Processing Properties of Pork as Affected by Electrical Stimulation, Post-Slaughter Chilling and Muscle Group

Left sides of 30 slaughtered pigs were electrically stimulated (ES); right sides were not stimulated (NES). Sides were placed in a conventional cooler (24 hr) or blast freezer (3 hr) or showered with a brine solution (15.8% salt, -5.6°C for 3 hr). Twenty-four hr postmortem, picnic shoulders were removed, dissected into four muscle groups and determinations made for certain processing properties. ES decreased (P < 0.05) pH values for predominantly white muscles, increased (P < 0.05) juice loss during cooking for shank muscles and decreased (P < 0.05) percentages of salt-soluble protein (SSP) for both predominantly red and shank muscles. Other muscle properties were not affected by ES. Rapid initial chilling did not affect (P > 0.05) processing properties of muscle groups.     

Processing Properties of Beef Semimembranosus Muscle as Affected by Electrical Stimulation and Postmortem Treatment

Semimembranosus muscles from paired sides-electrically stimulated (ES) and not-stimulated (NES)-of mature cows were used to determine effects of certain postmortem treatments (state of rigor/temperature) and of ES on processing properties. ES decreased (P<0.05) pH values for prerigor, prerigor/frozen and postrigor/frozen muscles, but did not affect (P>0.05) values for total protein or juice loss during cooking. State of rigor/temperature treatment affected pH and salt-soluble protein (SSP) values more than did ES treatment. pH values differed (P<0.05) between each state of rigor/temperature treatment for both ES and NES samples. Salt-soluble protein values were higher (P<0.05) for NES prerigor than for NES postrigor/frozen samples and higher (P<0.05) for NES postrigor than for NES postrigor/frozen samples. SSP values for ES muscles were higher (P<0.05) for ES postrigor samples than for ES postrigor/frozen samples but were not different for other comparisons. Regardless of ES treatment, freezing of semimembranosus muscles increased pH values (P<0.05) and decreased SSP values (P<0.05) in three of four comparisons.     

Functionality of high and low voltage electrically stimulated beef chilled under moderate and rapid chilling regimes

Chuck muscles from 24 beef carcasses electrically stimulated (ES) with either high or low voltage, or a combination of both, and submitted to conventional or rapid chilling regimes were used in a model system study (pH, salt-solubloe protein extraction, emulsifying capacity) and in frank-further fabrication and analysis (yield, color, texture). Glycolytic rates measured in the loin had no effects on the functional parameters or on the quality of frankfurters. The ultimate pH values of unstimulated carcasses remained higher than in any ES carcasses, and led to higher protein extraction (P ≤ 0·05). However, ES had no further influence on the emulsifying capacity or on frankfurter yield and quality parameters independently of the voltage used (P > 0·05). Chilling regimes had no influence on the functional parameters of the model system but slightly influenced the yield and chewiness of the frankfurters (P ≤ 0·05). Therefore, the use of any type of ES in combination with either conventional (Canadian) or more rapid chilling is unlikely to have commercial significance on the yield or quality of frankfurters.     

Effects of electrical stimulation, chilling temperature and hot-boning on the tenderness of bovine muscles

The objective of this study was to determine the effects of hot-boning, low voltage electrical stimulation (ES) and chilling temperature on the tenderness of bovine M. longissimus dorsi (LD) and M. semimembranosus (SM) muscles. LD (n=32) and SM (n=32) muscles were subjected to different post-mortem treatments; hot-boning (before 90min post-mortem), cold-boning (at 48h post-mortem), low voltage ES and rapid or slow chilling. Hot-boned muscles which were not electrically stimulated (NES) had higher Warner Bratzler shear force (WBSF) values (P<0.001) and shorter sarcomeres (P<0.001) than cold-boned muscles. Hot-boned muscles subjected to ES had lower pH values (P<0.001) post-stimulation and up to 8h post-mortem than NES muscles. At both chilling temperatures WBSF values were lower in ES hot-boned LD and SM muscles at days 2, 7 and 14 post-mortem than NES muscles. Hot-boned muscles subjected to slow chilling had longer sarcomeres (P<0.001) than those subjected to fast chilling. In hot-boned SM muscles, ES resulted in longer sarcomere lengths (P<0.001). However, ES did not have a significant effect on the sarcomere length of LD muscles. As indicated by WBSF values all muscles tenderised during ageing, including muscles which were 'cold shortened'. Proteolysis was not the main reason for differences in WBSF values between ES and NES muscles as judged by qualitative sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). A combination of slow chilling and ES had a positive effect on hot-boned muscles with respect to WBSF values.     

