RELATIONSHIP OF CHILLING RATE AND LOCATION WITHIN MUSCLE ON THE QUALITY OF HAM AND LOIN MUSCLES

Halothane negative Durocs (n=36) were slaughtered, and subjected to: accelerated chill (AC: −30C for 2 h, with air circulation, followed by equilibration at 4C for 20–22 h), conventional chill (CC: 4C for 22–24 h with water sprayed every 2 h until 12 h postmortem), and slow chill (SC: 10–12C for 12 h followed by equilibration at 4C for 10–12 h). Color, pH, and drip loss were determined for the Semimembranosus (SM) Biceps femoris (BF) , Longissimus thoracis (LT), and Longissimus lumborum ( LL). In the ham muscles, AC decreased b* values and drip loss. Decreased drip loss was restricted to the outer sites. Ham muscles were darkest in the mid location and lightest in the inner locations. In the Longissimus, AC decreased pH but did not affect color or drip loss. Compared to SC, AC proved beneficial, however, AC had no advantages over CC in pigs with minimal predisposition to quality problems.     

不同电压电击昏对猪肉品质的影响

30头品种、年龄、性别相同的杂交猪(体重120 kg±5 kg)随机分成3组,每组10头,分别用215、150、100V的电压在头部进行电击昏后屠宰.取背长肌测定各项肉质指标.结果显示:宰后45 min采用215 V电压电击昏组的猪肉pH值与150 V电压组差异显著(P<0.05),其它时间点差异不显著;215 V电压组与100 V电压组相比在45 min、1.5、2.5、24 h差异显著(P<0.05).150 V电压组与100 V电压组相比在1.5、2.5 h差异显著(P<0.05).击昏电压对宰后背长肌的色泽(L*和a*值)、滴水损失、蒸煮损失、嫩度、没有显著影响(P<0.05);宰后24 h 215 V组的细胞间空隙面积明显高于其它两个组.生产操作中建议击昏电压采用150 V电压.     

EFFECTS OF DIETARY GLYCINE BETAINE ON BLOOD CHARACTERISTICS AND PORK QUALITY

This study was conducted to determine the effects of dietary glycine betaine on pork quality and blood characteristics. A total of 80 female pigs (Landrace  ×  Yorkshire  ×  Duroc) were randomly allotted into one of four experimental diet groups. Each group of pigs fed with a commercial diet (control) added with 0.2 g glycine betaine (T1), 0.4 g glycine betaine (T2) and 0.6 g glycine betaine (T3)/kg diet during 40 days. Glycine betaine concentrations in plasma and loin muscle were significantly increased by dietary glycine betaine; however, triglyceride concentration in serum was decreased by dietary glycine betaine. Creatine phosphokinase concentrations in plasma had no significant difference among the dietary groups. Redness ( a* ) was significantly higher in T2 and T3; however, at the first and seventh days of storage, redness ( a* ) was not significantly different between dietary groups. Shear force was significantly higher in dietary glycine betaine groups at the first day of storage. Cholesterol content was significantly lower in T2 and T3, whereas T1 was not significantly different compared with the control group. In fatty acid composition, the ratio of saturated fatty acids was increased, whereas unsaturated fatty acids were decreased by dietary glycine betaine.

PRACTICAL APPLICATIONS

Glycine betaine is an amino acid (trimethylglycine) present in most organisms, and is an obligatory intermediate in the catabolism of choline. Glycine betaine has been reported to affect some aspects of pork qualities. As a result of this study, dietary glycine betaine should improve meat redness and reduce cholesterol. However, dietary glycine betaine did not influence creatine phosphokinase levels in plasma. These results will be helpful to the pork industry and meat scientists for improving meat qaulity.     

