Thawing of lamb loin chops in air and CO(2). Effect on colour and drip

Colour retention and drip loss was assessed during retail display for chilled lamb chops displayed fresh or stored in CO(2) for 7 weeks before display, and for chops frozen for various times and thawed in air or CO(2). A sensory panel found fresh lamb chops to have an acceptable display life of 1 day, while chops which had been frozen for 1 day and then thawed lasted 2 days. Holding chops for 7 weeks in a CO(2) atmosphere at - 1·5°C improved display life to 3 days, but frozen chops held for 7 weeks before thawing had deteriorated in colour, and only one group was acceptable on the initial day of display. Initially there were no differences in Hunter L values (brightness) due to treatment, but chilled chops or those frozen for 1 day showed a greater increase in L values by the second day than those frozen for 7 weeks, after which there was no change in brightness. Hunter a values (redness) were higher in chilled chops and those thawed after 1 day's frozen storage than those frozen for 7 weeks before thawing. Hunter b values (yellowness) were greater at all times in chilled chops held for 7 weeks and varied amongst the other treatments. The measured per cent drip from chops frozen for only 1 day was greater on thawing than drip from chops frozen for 7 weeks before thawing. Drip during display, assessed by a sensory panel, increased more in those chops stored either chilled or frozen for 7 weeks before display.     

The effects of electrical stimulation, thawing, ageing and packaging on the colour and display life of lamb chops

Electrical stimulation, freezing and thawing, ageing and type of packaging used during ageing are factors which could influence the final colour of meat. The experiment reported here determined the individual and additive effects of these factors in displayed lamb. Initial panel scores for colour of chops were increased by electrical stimulation and decreased by thawing and by ageing for up to six weeks. Chops from loins which had been aged in vacuum pack had higher initial scores than those aged in oxygen-permeable film. Hunter colour values for chops from stimulated carcasses were much less variable than those for chops from unstimulated carcasses. Stimulation, therefore, produced a more uniform product. Hunter L, a and b values all declined during display, the greatest decline being in a (redness). Hunter values were not good predictors of initial panel scores but Hunter a and hue (a b ) both declined with panel scores. With no ageing, the display life of stimulated chilled lamb was longer than that of unstimulated lamb, but this advantage disappeared after ageing for 2 weeks in a vacuum pack. The display life of thawed unstimulated lamb was only slightly inferior to that of chilled unstimulated lamb when both were vacuum-packed, but thawed stimulated lamb resulted in a much reduced display life. Ageing of loins in oxygen-permeable film adversely affected display life of chops. Total drip loss from rigor to the end of display was significantly affected by all treatments except stimulation. The dominant cause of drip loss was the freeze-thaw treatment. In chilled and thawed lamb, ageing increased drip. Packaging had a lesser effect on drip.     

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.     

Meat quality comparison between fresh and frozen/thawed ostrich M. iliofibularis

A pairwise comparison of the meat quality between fresh and frozen/thawed Musculus iliofibularis was conducted. Thirty-two (16 left; 16 right) muscles were collected and allocated to two treatments: fresh and frozen/thawed. Frozen vacuum-packed samples were stored for 1 month at -20°C before thawing. The fresh samples had higher pH (P<0.05), water binding capacity (P<0.05), CIE L* (P<0.0001), CIE a* (P<0.05) and Chroma values (P<0.05) than the frozen/thawed samples, indicating the fresh samples were bright red in appearance and had minimal exudate. The frozen/thawed samples lost 5.09±0.21% moisture during thawing and had a greater drip loss (P<0.0001) and shear force (P<0.001). No differences were obtained with regard to cooking loss, CIE b*, hue and TBARS. Protein oxidation (mM carbonyls/mg protein) was lower (P<0.05) in the frozen/thawed samples, which was attributed to the higher (P<0.0001) protein concentration negating the higher (P<0.001) carbonyl content. Industrial freezing and thawing regimes negatively affected the quality of ostrich meat.     

