Variations in water-holding capacity due to changes in the fibre diameter, sarcomere length and connective tissue morphology of some beef muscles under acidic conditions below the ultimate pH

The water-holding capacities (WHC) of six different beef muscles were measured over the pH range 5·7 to 4·0. Corresponding changes in the morphology of muscle fibres and connective tissue were observed by light microscopy. WHC increased over the pH range 5·1 to 4·0 in all muscles, with the M. longissimus dorsi (LD) having significantly higher (p < 0·05) swelling ratios than the other muscles at pH 4·3 and pH 4·0. In all muscles, swelling increased across and along the muscle fibre axis between pH5·1 and pH4·4. However, towards pH4·0, increased muscle fibre swelling occurred in predominantly 'white' fibre-type muscles, in particular the LD, whereas muscle fibre shrinkage occurred in predominantly 'red' fibre-type muscles. Increased swelling of perimysial collagen and endomysial reticulin was observed in all muscles between pH4·5 and pH4·0, while the appearance of elastin was unaffected by pH. Consequently, interactions between muscle fibre swelling and connective tissue swelling determined the extent of total muscle swelling in different muscles between pH 4·5 and pH 4·0.     

风鹅现有工艺加工过程中品质的变化规律

通过对风鹅现有工艺加工过程中pH值、色泽、盐分含量、水分含量、硫代巴比妥酸还原物(thiobarbituric acidreactive substance,TBARS)值、总氮含量、非蛋白氮含量、游离氨基酸含量和游离氨基酸态氮含量等指标的测定,研究风鹅肌肉中品质变化规律及脂肪氧化和蛋白质水解可能对风味产生的影响.结果表明,盐分含量在加工过程中不断上升,水分含量不断下降;pH值和TBARS值在一定范围内波动;总氮含量、非蛋白氮含量、游离氨基酸含量、游离氨基酸态氮含量变化差异显著,风干结束后风鹅肌肉中蛋白质水解指数约为3.8％,游离氨基酸含量占非蛋白氮含量的78％以上,含量最多的游离氨基酸含量为Arg、Thr、Glu、Leu和Ala等,而增加较多的游离氨基酸含量是Asp、Leu、Tyr、Val、Ile和Lys等,大部分游离氨基酸的含量都超过其阈值很多倍,可能对风鹅的风味产生重要影响.     

Antioxidant activity of carnosine in cooked ground pork

Carnosine (0·5-1·5%) reduced (P < 0·05) the formation of thiobarbituric acid reactive substances (TBARS) in cooked unsalted ground pork after 7 days of storage at 4°C. The antioxidant activity of carnosine was less in cooked salted ground pork, with only 1·5% carnosine inhibiting (P < 0·05) TBARS formation during refrigerated storage. The antioxidant activity of carnosine in cooked salted and unsalted ground pork was greater than those of the lipid-soluble free radical scavengers, butylated hydroxytoluene and α-tocopherol (P < 0·05) but less than that of sodium tripolyphosphate (P < 0·05). These data suggest that carnosine could be used to reduce the oxidative deterioration of cooked salted and unsalted ground pork.     

Effects of fattening on post-mortem pH of beef muscles

The pH of beef psoas major (PM) and longissimus dorsi (LD) muscles at 1·0 h after slaughter were examined among the following four groups: pithed fattening cattle (FP), non-pithed fattening cattle (FN), pithed calves (CP) and non-pithed calves (CN). Differences were observed only in PM muscles. The levels of pH were in the order of FP相似文献   

Pigment oxidation in ground veal: Influence of lipid oxidation, iron and zinc

The color stability of fresh ground veal from four different muscles (biceps femoris, longissimus dorsi, psoas major and supraspinatus) was characterized, and the effects of lipid oxidation, iron and zinc on this degradative process were investigated. Samples were minced and prepared in a manner consistent with retail production and analyzed for pH, myoglobin concentration, total and nonheme iron, and zinc. Pigment and lipid oxidation were measured on days 0, 3 and 6 of 4°C storage. B. femoris demonstrated the greatest extent of lipid oxidation, and was more color-labile than p. major or supraspinatus (P < 0·05), but no different from l. dorsi (P > 0·05). Total iron and myoglobin concentrations were lowest for l. dorsi (P<0·05). Zinc concentration in the four muscles followed the order supraspinatus ? b. femoris ? l. dorsi ? p. major (P < 0·05). Data analysis revealed that initial metmyoglobin formation (days 0 to 3) was significantly correlated with total iron (r = 0·69) or nonheme iron (r = 0·68) in b. femoris, but not any of the other muscles. Correlations between lipid and pigment oxidation in each of the four muscles were performed and the data support a strong relationship between these degradative processes in ground veal.     

