Chilling Rate Research Articles

Cryo Effect During Solidification on the Tribological Behavior of Aluminum-Alloy/Glass (SiO2) Metal Matrix Composites

The present investigation aims at producing cast aluminum alloy/SiO 2 composites in molds containing cryo cooled copper chills by dispersing particles in molten aluminum alloy above the liquidus temperature, the size of the particles dispersed being between 50 to 100μm. The dispersoid being added ranges from 3 to 12wt% in steps of 3wt%. The resulting composites cast using cryo cooled copper chills were tested for their wear behavior. Subzero cooled copper chills of different thickness (10—25mm) was used to study the effect of chilling rate on the wear behavior of the composite developed. The wear tests were carried out using a computerized pin on disc type wear testing machine as per ASTM 325 A 98 standards. The superior mechanical properties of the castings, particularly their ultimate tensile strength (UTS), hardness, and wear resistance are discussed in relation to their microstructure. Dispersoid content up to SiO2—9 wt% was found to increase the mechanical properties and therefore SiO2—9 wt% is considered as the optimum limit. Results of the investigation indicate that, strength, hardness and wear resistance of the composite developed is highly dependent on the chilling rate and also the dispersoid content of the composite. Wear resistance of cryo chilled Al alloy/SiO2 composites were remarkably improved by adding SiO2 particles. The effect of amounts of dispersoid content up to 3 wt% can be ignored for all the MMCs until a low sliding speed of 0.44 m/s. From SEM structural studies, wear surfaces of 9wt% composite chilled using copper chill of 25 mm thickness at low sliding speed showed slight groove formation than those of the other chilled MMCs. Chill thickness (25mm), coolant used (liquid nitrogen) and chill material (copper) however does significantly affect volumetric heat capacity of the chill and hence strength, hardness and wear resistance of the composite.

Progress in reducing the pale, soft and exudative (PSE) problem in pork and poultry meat

Research in the area of the pale, soft and exudative (PSE) pork and poultry meat is reviewed in this article with an emphasis on genetic, biochemical and metabolic factors contributing to the problem. Over the past five decades, there has been much more work in the pork meat area where a few genetic markers have been identified, and are currently used to remove susceptible animals from the herd. Some of the markers are linked to aberrant calcium regulation in the early postmortem muscle. The poultry industry is still not at the point of using genetic marker(s); however, some recent work has revealed several potential markers. The review also discusses environmental factors such as antemortem stress and early postmortem processing practices (e.g. chilling rate) that can influence the development and severity of the PSE phenomenon. Some of these factors are known to cause protein denaturation at the early stage of postmortem and directly contribute to poor water-holding capacity and inferior texture in fresh meat and later in processed products. A newer hypothesis suggesting that variation in protein oxidation, in response to antemortem stress and early postmortem tissue environment, can contribute to development of PSE pork is also discussed. Finally, a few recommendations for future work are proposed.

Use of calcium, potassium, and sodium lactates to control germination and outgrowth of Clostridium perfringens spores during chilling of injected pork

Inhibition of Clostridium perfringens spore germination and outgrowth during abusive chilling regimes was investigated by the incorporation of lactates of calcium (CaL), potassium (KL) and sodium (NaL) in injected pork. Lactates (Ca, K, or Na) were incorporated into injected pork samples at four different concentrations (1.0%, 2.0%, 3.0%, and 4.8%), along with a no-lactate control. A three-strain cocktail of C. perfringens spores was inoculated into the product (injected pork) to obtain a final spore population of ca. 2.0–2.5 log 10 CFU/g. Chilling of injected pork (control) from 54.4 to 7.2 °C within 6.5, 9, 12, 15, 18, and 21 h exponential chill rates resulted in C. perfringens population increases of 0.49, 2.40, 4.02, 5.03, 6.24, and 6.30 log 10 CFU/g, respectively. Addition of CaL at 1.0% or KL and NaL ⩾2.0% to injected pork was able to control C. perfringens germination and outgrowth to <1 log CFU/g, meeting the USDA-FSIS performance standard. However, extension of chilling rates beyond 9.0 h (up to 21 h) required addition of CaL (⩾2.0%), KL or NaL (⩾3.0%) to meet the stabilization performance standard. In general, CaL was more effective compared to KL or NaL for all the chilling regimes, in reducing the potential risk of C. perfringens germination and outgrowth.