Differentiation of Frozen and Unfrozen Beef Using Near-Infrared Spectroscopy

Freezing and thawing affects the quality of meat. The present paper focuses on using near-infrared (NIR) diffuse reflectance spectroscopy to detect whether beef has been frozen and thawed. Intact beef and drip or centrifuged meat juice of M longissimus dorsi slices from 40 cattle were used as samples. The meat juices were analysed using dry extract spectroscopy by infrared reflection (DESIR). From centrifuged juice 80 samples were classified 100% correctly, using crossvalidation, into frozen or unfrozen beef by the K nearest neighbours method. This was obtained by high-order principal components from 400–2500 nm spectra. Other multivariate techniques, smaller wavelength ranges and detecting refrozen, thawed beef also gave results between 90 and 100%. Analyses of drip loss, exudative properties, water-holding capacity and dry matter of meat juice supported the interpretation of the NIR measurements. The results showed that NIR might be used as a screening method to differentiate unfrozen and frozen beef. © 1997 SCI.     

Colour stability of thawed lamb chops. I. Effect of short-term frozen storage

The colour stability of thawed lamb chops was examined, by colour panel and colorimeter, under simulated retail display conditions. Chops held frozen at –20°C for 1 week had a display life of 3 days when thawed, compared with 2 days for fresh chops. When the frozen storage was increased to 8 weeks the display life was reduced to 1 day. When the whole loin was stored frozen for 8 weeks, chops cut from it and thawed had a 2-day display life. By comparison, vacuum-packed chops stored at –1.5°C for 8 weeks had a 3-day display life. The relationship between Hunter colour values and panel scores is discussed.     

Colour stability of thawed lamb chops. II. Chops from loins frozen for long periods

Colour stability was examined during simulated retail display of thawed chops cut from loins after frozen storage. When loins had been stored for 30 weeks at –20°C, the thawed chops had a 2-day display life. If chops were stored at –20°C for an additional 8 weeks before thawing, display life decreased to 1 day. When loins were thawed, then cut into chops, a display life of 4 days was obtained. Thawed chops from loins stored for 60 weeks behaved similarly. The experiment showed no adverse trend with increased frozen storage, except for increased drip, and indicates definite commercial possibilities for chops cut from loins stored frozen.     

THE EFFECTS OF FROZEN STORAGE AND PROTECTIVE STORAGE WRAP ON THE RETAIL CASE-LIFE OF PORK LOIN CHOPS

Loin chops from 60 pork carcass sides were utilized to evaluate the influences of frozen storage and protective storage wrap upon factors contributing to the retail case-life of thawed chops. The composite results of this study indicated that pork loin chops could be frozen and stored for 168 days or less at ?30° C and have a retail case-life of at least 6 days, under the conditions employed in the present study. The possible exception is an amount of drip in the packages of chops stored in certain protective wraps which may be unacceptable when displayed for prolonged periods.     

Effect of time of deboning and sample size on drip loss of pork

The effects of time of deboning and sample size on drip loss of pork samples (m. longissimus) was studied in relation to the weight loss of the carcass sides or joints using two groups of 16 carcasses. One side of each carcass was cut and sampled at 1 day post mortem and served as a control. The other carcass sides were sampled for meat quality measurements after storage for another 5 days, either without cutting (group 1, n=16) or after cutting into primal joints (group 2, n=16). It was found that weight loss of carcass sides and joints increased with time, but at a decreasing rate. Drip loss largely decreased when meat samples were taken at a later time post mortem. The 48 h drip loss of the meat samples taken at 6 days post mortem was approximately 6% lower than in samples taken at 1 day post mortem. This reduction in drip loss was of the same magnitude as the weight loss of the carcass sides or the joints during 5 days storage. It is suggested that 'leaking out' explains most of the reduction in drip loss when sampling at a later time post mortem, and is not due to an improvement of water-holding capacity of the meat. It was also found that standardising the sample size increased drip loss. The effect of sample size is discussed in relation to the carcass lean content. Storage had little or no effect on other meat quality traits. ?     

The relationships between initial pH, reflectance and exudation in pig muscle

Using data collected from several hundred pigs, the relationships of drip loss during storage, and reflectance, to pH(45) in the M. longissimus dorsi (LD) were both found to be biphasic. Muscles with a lower pH(45) lost more drip and were paler. Below pH 6·1, however, decreasing pH(45) had only a small effect on the weight of drip lost but a large influence on reflectance. In contrast, above pH 6·1, increasing pH(45) had a large influence on drip loss but only a small effect on reflectance. There was also a biphasic relationship between drip loss and reflectance with the discontinuity at 9·9% drip. Differences in pH(u) explained less than 15% of the variation in exudation and reflectance.     