The effects of conditioning on meat collagen: Part 4-The use of pre-rigor lactic acid injection to accelerate conditioning in bovine meat

Injection of fresh bovine muscle with 0·1 m lactic acid (to a level of 10% of original muscle weight) resulted in a pH decline to a minimum pH of 5·33 at 15°C only 3 h after injection. Untreated muscle reached the same pH after 26 h when held at the same temperature. Fresh, unconditioned meat colour was unaffected by pre-rigor 0·1 m lactic acid injection as assessed by visual inspection. The percentage of perimysial collagen extracted as the soluble form was significantly higher (P < 0·05) from three muscles of varying quality when pre-injected with 0·1 m lactic acid and conditioned from 1 to 14 days, than from conditioned untreated muscles. SDS-polyacrylamide gel electrophoresis of CNBr peptides from insoluble perimysium obtained from three muscles of varying quality revealed no obvious differences due to pre-rigor lactic acid injection before conditioning. However, analysis of the high molecular weight perimysial collagen CNBr peptides from lactic acid treated muscles by two-dimensional SDS-polyacrylamide gel electrophoresis revealed an increased incidence of degradation in this region compared with untreated controls. These data strongly suggest that pre-rigor injection of beef muscle with lactic acid may accelerate conditioning. The implications of this finding are discussed.     

Hydrolysis and loss of extractability of proteins during ripening of iberian ham

To elucidate the extent of the hydrolysis and loss of extractability of protein during the traditional ripening of Iberian ham, the evolution during processing of non-protein nitrogen (NPN) and protein fractions soluble in 0·03 m pH 7·1 phosphate and 1·1 KI + 0·1 m phosphate pH 7·4 buffers and 6 m urea was followed from Semimembranosus and Biceps femoris muscles. The NPN steadily increased during processing, showing maximum intensity at salting and drying. Electrophoretic study of the proteins extracted, and microscopical examination of the pellet obtained after consecutive extractions with the above buffers, revealed that hydrolysis and insolubilization are more intense in myofibrillar than in sarcoplasmic proteins. Protein aggregation involves mainly the myofibrillar fraction, and occurs during the first stage of processing.     

Contents of creatine, creatinine and carnosine in porcine muscles of different metabolic types

Creatine, creatinine and carnosine have been analyzed by hydrophilic interaction chromatography (HILIC) in seven different pork muscles of different metabolic type (Semimembranosus, Biceps femoris, Gluteus maximus, Longissimus dorsi, Gluteus medius, Trapezius and Masseter). As reported in previous literature, carnosine contents are related with the type of metabolism, being higher in those muscles with glycolytic metabolism. Creatine and creatinine also showed significantly higher concentrations in glycolytic muscles such as Semimembranosus, Biceps femoris, Gluteus maximus and Longissimus dorsi. Masseter, a red oxidative muscle, was characterized by the lowest contents of creatine, creatinine and carnosine and, finally, Gluteus medius and Trapezius, both intermediate muscles, had also intermediate contents of these studied compounds. Finally, a correlation between initial content of creatine and creatinine formation after cooking has been verified using pure standards and two different metabolic type muscles, Longissimus dorsi and Masseter, obtaining slightly higher creatinine amounts in Longissimus dorsi, probably due to its higher initial creatine content and its lower pH.     

不同产蛋白酶乳酸菌对风干牛肉蛋白质降解的影响

为探究产蛋白酶乳酸菌在风干牛肉发酵过程中对肌原纤维蛋白的影响.以牛肉为研究对象,分别接种乳酸乳球菌(S-1)、格氏乳球菌(S-2)、戊糖片球菌(S-3)制备风干牛肉,以不添加发酵剂的样品为对照组(CK),采用理化分析和十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(sodium dodecyl sulfate polyacryla...     

