Electrophoresis, rheology and meltability of imitation cheese containing rice starch as influenced by storage time.

摘要

Storage-induced rheological and proteolytic changes in imitation cheese samples containing 3% native (2.5, 15 or 28% amylose), pregelatinized, cross-linked or cross-linked and stabilized rice starch were compared with those of a control imitation cheese (0% starch, 3% casein). After 180 days of storage, the control showed significant decreases in textural hardness (from 136.5 to 114.9 N) and storage modulus (G'; 75.7 to 63.3 kPa) as well as significant increases in tan delta values (0.447 to 0.476). The starch-containing imitation cheese also showed significant reductions in G' with storage as well as significant increases in tan delta values. Most of the starch types increased hardness after 90 days, possibly due to starch retrogradation. Meltability of the control imitation cheese increased significantly from 130.5 mm after 14 days to 144.6 mm after 180 days. Similar meltability increases were observed in products containing starch. Urea-PAGE determinations show that the alphas1-casein fraction remained stable over 2 yr of storage, while the beta-casein fraction was hydrolysed to gamma-casein, probably via the action of the indigenous enzyme plasmin. This breakdown of beta-casein contributed to the weakening of the imitation cheese structure and its increased melting capacity. The partial replacement of the protein matrix with starch lessened the effects of proteolysis on imitation cheese hardness.