Development of rancidity in salmonoid steaks during retail display. A comparison of practical storage life of wild salmon and farmed rainbow trout

The quality of wild salmon and farmed rainbow trout from aquaculture, both packed in transparent vacuum-skin packaging, was followed during storage for 6 months in an illuminated freezer cabinet (product temperature -17 degrees C, half of the packs protected against light, and half of the packs fully exposed to light), combining (a) colour determination of the carotenoid-pigment flesh by tristimulus colorimetry, (b) determination of thiobarbituric-acid-reactive substances (TBA value), (c) carotenoid analysis and, at the end of the storage experiment, (d) sensory evaluation. Rancidity developed faster in steaks of wild salmon (TBA increased during 6 months of storage from 2.8 mumols malonaldehyde/kg flesh to 12.5 mumols/kg for light-protected packages, and to 17.6 mumols/kg for packages exposed to fluorescent light) as compared to steaks of farmed rainbow trout (TBA increased from 1.2 to 5.8 mumols/kg, independent of light exposure), a finding also confirmed by sensory evaluation. In both products, the carotenoid pigment was identified as astaxanthin; salmon steaks, the product more susceptible to developing rancidity, had the lower astaxanthin content (rainbow trout 9.1 mg/kg flesh, salmon 4.9 mg/kg, prior to storage). While the astaxanthin content remained virtually constant in salmon steaks during storage, the content decreased significantly in steaks of rainbow trout, an observation which suggests the role of astaxanthin as a sacrificial protector against radical processes.     

The retail display life of steaks prepared from chill stored vacuum and carbon dioxide-packed sub-primal beef cuts

Chilled striploins and cube rolls from ten Australian steers (grain-fed for 150 days) were trimmed of external fat and cut transversely into portions approximately 10 cm thick, each weighing between 750 and 1000 g. These 'retailer-ready' cuts were each wrapped in drip saver pads and slid inside a plastic sleeve before being individually placed into a clear plastic high oxygen barrier film, metallized film or conventional vacuum bag. Cuts in clear plastic and metallized film packs were packaged in an oxygen-free saturated carbon dioxide atmosphere (CO(2)-CAP), those in vacuum bags were conventionally vacuum-packed. All packs were returned to the chiller for further cooling. After 24 hr, half the clear plastic and metallized CO(2)-CAP packs were carbon dioxide master-packed in groups of eight. Retailer-ready cuts in both clear plastic and metallized film single unit and master-packed CO(2)-CAP packs were air freighted to New Zealand and sea freighted to Japan for assessment. The control vacuum packs were all consigned to New Zealand. Assessments in both countries after 39-89 days storage at between 0 °C and -1.0 °C indicated that fat colour stability limited the retail display life of steaks cut from meat in these retailer-ready packs to approximately 48 hr. In this regard, meat from single unit CO(2)-CAP, master pack CO(2)-CAP and vacuum packs performed similarly. Lean meat colour and sensory attributes remained acceptable for up to 48 hr after displayed product was rejected because of grey-green fat discoloration. The microbiological status of retailer-ready cuts removed from CO(2)-CAP packs after 89 days chilled storage was superior to that of cuts from vacuum packs. Clear plastic and metallized film CO(2)-CAP packs performed comparably.     

Antioxidant and modified atmosphere packaging prevention of discoloration in pork bones during retail display

The objective of this study was to evaluate the ability of antioxidants to prevent discoloration in pork rib bones. Pork rib bones were removed from carcasses, frozen (−20 °C, 24 h), split lengthwise, exposed to antioxidant solutions (ascorbic acid, citric acid, propyl gallate or ascorbic/EDTA mix), packaged (modified atmosphere [80% O₂ and 20% CO₂] or air), then displayed in a retail case at 4 °C for 8 days. Dark pigment formation was visually evaluated during the display period. Instrumental color was determined at the end of the 8-day display period. Visual bone discoloration increased over time for all treatments. After 2 days of display, samples treated with propyl gallate were visually redder, less discolored and less green/black than samples treated with other antioxidants. After 8 days of display, propyl gallate-treated samples had higher a* and b* values, as well as chroma (intensity). However, this difference was no longer large enough to be visually detected.     