RESPIRATORY DEFICIENT MUTANTS OF BOTTOM BREWER'S YEAST II. TECHNOLOGICAL PROPERTIES OF SOME RD MUTANTS

Five spontaneous respiratory deficient mutants of one strain of bottom brewer's yeast were studied, being chosen for differences in their cytochrome system, and in rates of growth and fermentation. Pilot plant experiments showed that these 5 mutants differed from the original type also in the utilization of nitrogen compounds, in the sequence of utilization of sugars, and in the pattern of sedimentation. The beers prepared using these mutants were more aromatic, had higher contents of nitrogen compounds and of anthocyanogens, lower contents of most free amino acids and substantially lower contents of higher aliphatic alcohols. Their pH values were higher as well as their buffering capacities. One of the 5 mutants studied produced beer of better flavour than the original type.     

Chemical composition characteristics of the longissimus and semimembranosus muscles for pigs from New Zealand and Singapore

A range of composition characteristics of the longissimus (LL) and semimembranosus (SM) muscles were compared between pigs raised in intensive and extensive production systems in New Zealand (NZ), and pigs raised in an intensive system in Indonesia for supply to the Singapore market (n = 8/group). Ultimate pH was slightly higher for the Singaporean LL muscles (P < 0.05), while LL muscle of the NZ extensive group was redder (higher a^∗ values) and contained more fat (P < 0.05). Muscle iron levels were highest for the NZ extensive group and lowest for a lighter group within the Singapore pigs (P < 0.05). Differences in fatty acid concentrations, which were also measured in a sample of the belly cut, could largely be attributed to the effects of diet, with higher levels of alpha linolenic acid for the NZ extensive group (P < 0.05) due to linseed in the diet, and much higher levels of linoleic acid and the P:S ratio for the Singapore group (P < 0.05). Some statistically significant differences in amino acid concentrations were shown between muscles and groups, but they were not large. With respect to compounds with potential bioactive properties, coenzyme Q_10, and taurine levels were higher in pork from NZ pigs, and carnosine levels were highest for the NZ intensive group (P < 0.05). The LL muscle contained more coenzyme Q₁₀ and taurine, but less carnosine than the SM muscle (P < 0.001). It is concluded that some of these composition differences in the pork from the muscles and groups compared may be of commercial importance, but several are likely to have been due to dietary or weight differences.     

羊乳酒在发酵过程中主要参数变化的研究

以新鲜羊奶为原料,采用乳酸菌和酵母菌共发酵方法,在29 ℃条件下振荡发酵羊乳,以pH值、酒精度、总氮及非蛋白氮含量为评价指标,通过凯氏定氮法、十二烷基硫酸钠-聚丙烯酰氨凝胶电泳法（SDS-PAGE）,对羊乳酒在发酵过程的不同时期蛋白质降解的动态变化进行了研究。研究结果表明,羊乳酒在发酵的过程中的pH值呈现先降低后升高再降至稳定的趋势;酒精度呈现缓慢增长的趋势;总氮含量变化不大;非蛋白氮含量随着乳酒发酵的进行缓慢升高;SDS-PAGE结果显示,羊乳酒中蛋白质发生了不同程度的降解,小分子蛋白增多,蛋白分子质量主要分布在17～35 kDa。     

Post-mortem evolution of non-protein nitrogen and its peptide composition in growing lamb muscles

Twenty-two 4-month-old lambs were used in two experiments to assess the effects of growth rate, induced by different feeding levels, and ageing (21 days, 4°C) on non-protein nitrogen (NPN) contents and their peptide composition. Muscle (Longissimus dorsi, Semimembranosus) and sex (male, female) effects were also studied. During ageing, NPN contents increased (15–20%). This variation represented 1.6–2.8% of total nitrogen. Peptides extracted from fresh muscles were in the range of molecular weight (MW) up to 12 kDa, the majority being less than 2.4 kDa (45–48%). During ageing, peptide average MW decreased (11.5–27.6%). High growth rate increased NPN contents at slaughter (+6–14%) and during ageing. Peptide average MW and post-mortem proteolysis rate as with to NPN variations were also higher. Differences between sex were observed at the end of the ageing period. Muscle effects were observed on the peptide class from 6.8 to 3.4 kDa.     

Effects of salt and temperature on proteolysis during ripening of Iberian ham

Fifty-five hams from Iberian pigs were processed using two different dry-curing techniques, traditional and modern. Salt content, non-protein nitrogen and its fractions (peptide, amino acid and volatile basic nitrogen) from Biceps femoris muscles were quantified. The existence of an overlapping effect of both temperature and salt content on the general non-protein nitrogen production was observed. The most intense proteolytic breakdown took place when higher temperatures were reached during the drying stage. The difference in salt concentration seems to contribute to generating different quantities in the non-protein nitrogen fractions. The inclusion at the end of the cellar stage of a stuffing period would permit increasing the accumulation of free amino acid in high salted hams.     

