Prediction of pork quality with near infrared spectroscopy (NIRS) 2. Feasibility and robustness of NIRS measurements under production plant conditions

Longissimus dorsi samples (685) collected at four processing plants were used to develop prediction equations for meat quality with near infrared spectroscopy. Equations with R(2)>0.70 and residual prediction deviation (RPD)≥2.0 were considered as applicable for screening. One production plant showed R(2) 0.76 and RPD 2.05, other plants showed R(2)<0.70 and RPD<2.0 for drip loss %. RPD values were ≤2.05 for drip loss%, for colour L*≤1.82 and pH ultimate (pHu)≤1.57. Samples were grouped for drip loss%; superior (<2.0%), moderate (2-4%), inferior (>4.0%). 64% from the superior group and 56% from the inferior group were predicted correctly. One equation could be used for screening drip loss %. Best prediction equation for L* did not meet the requirements (R(2) 0.70 and RPD 1.82). pHu equation could not be used. Results suggest that prediction equations can be used for screening drip loss %.     

Perspective of NIRS measurements early post mortem for prediction of pork quality

The potential of near-infrared spectroscopy (NIRS) measurements early post mortem was investigated to predict ultimate drip loss, colour, tenderness and intra-muscular fat of pork. Three locations (M. longissimus thoracis, M. longissimus lumborum and M. semimembranosus) in 102 pig carcasses were tested at the end of the slaughter line. A priori variation in pork quality was introduced using an experimental design covering: genotype, lairage time, pre-slaughter handling and day of slaughter. At 1 h post mortem a diode array VIS/NIR instrument (Zeiss MCS 511/522, 380-1700 nm) equipped with a surface fibre optic probe was used and at 1 day post mortem ultimate pH, drip loss, colour and shear force was measured on similar locations. Results indicated that it was possible to predict intra-muscular fat content (correlation (R(2) of 0.35 with multiple linear regression), standard error of prediction (SEP)=3.6 g/kg), but the configuration has to be refined for on-line application (bigger aperture). For drip loss no correlation was achieved with the PLS method. Even extremes (low drip loss (<2.5%) or high drip loss (>4.5%)) in drip loss were not discriminated. Predicting drip loss with NIRS early post mortem is not successful, although NIRS in the slaughter line has potential as a fast predictor of intra-muscular fat. Possibilities for using the NIRS technique to get to know more about muscle metabolism and post mortem changes are promising.     

Prediction of pork quality attributes from near infrared reflectance spectra

Near infrared spectroscopy (NIRS) is one of the most promising techniques for large-scale meat quality evaluation. We investigated the potential of NIRS-based models to predict drip loss and shear force of pork samples. Near infrared reflectance spectra (1000-2500 nm), water-holding capacity, shear force, ultimate pH, and colour (L(?), a(?), b(?)-value) of 96 pork longissimus muscles were recorded at 2 days post mortem. Stepwise multiple linear regression (SMLR) and partial least squares regression (PLSR) analyses were used to formulate models for drip loss and shear force. Prediction models for drip loss correlated moderately strong with measured drip loss (R=0.71-0.74), which is similar to the correlation obtained using a combination of ultimate pH, filter paper test, and L(?)-value (R=0.74). The current results indicate that NIRS enables the classification of pork longissimus muscles with a superior or inferior water-holding capacity as having a drip loss lower than 5% or higher than 7%. No useful models could be constructed for shear force.     

The use of visible and near-infrared reflectance spectroscopy to predict colour on both intact and homogenised pork muscle

Visible and near-infrared reflectance spectroscopy (VIS/NIRS) was used to predict colour on pork muscle samples. Colour values were measured on 44 pork muscles (n=44) using a Minolta digital camera to determine CIE L* (lightness), CIE a* (redness) and CIE b* (yellowness). Samples were scanned in the visible and near-infrared region of the spectra on a monochromator instrument (400–2500 nm) on both intact and homogenised presentation to the instrument. Two mathematical treatments (first and second derivative) and two scatter transformations to the spectra were explored, none and standard normal variate and detrend (SNV-D). Predictive (VIS/NIRS) calibrations were developed using a modified partial least-squares regression (mPLS) with internal cross validation. The highest coefficients of determination in calibration (R²_cal) and lower standard errors in cross validation (SECV) were found for both CIE L* and a*, in homogenised presentation, while poor calibration statistics were found on intact presentation.     