Influence of dietary inclusion level of manganese on pork quality during retail display

Boneless pork loins (n = 112) were used to test the influence of dietary manganese (Mn) inclusion level on pork quality traits during retail display. Crossbred barrows and gilts were fed diets formulated with 0, 20, 40, 80, 160, or 320 ppm Mn from Availa^®Mn (AvMn; a Mn–amino acid complex) from 23.8 to 106.8 kg live weight. At approximately 48 h postmortem, boneless pork loins were fabricated into longissimus thoracis et lumborum (LM) chops, which were subsequently placed in open-topped, coffin-chest display cases (2.6 °C) under continuous warm-white, fluorescent lighting (1600 lx) for 7 days. Dietary Mn level had no effect on LM pH (P = 0.47), purge volume (P = 0.60) and loss (P = 0.53), or moisture loss (P = 0.95) during retail display. Chops from pigs fed 80 ppm Mn received higher (P < 0.05) American and Japanese color scores than pigs fed 0 and 40 ppm Mn. Even though the LM from pigs fed 80, 160, and 320 ppm Mn tended to be darker (lower L^* values; P = 0.07) than chops from pigs fed 40 ppm Mn, a^* (redness) and b^* (yellowness) values, as well as hue angle and chroma, were not (P  0.19) affected by dietary Mn. On days 0 and 1, the reflectance ratio of 630 nm/580 nm was similar (P > 0.05) among dietary Mn supplementation levels; yet, by day 4 of retail display, chops from pigs fed 80 ppm Mn had higher (P < 0.05) reflectance ratios than chops from pigs fed 0, 20, 40, and 160 ppm, whereas LM chops from pigs fed 40 ppm Mn had lower (P < 0.05) reflectance ratios than all other dietary treatments on day 7 (Mn supplementation level × display day; P = 0.04). Although TBARS were greater (P < 0.001) on day 7 than 0 of retail display, TBARS values did not (P = 0.43) differ among dietary Mn levels. Results indicate that supplementing swine diets with 80 ppm Mn may improve pork color during retail display without increasing the likelihood of lipid oxidation.     

Effect of vacuum ageing on quality changes of lamb steaks from early fattening lambs during aerobic display

The effects of vacuum ageing on the quality changes of lamb steaks during retail display were assessed. Biceps femoris and Quadriceps femoris muscles from thirty early fattening lambs fed barley straw and concentrate or alfalfa and concentrate were used. Half of the muscles were vacuum aged for three weeks (VA), and the other half were not aged (control). Control and VA muscles were sliced and aerobically displayed. Weight loss, pH, aldehyde contents, instrumental color characteristics and color acceptance were measured at display days 1, 3, 7 and 14. At day 1 redness was higher in VA lamb. However, redness of VA lamb decreases more rapidly during further storage. Redness and color acceptance decreased in VA lamb from day 3, whereas in not-aged lamb the decrease was observed from day 7 onwards. From days 7 to 14 a drop of color acceptance accompanied by an increase in pH and a decrease in lightness was observed in control and VA lamb.     

Effect of tray liners on the drip loss of lamb chops during retail display

The amount of drip lost by lamb chops during display was affected by the type of tray liner used. In one study involving chilled and frozen/thawed meat, the use of an absorbent paper liner increased the drip loss and influenced whether or not the quantity of drip was affected by freezing/thawing. In another study, thawed chops held for 24 h on plastic coated trays without liner or on a plastic coated liner had less than 2% drip loss, whereas adjacent chops from the same loin processed and held in the same way but displayed on liners of absorbent paper or paper pouches of diatomaceous earth lost 4·3% and 5·6% drip, respectively. This effect of the material in contact with the meat should be considered when reporting drip loss data and when comparing results with those of other researchers.     

