Quality changes during superchilled storage of pork roast

Quality parameters (sensory, physical, biochemical and microbiological) of superchilled vacuum packed boneless pork roasts were studied during storage for 16 weeks. Superchilling of vacuum packed pork roast at a temperature of −2.0 °C improved shelf life significantly compared to traditional chilled storage at +3.5 °C. Superchilled pork roasts maintained good sensory quality and low microbiological counts during the whole storage period. The drip loss in superchilled samples was lower and showed less variation than in the references and the temperature abused roasts. The consequences of an interrupted cold chain during storage were also investigated. Superchilled samples with temperature abuse resembled chilled samples with respect to drip loss and microbial levels. To take advantage of all the benefits of superchilling and successfully implement the process in the food industry a stable, controlled temperature during storage is critical.     

Effects of supranutritional dietary vitamin E levels on subcellular deposition of α-tocopherol in the muscle and on pork quality

The influence of three levels of vitamin E in the diet of pigs on the subcellular deposition of α-tocopherol in the muscle and on selected quality characteristics of pork meat (oxidative stability of lipids, colour, drip loss, microbial growth) was studied. The content of α-tocopherol in adipose tissue and L. dorsi muscle as well as in mitochondrial and microsomal fractions of the muscle significantly increased (P < 0.05) with increasing levels of dietary vitamin E. The differences in the concentrations of α-tocopherol in the subcellular fractions were evident in the enhanced stability of the membranes when exposed to metmyoglobin/hydrogen peroxide. The beneficial effect of dietary vitamin E on the oxidative stability of pork lipids during the storage of pork chops and ground pork was also demonstrated. Even though lipid oxidation increased in all cases during storage, the pork products from the pigs receiving the highest level of vitamin E (200 IU kg^?1 feed) exhibited the smallest increase in thiobarbituric acid reactive substances. In addition, increased colour stability and decreased drip loss were observed on keeping pork chops, which had been previously frozen for three months, at 4°C under fluoresent light for 10 days. The possible effect of α-tocopherol on membrane fluidity in this context is discussed.     

南极磷虾肉糜冷藏过程中蛋白水解酶的稳定性及自溶特性

以总蛋白酶活力为指标,研究3 种自制南极磷虾肉糜（虾肉糜）5 ℃冷藏过程中蛋白水解酶的稳定性,并以蛋白质组分、汁液流失率为指标,结合感官评价,研究其自溶特性。结果表明：在冷藏过程中,虾肉糜所含的消化腺蛋白酶稳定性较高,未充分漂洗的虾肉糜受到持续的水解;虾肉糜的自溶特性主要表现为盐溶性蛋白、碱溶性蛋白的降解和水溶性蛋白的增加,且汁液流失率增大和感官品质劣化。未漂洗虾肉糜的自溶现象尤为显著,不宜冷藏保存,而2 次漂洗虾肉糜在冷藏过程中自溶特性不显著,虽然存在一定的蛋白质组分变化和汁液流失率增加现象,但感官品质未大幅下降,因而适宜于短时间内在5 ℃进行冷藏保存。     

Drip loss,peroxidase and sensory changes in kiwi fruit slices during frozen storage

The biochemical, sensory and drip loss changes that occur during processing and prolonged frozen storage of kiwi fruit slices (cvs Abbott and Hayward) were studied. Fruit slices were frozen at ?40°C, packed in polyethylene bags and stored at ?18°C for 11 months. Maturity characteristics (pH, acidity, dry matter, soluble solids) were determined on raw fruit. Objective (proteins, peroxidase (EC 1.11.1.7) activity, drip loss) and subjective (sensory tests) analyses were carried out during processing and storage, and indicated a good quality of the frozen kiwi fruit slices after 11 months of storage. There were significant differences (P < 0.05) between the studied varieties with respect to drip loss during frozen storage and colour after 11 months. Best results were obtained with cv Hayward. This variety showed less drip loss after thawing and after 11 months storage presented the same green colour as after freezing, while cv Abbott became yellowish-green.     