Cryogenic effects during casting on the wear behavior of aluminum-alloy/glass MMCs

This paper studies the wear behaviour of aluminum alloy/glass composites cast using cryogenically cooled copper chills. The size of the glass particles range from 50 to 100 μm and the content by weight ranges from 3% to 12% in steps of 3%. The superior mechanical properties of the castings, particularly their ultimate tensile strength (UTS), hardness and wear resistance, are discussed in relation to their microstructure. Results of the investigation indicate that, strength, hardness and wear resistance of the composite developed are highly dependent on the chilling rate and also the dispersoid content of the composite. The wear mechanisms are also studied using scanning electron microscopy.

Carvacrol, Cinnamaldehyde, Oregano Oil, and Thymol Inhibit Clostridium perfringens Spore Germination and Outgrowth in Ground Turkey during Chilling†

Inhibition of Clostridium perfringens by plant-derived carvacrol, cinnamaldehyde, thymol, and oregano oil was evaluated during abusive chilling of cooked ground turkey. Test substances were mixed into thawed turkey product at concentrations of 0.1, 0.5, 1.0, or 2.0% (wt/wt) along with a heat-activated three-strain C. perfringens spore cocktail to obtain final spore concentrations of ca. 2.2 to 2.8 log CFU spores per g of turkey meat. Aliquots (5 g) of the ground turkey mixtures were vacuum packaged and then cooked in a water bath, where the temperature was raised to 60°C in 1 h. The products were cooled from 54.4 to 7.2°C in 12, 15, 18, or 21 h, resulting in 2.9-, 5.5-, 4.9-, and 4.2-log CFU/g increases, respectively, in C. perfringens populations in samples without antimicrobials. Incorporation of test compounds (0.1 to 0.5%) into the turkey completely inhibited C. perfringens spore germination and outgrowth (P ≤ 0.05) during exponential cooling in 12 h. Longer chilling times (15, 18, and 21 h) required greater concentrations (0.5 to 2.0%) to inhibit spore germination and outgrowth. Cinnamaldehyde was significantly (P < 0.05) more effective (<1.0-log CFU/g growth) than the other compounds at a lower concentration (0.5%) at the most abusive chilling rate evaluated (21 h). These findings establish the value of the plant-derived antimicrobials for inhibiting C. perfringens in commercial ground turkey products.

Control of Clostridium perfringens in Cooked Ground Beef by Carvacrol, Cinnamaldehyde, Thymol, or Oregano Oil during Chilling

Inhibition of Clostridium perfringens spore germination and outgrowth by carvacrol, cinnamaldehyde, thymol, and oregano oil was evaluated during abusive chilling of cooked ground beef (75% lean) obtained from a local grocery store. Test substances were mixed into thawed ground beef at concentrations of 0.1, 0.5, 1.0, or 2.0% (wt/wt) along with a heat-activated three-strain C. perfringens spore cocktail to obtain final spore concentrations of ca. 2.8 log spores per g. Aliquots (5 g) of the ground beef mixtures were vacuum-packaged and then cooked in a water bath, the temperature of which was raised to 60°C in 1 h. The products were cooled from 54.4 to 7.2°C in 12, 15, 18, or 21 h, resulting in 3.18, 4.64, 4.76, and 5.04 log CFU/g increases, respectively, in C. perfringens populations. Incorporation of test compounds (≥0.1%) into the beef completely inhibited C. perfringens spore germination and outgrowth (P ≤ 0.05) during exponential cooling of the cooked beef in 12 h. Longer chilling times (15, 18, and 21 h) required greater concentrations to inhibit spore germination and outgrowth. Cinnamaldehyde was significantly (P < 0.05) more effective (<1.0 log CFU/g growth) at a lower concentration (0.5%) at the most abusive chilling rate evaluated (21 h) than the other compounds. Incorporation of lower levels of these test compounds with other antimicrobials used in meat product formulations may reduce the potential risk of C. perfringens germination and outgrowth during abusive cooling regimes.

Should electrical stimulation be applied when cold shortening is not a risk?

This experiment was designed to show whether delayed high voltage stimulation (ES) is more beneficial than no stimulation (NS) to secure tenderness under circumstances where rigor conditions are difficult to control due to variations in carcass size, fatness and/or chilling capacity. Ten Charolais carcasses were split during slaughter, the left sides were stimulated at 45 min post-mortem for 45 s, and the right sides were left unstimulated. The carcass sides were then chilled at a medium chilling rate. Sarcomere length measurements confirm that there was neither cold nor heat shortening in the M. longissimus (LD). LD from ES sides aged for 2 days was more tender than non-stimulated LD (NES), although prolonged ageing eroded the advantage of ES to a non-significant advantage after 14 days. Initial tenderness differences coincided with lower 24 h calpain activity, suggesting an early onset of proteolysis and ageing (tenderisation). In contrast to conventional early ES, delayed ES, appears to be beneficial for the early development of tenderness without too much interference with enzyme. Myofibril fragment length (MFL) was a good indicator of the development of tenderness during prolonged ageing but not for the early post-mortem variation in tenderness. No colour ( L*, a*, b*) differences, occurred due to stimulation treatment, while drip loss was slightly higher at 24 h post-mortem for ES meat.