The effect of pH on shelf-life of pork during aging and simulated retail display

The pork industry uses pH to differentiate product of varying quality; thus, the effect of pH on shelf-life is important as time during transport is extended. The objective was to develop regression equations to predict shelf-life over a range of ultimate pH (5.42–6.26). Shelf-life was evaluated after vacuum aging pork loin sections 0, 7, 14, 21, or 28 d and during 3 d of simulated retail display (4.5 °C) for pork loin chops. Correlation coefficients indicated a strong relationship between pH and quality measurements. Regression analysis with Aging Day and pH was able to explain 87% of the variation in aerobic plate counts for pork. After 28 d of vacuum aging, loin sections from the upper end of the pH distribution had about a 3 log(1000X) greater aerobic plate count than did the lower end pH product. An increase in pH resulted in pork with lower L*, a*, b* and R₆₃₀ − R₅₈₀ values and as Aging Day increased, instrumental measurements of color increased slightly. Although higher pH is associated with improved pork quality, higher pH and longer aging periods will result in increased microbial proliferation and decreased shelf-life. Thus, an intermediate pH may provide the most desirable combination of quality and shelf-life when extensive aging is used.     

Effect of packaging and display variables on retail display of frozen lamb chops

Display conditions of packaging and lighting and the length of frozen storage of the carcass before cutting were examined for their effect on the colour of frozen chops during display. Lighting effected a greying and loss of saturation of the colour, while packaging film affected brightness and hue angle. Length of storage affected hue and saturation. Display time affected brightness and hue in a linear manner.     

The importance of chill rate when characterising colour change of lamb meat during retail display

An experiment was conducted to compare the effect of two chilling rates (Con and Fast) on colour change of lamb meat during simulated retail display. Measurements were made on 3 muscles; LD (m. longisimuss dorsi), SM (m semimembranosus) and ST (m. semitendinous). Meat samples from 32 Merino crossbred lambs were vacuum packed and stored for 5 days at 2 °C, then cut and overwrapped in polyvinyl chloride film on black polystyrene trays, stored in a display cabinet at 4 °C with lights on and measured twice daily for 4 days, using a Hunterlab minilab 45/20 L D65, aperture 10°. Sarcomere length was shorter, shear force higher and colour change greater in meat from the Fast treatment compared to the Con treatment. Colour differences between treatments were likely due to oxygenation (bloom) as well as oxidation effects. Chill rate is important when characterising colour change during display and should be considered in measurement protocols.     

Oxidative stability and its relationship with natural antioxidants during refrigerated retail display of beef produced in Argentina

The objective of this study was to determine if pasture or grain diets affect oxidative/antioxidative status and the color stability of beef during retail display. Ten crossbreed steers were fed on pasture. Five of them were randomly assigned to remain on this diet, and the other five were finished on feedlot system (grain diet) during 110days until slaughter. Slices of Psoas major steaks were randomly distributed among retail display times (1, 3, 5, 7 and 9days). Lipid and protein oxidation were higher in Psoas major steaks from grain diet than in pasture diet (P<0.05). After 3days of display, lipid oxidation increased in meat from grain diet, whereas in meat from pasture diet the first evidence was after 7days (P<0.05). Protein oxidation was higher in meat from grain diet than in meat from pasture diet at day 9 of display (1.15±0.92 vs. 1.91±0.70μg/g, respectively; P<0.05). Antioxidant vitamins, α-tocopherol and β-carotene were higher at time=0 in pasture Psoas major steaks (P<0.05) and were differentially reduced throughout storage. While α-tocopherol decreased 41% and 57% for pasture and grain beef respectively (P<0.05), β-carotene levels remained practically unaffected in grain beef. After 7days of display "a" value was higher for Psoas major steaks from pasture diet (P<0.05). Besides, "L" parameter showed higher values for samples from grain diets but it was no affected by display time. No differences were observed between both treatments for "b" value, but a significant decrease (P<0.05) was observed along storage. Superoxide dismutase and catalase activity was stable throughout storage, while glutathione peroxidase activity decreased significantly (P<0.05). The results in this study demonstrated that the higher initial level and synergistic action (under light and air) of α-tocopherol and β-carotene found in pasture-finished animals improved the oxidative and color stability of beef, as showed by a better retention of redness at the end of retail display.     