Application of NIRS for predicting fatty acids in intramuscular fat of rabbit

The aim of this study was to evaluate the use of near infrared reflectance spectroscopy (NIRS) for predicting fatty acid content in intramuscular fat to be applied in rabbit selection programs. One hundred and forty three freeze-dried Longissimus muscles (LM) were scanned by NIRS (1100-2498nm). Modified Partial Least Squares models were obtained. Equations were selected according to standard error of cross validation (SECV) and coefficient of determination of cross validation (R(2)(CV)). Residual predictive deviation of cross validation (RPD(CV)) was also studied. Accurate predictions were reported for IMF (R(2)(CV)=0.98; RPD(CV)=7.57), saturated (R(2)(CV)=0.96; RPD(CV)=5.08) and monounsaturated FA content (R(2)(CV)=0.98; RPD(CV)=6.68). Lower accuracy was obtained for polyunsaturated FA content (R(2)(CV)=0.83; RPD(CV)=2.40). Several individual FA were accurately predicted such as C14:0, C15:0, C16:0, C16:1, C17:0, C18:0, C18:1 n-9, C18:2 n-6 and C18:3 n-3 (R(2)(CV)=0.91-0.97; RPD(CV)>3). Long chain polyunsaturated FA and C18:1 n-7 presented less accurate prediction equations (R(2)(CV)=0.12-0.82; RPD(CV)<3).     

The effect of ionising radiation on the colour of beef, pork and lamb

The effect of irradiation (0 and 5 kGy) of beef, pork and lamb portions in retail overwrap packs and subsequent storage at 4°C was studied in relation to colour changes. The colour of the exterior surface of beef and pork was measured on the same samples on each day of storage for up to 7 days post irradiation. On day 7 the colour of a freshly cut surface was measured. The colour of both the exterior and a freshly cut surface of lamb, in similar retail overwrap packs was measured at 2, 5 and 7 days, post irradiation, different samples being used on each day of measurement. L* values of irradiated beef increased significantly with storage and a* values for unirradiated samples decreased significantly with storage. For lamb there was a general increase in L* and h(o) values and a decrease in a*, b* and C* values with storage. Analyses of the day 7 data showed statistically significant effects for species on all CIELAB parameters. Irradiation resulted in significantly higher hue angle (h(o)) values and the a*, b* and C* values were significantly higher on the exterior than freshly cut surface. There were a number of statistically significant 2 factor and 3 factor interactions. The role of formation of a carboxyhaem pigment in the colour of irradiated meat is discussed. The problem of interpretation of pigment changes from CIELAB values is highlighted.     

冷却猪肉新鲜度的色差快速分析评价方法

为了得到冷却猪肉新鲜度的变化规律,本研究以冷却猪肉里脊部分为研究对象,进行球蛋白沉淀实验、感官评价、pH值、水分含量、肉浸液以及肌肉表面颜色值测定。结果表明：球蛋白沉淀实验、pH值能够较好地反应肉品新鲜度的变化,色差分析符合一定的规律：肌肉表面色差测定中,20℃条件下,a*变化与贮藏时间显著相关(P＜0.05),L*变化显著(P＜0.05);4℃条件下,b*、C变化与贮藏时间极显著相关(P＜0.01),L*值与pH值极显著相关(P＜0.01);对于肉浸液,L*、b*、C、ΔE*均发生显著性变化(P＜0.05),20℃条件下L*、b*、C、ΔE*与贮藏时间和pH值显著相关(P＜0.05),而4℃条件下,L*、C、ΔE*与贮藏时间显著相关(P＜0.05),L*、a*、b*、C、ΔE*值与pH值极显著相关(P＜0.01);冷链过程中,当L*高于48.73、a*高于4.72、b*高于9.18时可认定冷却肉为新鲜肉。     

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。     

THE RELATIONSHIP BETWEEN COLOR AND WATER-HOLDING CAPACITY IN POSTRIGOR PORCINE LONGISSIMUS MUSCLE

A total 264 pork loins were selected to represent a wide range of pork quality of the longissimus thoracis et lumborum. CIE L*C*h color space showed a closer relationship to the subjective color score than L*a*b*color space. Lightness (L*) was the best measure to predict water-holding capacity (WHC). There were highly significant (p < 0.001) correlations between the measures of color and WHC, and curvilinear relationships between either WHC and color or pHu were observed. In normal muscle color range (reddish-pink), there was considerable variation in WHC. Within the RSE + RFN groups of muscles, less variation of WHC could be accounted for by variations in color measurements. Color and WHC were not closely related and suggest that the RSE (reddish-pink, soft, exudative) condition should be classified as a separate quality category of pork muscle.     