Nonprotein Nitrogen (NPN) and Free amino acid contents of dry, fermented and nonfermented sausages

Fermented and nonfermented sausages were analyzed for concentration changes in total and nonprotein nitrogen (NPN) and in free amino acid profiles during processing. Sausages fermented by Pediococcus pentaceous at 38°C and heated to 60°C had increases (p < 0·05) in total N and NPN contents and increases in concentration (≥5 mg per 100 g dry sample) for 14 of 20 free amino acids. Nonfermented sausages had no increase (p > 0·05) of NPN content and increases in only 6 of 20 free amino acids after heating to 60°C. When the effects of three starter cultures were compared, NPN concentrations after fermentation and heating and after drying were highest to lowest in the following order: P. pentaceous >P. acidilactici with M. varians >P. acidilactici. Variations of free amino acid patterns in the fermented, dried sausages were found which indicated differences in metabolic activity between the cultures. These variations did not (p > 0·05) affect sensory scores for the dried sausages. Overall, these results for rapidly fermented and mildly heated dry sausages were similar to results previously reported for 'European-style' dry sausages processed with prolonged low temperature fermentations.     

茶枝柑果肉发酵过程中感官特性及抗氧化活性的变化

本文旨在研究酵母发酵茶枝柑果汁过程中感官、化学成分和抗氧化活性的变化,促进茶质柑果肉资源的合理利用。从组织状态、色泽、酸味、甜味、苦涩、香气六个方面评价其感官特性;测定发酵过程中总酸、还原糖、总酚、总黄酮的含量;通过GC-MS检测其香气成分及相对含量;结合DPPH·清除率和·OH清除率评价其抗氧化活性。研究表明,采用0.5%接种量接种安琪酵母,40 ℃发酵96 h后的茶枝柑发酵果汁口感酸甜适中,苦涩感较弱,带有果香味和发酵风味;挥发性香味物质经0~96 h发酵,烯烃含量最高由53.70%增加至77.77%,主要成分为d-柠檬烯和γ-萜烯;其次是醇类由34.50%降至16.05%,酯类由7.74%降至2.44%;醛酮与酚类含量较少(<1%)。发酵过程中总酸、还原糖含量逐渐减少,总酚、总黄酮含量先大幅减少后略有增加;发酵过程中DPPH·清除率逐渐降低,与总酚、总黄酮、总酸及还原糖含量均呈显著相关(P<0.05);·OH清除率逐渐降低,与总酸含量呈极显著相关(P<0.01),与总黄酮含量和还原糖含量呈显著相关(P<0.05);·OH清除率与总酚含量无显著相关性(P>0.05)。     

Free amino acids and dipeptides in porcine muscles: differences between `red' and `white' muscles

Three porcine muscles (m. longissimus dorsi, masseter and trapezius), chosen to represent the three main metabolic types, from 18 carcasses had their free amino acids and dipeptides quantified by reverse-phase high performance liquid chromatography (HPLC) in aqueous extracts derivatized with phenyl isothiocyanate. Of the 25 measured compounds, four amino acids and the dipeptide carnosine were closely related to the metabolic type of the three muscles. Masseter, a red oxidative muscle, had the highest contents of aspartic acid, glutamine and taurine. Longissimus dorsi, a white glycolytic muscle was characterised by the highest contents of β-alanine and carnosine. Trapezius, an intermediate muscle, had intermediate contents. These results show that free amino acid and dipeptide contents could partly explain differences in taste of muscles from the same species.     