Effect of low-voltage electrical stimulation after dressing on color stability and water holding capacity of bovine longissimus muscle

The effect of low voltage electrical stimulation after dressing (ES) on color stability and water holding capacity (WHC) of beef was investigated. Nine Swedish red cattle were slaughtered and the left side was electrically stimulated (80 V, 35 s) approximately 30 min after stunning, whereas the other side was not treated and used as control. Color and its stability, WHC, and protein solubility were evaluated on longissimus lumborum muscles from the two sides. ES produced a brighter red color at 24h mainly by increasing the oxygenation capacity of myoglobin (P<0.01), which was attenuated by postmortem aging. ES did not affect WHC, protein solubility and color stability (P>0.05). Therefore, this technology could accelerate meat tenderization without any negative effect on commercial attributes, such as color or drip of bovine longissimus muscle.     

The protective effect of electrical stimulation and wrapping on beef tenderness at high pre rigor temperatures

A three factorial experimental design involving electrical stimulation (ES/NES), wrapping (wrapped/unwrapped) and pre rigor temperature (15 °C or 35 °C) was applied to 70 beef M. longissimus lumborum muscles to obtain a wide variation in shear force and drip loss. The shear force of all treatment groups decreased during ageing. As anticipated, wrapping and electrical stimulation had positive effects on shear force. However, high pre rigor temperature (35 °C) did not result in higher shear force values if the muscles were electrically stimulated, wrapped or both. The results suggested that electrical stimulation protects against the negative effects of high pre rigor temperatures. The drip loss of all treatment groups increased during ageing in a manner that was unrelated to treatment but was correlated to tenderness (r² = 0.70; p < 0.0001). It was concluded that the application of electrical stimulation, whatever the pre rigor temperature, protects beef from toughening through the prevention of rigor shortening and the avoidance of inhibition of ageing enzymes.     

Evaluation of Extra Low Voltage Electrical Stimulation Systems for Bovine Carcasses

Two extra low voltage electrical stimulation (ES) systems have been evaluated for their effect on the tenderness of beef semimembranosus (SM), longissimus dorsi (LD), gluteus medius, biceps femoris and semitendinosus muscles. Warner-Bratzler shear force values indicated that both ES systems worked satisfactorily; ES samples had values which (a) were significantly (P < 0.001) lower than obtained for unstimulated (NES) samples where both were held under chilling conditions which should have produced considerable toughening, and (b) were not significantly different from NES samples restrained from shortening. Comparing ES samples with unrestrained and restrained NES samples, held under identical rapid chilling conditions, showed not only that the ES systems worked, but how well they worked. The SM and LD muscles appeared preferable for evaluation purposes.     

Effect of different electrical stimulation and chilling treatments on pork quality

The effect of different chilling and electrical stimulation (ES) treatments on the carcass and eating quality of pork has been examined. Preliminary trials (Study I), with a variety of ES treatments, indicated that, on the basis of pH fall, drip loss and tenderness, the most effective was that using 700 V peak at 12·5 Hz for 90 s applied at 20 min post-slaughter. These ES parameters were used throughout the main study (II) using 80 pigs, one side of which was stimulated and the other not, before being chilled rapidly (10°C in deep loin within 2–3 h of slaughter) or conventionally (10°C in deep loin within 5 h of slaughter).

Changes in pH and temperature during chilling were observed and, after chilling, quality assessments on LD and Sm muscles included drip loss, muscle opacity and instrumental toughness at 3 days post-slaughter.

Electrical stimulation, 20 min post-slaughter, improved tenderness of the LD and, to a lesser extent, the Sm of rapidly chilled pig sides. This advantage was gained without producing PSE pork. In fact, drip loss from the LD was consistently less from the sides which had been stimulated.     

