Reducing the cut speed ramp-up rate and the stirring speed signi ficantly increased the curd particle size. Overfilling Ost IV vats sig nificantly increased curd the particle size but had no significant eff ect on whey fat losses. (C) 1998 Elsevier Science Ltd. All rights rese rved.