Ultrastructure of low-fat ground beef patties with added whey protein concentrate

Abstract

Microstructure of gels formed at 71°C from different mixtures of beef myofibril protein (BMP; 6.1% protein) and whey protein (WP) were studied by transmission electron microscopy (TEM). At a ratio of30:10 (w/w) of whey protein concentrate (WPC; 79.5% protein) to BMP, WP formed a network of aggregated clusters in which beef myofibril proteins were embedded. WP apparently acts as a filler and possibly as a cementing agent for the meat pieces. At a lower ratio of 10:30 (wl w), the WP aggregates occupied and increased the interstitial spaces between the myofibril protein and reinforced the network. The location of WP in the interstitial spaces might explain its water binding ability in beef patties formulated with WP and water. WP protected the beef myofibril protein structure during heating as less disintegration in the Z-line was observed in gels with WP compared to the control. Low-fat (10% fat) ground beef patties with added 10% water and 1–4% whey protein concentrate (WPC), cooked to three different internal temperatures (60, 70 and 80°C), were evaluated for their cooking characteristics and examined by TEM. For all levels of addition, WPC improved the cooking yield compared to a non-formulated control of 10% fat. Fat retention was also improved at the highest level of WPC addition. The increased cooking yield was shown to be caused principally by the better water retention. The textural parameters, hardness and chewiness, were not affected by WPC addition but increased with increasing cooking temperature. These temperature-induced changes were matched by marked changes to the ultrastructure of the meat products.