Tenderness Improvement of the Major Muscles of the Beef Carcass by Electrical Stimulation

Steaks (arm; blade; seven-bone; rib, small-end; top loin; tenderloin; top sirloin; tip, cap-off; and round) from electrically stimulated (ES) and control sides of 20 beef carcasses were cut and frozen at 5 days postmortem. Forequarter muscles that were improved by ES were the longissimus dorsi (rib steak), the subscapularis and supraspinatus (blade steak), and the superficial pectoral (arm steak). Hindquarter muscles that were improved by ES were the longissimus dorsi (top loin steak), the biceps femoris and gluteus medius (top sirloin steak), and the semimembranosus and biceps femoris (round steak). ES, in addition to improving tenderness of the longissimus dorsi, increased tenderness of other major muscles in the carcass.     

ACCELERATED RESTRUCTURING OF BEEF

Restructured steaks manufactured by two comminution methods from prerigor electrically stimulated (PES) beef, nonstimulated counterparts (NES) and postrigor non-electrically stimulated (C) samples were compared. After frozen storage for 0,14, and 42 days, samples were subjectively evaluated for appearance and palatability traits. Objective measurements included Hunter Color, TBA, Kramer, and Instron values. Electrical stimulation reduced peak force but did not consistently improve sensory panel scores. Comminution method did not consistently affect any traits. Results suggested that subjective appearance was affected more by storage time than other treatments and that prerigor beef may be effectively utilized in restructured beef without affecting palatability traits.     

EFFECTS OF ELECTRICAL STIMULATION AND SUBPRIMAL STORAGE TIME ON PALATABILITY OF HOT-BONED BEEF

Sides from 33 forage-fed steers were electrically stimulated and hotboned (ESHB) and muscles were vacuum-packaged either within 2 h (17 sides) or at 24 h (16 sides). Opposite sides were not electrically stimulated and were cold-boned (NESCB) and vacuum-packaged at 24 h. For ESHB muscles, packaging time did not affect (P<0.05) palatability. Longissimus steaks from ESHB sides (pooled across packaging treatments) had lower (P<0.05) shear force values than steaks from NESCB sides. As storage time of muscles increased from 7 to 21 days, shear force values generally decreased. Combining electrical stimulation with hot-boning enabled the removal of muscles without detrimental effects on beef palatability.     

Postmortem Muscle Metabolism and Meat Tenderness

Left sides of 75 steers were electrically stimulated (ES) and right sides were nonstimulated controls (NES). NES sides had the highest pH, lowest temperature, were slower-metabolizing (lower R values), and produced steaks that had the least desirable sensory ratings compared to ES sides. Carcass weight, fat thickness, temperature and pH accounted for 31, 32, 34 and 16% of the variation, respectively, in overall tenderness ratings for steaks from NES sides and accounted for 0, 0, 0 and 7% of the variation, respectively, for steaks from ES sides. R values accounted for 28 and 32% of the variation in overall tenderness ratings of steaks derived from NES and ES sides, respectively. Thus, metabolic rate (R value) is a good indicator of postmortem tenderness.     

Varying the temperature of the liquid used for high-pressure processing of prerigor pork: effects on fresh pork quality, myofibrillar protein solubility, and frankfurter textural properties

