D.J. Troy

Effects of fat level, oat fibre and carrageenan on frankfurters formulated with 5, 12 and 30% fat

The effects of fat level (5, 12 and 30%), carrageenan and oat fibre on the hydration/binding properties, colour and flavour characteristics of frankfurters were investigated. Decreasing the fat content from 30% to 5% significantly increased cook loss and decreased water holding capacity and emulsion stability. Reduced-fat products were also darker and redder compared with the 30% fat controls. Addition of carrageenan or oat fibre reduced cook loss and increased both water holding capacity and emulsion stability. Sensory evaluation indicated that decreasing fat from 30% to 5% increased the intensity of smokiness, spiciness and saltiness and reduced the overall acceptability of the flavour. Carrageenan or oat fibre did not alter the colour of the frankfurters and neither ingredient had a significant effect on the flavour characteristics assessed. The results demonstrate that carrageenan or oat fibre can partially offset some of the changes which occur in low-fat frankfurters when added water replaces fat and protein level is constant.

Meat quality of steers finished on autumn grass, grass silage or concentrate-based diets.

The objective of this experiment was to determine the effect of varying the proportions of autumn grass and concentrates and grass silage and concentrates on the quality of meat from cattle with similar rates of carcass growth. Fifty continental crossbred steers were assigned to five treatments. The experimental diets offered were (1) grass silage ad libitum plus 4 kg concentrate (SC), (2) 1 kg hay plus 8 kg concentrate (CO), (3) 6 kg grass dry matter (DM) plus 5 kg concentrate (CG), (4) 12 kg grass DM plus 2.5 kg concentrate (GC) and (5) 22 kg grass DM (GO). The experiment lasted 85 days after which all animals were slaughtered. The right side m. longissmus dorsi was excised from all animals 24 h post slaughter for assessment of meat quality. Treatments SC and CO resulted in animals with whiter (P<0.05) subcutaneous and kidney/channel fat than all other treatments. There was an interaction (P<0.05) between ageing time and treatment with treatment GC having higher (P<0.05) tenderness, texture and acceptability values after 2 days ageing, but not after 7 or 14 days ageing. It is concluded that supplementing grass with low levels of concentrate produced the most tender and acceptable meat at 2 days post mortem, but that further ageing eliminated all treatment effects on eating quality of beef.

The eating quality of meat of steers fed grass and/or concentrates

The objective was to determine, relative to animals expressing their full potential for carcass growth, the impact on meat quality of increasing carcass growth of grazing steers by supplementing with concentrates or by increasing grass supply. Sixty-six continental (Limousin and Charolais) crossbred steers (567 kg) were assigned to one of six diets: (1) 18 kg grass dry matter (DM); (2) 18 kg grass DM grass and 2.5 kg concentrate; (3) 18 kg grass DM and 5 kg concentrate; (4) 6 kg grass DM and 5 kg concentrate; (5) 12 kg grass DM and 2.5 kg concentrate; or (6) concentrates daily. Animals were slaughtered after an average of 95 days. Samples of the M. longissmus dorsi (LD) were collected at the 8-9th rib interface and subjected to sensory analysis and to other assessments of quality following 2, 7, or 14 days aging. Carcass weight gain averaged 360, 631, 727, 617, 551 and 809 g/day for treatments 1 to 6, respectively. There was no difference between diets for colour, Warner-Bratzler shear force (WBSF) or any sensory attribute of the LD. WBSF was negatively correlated with (P<0.05) carcass growth rate (-0.31) but only a small proportion of the variation in meat quality between animals could be attributed to diet pre-slaughter or carcass fatness. It is concluded that high carcass growth can be achieved on a grass-based diet without a deleterious effect on meat quality.

Effects of fat level and maltodextrin on the functional properties of frankfurters formulated with 5, 12 and 30% fat.