Live transportation of Macrobrachium rosenbergii (De Man) in chilled sawdust

Three cooling rates of 1.26±0.09°C h−1 within 8 h (slow, T1), 2.52±0.18°C h−1 within 4 h (moderate, T2) and 5.04±0.36°C h−1 within 2 h (fast, T3) were tested to cold-anaesthetize farm raised Macrobrachium rosenbergii (De Man) (45–52 g) in each case from 25°C down to 15±1°C in a refrigerated chilling tank, provided with aeration. The cold-anaesthetized prawns subjected to each chilling rate were packed in an insulated cardboard box (triplicate) between two layers of moist and chilled (2–3°C) sawdust, and kept inside a chilled storage cabinet at 15±1°C, for set durations of 6, 9, 12, 15 and 18 h. Survival was determined by revitalizing the prawns in aerated water with an initial temperature of 20°C, which was raised to 29±1°C within 3 h. The experiment was repeated using berried females acclimated to brackishwater of 12 g L−1 salinity and the percentage survival recorded after live storage for durations ranging from 6 to 24 h at intervals of 3 h. Statistically valid safe durations for obtaining 100% survival of the cold anaesthetized and live stored prawns were determined using probit analysis at the three chilling rates tested, and were found to be 7.39, 6.98 and 4.54 h in the case of adult prawns, and 7.87, 8.17 and 6.43 h for berried females for T1, T2 and T3 respectively. For practical purposes, the durations that yielded 95% survival rates were computed to be 16.47, 12.14 and 8.35 h in the case of adult prawns and 18.49, 19.02 and 11.11 h for berried females for T1, T2, and T3 respectively. The berried prawns revitalized after live storage were incubated in tanks and the zoea larvae reared up to postlarvae (PL-5), and compared against a control. No significant difference was found in larval hatch fecundity, survival rate and the production of PL L−1 between the treatment and control, indicating that the method of cold anaesthetization and live storage of berried prawns could be used for successful transportation of broodstock.

Effects of newer slurry ice systems on the quality of aquatic food products: a comparative review versus flake-ice chilling methods

The application of slurry ice systems—consisting of ice-water suspensions prepared from marine water and chilled at subzero temperatures—to the storage of aquatic food products is receiving increasing attention. Such binary systems—described in the scientific literature as flow ice, fluid ice, slush ice or liquid ice—afford two main advantages concerning the handling and storage of seafood: a faster chilling rate as compared with flake-ice or refrigerated seawater (RSW), deriving from its higher heat-exchange capacity, and the reduced physical damage caused to seafood products by its spherical microscopic particles as compared with conventional ice. Oxidation and dehydration mechanisms may also be limited by the overall coverage of the whole surface of the products. In this article we review the theoretical rationale of slurry ice systems, their main technical features, and current and future practical applications aimed at increasing the added value of aquatic food products.

Interrelationships amongst carcass and meat quality characteristics of sheep

The relationships between various carcass and meat quality characteristics of sheep were studied. Relationships were determined by regression, using data obtained from sheep belonging to a wide range of breeds, sex types and slaughter weight (32–62 kg). The chilling rate of the M. longissimus dorsi (LD) post-mortem was negatively correlated with carcass weight ( r=−0.42, P<0.01), back fat thickness ( r=−0.54, P<0.001) and the cooking loss of the M. infraspinatus (IS) muscle ( r=−0.44, P<0.001). Correlation between chilling rate and shear force of the IS muscle was not significant, which was also the case between chilling rate and the cooking loss and shear force of the LD and M. triceps brachii muscles. A positive relationship was observed between total collagen and cooking loss ( r=0.34, P<0.05) and between heat-insoluble collagen and cooking loss of the LD muscle ( r=0.37, P<0.01). Generally collagen content was positively correlated with lean content and negatively with fat content. Carcass weight was significantly ( P<0.001) correlated with intramuscular fat ( r=0.61), moisture ( r=−0.76), cooking loss ( r=−0.49), shear force ( r=−0.41) and hue angle ( r=−0.41). Shear force was positively associated with cooking loss ( r=0.42, P<0.001), but negatively with intramuscular fat content ( r=−0.55, P<0.001). Cooking loss was positively correlated with moisture content ( r=0.55, P<0.001).