Optimisation of colour stability of cured ham during packaging and retail display by a multifactorial design

A multifactorial design, including (1) percent residual oxygen, (2) oxygen transmission rate of packaging film (OTR), (3) product to headspace volume ratio, (4) illuminance level and (5) nitrite level during curing, was established to investigate factors affecting light-induced oxidative discoloration of cured ham (packaged in modified atmosphere of 20% carbon dioxide and balanced with nitrogen) during 14 days of chill storage. Univariate statistical analysis found significant effects of all main factors on the redness (tristimulus a-value) of the ham. Subsequently, Response Surface Modelling of the data further proved that the interactions between packaging and storage conditions are important when optimising colour stability. The measured content of oxygen in the headspace was incorporated in the model and the interaction between measured oxygen content in the headspace and the product to headspace volume ratio was found to be crucial. Thus, it is not enough to keep the headspace oxygen level low, if the headspace volume at the same time is large, there will still be sufficient oxygen for colour deteriorating processes to take place.     

Effects of lactic and acetic acid salts on quality characteristics of enhanced pork during retail display

The objective of this study was to evaluate the sensory and physical characteristics of pork chops from loins enhanced to 110% of original weight with either (1) potassium lactate, potassium diacetate, phosphate and salt, (2) sodium lactate, phosphate and salt, (3) potassium lactate, phosphate and salt, (4) sodium acetate, phosphate and salt, or (5) phosphate and salt. A trained sensory panel evaluated pork flavor, saltiness, bitterness, soapy flavor, acid flavor, juiciness and tenderness of cooked chops. Visual color of raw chops was also evaluated. After 96 h in display, chops enhanced with lactate/diacetate had significantly lower (P<0.01) aerobic plate counts than control (unpumped) chops, or those pumped with other solutions. Lactate/diacetate-enhanced chops maintained higher a* and b* values during display, and had less visual discoloration after 96 h display. Chops pumped with lactate, acetate or the lactate/diacetate mixture were more tender and juicy, and had more pork flavor than controls or those pumped with phosphate/salt only. There appears to be a significant advantage to using a lactate/diacetate enhancement solution over either lactate or acetate alone.     

瓶装食用油反复开封氧化酸败的研究

研究了瓶装食用油反复开封氧化酸败问题,结果表明:随着使用过程反复开封包装瓶,瓶内油脂逐渐被氧化,开封次数越多、使用时间越长,油脂氧化越严重;瓶装食用油反复开封后储存温度越高,氧化越严重;添加抗氧化剂可延缓瓶装食用油在反复开封使用过程中的氧化酸败;在无添加抗氧化剂的情况下,食用油的氧化速度与其多不饱和脂肪酸含量呈现正相关。     

小麦胚芽贮藏期内脂质水解酸败机理解析

以小麦胚芽为研究对象,构建脂质水解酸败的模拟体系以及原位体系,解析小麦胚芽贮藏期内脂质水解酸败的机理。结果表明:光照、氧气和脂肪氧合酶未对小麦胚芽模拟体系中的游离脂肪酸含量产生明显影响,而脂肪酶则显著提升游离脂肪酸生成量;此外,游离脂肪酸生成量随水分活度增加而增加,于水分活度为0.75时达峰值,且小麦胚芽内部结合水和不易流动水含量也呈显著增加趋势,水分以及脂质流动性增加;小麦胚芽原位体系中游离脂肪酸含量随贮藏时间延长而逐渐增加,磷脂酰胆碱含量恰相反,且小麦胚芽脂质体膜遭到破坏,游离出的甘油三酯聚集形成油滴。由此可见,小麦胚芽脂质水解酸败模式主要表现为其脂质体膜中的磷脂酰胆碱降解而释放甘油三酯,而后甘油三酯经由脂肪酶催化水解生成大量的游离脂肪酸,从而产生水解酸败现象。     

The display life of retail-packaged beef steaks after their storage in master packs under various atmospheres