FAT THICKNESS AND LOIN EYE AREA EFFECTS ON PORK CARCASS QUALITY MEASURES

Pork carcasses (n = 133), varying in fatness and muscling, were selected to evaluate the relationship between pork carcass cutability and pork meat quality. Carcasses were selected with three levels of 10^th rib fat (TRBF: < 2.03 cm, n = 60; 2.03 - 2.54 cm, n = 31; and > 2.54 cm, n = 42) and three levels of loin eye area (LEA: < 35.5 cm², n = 33; 35.5 – 41.9 cm², n = 52; and > 41.9 cm², n = 48). Data were collected on the longissimus muscle of ribbed carcasses. Carcasses in the leanest TRBF group had less (P < 0.05) marbling, and softer (P < 0.05) and more watery (P < 0.05) lean than the fatter categories. Carcasses in the leanest category were also redder in color (P < 0.05; higher a* values) than the fattest category. Carcasses in the smallest LEA group had higher (P < 0.05) marbling and firmness scores than the largest LEA group and carcasses in the largest LEA group had more (P < 0.05) exudative loin muscles than the remaining LEA groups. Collectively, these data indicate that selection for reduced carcass fatness and increased carcass muscling, in swine, has significant negative effects on pork meat quality.     

EFFECTS OF INHERENT MUSCLE QUALITY DIFFERENCES UPON THE PALATABILITY AND COOKING PROPERTIES OF VARIOUS FRESH, CURED AND PROCESSED PORK PRODUCTS

Ham steaks, loin chops, bacon slices, shoulder roasts and sausage patties fabricated from three muscle quality groups were utilized to evaluate the effects of muscle quality on palatability and cooking properties. Irrespective of muscle quality (pale, soft, exudative (PSE) versus normal versus dark, firm, dry (DFD)) all pork cuts evaluated were well within the acceptable range in palatability. In addition, results indicated that inherent muscle quality differences were of little relevance to the eating quality of pork. However, meaningful differences in cooking losses were observed from loin chops and bacon slices.     

EFFECTS OF LATE CASTRATION AND FEEDING TIME ON BOVINE MUSCLE QUALITY

Hereford bulls were late castrated by emasculation at approximately 1 year old or left intact, and fed for 0, 60 or 90 days before slaughter to evaluate various traits of the M. longissimus. More days on feed resulted in increased carcass weight, fat thickness, USDA quality grade, ribeye area and percentage kidney, pelvic and heart fat, with no difference from late castration. Percentage of soluble collagen was highest for M. longissimus steaks from the 60 day feeding group, and lowest among those fed 90 days. Steaks from the controls were lighter colored while those from steers fed 60 days were the most red. No sensory differences occurred except for off-flavor.     

HALOTHANE-GENOTYPE AND DURATION OF REFRIGERATED STORAGE EFFECTS ON THE QUALITY OF VACUUM-PACKAGED PORK LOINS

Loins (n=72) from halothane negative (NN) and carrier (Nn) pigs were vacuum-packaged and stored for 0, 3, or 6 weeks at 2C. Samples from Nn pigs had more (P<0.001) purge loss than NN-loins after 3 and 6 weeks of storage. Color scores for chops of Nn pigs were lower (P<0.001) than for the NN animals after 0 and 3 weeks; but after 6 weeks of storage, chops from Nn and NN pigs received similar American color scores. Chops from Nn pigs were lighter (P<0.001) and less (P<0.001) red than chops from the NN animals; however, L* values of chops from Nn pigs decreased, and a* values increased, from 0 to 3 weeks of storage. Although initial quality traits of chops from Nn pigs were inferior to those of NN, pork color of Nn-pigs appeared to be improved with extended storage.     

ULTRA-RAPID CHILLING: CHILLING RATE EFFECTS ON THE APPEARANCE OF LAMB CARCASSES AND TENDERNESS OF LAMB CHOPS

The effects of different chilling rates on the visual attributes of lamb carcasses and the tenderness of lamb chops were investigated. Carcasses (n=72) were chilled at -20C, -10C, -4C or + 4C. After chilling all carcasses were stored at +4C for up to 8 days. Samples were taken at 2, 6 and 9 days postmortem for sarcomere length, Warner-Bratzler shear force and sensory analysis. Carcasses were visually appraised at 2, 6 and 9 days postmortem for fat color, flank color, visible vein color, wetness and overall acceptability. Carcasses chilled at -20C had significantly higher Warner-Bratzler shear force values than the other chilling treatments at 2 and 6 days but not at 9 days postmortem. No difference (P> 0.05) was found in Warner-Bratzler shear force or sensory tenderness between any of the treatments by 9 days postmortem. Carcasses did not differ (P>0.05) in fat color, flank color or overall acceptability at any stage postmortem. Carcasses chilled at -20C had slightly darker (P< 0.05) vein color at 2 days postmortem but this was not evident by 6 days postmortem. Carcasses that were chilled at -20C had significantly lower evaporative weight losses than carcasses in any of the other treatments. Rapid chilling did not adversely affect the tenderness of lamb chops or appearance of lamb carcasses at 9 days postmortem compared with conventional chilling.     