The effects of fat level (5, 12 and 30%) and maltodextrin on emulsion stability, cook loss, colour, texture and sensory characteristics of frankfurters were investigated. Three fat levels (5, 12 and 30%) were formulated containing added maltodextrin. For each fat level a control was prepared without added maltodextrin giving a total of 6 treatments (3×2 factorial design). Reducing the fat from 30 to 5% increased cook loss and decreased emulsion stability. Panellists detected an increase in juiciness and a decrease in overall texture, overall acceptability when the fat level was reduced from 30 to 5%. Instron texture profile analysis showed a decrease in hardness, chewiness and gumminess and an increase in springiness with decreasing fat level. Maltodextrin addition caused a significant decrease in cook loss of the frankfurters but also decreased the emulsion stability. An interactive effect (P<0.05) occurred between fat level and maltodextrin resulting in no significant difference in hardness, gumminess and chewiness values when maltodextrin was present in the reduced-fat (5 and 12%) frankfurters. Saltiness, overall flavour intensity, overall texture and overall acceptability were unaltered (P>0.05) by maltodextrin. The results indicate that maltodextrin can be used as a suitable fat replacer since it offset some of the changes brought about by fat reduction, decreasing cook loss and maintaining a number of textural and sensory characteristics of the frankfurters.

Effects of salt level and high hydrostatic pressure processing on frankfurters formulated with 1.5 and 2.5% salt.

The effects of salt level and high pressure processing on cook loss, emulsion stability, colour, textural and sensory characteristics of frankfurters were investigated. Two salt levels (1.5 and 2.5%) and two pressure treatments (150 and 300 MPa) were examined. For each batch a control was set up which was non-pressure treated. Cook loss values were significantly decreased in 150 MPa products at the 2.5% salt level compared to controls. Significantly lower cook losses were recorded at the lower salt level after the application of 150 MPa pressure. The stability of the meat emulsions was significantly increased at the lower salt level, especially after 150 MPa pressure. Sensory analysis results for overall flavour acceptability after pressure application of 150 MPa and 300 MPa were similar to control products and panellists preferred products formulated at 1.5% salt after pressure treatment (150 MPa). Hardness, cohesiveness, gumminess and chewiness were also improved after pressure treatment. The results demonstrate that high pressure technology is a viable process that partially compensates for the reduction of salt levels in frankfurters.

Effects of fat level, tapioca starch and whey protein on frankfurters formulated with 5% and 12% fat

The effects of fat level (5% and 12%), tapioca starch and whey protein on the hydration/ binding properties, colour, textural and sensory characteristics of frankfurters were investigated. Decreasing the fat content increased cook loss and decreased emulsion stability and product lightness. Fat reduction increased smoke, spice and salt intensities and increased overall flavour intensity and juiciness. Texture profile analysis (TPA) indicated that fat reduction decreased gumminess and cohesiveness but the other parameters measured were unaffected. Addition of tapioca starch or whey protein reduced cook loss and increased emulsion stability. Whey protein did not effect the sensory characteristics but tapioca starch increased overall flavour intensity. Both ingredients increased hardness, adhesiveness, gumminess and chewiness as measured by TPA. Two-factor interactions between fat level and ingredient were observed for several parameters. The results indicate that both ingredients can partially offset some of the changes which occur in low-fat frankfurters when fat is replaced with added water and protein level is constant.

The role of endogenous proteases in the tenderisation of fast glycolysing muscle.

The activities of lysosomal cathepsins and the calpain-calpastatin system were measured to determine their involvement in the more rapid tenderisation of fast glycolysing muscle. The rate of pH fall of M. longissimus dorsi (LD) of Hereford cross Friesian heifers (n = 52, Experiment 1; n = 36, Experiment 2) was measured. Muscles were selected according to their rate of glycolysis; slow and fast (n = 16, Experiment 1; n = 10, Experiment 2). Fast glycolysing muscles were rated more tender in sensory analysis and had a lower shear force than slow glycolysing muscles. Slow glycolysing muscles had shorter sarcomere lengths. Low pH conditions in fast glycolysing muscle correlated with the enhanced release of cathepsins B and L from lysosomes. Calpain I activity was higher and calpastatin activity was lower in fast glycolysing muscle early post mortem. SDS-PAGE electrophoresis patterns showed increased proteolysis, such as the earlier appearance of the 30 kDa fragment in fast glycolysing muscle. Transmission Electron Microscopy (TEM) results showed a greater degree of ultrastructural breakdown early post mortem in fast glycolysing muscle. The results suggest that the increase in tenderness in muscles that undergo fast glycolysis early post mortem may be caused by proteolysis by released lysosomal cathepsins and calpain I uninhibited by calpastatin.