CONTROL OF CLOSTRIDIUM PERFRINGENS IN A MODEL ROAST BEEF BY SALTS OF ORGANIC ACIDS DURING CHILLING1

ABSTRACTControl of Clostridium perfringens germination and outgrowth by the following salts of organic acids, sodium lactate [Purasal™S/SP (Purasal); 1.50, 3.00 and 4.80%], sodium lactate supplemented with sodium diacetate [Purasal™ Opti.form™ (Optiform), 1.50, 3.00 and 4.80%], buffered sodium citrate [Ional™ (Ional), 0.75, 1.00 and 1.30]) and buffered sodium citrate supplemented with sodium diacetate [Ional Plus™ (Ional Plus), 0.75, 1.00 and 1.30%] was evaluated during continuous chilling of a model roast beef product. Beef rounds were ground through an 1/8′’ plate and NaCl, potato starch and potassium tetra pyrophosphate were added to final concentrations of 0.85, 0.25 and 0.20%, respectively, and mixed. Portions (250 g) of the meat were mixed with either Purasal (1.5, 3.0 or 4.8%), Optiform (1.5, 3.0 or 4.8%), Ional (0.75, 1.0 or 1.3%) or Ional Plus (0.75, 1.0 or 1.3%) along with a control that did not have any added antimicrobials. Each product (10 g) inoculated with C. perfringens spores (ca. 2.2 log10 spores/g) was packaged into vacuum bags (2 in. × 3 in.), vacuum sealed, heated to 60C within 1 h, and subsequently chilled from 54.4C to 7.2C in 18 or 21 h following exponential chilling rates. Products were sampled immediately after cooking to enumerate the C. perfringens populations (spores surviving heat treatment) and subsequent to chilling (total C. perfringens populations, including spores and vegetative cells resulting from germination and outgrowth of the spores). Chilling of cooked, model ground roast beef resulted in germination and outgrowth of C. perfringens spores; the population densities increased by 4.13 and 4.40 log10 CFU/g, following 18 and 21 h chill rates, respectively. Incorporation of Purasal (1.5–4.8%), Optiform (1.5–4.8%), Ional and Ional Plus (0.75–1.3%) substantially (P ± 0.05) inhibited germination and outgrowth of C. perfringens spores. Incorporation of antimicrobial ingredients resulted in ± 1.0 log10 CFU/g increase of the pathogen, except for model roast beef with Ional Plus at 0.75% concentration, following 18 h chilling rate. Similar results were obtained when 21 h chilling rate was followed, with roast beef containing ingredients (at all the concentrations) resulting in either reductions or ± 1.0 log10 CFU/g growth in total C. perfringens populations, except for Purasal and Ional Plus at 1.5 and 0.75% concentrations, respectively. Use of sodium salts of organic acids in formulation of model roast beef can reduce the risk of C. perfringens spore germination and outgrowth during extended chilling rates.

Turkey Carcass Chilling and Protein Denaturation in the Development of Pale, Soft, and Exudative Meat

Pale, soft, and exudative (PSE) meat is a growing problem in the turkey industry and has been associated with processing conditions such as slow carcass chilling. The development of PSE meat is caused by protein denaturation resulting from a rapid rate of pH decline early postmortem (PM) while carcass temperatures are still elevated. This research was conducted to determine the relationship of slow chilling to protein denaturation and PSE development. A total of 48 toms were conventionally processed in 2 trials at 22.5 wk of age, and chilled at 0, 10, 20, or 30°C for either 45 or 90 min before deboning (at 60 or 105 min PM). Temperature and pH of the breast muscle was recorded at 15 min PM, at the time of deboning (60 or 90 min PM), and at 24 h PM. Color was determined at deboning and again at 24 h PM. Gel strength, cook loss, expressible moisture, total protein solubility, and bound phosphorylase quantities were determined on the fillets at 24 h PM. There was no difference in carcass temperature at 15 min PM, but by 105 min PM each temperature treatment was significantly different, with the carcasses chilled at 0 and 10°C having the lowest temperature, the 30°C-chilled birds having the highest temperature, and the 20°C-chilled carcasses being intermediate but significantly different from either extreme. The carcass temperature differences at 105 min PM indicated that the carcass experienced differing chilling rates. To varying degrees, slower rates of chilling resulted in lower pH, greater degree of lightness (L* value), greater cook loss, and reduced gel strength. However, chilling rate had no effect on total protein solubility or myofibrillar phosphorylase for any of the treatments. Chilling rate seems to contribute to PSE turkey meat characteristics but by a mechanism independent of total protein solubility or myofibrillar phosphorylase.