Prediction of fluid losses from pork using subjective and objective paleness

Meat paleness in pork Longissimus dorsi (LD) 1 day post-mortem (p-m) was measured subjectively using Japanese Pork Colour Scores (JPCS) and objectively using a Colormet fibre-optic (FO) meat probe (400–700 nm). Water-holding capacity (WHC), fluid loss during thin-slicing, and drip loss were measured in unfrozen and in frozen and thawed (FT) samples. FT caused a decrease in WHC, and an increase in slicing and drip loss (P < 0·001). FO interactance (i) was correlated (P < 0·01) with unfrozen WHC (R = 0·55), with FT WHC (r = −0·45 at 440 nm), with FT slicing loss (R = 0·81), with unfrozen drip loss (R = 0·66), and with FT drip loss (R = 0·61). Objective measurements proved that the development of pork paleness takes several days p-m and that paleness is increased by FT. Where fluid losses were predictable from paleness, the FO probe was superior to subjective evaluation by JPCS.     

Effect of low voltage electrical stimulation of pig carcasses and ageing on sensory attributes of fresh pork

The effect of electrically stimulating pig carcasses and ageing on sensory attributes of pork was evaluated in this study. A total of 48 female pigs [Duroc×Large White/Landrace (A; n=24) and Large White/Landrace (B; n=24)] were randomly allocated immediately prior to slaughter to one of two low voltage stimulation treatments; no stimulation or 150 mA applied for 30 s at 2 min post-exsanguination. Each side of the carcass was then randomly allocated to an ageing treatment of either 2 or 7 days post-slaughter. Muscle pH of the M. longissimus lumborum was lower (P<0.001) in electrically stimulated carcasses when measured from 40 min to 8 h post-slaughter compared with non-stimulated carcasses. Percentage drip loss, muscle lightness and PSE incidence were not influenced (P>0.05) by electrical stimulation. Electrical stimulation of pig carcasses and ageing pork for 7 days post-slaughter both improved (P<0.001) consumer scores for tenderness, juiciness, overall liking and quality category, however the interaction term of electrical stimulation and ageing was not significant for any of the sensory attributes. Pork from non-stimulated carcasses that was aged for 2 day post-slaughter was less tender (P<0.01) compared with pork in all other treatments. These results indicate that electrical stimulation (150 mA applied for 30 sec at 2 min post-exsanguination) was effective in improving eating quality attributes of pork, particularly when pork was aged for only 2 days post-slaughter, without detrimentally affecting colour or drip loss.     

调理低脂猪肉丸的研制

本论文研究腌制时间,大豆分离蛋白(sPD、食盐、谷氨酰胺转氨酶(TG酶)的添加量等工艺参数对调理低脂猪肉丸硬度、弹性、蒸煮损失率、感官品质的影响,并通过正交试验对加工工艺进行了优化.结果表明,影响调理低脂猪肉丸品质的主次因素为:食盐>腌制时间>大豆分离蛋白>谷氨酰胺转氨酶;最优加工工艺为:腌制时间12h、大豆分离蛋白2...     

猪肉冰温贮藏过程中的品质变化与机理研究

研究表明浅度冻结、合理的贮藏条件及贮存期不会显著影响原料肉及肉制品的加工和食用品质.据此,本研究提出了“冰而鲜”的冰温保鲜的新技术:即将鲜肉经过预冷后,用尽快的降温速度使肉通过最大冰晶生成带(-5℃左右),并在-5℃的温度下进行贮藏的方法.同时系统研究了不同的降温温度(-36℃与-5℃)和不同的降温方式(风冷与浸渍)对...     