The objective was to evaluate high-pressure processing (HPP) with varying liquid (water) temperatures on pork quality and textural properties of frankfurters. HPP pressurization liquid temperatures were 15.5 °C (HPP Low) and 29.4 °C (HPP Med). Analyses were conducted using paired boneless loins and paired boneless hams. Loins were evaluated for pH, purge loss, objective color, subjective color, firmness; and changes in color after a bloom period. Eight independent batches (2 batches each of HPP Low, paired untreated, HPP Med, and paired untreated) of frankfurters were manufactured from the outside portion of the ham and the knuckle. Both HPP treatments resulted in higher (P < 0.05) ultimate pH and less (P < 0.05) purge loss of the loin. Loin tenderness was not different among either HPP treatment temperature groups when compared to untreated controls except HPP Med chops were more tender (P = 0.02) than untreated controls. Salt-soluble protein extractability of inside ham muscles was lower (P < 0.05) for both HPP treatment levels when compared to untreated controls, but was not different between the 2 HPP treatment levels. Textural properties of frankfurters were not different for either HPP treatment group when compared to its respective untreated control for any parameter except springiness. HPP Low frankfurters had lower (P = 0.10) springiness values than untreated controls. Fracturability of HPP Med samples was lower (P = 0.12) than untreated controls. Overall, HPP caused higher ultimate pH and increased water-holding capacity, but did not affect tenderness of fresh meat or textural properties of frankfurters. PRACTICAL APPLICATION: HPP can be used on prerigor pork as means to improve fresh pork quality. Loins from HPP-treated pork sides had higher ultimate pH values and less package purge loss. Tenderness values were not affected positively or negatively by HPP treatment. The high pH and water-holding capabilities of treated samples have positive implications for further processing applications. Frankfurter textural properties suggest emulsified products can be made with pressurized pork without sacrifice to the textural profile.     

以多糖为基质的脂肪模拟物替代动物脂肪在法兰克福香肠中的应用

将以多糖（魔芋粉、κ-卡拉胶和大麦β-葡聚糖）为基质的脂肪模拟物分别以20%、40%、60%和80%的比例替代猪脂肪用于法兰克福香肠生产中,探讨猪脂肪的不同替代比例对法兰克福香肠品质特性和感官特性的影响。结果表明,随着脂肪模拟物替代比例的增加,香肠的水分含量和碳水化合物含量显著增加（P<0.05）,而总脂质含量、蛋白含量、灰分含量、能量值和脂肪卡路里值显著降低（P<0.05）。而且,随着脂肪替代物替代量的增加,香肠的蒸煮损失率、乳化稳定性显著降低（P<0.05）,亮度值增加,硬度以及咀嚼性降低。另外,低场核磁结果表明替代脂肪能够显著缩短香肠的弛豫时间（P<0.05）,说明其能增强蛋白质网络对水分子的束缚能力。然而,较高的脂肪替代比例（60%和80%）显著降低肉糜在加热终点的储能模量（G′）和损失模量（G′′）（ P<0.05）,而且降低了法兰克福香肠的总体可接受性。上述研究结果表明,以多糖为基质的脂肪模拟物能够在法兰克福香肠中部分替代猪脂肪,且以40%的替代比例为最佳。     

EFFECTS OF TYPES OF FAT AND OF RATES AND TEMPERATURES OF COMMINUTION ON DISPERSION OF LIPIDS IN FRANKFURTERS

ABSTRACT— The effect of time, temperature and rpm of comminution of emulsions was determined on the dispersion of approximately 25% of beef fat, pork fat or cottonseed oil in frankfurters. The numbers of lipid particles 5 μ or less in diameter increased in frankfurters containing either beef or pork fat as comminution was continued to higher temperatures, with pork fat dispersed more thoroughly. Fat tended to separate from frankfurters containing beef fat in particles 200 μ or more in diameter. In contrast, no specific degree of dispersion of particles 5 μ or less in diameter consistently indicated emulsion stability, or its lack. Increased rpm during comminution produced an increased dispersion of beef or pork fat. Under the same conditions pork fat was dispersed more finely than beef fat. Dispersion of cottonseed oil produced finely dispersed particles beyond the resolution of light microscopy, as was confirmed by electron microscopy which showed a substantial number of particles to be less than 1 μ in diameter.     

WATER-HOLDING AND COLOR CHARACTERISTICS OF BEEF FROM ELECTRICALLY STIMULATED CARCASSES

Electrical stimulation (ES) was applied to the right sides of 15 beef carcasses and the corresponding left sides were used as nonstimulated (NS) controls. Data collected included: postexsanguination pH (0.5, 3, 6, 24 h), L, a, and b color values, drip loss, and expressible moisture. Muscles from ES carcasses tended to have more accelerated postmortem pH declines than the corresponding muscles from NS carcasses. M. triceps brachii had a lower pH at 0.5 h (P < 0.05) , M. longissimus thoracis had a lower pH at 0.5 h (P = 0.055) and 3 h (P < 0.05), and M. semimembranosus had a lower pH at 0.5 and 3 h (P < 0.05), respectively. Hunter L, a, and b values did not differ within ES and NS treated muscles. Additionally, ES did not influence color values of the M. semimembranosus. ES did not affect drip loss or expressible moisture in beef muscles.     

