An in situ system involving incubation of 60- to 80-g pieces of muscle at 4 degrees C under different conditions was used to determine the effects of time of postmortem storage, of pH, and of temperature on activities of mu- and m-calpain activity in bovine skeletal muscle. Casein zymograms were used to allow measurement of calpain activity with a minimum of sample preparation and to ensure that the calpains were not exposed to ionic strengths of 100 or greater before assay of their activities. In 4 of the 5 muscles (longissimus dorsi, lumbar; longissimus dorsi, thoracic; psoas major; semimembranosus; and triceps brachii) studied, mu-calpain activity decreased nearly to zero within 48 h postmortem. Activity of m-calpain also decreased in the in situ system used but at a much slower rate. Activities of both mu- and m-calpain decreased more slowly in the triceps brachii muscle than in the other 4 muscles during postmortem storage. Although previous studies have indicated that mu-calpain but not m-calpain is proteolytically active at pH 5.8, these studies have used calpains obtained from muscle at death. Both mu- and m-calpain are proteolytically inactive if their activities are measured at pH 5.8 and after incubating the muscle pieces for 24 h at pH 5.8. Western analysis suggested that neither the large 80-kDa subunit nor the small 28-kDa subunit of m-calpain was autolyzed during postmortem storage of the muscle pieces. As has been reported previously, the 80-kDa subunit of mu-calpain was autolyzed to 78- and then to a 76-kDa polypeptide after 7 d postmortem, but the 28-kDa small subunit was not autolyzed; hence, the autolyzed mu-calpain molecule in postmortem muscle is a 76-/28-kDa molecule and not a 76-/18-kDa molecule as previously assumed. Because both subunits were present in the postmortem calpains, loss of mu-calpain activity during postmortem storage is not due to dissociation of the 2 subunits and inactivation. Although previous studies have shown that the 76-/18-kDa mu-calpain molecule is completely active proteolytically, it is possible that the 76-/28-kDa mu-calpain molecule in postmortem muscle is proteolytically inactive and that this accounts for the loss of mu-calpain activity during postmortem storage. Because neither mu- nor m-calpain is proteolytically active at pH 5.8 after being incubated at pH 5.8 for 24 h, other proteolytic systems such as the caspases may contribute to postmortem proteolysis in addition to the calpains.

The effects of heating rates (17, 38 and 85"Clhr) and protein concentration (10, 20, 30, 40, and 50 mg/mL) on gels made of extracted salt-soluble proteins were evaluated. Gel strength decreased when heating rate was increased. A greater water loss from compressed gels occurred at protein concentrations of 10 and 20 mg/mL than at 30 to 50 mg/mL. Protein loss in the expelled water, after compression, was less for the slower heating rates while the total amount of protein in the cxpellcd water increased with increasing protein concentration in the system. SDS gel electrophoresis demonstrated a change in some of the cxpclled proteins at different heating rates.

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The objective of this study was to assess the effects of roselle extract (0%–1%), potato peel flour (0%–2%), and beef fat (0%–15%) on physicochemical properties (instrumental color, pH, cooking properties, and texture profile analysis), antioxidant capacity (DPPH, ABTS, and ORAC), and total phenols in beef patties using response surface methodology. Addition of roselle extract increased the antioxidant capacity and total phenols, but decreased pH, instrumental color, cooking yield, moisture retention, springiness, and cohesivity. The addition of potato peel increased b* value, hardness, cooking yield, and moisture retention but decreased springiness, and cohesivity (p < .05). The resulting optimal formula included 0.61% of roselle extract, 1.27% of potato peel flour, and 3.04% of beef fat. The use of these nontraditional ingredients to develop low‐fat beef patties, with antioxidant capacity and without loss of physicochemical quality, could provide an alternative for health‐conscious consumers. Practical applications The increase in consumer awareness for health and disease prevention opens a new market to modified meat products with healthier ingredients. New meat products can be designed by improving their nutritional profile either by reducing fat content and/or adding new ingredients, such as roselle extract and potato peel. However, the challenge for the meat industry is not easy because this kind of product should maintain traditional quality and an accessible cost. The objective of this research was to assess the effects of roselle extract, potato peel flour, and beef fat on physicochemical and antioxidant properties using response surface methodology. Roselle extract decreased physicochemical characteristics but increased antioxidant properties while potato peel showed an opposite effect. The models developed in this study could be used by the food processor to optimize the quality characteristics of beef patties as a function of roselle extract, potato peel, and beef fat.