Influence of meat exudates on the quality characteristics of fresh and freeze-thawed pork

The influence of the accumulated exudates released from pork loin of itself on the quality characteristics of fresh and freeze-thawed pork during cold storage was investigated. Pork loins were divided into four groups (fresh pork with exudates, fresh pork without exudates, freeze-thawed pork with exudates and freeze-thawed pork without exudates) and stored at 1.0 °C for 7 days. Exudate amount increased due to freeze-thawing and with storage, and most quality traits such as drip loss, cooking loss, tenderness, lightness, redness, and moisture content were affected by freeze-thawing (p < 0.05). Freeze–thaw increased drip loss but decreased moisture content, cooking loss, tenderness, lightness and redness of meat (p < 0.05). Microbial growth was solely affected by exudate removal and the removal of initial exudates decreased microbial growth (p < 0.05). Exudates were positively correlated with total protein content and total plate count but negatively correlated with pH and cooking loss. Therefore, removing meat exudates and avoiding freeze can slow down the quality deterioration of pork during cold storage.     

发酵酸鱼贮藏过程中理化与感官品质变化研究

本文以发酵成熟的酸鱼为研究对象,真空包装后在不同温度(4、25、35℃)条件下进行保藏试验,以感官评价、失水率、全质构、蛋白质组成、微观结构等为主要指标评价发酵酸鱼在不同贮藏条件下的品质变化与保藏特性。结果表明,保藏期90 d内,35℃贮藏加速产品感官品质劣变,失水较多,硬度变大,蛋白组成变化显著,蛋白质降解相对剧烈,肌肉纤维收缩严重,纤维间隙增大;室温(25℃)条件下贮藏期内产品感官品质较35℃相对稳定;与25和35℃条件下相比,冷藏(4℃)对发酵酸鱼的外观、气味、滋味和口感保持较好,低温有利于减缓酸鱼中水分流失、质构变化以及蛋白质的降解,90 d内能较好保持产品的感官品质和组织结构。     

STORAGE STABILITY OF PORK FROM BERKSHIRE AND HAMPSHIRE SIRED PIGS FOLLOWING DIETARY SUPPLEMENTATION WITH VITAMIN E

Effects of vitamin E supplementation on pork quality of two genotypes were evaluated using 240 pigs (initial body weight was 87 0.35 kg). Berkshire or Hampshire sired pigs were fed either 12, 55, 99, 174, and 351 IU/kg of vitamin E for 6 weeks prior to slaughter. Loins from Hampshire sired pigs had increased (P < 0.001) levels of drip loss, were paler, more red, and more yellow than loins from Berkshire sired pigs following refrigerated display storage for up to 8 days or vacuum packaged storage for up to 55 days. Vitamin E supplementation did not improve fresh pork quality in either genotype. However, results indicate that vitamin E supplementation improved oxidative stability of pork chops during refrigerated display storage and this effect was more pronounced in the leaner Hampshire sired pigs. Therefore, vitamin E supplementation could be strategically applied to improve storage stability in select genotypes.     

Effects of Dietary Rape Seed Oil, Copper(II) Sulphate and Vitamin E on Drip Loss, Colour and Lipid Oxidation of Chilled Pork Chops Packed in Atmospheric Air or in a High Oxygen Atmosphere

The effect of addition of rapeseed oil (canola), CuSO(4) and vitamin E (all-rac-α-tocopheryl acetate) to pig diets on pork meat quality (lipid oxidation, colour and drip loss) was studied. Pigs were reared on ten different diets, either a control diet (no supplementation of rapeseed oil, CuSO(4) or vitamin E) or 6% rapeseed oil diets supplemented with CuSO(4) (0, 35 or 175mg/kg) and vitamin E (0, 100 or 200mg all-rac-α-tocopheryl acetate/kg). The natural content of vitamin E originating from feed ingredients amounted to 9-23mg vitamin E (α-tocopherol) per kg feed. Muscle vitamin E levels reflected the dietary intake and pigs fed the control diet had significantly lower levels than pigs fed rapeseed oil diets. The quality of fresh pork chops packed in air or in 80% O(2):20% CO(2) was followed during chill storage for 8 and 13 days, respectively. Colour, as measured by tristimulus colorimetry of pork chops packed in 80% oxygen atmosphere, was significantly improved with respect to redness when compared to chops packed in air, regardless of dietary treatment. The low vitamin E content in pigs fed the control feed significantly decreased a values and the oxidative stability of pork chops during chill storage compared to the other feeding groups. Packing of chops in a high-oxygen atmosphere increased lipid oxidation, especially in chops with low levels of vitamin E. Supplementation of rapeseed oil diets with 100 or 200mg vitamin E significantly decreased lipid oxidation of chill stored chops. Supplementation with CuSO(4) did not influence meat quality attributes (drip loss, colour stability and lipid oxidation) for any of the storage conditions.     