절식, 스트레스 및 냉각속도가 돼지도체의 사후 대사속도와 등심근의 육질에 미치는 영향

본 실험은 현장에서 발생할 수 있는 도축 전개체 관리와 도축 후 냉각온도의 편차가 숙성기간동안 육질에 미치는 영향을 관찰하기 위해 설계되었다. 총 20 두 랜드레이스를 도축 하루 전날부터 절식(n = 10)한 처리구와 도축일 아침까지 급여(n = 10)한 처리구 중에 각각 5마리씩을 무작위 선발하여 도축 전 스트레스(n = 10)와 무 스트레스(n = 10) 처리하엿다. 분할 후 좌도체는 <TEX>$6^{\circ}C$</TEX>에 우도체는 -<TEX>$3^{\circ}C$</TEX>의 도체 냉각실에서 24시간 냉각하였다. 사후 강직기와 도축 후 24시간의 pH, 온도, 유리 칼슘이온, 단백질 분해도를 측정하였으며, 1일째 근절길이, <TEX>$1^{\circ}C$</TEX>에서 3일 및 7일째 드립량, 1, 3, 7일째 육색, 전단력 및 가열 감량을 측정하였다. 본 실험 조건에서 도축 직전 15분 동안 몰이스트레스는 유리 칼슘량을 제외한 대사속도 및 육질 특성에 영향을 주지 않았다. 절식하지 않은 구는 절식한 처리구와 비교하여 1시간과 24시간에 빠른 pH 하강을 보였고 (P < 0.1), - <TEX>$3^{\circ}C$</TEX> 냉각 조건에서는 <TEX>$6^{\circ}C$</TEX>에서 냉각한 처리구와 비교하여 도축후 3시간부터 완만한 pH 강하속도(P < 00.1)을 보였으나 최종 pH가 5.7 <TEX>${\sim}$</TEX> 5.8로 처리 구간에 큰 차이가 없었다. pH 6.2에서 절식과 냉각방법간에 상호 작용이 있었는데, 절식하지 않은 도체를 <TEX>$6^{\circ}C$</TEX>에서 냉각했을 경우 온도가 <TEX>$33.3^{\circ}C$</TEX>로 절식시킨 처리구를 - <TEX>$3^{\circ}C$</TEX>에서 냉각한 처리구와 비교하여(<TEX>$22.2^{\circ}C$</TEX>) <TEX>11$^{\circ}C$</TEX> 더 낮은 온도를 보였다. 근절길이는 1.7 <TEX>${\sim}$</TEX> 1.8 <TEX>${\mu}m$</TEX>로 처리간에 큰 차이를 보이지 않았으나, 24시간째 전단력은 절식처리구에서 약 2kg 높았다(P < 0.05) 영향을 받았는데, 절식시킨 시험구에서 낮은 값을 보였다. 냉각실 온도는 전단력과 육색에 영향을 미치지 않았으나, -<TEX>$3^{\circ}C$</TEX> 냉각이 가열 감량을 유의적으로 감소시켰다(P < 0.05), 숙성기간 동안 전단력은 사료 급여를 하지 않은 도체에서 도축 후 1일에 약 6.5 kg으로 도축전까지 급여한 구보다 높았는데( P <0.05), 이 결과는 빠른 pH 하강과 유리 칼슘이온의 방출로 높은 도체 온도에서 단백질 분해 효소의 높은 활성과 관련된 것으로 판단되었고, 이것은 빠른 Desmin 분해 속도가 뒷받침하였다. 하지만 숙성 7일째에는 처리간의 전단력 차이는 관찰되지 않았다. 가열 감량 숙성기간동안 가열 감량을 크게 증가시켜 숙성 7일째에는 유의적으로 높은(P < 0.01) 가열 감량을 유발하였다. 이러한 결과는 육색과도 연관 되었는데, 육색은 결과는 육색과도 연관 되었는데, 육색은 진공포장 후 7일 동안 <TEX>$1^{\circ}C$</TEX>에서 숙성한 결과 절식시킨 시험구와 지교하여 도축 전 급여가 더 밝고 붉은색(P < 0.05)을 나타냈다. 명도는 숙성 7일째에 유의적으로 증가하였고, 적색도는 3일째에 증가하였으나 7일째에는 변화가 없었다. 이러한 변화는 통계적으로는 유의성이 관찰되었으나 그 차이점은 미미했다. 본 실험결과는 도축 전날까지 급여 또는 절식 여부는 숙성 3일 이상일 경우 연도에는 영향을 미치지 않으나, 도축일 아침까지 급여가 보수력을 감소시키므로 도축 하루 전날부터 절식하는 것이 육질을 증가시킨다는 것을 시사하고 있다. The study was conducted to investigate the effects of practical variations in feed restriction, pre-slaughter handing and chilling regime on pork quality during ageing. A total of twenty male landraces were allocated into three treatments(i.e., pre-slaughter feeding, stress and chilling regime) in a factorial arrangement. pH, temperature, free calcium ions, WB-shear force, sarcomere length, cooking loss, drip loss and objective color were determined during rigor development and/or 1, 3, 7 d postmortem. Pre-slaughter chasing stress for approximately 15 min had no effects on pH/temperature profile and objective meat quality. There was an interaction(P < 0.05) between the fasting treatment and chi1ling regime for muscle temperature at pH 6.2. Sarcomere length indicated that the current experiment conditions did not induce muscle shortening, with 1.7 to 1.8 <TEX>${\mu}m$</TEX>, in spite of a significant effect of the fasting treatment (P<0.01). Pigs fed until the morning of slaughter showed a low WB-shear force(P < 0.05) until 3 d at I "C. The treatment also resulted in a higher Hunter L* and a*(P < 0.05) at 24 h and 7 d. Fasted pigs showed a significantly(P < 0.05) reduced cooking loss. The current results indicated that feeding upon the morning of slaughter became detrimental on meat color and the negative effect on cooking loss were linearly elevated with increased ageing time. On the other hand, WB-shear force did not distinguishable after 3 d. Collectively, it appeared that feed restriction from a day before slaughter could produce more a desirable meat quality at the time of consuming. However, the limited effect of animal handling and chilling rate on meat quality is not necessarily to extend to that these do not affect pork quality, as that largely depends on experimental design.