THE EFFECTS OF DELAYED CHILLING AND ALTERED CARCASS SUSPENSION UPON BEEF MUSCLE: I. PHYSICAL AND TEXTURAL PROPERTIES

A total of 60 bovine carcasses from crossbred heifers, 12 to 16 months of age with carcass weights of approximately 260 kg were utilized in two related experiments to evaluate the effects of delayed chilling and altered carcass suspension on certain physical and textural properties of beef muscle. Hip-free suspension (suspension by the os coxae from a hook inserted through the obturator foramen with the limbs hanging free) significantly (P<0.05) reduced the shear force values obtained on samples from the longissimus dorsi (LD) and semimembranosus (SM) muscles but had no effect (P>0.05) on shear force values obtained on samples from the psoas major (PM) muscle. The only other physical property affected by altered carcass suspension was objective measurement of lean color in the SM. Carcasses suspended from the aitchbone had darker SM muscles. Delayed chilling treatments had no effect (P>0.05) on 2-h SM pH values or 144-h pH values for any of the muscles studied. However, carcasses held at either 13°C or 22°C for 24 h had higher (P<0.05) SM pH values. When delayed chilling treatments affected muscle color, treated sides had darker lean than their conventinally chilled counterparts. Textural properties (shear values and taste panel tenderness ratings) and amount of expressible juice generally were unaffected by the delayed chilling treatments evaluated.     

THE EFFECTS OF DELAYED CHILLING AND ALTERED CARCASS SUSPENSION UPON BEEF MUSCLE: II. HISTOLOGICAL AND CHEMICAL PROPERTIES

A total of 60 bovine carcasses from “exotic”— crossbred heifers, 12 to 16 months of age with carcass weights of approximately 260 kg were utilized in two separate but related experiments to evaluate the effects of delayed chilling at 2 temperatures (13 and 22°C) for 12 or 24 h and altered carcass suspension on certain histological and chemical properties of beef muscle. Hip-free suspension (suspension by the os coxae from hooks inserted through the obturator foramen with the limbs hanging free) produced substantially greater alteration of the histological properties of the muscles evaluated than did delayed chilling. Such alterations resulted in longer semimembranosus (SM) and longissimus dorsi (LD) sarcomeres, shorter psoas major (PM) sarcomeres, smaller SM and LD muscle fiber diameters, larger PM muscle fiber diameters, fewer SM and LD wavy fibers, more PM wavy fibers, and shorter SM muscle fiber fragment lengths (P<0.05). Neither hip-free suspension nor delayed chilling produced consistent differences (P<0.05) in either the intramuscular collagen content, the heat solubility of the intramuscular collagen, or the histological properties of the intramuscular collagen fibers.     

茶多酚和鼠尾草对猪肉的抗氧化效果

比较研究茶多酚和鼠尾草对猪肉的抗氧化效果.通过改进猪肉过氧化值(POV值)和硫代巴比妥酸值(TBA值)的测定方法,分析分别添加茶多酚(1.0%)和鼠尾草(1.0%)的猪肉在5℃下贮藏10d(0d,2d,4d,6d,8d,10d)期间的脂肪氧化程度,同时对样品进行感官评定.结果表明:1.0%茶多酚处理组的POV值显著高于时照组(P<0.05),1.0%鼠尾草处理组的POV值极显著低于对照组(P<0.01);在前4天内各组间TBA值差异不显著(P>0.05),1.0%茶多酚处理组的TBA值在第6天及以后显著低于时照组(P<0.05),1.0%鼠尾草处理组的TBA值从第4天以后显著低于1.0%茶多酚处理组(P<0.05).第10天时,各组感官评定(气味、颜色、状态)总分为:1.0%鼠尾草处理组>1.0%茶多酚处理组>对照组.以上结果表明鼠尾草对猪肉的抗氧化效果明显优于茶多酚.