Increase in retail display of frozen lamb chops with increased loin storage time before cutting into chops

There is a steady deterioration of the colour of lamb chops during frozen storage. Storing meat in carcass form or as primals before cutting and packaging minimizes the exposure of the meat surfaces to deteriorating environmental effects. This experiment examines the effects of storage conditions (form, time and temperature) on the display life of frozen chops. Loins were removed from recently frozen carcasses and stored for 0, 10, 20 or 30 weeks at temperatures of -5°C, -10°C and -20°C. Chops were cut from the stored loins, packaged in oxygen permeable film, stored in the dark at -20°C for 0,4,8 or 12 weeks and then displayed at -20°C under continuous lighting. The retail display life of the chops was assessed by an experienced colour panel. The most rapid colour deterioration occurred in chops cut from unstored frozen loins and held for 12 weeks prior to display (display life of less than 1 day). Chops cut from loins stored for 30 weeks at -20°C, and then held for 12 weeks prior to display had a display life of 23 days. Both increased loin storage temperature and an increased duration of chop storage before display decreased the retial display life. This study indicates that frozen storage of cut chops for as little as 4 weeks reduces the display life by almost 80% so that whole carcasses or loins rather than cut chops should be shipped to distant markets. unstored frozen loins and held for 12 weeks prior to display (display life of less.     

The use of filter paper to estimate drip loss of porcine musculature

Two simple, accurate, rapid and economical methods for determining variations in drip loss of lean, prepackaged, post-rigor porcine musculature during storage have been developed. Laboratory grade filter paper having a 45 mm diameter was placed on the cut surface of the muscle (after 10-15 minutes' exposure) and scored for wetness (0 to 5) within 3 s or weighed for fluid accumulation. The tests on 40 randomly selected longissimus muscles that appeared to represent 'normal' quality characteristics proved to be nearly perfectly and positively correlated to % 48 h drip loss. Statistically, the relationship was non-curvilinear and, when regression equations were used to predict drip losses on a separate group of 27 muscles having considerable variation in quality, the correlations between the predicted and actual values were nearly perfect (r = 0·97 for score and 0·95 for weight). These two methods have not been compared to other, more sophisticated, ones currently used, but the results of this investigation suggest that the two methods may be useful to the meat industry, especially for practical applications.     

Use of a centrifuging method to measure the drip of pork longissimus dorsi slices before and after freezing and thawing

A method has been developed in which the drip from post-mortem muscle is removed by centrifuging in tubes fitted with perforated teflon discs. Measurement of a number of samples showed that the weight lost after 1 1/2 h centrifuging correlated with the free drip of slices from the same muscle. There was also a good correlation between the free and centrifuged drip from frozen muscle slices. Thus the centrifuging method measures parameters which influence the water holding capacity of meat and offers a means of assaying, more quickly, the potential drip loss in meat slices both before and after freezing.     

The effect of simulated transport of fresh meats on their water-holding capacity as assessed by various methods

This study was designed to establish the effects of transport vibrations on the water-holding capacity of fresh non-stimulated veal and pork and electrically- and non-stimulated beef. Furthermore, drip production was followed during storage by various methods which were compared for their suitability in industrial practice and scientific research. During storage, the amount of drip increased, whilst the rate of drip formation decreased. Filter paper wetness measured at 1 day post mortem was positively correlated with drip lost over a period of 2 weeks of refrigerated storage in poly-ethylene bags (method 1) and poly-propylene containers (method 2). This suggests that the filter paper wetness test may be useful to predict drip loss of stored meat. Simulated transport did not result in higher drip losses, although a significant increase in filter paper wetness from the fresh cut surface of veal and pork was found, suggesting that transport affects the initial rate of drip production, but not the total amount of drip. In beef, transport simulation resulted in an increase in filter paper wetness from the surface of electrically-stimulated meat, stored for 1 or 2 weeks, indicating that fluid loss was elevated due to transport vibrations. However, this effect seemed to be related to the intrinsic water-holding capacity of the sample: meat with a low intrinsic water-holding capacity seemed to be more sensitive to transport vibrations than meat with a high intrinsic water-holding capacity.     