Inhibitory effects of organic acid salts on growth of Clostridium perfringens from spore inocula during chilling of marinated ground turkey breast

Inhibition of Clostridium perfringens germination and outgrowth by salts of organic acids such as sodium lactate, sodium acetate, buffered sodium citrate and buffered sodium citrate supplemented with sodium diacetate was evaluated during continuous chilling of ground turkey. Turkey breast meat was injected with a brine-containing NaCl, potato starch and potassium tetra pyrophosphate to yield final in-product concentrations of 0.85%, 0.25% and 0.20%, respectively. The meat was ground, mixed with either sodium lactate (1%, 2%, 3% or 4%), sodium acetate (1% or 2%), buffered sodium citrate (Ional™, 1%) or buffered sodium citrate supplemented with sodium diacetate (Ional Plus™, 1%), in addition to a control that did not contain added antimicrobials. Each product was mixed with a three-strain C. perfringens spore cocktail to obtain final spore concentrations of ca. 2.8 log 10 spores/g. Inoculated products (10 g) were packaged into cook-in-bags (2×3 in.), vacuum sealed, cooked at 60 °C for 1 h, and subsequently chilled from 54.4 to 7.2 °C in 15, 18 and 21 h following exponential chilling rates. Products were sampled immediately after cooking and then after chilling. Chilling of cooked turkey following 15, 18 and 21 h chill rates resulted in germination and outgrowth of C. perfringens spores to 6.6, 7.58 and 7.95 log 10 CFU/g populations, respectively, from initial spore populations of ca. 2.80 log 10 CFU/g. Incorporation of sodium lactate (1%), sodium acetate (1%), Ional or Ional Plus (1%) substantially inhibited germination and outgrowth of C. perfringens spores compared to controls. Final C. perfringens total populations of 3.12, 3.10, 2.38 and 2.92 log 10 CFU/g, respectively, were observed following a 15-h exponential chill rate. Similar inhibitory effects were observed for 18 and 21 chill rates with the antimicrobials at 1% concentrations. While sodium lactate and sodium acetate concentrations of 1% were sufficient to control C. perfringens germination and outgrowth (<1.0 log 10 CFU/g growth) following 15 h chill rates, higher concentrations were required for 18 and 21 h chill rates. Ional at 1% concentration was effective in inhibiting germination and outgrowth to <1.0 log 10 CFU/g of C. perfringens for all three chill rates (15, 18 and 21 h) tested. Use of sodium salts of organic acids in formulation of ready-to-eat meat products can reduce the risk of C. perfringens spore germination and outgrowth during chilling.

