Effect of long-term heat exposure on rheological and intrinsic water characteristics of bone-derived beef stocks

Bone-derived protein stocks are used in food industry to enhance taste of soups, sauces, and a range of other products. Both during commercial manufacturing and when used for culinary purposes, the stocks may be exposed to high temperatures for an extended time period. The present study investigated the effect of retention at 90°C for 0, 3, 6, 9, 24, 48, 72, and 168 hr on the functional attributes of concentrated bone-derived beef stocks (57% Dry matter (DM)). Visual inspection and rheological analyses showed that during increasing heat exposure, the gel strength as well as viscosity of the concentrated stocks decreased incrementally and significantly (P > 0.001). Nuclear magnetic resonance (NMR) relaxation measurements conducted on the beef stocks also revealed strong effects of heat exposure on the transverse (T₂) relaxation time, which increased incrementally and significantly (P > 0.001) with longer heat exposure. Thus, the present study demonstrated that heat-induced changes in rheological properties of bone-derived beef stocks can be ascribed to changes in intrinsic water–protein interactions and water attributes as a result of heat-induced protein modifications. In conclusion, the study proves that NMR relaxometry is a valuable tool for monitoring changes in intrinsic water mobility that are manifested in modified functional attributes of concentrated beef stocks.