The effect of high post-mortem temperature on the development of pale, soft and exudative pork: Interaction with ultimate pH

The effects of post-mortem temperature and ultimate pH (pH(u), 24 h post mortem) on the development of the pale, soft and exudative (PSE) characteristics in pig longissimus dorsi muscle were studied. Ten out of the 13 pigs used received pre-slaughter injections of adrenaline in order to deplete muscle glycogen stores. The two muscles from each pig were held at 12 or 35°C during rigor mortis development. Results from covariance analysis, using pH(u) as covariate, showed that a high temperature (35°C) resulted in a dramatic increase in internal light scattering (FOP) 24 h post mortem and a significant decrease in water- and salt-soluble proteins. Cooking loss, sarcomere length and drip loss did not vary significantly with rigor temperature. Interaction between temperature and pH(u) was estimated by assessing the relationship between pH(u) and the difference between the two rigor temperatures for selected traits. The best predictive model was a segmented quadratic model with a plateau which gave significant results for FOP, drip loss, water- and salt-soluble proteins. The effect of temperature decreased curvilinearly when pH increased until a constant value above which no noticeable difference was recorded (drip loss, water- and salt-soluble proteins) or a constant difference was reached (FOP). The pH values corresponding to the convergence points differed from one trait to another. They ranged from 5·72 to 6·22. These results illustrate the importance of muscle glycogen content at slaughter and subsequent pH(u) with regard to the development of temperature-induced PSE meat.     

Strawberry varieties for industrial jam production

Twelve strawberry varieties were investigated for potential use by the jam processing industry. Chemical, physical and sensory analyses were performed with fresh and thawed fruits and with jams made from the fruits. Fresh fruits were analysed for dry matter, soluble solids, pH, titratable acids and ascorbic acid. Total anthocyanin and degradation indexes were determined in both fresh fruits and in jams. Firmness of fresh and thawed fruits, as well as the amount of juice lost upon thawing (drip loss) were tested for each variety. Except for colour, no significant correlation (P<0.05) existed between the chemical analyses and the sensory parameters. There was significant relationship between total anthocyanin content and visual colour as judged by a taste panel. There was no correlation between firmness of fresh and thawed fruits. Drip loss and firmness of fresh fruits and jams gave a negative correlation. There was no relationship between drip loss and texture measurements in thawed fruits. Except for colour, there were no correlations between the chemical analyses. Based on the results, Jonsok, Totem and Bounty varieties appeared suitable for industrial jam production when compared to the Senga Sengana variety now in use.     

Fibre optic probe measurements in landrace pigs of different halothane phenotypes

Fibre Optic Probe (FOP) measurements were made in the longissimus dorsi muscle of 70 halothane-positive (HP) and 70 halothane negative (HN) pigs of a synthetic Landrace strain at 45 min (FOP(1)), 3 h (FOP(3)) and 17h (FOP(17)) post mortem. Measurements of pH, rigor and temperature were also made in the slaughterline. Carcasses were sampled (longissimus dorsi, 2-4 lumbar vertebrae) at 18h post mortem and meat quality objectively assessed. The incidence of slight PSE (visual score) was 49% in HP and 10% in HN pigs, while the incidence of serious PSE was 20% and 4%, respectively. Yet, the percentage drip loss during 48 h storage in HN/PSE pigs was higher than in HP/PSE pigs (10·2 vs 7·5%), which was associated with a lower ultimate pH (5·25 vs 5·44). Therefore, it is suggested that the remaining PSE problem in HN Landrace pigs, although less in frequency, might be more serious. In the whole population, of all FOP measurements taken correlations with colour (Hunter L(?)-value) and percentage drip loss were highest for the FOP(17) measurements (r = 0·82 and 0·69, respectively). FOP(1) was better related than pH(1) to colour, while the relationships with drip loss were of a similar magnitude. Differences in FOP values between HP and HN pigs were larger for FOP(1) (148 vs 108) than for FOP(3) (148 vs 125) or FOP(17) (153 vs 130). The relationship between FOP1 and ultimate meat colour (L(?)-value) appeared to be higher in HP (0·60) than in HN (0·48) pigs, while for the relationship between FOP(1) and percentage drip loss the reverse was true (0·48 and 0·60, respectively). The effect of halothane phenotype on the relationships found, may partially explain the different results of reflectance measurements reported in the literature as to their predictive value for ultimate meat quality. The results suggest that the measurement of reflectance in the slaughterline offers opportunities for identifying (potential) PSE carcasses. The large genetic influence of halothane phenotype on this parameter, may eventually justify its use as a base for payment for meat quality to the producer.     