Effect of delay time before chilling on toughness in pork with high or low initial pH

Paired M. longissimus dorsi muscles from 56 carcasses of Danish Landrace and Yorkshire breeds, slaughtered at approximately 90 kg live weight, were utilized to study the potential of cold induced toughness in pork. Based upon the pH value 45 min post stunning, the carcasses were divided in two groups: a low (5·7 ≤ pH < 6·1) and a high one (6·1 ≤ pH ≤ 6·5). The effects on Warner-Bratzler shear force, sarcomere length and myofibril fragmentation of inserting a delay time of 0, 2 and 4 h before carcasses entered the chilling tunnel (operating at -28°C to -22°C) were investigated on early excised muscles as well as on muscles removed 30 h post stunning. The left LD muscle from each carcass served as a control while all right sides were used for treatments. pH and temperature measurements obtained from LD muscles left on carcasses during chilling showed that LD muscles belonging to the high pH group involve a risk of cold shortening even when a 2 h delay was used before passing in to the chilling tunnel. Comparing pH groups, however, sarcomere lengths did not differ in control sides whereas the Warner-Bratzler shear force values were significantly higher in LD muscles taken from the high pH group. Early excision of the LD muscle resulted in shorter sarcomere lengths and increased WB shear force only for carcasses belonging to the high pH group, which, however, could be avoided by introducing a 4 h delay time before rapid chilling. The effect of delay time on tenderness from muscles excised from the carcass 30 h post stunning was much less but a 4 h delay did significantly (P < 0·05) improve tenderness in carcasses with high initial pH. Coefficient of correlation between Warner-Bratzler shear force and sarcomere length was -0·12 and nonsignificant in the low pH group, whereas it was -0·57 and highly significant in the high pH group.     

Effect of citric acid and citrate on the shelf stability of canned liver paste processed at reduced F(0) values

Citric acid and the combination of citric acid and citrate, in a few cases enriched with potassium sorbate, were tested for their stabilizing effect in a canned liver paste processed at reduced F(0) values. pH values of the rest products ranged from 5·24 to 5·76; a(w) values varied from 0·950 to 0·972. F(0) values of 0·05, 0·30 and 0·85 were applied. Before sterilization, the paste doughs were contaminated with mixtures of bacterial spores. Heated packages were challenged by incubation at 30 and 55°C for up to about 2 years. Incubated packages with the standard formulation at an F(0) of 0·05 showed the first blown cans at 30°C after 24 days. Starting from this point, at this F(0) value products with a variable, but increased, bacteriological stability were observed. At an F(0) of 0·30 a perfectly stable product at 30°C was observed after addition of 0·14% w/w citric acid only (product pH 5·69). Moreover, all tested combinations of additives at F(0) values of 0·30 and 0·85 yielded stable products at this incubation temperature. At the higher F(0) value a clear effect with respect to delaying thermophilic spoilage was observed. The effect of the application of potassium sorbate-in combination with both other additives-at F(0) values of 0·30 and 0·85 proved to be negligible.     

The influence of pre-slaughter oral loading of acid or base on post-mortem changes in Longissimus Dorsi muscle of pork

Twenty-four pigs were assigned to one of four ad libitum water treatments: control, sodium bicarbonate (12·6 g/litre), low ammonium chloride (4 g/litre) or high ammonium chloride (8 g/litre) for 5 days, to study the influence of an oral acid or base load on post-mortem changes in longissimus dorsi muscle and ultimate pork quality. Physiological changes before slaughter were monitored by measuring blood pH, pCO(2) and HCO(3)(-). The influence of dietary treatments on post-mortem changes and ultimate meat quality was determined by measuring glycolytic enzymes and intermediates, and muscle pH, color and water-holding capacity (WHC). As expected, sodium bicarbonate generated a metabolic alkalosis, whereas ammonium chloride resulted in a metabolic acidosis. Pre-slaughter acid-base status was positively correlated with muscle WHC (P < 0·05). However, no significant dietary treatment effect was observed in muscle quality traits such as color (a, b, L) and WHC. Muscle pH(45) was significantly (P < 0·05) higher in bicarbonate than control and high ammonium chloride treatments. The activity of Ca(2+)-dependent protein kinase was significantly (P < 0·05) higher at 45 min post-mortem but that of pyruvate kinase was significantly lower at 2 and 4 h post mortem in bicarbonate-treated pigs. At 45 min post mortem, the activity of fructose-1,6-diphosphatase in the control pigs was significantly higher (P < 0·05) than on other treatments. The concentration of glycogen was significantly (P < 0·05) higher in bicarbonate and high ammonium chloride pigs; bicarbonate-treated pigs also has significantly higher adenosine-5'-triphosphate (ATP) and pH values than other treatment groups (P < 0·05) at early post-mortem. It was concluded that pre-slaughter oral loading of acid or base could induce changes in muscle metabolism and post-mortem muscle pH. Further research is required to confirm that altering diet acidogenicity or alkalinogenicity may be a means of enhancing ultimate pork quality.