The relationship between early post-mortem pH and the tenderisation of beef muscles

The rate of early post-mortem pH fall in bovine muscle was studied to determine its influence on the rate and extent of the tenderisation process. The pH of M. longissimus dorsi (LD) and M. semimembranosus (SM) muscles of Hereford cross Friesian heifers (n = 127) was taken up to 24 h post mortem. Twenty-four LD and 24 SM muscles were selected according to their rate of pH fall; slow (n = 8), intermediate (n = 8) and fast (n = 8) and were sampled at 2, 7 and 14 days post mortem for sensory, mechanical, physicochemical and biochemical analysis. Fast glycolysing LD muscles were rated more tender in sensory analysis and texture assessment whereas slow glycolysing muscles were considered significantly tougher (p < 0.001). Fast glycolysing LD had a significantly lower shear force (p < 0.001) at each stage of ageing. Slow glycolysing LD and SM had the highest shear force values. No significant difference was found in intramuscular fat or moisture content between the groups. Slow glycolysing LD muscles had shorter sarcomere lengths at 2 days post mortem. SDS-PAGE electrophoresis patterns showed increased proteolysis, such as the earlier appearance of the 30 kDa fragment, which is believed to be a good indicator of tenderness, in fast glycolysing muscle. These results suggest that the rate of post-mortem pH fall plays an important role in proteolysis and tenderisation.

Non-destructive prediction of selected quality attributes of beef by near-infrared reflectance spectroscopy between 750 and 1098 nm

Heifers (n = 70) were slaughtered and hung conventionally in an industrial meat plant. Near infrared (NIR) spectroscopy was studied for its ability to predict selected meat quality attributes, i.e. Warner-Bratzler shear force (WBSF), sensory tenderness, texture, flavour and acceptability. Freshly cut steaks (2.5 cm thick) were taken from the longissimus dorsi (LD) muscle at 1, 2, 7 and 14 days post mortem for NIR analysis. Other samples (also 2.5 cm thick) were taken at 2, 7 and 14 days post mortem, vacuum-packaged in plastic bags and stored at -20 °C for WBSF measurement and sensory analysis. Heifers were slaughtered in two groups; between slaughterings, replacement of the spectrophotometer lamp and lamp assembly was necessitated by a bulb failure. Using principal component regression (PCR), correlation coefficients of 0.82 and 0.73 were obtained for the prediction of WBSF in sample sets 1 and 2, respectively. On merging both sample sets, this value was lowered slightly (r = 0.61). Correlation coefficients obtained for the prediction of tenderness, texture, flavour and acceptability were 0.67, 0.53, 0.51 and 0.46 respectively (set 1); 0.72, 0.71, 0.45 and 0.67 (set 2); 0.53, 0.54, 0.24 and 0.42 (combined sets).

Eating quality of low-fat beef burgers containing fat-replacing functional blends

Tapioca starch, carrageenan, oat fibre, pectin, whey protein and a commercial mixture of carrageenan and locust bean gum were assessed for their ability to mimic fat characteristics in cooked low-fat (10%) beef burgers. Thirteen different blends of the ingredients were formulated in order to examine their effects on quality parameters of low-fat beef burgers. The beef burgers were tested for cook yield, water-holding capacity (WHC), retention of shape, sensory and mechanical texture analysis. Most blends significantly (P<0.05) increased both cook yield and WHC, in particular blends containing tapioca starch, oat fibre, whey protein and the carrageenan/locust bean gum mixture. These blends substantially reduced both Warner–Bratzler and Kramer shear values. Sensory analysis showed that beef burgers containing tapioca starch, oat fibre and whey protein were acceptable in terms of flavour and texture. The low-fat control was found to be the toughest and driest of the beef burgers examined. This study shows that blends of these ingredients can be used to offset the poor quality associated with low-fat beef burgers. © 1999 Society of Chemical Industry