Rapid chilling cannot prevent inferior pork quality caused by high preslaughter stress

The present experiment investigated whether increasing chilling rate could improve meat quality in pigs exposed to either minimal or high stress immediately preslaughter. Pigs (n = 192) were offspring of halothane-free lines. On various days, four groups of 48 pigs were processed at a commercial plant. Within each group, half the pigs were exposed to either minimal or high preslaughter stress. Before entering the cooler at 45 min postmortem, carcasses of both minimal and high preslaughter stress treatments were allocated randomly to either conventional (+4 degrees C for 22 h) or rapid (three-phase chilling tunnel: -15, -10, and -1 degrees C for 15, 38, and 38 min, respectively, followed by storage at 4 degrees C until 22 h postmortem) chilling. Temperature and pH were measured in the blood at exsanguination and in the longissimus lumborum (LL) and semimembranosus (SM) muscle at 0.5, 2.5, 4.5, 6.5, and 22 h postmortem. Meat quality attributes (water-holding capacity and objective color measurements) were assessed on the LL. Preslaughter stress level affected pH and temperature in both blood and muscle, with lower (P < 0.001) pH values and higher (P < 0.001) temperatures for pigs exposed to high vs. minimal stress. Rapid chilling led to a faster (P < 0.001) temperature decline regardless of preslaughter stress level. Rapid chilling did not (P > 0.05) influence the rate of pH decline in the LL muscle, but reduced (P = 0.061) pH decline in the SM. Rapid chilling, as opposed to conventional chilling, decreased (P < 0.05) electrical conductivity in the LL, regardless of preslaughter stress; however, it could not compensate for the detrimental effect (P < 0.05) of stress on drip loss, filter paper moisture absorption, and meat color (L* value). Results from the present study indicated that increasing chilling rate is not a suitable method to resolve pork quality problems caused by inadequate preslaughter handling.

Influence of Delayed Harvest Time on Physico‐chemical Properties of Sweetpotato Starch

AbstractEight varieties of sweetpotato [Ipomoea batatas (L.) Lam] were transplanted in June, and harvested in October, November, December 1999 and January 2000. Starch content and starch properties of the tuberous roots were compared on delaying the harvest date. The shoot tops got blighted in early December and chilling injury rate of roots (average of eight varieties) increased up to 76.7% in January with decrease in temperature. Starch contents in October (24.0 g/100 g fresh weight, fw) and November (25.0 g/100 g fw) were almost the same, but the content decreased remarkably in December (21.2 g/100 g fw) and January (15.5 g/100 g fw). In December and January, the sucrose content of the roots had higher values. Hardness and leaked water percentage (LWP) of the starch gels remarkably increased from November to December (hardness: 76.4 to 112.3 g, LWP: 6.6 to 10.9%). On the contrary, the changes in amylose content and pasting properties of the starches were not consistent with decrease in temperature. This suggests that the effect of low temperature on these properties is insignificant after the growth period of sweetpotato. There were significant differences among the varieties in terms of starch retrogradation. The selection of varieties such as Kyushu 123 with the lowest percentage of retrogradation and Kyukei90142‐8 with the lowest chilling injury rate will help to lengthen the storage time in the field at least until December.

Sensory quality and the incidence of PSE of pork in relation to crossbreed and RN phenotype

The effects of crossbreed and of RN phenotype on pork and its eating quality were evaluated in four different pig crossbreeds [involving Swedish Landrace (L) × Yorkshire (Y) sows and Hampshire (H), Duroc (D), Yorkshire (Y) or Hampshire × Yorkshire (HY) as the terminal sire]. Pigs from the LYH crossbreed were also classified as either carriers or non-carriers of the RN − allele. In the crossbreeds investigated, M. longissimus dorsi (LD) and M. semimembranosus (SM) from LYH were found to have the lowest pH as measured 24 h post-mortem (pH 24 h ). The low pH in the LYH crossbreed was due to the large proportion of RN − carriers it had (approximately 70%). The non-carriers of the RN − allele in the LYH crossbreed had a pH 24 h close to that of LYD, LYY and LYHY. In a selected group of pigs ( N=50), the ultimate pH in the ham muscles M. biceps femoris (BF), M. quadriceps femoris (QF), M. gluteus medius (GM) and M. semitendinosus (ST) was also found to be lower in RN − carriers of LYH than in the other crossbreeds. As determined visually, LYD had the highest frequency (2%) of pale, soft and exudative meat (PSE), in LD. Ham from RN − carriers of LYH had the highest frequency (23%) of PSE meat around the femur, indicating that when the pH is low, the deep musculature, in which the chilling rate can be slow, is particularly sensitive to the development of PSE. According to assessments by members of a trained sensory panel, tenderness was significantly greater in LD from carriers of the RN − allele in LYH than in LD from LYD, LYHY and non-carriers of LYH. The tenderness of LD from LYY was rated as intermediate. The intramuscular fat content was found to be highest in LD from LYD, no relationship between intramuscular fat content and tenderness being found. The RN − carriers of LYH received the highest ratings in terms of juiciness. In conclusion, the sensory ratings demonstrated the great eating quality of LD from carriers of the RN − allele, indicating that abandoning the Hampshire crossbreed or eliminating the RN − allele from it, would result in the meat being less tender.