Beef strip loins were divided into four portions. One portion of each loin was vacuum-packaged and then stored at −1·5°C. The other portions were each divided into three steaks, which were retail-packaged. The retail packs were master-packaged under atmospheres of N₂, CO₂, or O₂ + CO₂ (2 : 1, v/v) and then stored at 2°C. Product was assessed after storage times of up to 60 days. At each assessment, a vacuum pack and a master pack of each type, each containing product from the same loin, were withdrawn from storage. The vacuum-packaged product was cut into three steaks, which were retail-packaged. The newly prepared retail packs and those from the master packs were displayed in a retail cabinet, at air temperatures that averaged between 3 and 5·7°C, and were assessed twice daily until the product was judged to be unacceptable. When first assessed, steaks cut from vacuum-packaged product were generally considered desirable, with little metmyoglobin in the surface pigment, although the edges of same steaks were discoloured. Steaks stored under N₂ or CO₂ for 4 days or less were only slightly desirable at best, with metmyoglobin forming relatively large fractions of the surface pigment. However, after storage under N₂ or CO₂ for 6 days or more, metmyoglobin fractions were low, and the steaks bloomed to a desirable red colour. Steaks stored under O₂ + CO₂ had lower metmyoglobin fractions, and were desirable after storage for up to 8 days. However, the fractions of metmyoglobin increased, and steaks were judged to be less desirable after longer storage times. Steaks stored under O₂ + CO₂ for 20 days were unacceptable. After storage, the numbers of bacteria on steaks from vacuum packs and N₂, CO₂, and O₂ + CO₂ atmospheres were, respectively, <10⁴, <10⁶, <10⁵, and <10⁴ CFU/cm². The flora from steaks stored under CO₂ were composed wholly of lactic acid bacteria. Other flora were dominated by lactic acid bacteria, but contained fractions of enterobacteria and/or Brochothrix thermosphacta.

The appearance of product from vacuum packs generally was unacceptable after 72 h of display. The display life of steaks stored under N₂ or CO₂ was shorter than that of the product from vacuum packs when product was stored for 2 days or less, or 46 days or more. After other storage times, the product from vacuum packs or master packs with N₂ or CO₂ atmospheres had a similar display life. The display life of product stored under O₂ + CO₂ was similar to that of product from vacuum packs or CO₂ or O₂ + CO₂ was similar to that of product from vacuum packs after storage times of 8 days or less but was shorter after storage times of 12 or 16 days. The flora on displayed product from vacuum packs or CO₂ or O₂ + CO₂. atmospheres did not attain the maximum number of 10⁷ CFU/cm². and the product did not develop off-odours of microbial origin. However, numbers of 10⁷ CFU/cm² were approached or attained during display of product stored under N₂ for 28 days or longer, and some of that product developed moderate off-odours. It then appears that, under temperature regimes that are common in commercial practice, retail-packaged strip-loin steaks with a display life of 2 days or longer can be obtained from master packs after storage periods of up to about 2, 4, or 7 weeks, respectively, with master-pack atmospheres of O₂ + COPin2 (2 : 1, v/v), N₂, or CO₂.     

Improvement of shelf-life of buffalo meat using lactic acid, clove oil and vitamin C during retail display

Buffalo meat steaks dipped in either (1) distilled water (control), (2) lactic acid (LA), (3) LA + clove oil (clove), or (4) LA + clove + vitamin C (Vit C) were displayed at 4 ± 1 °C, illuminated by a standard fluorescent lamp. The pH, 2-thiobarbituric acid reactive substances (TBARS), instrumental colour (CIE L^∗, a^∗, b^∗), aerobic plate counts (APC), psychrotrophic counts (PPC), coliform counts and sensory colour and odour were determined up to 12th day of display at 3 days interval. Results showed that, all the treatments have significantly (P < 0.05) reduced the TBARS values compared to control. Among treatments, use of LA + clove has exhibited significantly (P < 0.05) lowest TBARS values throughout display period than others. Buffalo meat steaks treated with either LA + clove or LA + clove + Vit C had significantly (P < 0.05) lower APC, PPC and coliform counts than control or LA treated samples. LA + clove + Vit C treated samples maintained significantly (P < 0.05) higher a^∗ and b^∗ values during display as well as improvement in sensory colour and odour than others. Treatment with either LA + clove or LA + clove + Vit C extended the display life of buffalo meat steaks at 4 ± 1 °C. There appears to be a significant advantage to using LA + clove or LA + clove + Vit C over LA alone.     