Palatability and Appearance Traits of Beef/Pork Meat Patties

Eight beef/pork ground meat blends were made from mature (cows or sows) and youthful (steers or barrow) beef and/or pork lean. Blends were stored at — 27°C for either 14 or 150 days. Storage time decreased overall desirability scores of blends made with 20% pork fat and 80% youthful beef lean. No differences were found for flavor or overall desirability scores within the 14-day storage treatment. The consumer panel did not detect differences among treatments for source of fat or species. Results indicated beef/pork patties containing 40–80% mature lean and a minimum of 10% beef fat were equal to all-beef controls (100% beef patty) for visual and palatability traits.     

RETAIL APPEARANCE OF ELECTRICALLY STIMULATED BEEF

Top round steaks (adductor) and ground beef from the top round were obtained from both sides of ten U.S. Choice carcasses. Left sides were electrically stimulated (ES) with 17 impulses (1.8 set duration, 1.8 set interval) of 550 volts of alternating current at 5 amps. Steaks and ground beef from top rounds from nonstimulated right sides served as control (CON) samples. Steaks and ground beef were displayed under simulated retail conditions for 4 and 3 days, respectively. Steaks were weighed prior to and at the termination of the display interval to determine percentage weight loss. Samples for microbiological evaluation were obtained prior to and at the termination of the display interval. No significant differences were observed for muscle color, surface discoloration or overall appearance for samples of ground beef at any retail display interval. With one exception, muscle color was brighter and surface discoloration was reduced for round steaks from ES sides. Few significant differences in overall appearance were observed between ES and CON samples during the display period. No significant differences between ES and CON samples were observed for bacterial counts either initially or at the termination of the display period for either steaks or ground beef samples. Percentage weight loss was not significantly different between ES and CON steaks. These data suggest that electrical stimulation may enhance, and certainly does not detract from, the appearance of round steaks displayed under retail market conditions.     

The effects of a beta-agonist treatment, vitamin D3 supplementation and electrical stimulation on meat quality of feedlot steers

In this study, 20 young steers received no beta-agonist (C), 100 animals all received zilpaterol hydrochloride (Z), with 1 group only receiving Z while the other 4 groups received zilpaterol and vitamin D3 at the following levels (IU/animal/day) and durations before slaughter: 7 million for 3 days (3D7M); 7 million for 6 days (6D7M); 7 million for 6 days with 7 days no supplementation (6D7M7N) and 1 million for 9 days (9D1M). Left carcass sides were electrically stimulated (ES) and the right side not stimulated (NES). Samples were aged for 3 or 14 days post mortem. Parameters included Warner-Bratzler shear force (WBSF), myofibril filament length, sarcomere length and calpastatin and calpain enzyme activity. Both ES and prolonged aging reduced WBSF (P<0.001). 6D7M, 6D7M7N and Z remained significantly tougher than C (P<0.001), while 3D7M and 9D1M improved WBSF under NES conditions. ES is more effective to alleviate beta-agonist induced toughness than high vitamin D3 supplements.     

Characteristics of Frankfurters Prepared from Mutton and Fowl

The nutritional, chemical, physical, and sensory properties of mutton:fowl (M/F) frankfurters were compared to those of an all beef frankfurter. The beef frankfurter was higher in fat and lower in moisture (P 0.05) than the experimental product. The 1M/1F and 2M/ 1F frankfurters were higher (P 0.05) in niacin and thiamin than the beef frankfurters. The mineral content of the experimental frankfurters was consistent with that of other processed meat products. The water-holding capacity (WHC) and emulsion stability (ES) of the 2M/1F frankfurters were superior (P 0.05) to those of the 1M/1F. The beef frankfurter was redder and firmer (P 0.05) than the experimental frankfurters. The M/F frankfurters were preferred over the beef for juiciness and flavor.