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The aim of this work was to evaluate the physicochemical, sensory and nutritional properties of beef patties with added combinations of flaxseed (FS) and tomato paste (TP). Treatments were as follows: control = 0%FS + 0%TP; T1 = 0%FS + 20%TP; T2 = 5%FS + 15%TP; T3 = 10%FS + 10%TP; T4 = 15% FS + 5%TP; and T5 = 20%FS + 0%TP. Sensory properties for treatments T1 and T2 were similar to the control, while T3 showed acceptable sensory scores (>5.0). The α-linolenic acid content of beef patties increased as FS addition increased. The polyunsaturated fatty acid (PUFA)/saturated fatty acid ratio increased from 0.24 in the control treatment to 4.49 in T5. The PUFAs ratio n6/n3 decreased from 7.18 in the control treatment to 0.29 in T5. A combination of FS and TP can be used as novel ingredients to develop beef patties with better nutritional profile without demerit of their sensory and physicochemical properties.Calidad nutricional de hamburguesas de res adicionadas con linaza y pasta de tomate RESUMEN El objetivo de este trabajo fue evaluar las propiedades fisicoquímicas, sensoriales y nutricionales de hamburguesas de res adicionadas con combinaciones de linaza (FS) y pasta de tomate (TP). Los tratamientos fueron: control = 0%FS + 0%TP; T1 = 0%FS + 20%TP; T2 = 5%FS + 15%TP; T3 = 10% FS + 10%TP; T4 = 15%FS + 5%TP; and T5 = 20%FS + 0%TP. Las propiedades sensoriales para los tratamientos T1 y T2 fueron similares al control, mientras que T3 mostró puntuaciones sensoriales aceptables (>5,0). El contenido de ácido α-linolénico de las hamburguesas de res se incrementó al aumentar la adición de FS. La relación PUFA/SFA aumentó de 0,24 en el tratamiento testigo a 4,49 en T5. La relación n6/n3 de ácidos grasos poliinsaturados disminuyó de 7,18 en el tratamiento testigo a 0,29 en T5. La combinación de linaza y pasta de tomate puede utilizarse como nuevos ingredientes para elaborar hamburguesas de res con mejor perfil nutricional sin demérito de sus propiedades sensoriales y fisicoquímicas. ARTICLE HISTORY

The effects of supplementation of zilpaterol hydrochloride (ZH; 0 or 10 mg/lamb daily) and soybean oil (SBO; 0% or 6%) on carcass traits, body fat deposition, chemical, physicochemical, sensory quality, and fatty acid composition of the longissimus thoracis muscle (LTM) of ewe lambs were studied using a randomised complete design with a 2 × 2 factorial arrangement. After a 32-day feeding period, all ewes were slaughtered and LTM collected. Interactions between ZH × SBO were not observed (P > 0.05) for any of the variables evaluated. Feedlot performance was not modified (P > 0.05) by ZH and SBO supplementation. Biological yield and hot carcass weight were increased by ZH supplementation (P < 0.05). ZH and SBO supplementation did not alter body fat deposition (kidney, pelvic and heart, renal, thickness and intramuscular fat) and the empty bodyweight (P > 0.05). Meanwhile, feeding ZH decreased colour parameters (L*, a*, b* and CHROMA) (P < 0.05), but not others characteristics of LTM (P > 0.05). Sensory panelists observed an increase in appearance (P < 0.001) by ZH supplementation. Additionally, ZH decreased (P < 0.05) the content of C20:5n3 (eicosapentaenoic acid), C22:6n-3 (docosahexaenoic acid) and total omega-3 fatty acids, compared with the zero ZH group. Physicochemicals and sensory characteristics, and fatty acid composition of meat were not modified by SBO (P > 0.05). In conclusion, ZH supplementation to ewe lambs increased biological yield and hot carcass weight, without changes in body fat deposition and decreased eicosapentaenoic acid, docosahexaenoic acid and omega-3 contents and caused a decrease in colour of LTM. However, feeding SBO caused no changes in the carcass or meat quality traits and minimal changes in fatty acid composition of LTM.