微冻对南美白对虾质构的影响

以南美白对虾为对象,研究了其在-3℃微冻条件下质构参数(硬度、弹性、剪切力,咀嚼性、黏附性、胶黏性)的变化,同时考察了TVBN值、汁液流失率和感官特性的变化。结果表明:随着贮藏时间的延长,TVBN和汁液流失率均呈上升趋势;在贮藏至第14天以前,硬度、弹性、剪切力、咀嚼性呈上升趋势,之后逐渐下降,而黏附性一直呈现上升趋势,胶黏性呈下降趋势;结合TVBN值、汁液流失率和感官特性测定结果,南美白对虾质构测定结果能够较客观的表现其品质。     

Evaluation of Poultry Protein Isolate as a Food Ingredient: Physicochemical Properties and Sensory Characteristics of Marinated Chicken Breasts

The possibilities of replacing soy protein isolate (SPI) and reducing the amount of phosphate in marinated chicken breasts using poultry protein isolate (PPI) were investigated. PPI, prepared from mechanically separated turkey meat through the pH‐shift technology, was used as a marinade ingredient for chicken breasts at 2 different concentrations (1.0% and 1.5%, w/w on a dry weight basis). Product characteristics were compared to samples marinated with salt, phosphate, or SPI. All the 5 treatments were subjected to instrumental and sensory analyses. Tumbling yield, drip, and cooking losses as well as expressible moisture showed that PPI can be used as a substitute for SPI in brine. The sensory analysis revealed that there were no differences among treatments in terms of appearance, color, flavor, saltiness, juiciness, tenderness, and overall acceptability of the marinated chicken breasts. However, chicken breasts marinated with phosphate had significantly higher aroma acceptability scores than those treated with 1% PPI.     

冰温结合气调包装对牛肉品质的影响

本文以牛肉为研究对象,以冰温技术结合O2/CO2气调包装技术对其进行贮藏保鲜试验,并对贮藏过程中牛肉的菌落总数、挥发性盐基氮(TVB-N)含量、色差值(L*值、a*)以及汁液流失率进行定期测定,同时从色泽和气味方面做以感官评价。结果表明:50%O2+50%CO2组和30%O2+70%CO2组在货架期上要高于对照组和80%O2+20%CO2组至少4 d;但是各组的TVB-N值之间无显著性差异;高浓度的氧气使得汁液流失率增大,不利于牛肉水分的保持;同时,高浓度的O2使牛肉在贮藏早期有很好的颜色,但是贮藏后期在色泽上劣变较快,并加速了牛肉的腐败变质,从而加速了不良气味的产生。高浓度的CO2不利于良好色泽的保持,但是能够很好地控制牛肉的腐败。综合几种冰温结合气调的保鲜技术来看,50%O2结合50%CO2组对牛肉有更好地贮藏保鲜效果。     

Evaluation of various infused cryoprotective ingredients for their freeze-thaw stabilizing and texture improving properties in frozen red hake muscle

ABSTRACT:  Various cryoprotective ingredients were evaluated for their freeze–thaw stabilizing and texture improving properties during 6-mo frozen storage when red hake ( Urophycis chuss ) fillets were injected with sorbitol–sodium tripolyphosphate (STPP) (40% to 60% : 3%), 1.5% alginate, or 0.75% alginate with soy protein isolate (SPI)–sorbitol–STPP (5% to 10% : 40% : 3%). Injection of 10% SPI, 1.5% alginate, or 0.75% alginate–5% SPI effectively improved water binding and retarded the freeze-induced texture changes when drip and cooking loss, centrifugal expressible moisture, protein extractability, SDS-PAGE profile, and Instron and sensory texture were assessed. The sorbitol and STPP combination was not as effective as alginate and SPI. Freeze-susceptible whitefish can be injected with proper cryoprotective ingredients for improved frozen storability.     