Modelling post-mortem tenderisation-II: Enzyme changes during storage of electrically stimulated and non-stimulated beef

Levels of calpains I and II, cathepsins B and L and β-glucuronidase were determined in extracts of electrically stimulated and control beef M. Pectoralis profundus stored at temperatures between 0 and 30°C and varied to avoid muscle shortening. The level of lysosomal enzymes remained essentially unchanged throughout storage. The levels of calpain II were largely unaffected by the early treatments and decreased slightly throughout ageing. The level of calpain I, in both stimulated and control meats, was unaffected by temperature prior to the attainment of about pH 6·2 and thereafter the loss was accelerated at higher temperatures. In the extreme case studied, that of stimulated meat held at 15°C, 73% of the activity was lost in the first 24 h. After ageing, the level was about 11% of the initial when stored at 1°C and 25% when stored at 15°C. The exponential decay constants for the decrease in the levels of calpain I were 0·01 h(-1) at 1°C and 0·06 h(-1) at 15°C, and were the same as those for the previously determined rate of tenderisation. This suggested that the rate of proteolysis by calpain I was linked to the rate of tenderisation.     

Predictive value of slaughterhouse measurements of ultimate pork quality in seven halothane negative Yorkshire populations

An experiment with 1969 pigs, belonging to Yorkshire sire lines, was set up in cooperation with seven Dutch breeding organizations. The pigs, which were claimed to be halothane negative, were slaughtered in weekly batches. Light reflectance was determined with the Hennessy Grading Probe (HGP) and Fibre Optic Probe (FOP), in addition to pH(1) and rigor mortis at 45 min post mortem (p.m.). Further meat quality determinations were performed either in the slaughterhouse at 20 h p.m., or in the laboratory at 24 h p.m.. At first sight, both the scatter of light (HGP-PSE, FOP) and pH, measured at 45 min p.m., appeared to be indicative of the ultimate meat quality score. More accurate analyses, however, showed that the value of reflectance values is limited and less suitable in comparison to pH(1), especially with reference to the prediction of ultimate quality characteristics of water holding capacity. The correlations for pH(1) with drip loss were rather consistent, ranging from -0·34 to -0·52 per breeding population. In contrast, HGP-reflectance values ranged from -0·27 to 0·34, while those based on FOP(1) had a range from nearly zero (0·02) to 0·20. The proportion of variation (R(2) × 100%) in drip loss, explained by a set of slaughterline measurements, ranged from 13 to about 28% per breeding population. The use of measurements carried out at 20 h p.m. improved the R(2) × 100% for drip loss to a range from 50 to 62%.     

Physicochemical and Sensory Qualities of Fresh Pork Chops as Affected by Phosphate, Ascorbate or Sorbate Dipping Prior to Irradiation

Fresh pork chops were dipped for a target absorption of 0.5% sodium tripolyphosphate (STPP), 550 ppm sodium ascorbate (SA), or 0.1% potassium sorbate (PS) prior to irradiation (1.0 kGy). Untreated pork chops, both irradiated and unirradiated, were used as controls. Dipping with STPP decreased drip loss and improved color and lipid stability of irradiated chops and resulted in better tenderness and juiciness scores than undipped, irradiated samples. Also, STPP treated chops had similar or better physicochemical and sensory properties than untreated (no irradiation, no dipping) controls. Dipping with SA or PS had little effect compared with STPP, but improved some sensory qualities.