Factors influencing frozen display life of lamb chops and steaks: Effect of packaging and temperature

Frozen lamb loin and rib chops and leg steaks were wrapped in film of high oxygen permeability or vacuum packaged in film of low oxygen permeability and stored in the dark at -10, -20 or -35°C for periods from 0-20 weeks. After storage, the wrapped cuts were displayed in an open-top cabinet operating at -20°C under continuous fluorescent lighting (Philips Deluxe 32°). Cuts were evaluated by a trained colour panel to determine acceptable display life, and chop lean colour was evaluated using a Hunter colorimeter. Cuts wrapped in oxygen permeable film had better colour retention during storage and display. Storage of the frozen chops reduced the display life, with the largest effect occurring during the first 4-5 weeks' storage. Cuts stored at -10°C had no display life after 10 weeks' storage, whereas cuts stored at -20 and -35°C had some acceptable display life even after the longest storage period tested. Rib chops in general had better colour stability than loin chops.     

Effects of dietary rosemary extract on lamb spoilage under retail display conditions

A dietary rosemary extract (RE) was tested to extend the shelf life of raw lamb meat. Lambs were supplemented with 0.6 mg kg⁻¹ RE during fattening (from 13 to 25 kg live weight). Meat spoilage (total viable counts, psycrophilic bacteria, Enterobacteriaceae, molds and yeasts), TBARS, CIE L*a*b* color and the sensory traits of lamb cuts were analyzed on days 0, 7, 14 or 21 under retail display conditions (70/30 O₂/CO₂ atmosphere, 2 °C temperature and 1600 lx lighting). Supplementation of the lamb diet with RE was effective (P < 0.05) in prolonging the time chilled-packed lamb cuts could be kept under retail display conditions. Dietary rosemary clearly inhibited lipid oxidation and rancidity, and was moderately efficient in preventing sensory deterioration and microbial spoilage. Although the results concerning meat preservation were limited, the dietary use of rosemary extracts in lambs seems to be promising as a nutritional strategy for improving meat quality.     

贮藏过程中酸败引起的米糠谷蛋白功能性质变化

将新鲜米糠在25℃、相对湿度85%的条件下贮藏不同时间得到不同酸败程度米糠,随后脱脂制备米糠谷蛋白,研究米糠酸败对米糠谷蛋白功能性质的影响。结果表明:米糠谷蛋白羰基含量随贮藏时间延长而增加,表明米糠谷蛋白在贮藏过程中发生了氧化;随着贮藏时间的延长,米糠谷蛋白溶解性下降了40%;米糠谷蛋白持水性、持油性、起泡能力、泡沫稳定性、乳化性和乳化稳定性则随着贮藏时间延长均先上升后下降,其中持水性和持油性分别在贮藏3d和1d后达到最大值,分别为212.61%和657.25%;起泡能力和乳化性均在贮藏1d后达到最大值,分别为75.06%和76.27m2/g,泡沫稳定性和乳化稳定性则在贮藏3d后达到最大值,分别为69.30%和20.60min。表明米糠短期贮藏可提高谷蛋白功能性质,而长期贮藏则会降低。     

Humidification of unwrapped chilled meat on retail display using an ultrasonic fogging system

The effects of an ultrasonic humidification system on unwrapped meat in a chilled retail display cabinet were assessed. Humidification raised the relative humidity of the cabinet air from a mean of 76.7% to just below saturation at 98.8%. This reduced the mean evaporative weight loss from whole samples of meat after 14 h from 1.68% to 0.62% of their initial weight. The rate of deterioration in the appearance of the meat due to dehydration was reduced to the extent that while the unhumidified trial was terminated after 14 h because all samples were judged to be unacceptable, the humidified trial was continued for 24 h without any major changes in appearance.Levels of presumptive pseudomonas bacteria were relatively high in water samples taken from the humidification system and defrost water during the humidified trial, but Legionella spp. were not isolated. Significant increases in the numbers of bacteria on the meat during either trial were only found in one case, that of humidified minced beef. However, some of the samples had high counts even before display, and this may have masked any effect due to humidification. Differences in levels of air-borne contamination were small and inconsistent.Air temperatures were raised by humidification by between 1 and 2 °C and this was reflected in similarly raised product temperatures. Temperatures of air leaving the evaporator indicated that this was due to icing of the evaporator in the periods leading up to defrosts.