南美白对虾冰温气调保鲜效果评价

将鲜南美白对虾进行空气包装(AP)、真空包装(VP)、气调包装(MAP,75% CO2/25% N2),分别冰温(－2.3～0℃)贮藏和冰藏,通过研究样品贮藏过程中多酚氧化酶(PPO)活力、总挥发性盐基氮(TVB-N)、菌落总数(TPC)、汁液流失率(DL)的变化,结合感官指标评价冰温气调保鲜的效果。结果表明：南美白对虾的PPO活力变化与腐败变质同步;冰温结合MAP能有效防止褐变,货架期可达10d,比冰藏结合AP延长了约3倍,此时样品色泽良好,TPC、TVB-N、DL分别为5.4(lg(CFU/g))、25.6mg/100g、3.13%,而其他包装样品已腐败。VP也能较好的保持色泽,但贮藏后期汁液流失相对严重,影响外观。     

不同注水量对猪肉食用品质的影响

通过研究不同注水量(0、10%、20%、30%、40%)对猪肉色泽、pH、剪切力、滴水损失、蒸煮损失、压榨损失、离心损失、贮藏损失、拿破率的影响,比较分析正常猪肉与不同比例注水猪肉食用品质的差异。结果表明:随着注水量的增加,L*、b*、滴水损失、蒸煮损失、压榨损失、离心损失、贮藏损失显著增大(p<0.05),a*、剪切力随着注水量的增加显著减小(p<0.05);当注水量小于20%时,注水猪肉的L*、压榨损失、贮藏损失、离心损失与正常猪肉差异显著(p<0.05),而当注水量大于等于20%时,注水猪肉的L*、a*、压榨损失、贮藏损失、离心损失、剪切力值、蒸煮损失、滴水损失均与正常猪肉存在显著性差异(p<0.05)。与正常猪肉相比,注水后的猪肉亮度增加,保水性变差,嫩度有所增加。相关性分析表明,注水后肉块保水性的变化影响色泽的改变,同时也会影响嫩度的变化。     

冰温贮藏对猪肉宰后品质及糖酵解途径相关酶活性的影响

为研究冰温贮藏对猪肉感官品质和宰后糖酵解途径中乳酸代谢的影响,以猪里脊肉为对象,分别采用冰温(-1℃)和冷鲜(4℃)贮藏方式,测定其宰后0.5、2、6、12、24、72、120、168h时包括汁液损失率、色泽、pH值在内的品质指标以及糖酵解及相关代谢途径主要酶的活力.结果表明:冰温贮藏可有效降低猪肉品质劣变,减缓糖酵解...     

宰后成熟过程中猪肉保水性的变化

以三元猪背最长肌为研究对象,在第4、8、12、16、20、24、28、32和36 h分别检测蒸煮损失率、滴水损失率、贮藏损失率、剪切力值和pH值的变化情况,研究宰后成熟过程中猪肉保水性的变化规律。结果表明,蒸煮损失率呈先升高后降低的趋势,在第20 h蒸煮损失率达到最大值32.80%;贮藏损失率和滴水损失率呈先下降后上升再下降的趋势;剪切力值在4~12 h内显著性上升（p<0.05）,且在12 h达到最大62.29 N;pH值呈整体先下降后上升再下降最后趋于稳定的变化趋势;其中,成熟时间与剪切力值呈显著负相关（p<0.01）,pH值与蒸煮损失率呈极显著负相关（p<0.01）,滴水损失率与贮藏损失率呈较高的相关性（p<0.01）。综合指标,猪肉在宰后成熟36 h内保水性有先变弱后增强的趋势,在12~16 h内进入僵直高峰点,随后进入解僵成熟期。该研究结果可为后续深入研究宰后成熟过程中猪肉嫩度变化规律及机理提供基础指标和参考依据。