Color of uncooked and cooked broiler leg quarters associated with chilling temperature and holding time

Discoloration of raw or cooked tissue can occur from cell disruptions and blood migration caused by slow or variable chilling rates. Color parameters established by the Commission International D'Eclairage for measuring lightness, redness, and yellowness (L*, a*, and b* respectively) were determined on two groups (A and B) of uncooked and cooked leg quarters chilled at +4, 0, -3, -12, or -18 C. At Day 7, group A was evaluated for color, and group B was moved to -18 C for seven additional days and then evaluated. Group B represented cooling, freezing, thawing, and cooking steps. Color was measured on surfaces of thawed, uncooked parts (UCS), on surfaces of cooked parts (CS) 75 or 85 C internal temperature), and on cooked meat (CM) adjacent to the femur. UCS samples at -3 C were significantly redder (a* = 8.91) than -18 C samples (a* = 5.04). The A-CS a* values showed a significant interaction between chill temperature storage and internal temperature (IT). Samples at 75 C IT had higher a* values (redder). CM samples held at +4 and 0 C were significantly lighter (higher L* values). A significant interaction effect occurred for CM a* values due to storage chill temperature and IT. Generally, 75 C IT samples were redder (higher a* values). UCS and CS color was not influenced by chilling at +4 to -18 C for 7 d and then at -18 C for 7 d. CM was affected by a combination of chill temperature history and IT.

The role of carcass chilling rate in the development of pale, exudative turkey pectoralis

Pale, soft, and exudative meat is a growing problem in the turkey industry that has been associated with processing conditions such as improper chilling. This condition is caused by accelerated postmortem glycolysis while carcass temperatures are still elevated, resulting in protein denaturation and poor meat quality. To evaluate the involvement of chilling rate, 48 toms were conventionally processed at 17.5 wk of age and chilled at 0,10, 20, or 30 C for 45 or 90 min and deboned. Temperature and pH of the breast fillet were recorded at 15 min, deboning time, and at 24 h postmortem (PM). Drip loss, L* value, expressible moisture, gel strength, and cook loss were determined on the fillets at 24 h PM. At 15 min PM, there were no temperature differences among treatments. At deboning, the carcasses chilled at 30 C had the highest fillet temperature and had significantly lower pH values when compared to those chilled at 0 and 10 C. L* value was significantly higher in carcasses chilled at 30 C and deboned at 60 min PM when compared to 0 and 10 C chilled carcasses. There were no significant differences in L* values at 105 min and 24 h PM among any treatment group. Drip loss and cook loss were significantly higher in carcasses chilled at 30 C compared to the remaining treatments. There were no differences in expressible moisture at 60 or 105 min PM or gel strength at 60 min PM in any of the treatments. However, at 105 min PM, carcasses chiled at 0 C had higher gel strength when compared to the remaining treatments. These results indicate that there is a relationship between chilling rates and meat quality with slower chilling producing PSE-like characteristics.

Influence of Chemical Characteristics of Beef Inside and Outside Semimembranosus on Color Traits

ABSTRACTThe influence of prerigor temperature and pH on muscle chemistry of the inside semimembranosus (ISM) and outside semimembranosus (OSM) in relation to initial color and color uniformity and stability was investigated. Cold‐boned ISM had a slower (p &lt; 0.05) chill rate; faster (p &lt; 0.05) pH decline; higher (p &lt; 0.05) transmission values; and less (p &lt; 0.05) metmyoglobin reducing ability, oxygen consumption, water holding capacity and color stability than the OSM. Cold‐boned steaks were 2‐toned in color and visually unacceptable at d 3 of display. Hot‐boned ISM and OSM chilled at the same rate and had similar pH declines, similar chemical characteristics and uniform stable color for 5 d of display. Chilling beef ISM faster should produce uniform stable color.