A second mutant allele (V199I) at the PRKAG3 (RN) locus-II. Effect on colour characteristics of pork loin

Three alleles at the PRKAG3 (RN) locus that influence the glycogen content of pork were found to be segregating in Hampshire×Landrace crossbred pigs, RN(-), rn(+) as well as second mutant allele V 199I (here denoted rn*). The effect of these three alleles on ultimate pH, pigment content, internal reflectance (FOP), surface colour measured by tristimulus colorimetry (L*, a*, b*) and fractions of deoxymyoglobin (Mb), oxymyoglobin (MbO(2)) and metmyoglobin (MetMb) of pork loin was studied. Moreover, the effect of sex, entire male versus female pigs, on these traits was also analysed. The three PRKAG3 alleles affected ultimate pH, internal reflectance, colour and distribution of myoglobin derivatives of pork loin, while the pigment content was not influenced. Ultimate pH values of loins from the three genotypes were found to be in the order RN(-)/- genotypes rn(+)/rn(+) genotype=rn(+)/rn* genotype=rn*/rn* genotype. The RN(-) allele was dominant resulting in higher redness (a* value) and yellowness (b* value), while the rn* allele tended to result in lower redness and yellowness compared with the rn* allele. The RN(-) allele was dominant over the rn* allele in lightness (L* value) giving a lighter colour. Surface colour differences were mainly explained by differences in the distribution of the myoglobin derivatives. Finally, surface lightness was higher and pigment content, redness and fraction of MbO(2) lower in loin from entire males compared with females.     

Colour in short-term thermo-mechanically densified veneer of various wood species

Effect of short-term thermo-mechanical (STTM) densification temperature and pressure on the surface colour of veneer of four wood species—alder (Alnus glutinosa Gaertn.), beech (Fagus sylvatica L.), birch (Betula verrucosa Ehrh.), and pine (Pinus sylvestris L.) as well as possible correlations among all determined colour parameters (L*, a*, b*, h, C* and ?E) were investigated. Veneer sheets were densified at temperatures of 100, 150 or 200 °C and pressures of 4, 8 or 12 MPa for 4 min. The results were compared with those of non-densified veneers. The colour change of the samples was evaluated by CIEL*a*b* and L*h*C* colour co-ordinate systems. The results indicated: the temperature and pressure of densification affected to a big extent the colour of the veneer samples, with the effect of densification temperature being more evident than that of pressure. After the densification process, the veneers darkened. Colour changes are most pronounced at the highest densification temperature of 200 °C and very small at the lower temperatures of 100 and 150 °C for all investigated wood species. The change in a* is more pronounced than the change in L* or b*. In general, alder and birch veneer samples are characterized by the highest values of total colour difference followed by pine and beech samples among the four species. The quadratic models can be used for the prediction of surface colour in the densification process. The results of this study indicate that it is possible to govern surface colouration of wood veneers during densification process on an industrial basis.     

基于近红外光谱技术的大米品质分析与种类鉴别

应用近红外光谱(NIRS)技术建立了大米食味品质分析与种类快速鉴别的方法。提取了102份粉碎后大米样品的近红外光谱,采用偏最小二乘法(PLS)建立了大米水分、蛋白质和直链淀粉定量分析模型,对模型预测结果的准确性进行了评价。预测模型的内部交叉验证决定系数(R2)分别为:0.992、0.9792和0.9736;内部交叉验证标准差(RMSECV)分别为:0.141、0.201和0.209;模型外部验证决定系数(R2)分别为0.9861、0.912和0.9373;外部验证标准差(RMSEP)分别为0.179、0.206和0.243。通过计算样品的近红外光谱图之间的欧氏距离来反映不同样品间的差异,对不同属性和不同产地的大米进行了定性聚类分析,种类识别准确率达到100%。结果表明,NIRS分析技术可以用于对大米品质和种类的快速无损检测。     

Degradation kinetics of tomato juice quality parameters by ozonation

Tomato juice samples were ozonated with control variables of ozone concentration (1.6–7.8 %w/w) and treatment time (0–10 min). Effects of ozone processing variables on quality parameters of pH, ^oBrix, titratable acidity (TA), cloud value, non-enzymatic browning, colour values ( L *, a *, and b *) and ascorbic acid (AA) content were determined. No significant changes ( P  > 0.05) in pH, ^oBrix, TA, cloud value and Non enzymatic browning (NEB) ( P  ≤ 0.05) were found with ozonation. L *, a * and b * colour values were significantly affected by ozone concentration and treatment time. A significant reduction of AA (96 %) was observed at an ozone concentration of 7.8%w/w and a treatment time of 10 min. Results presented in this study indicate that visual colour and nutritional quality is significantly affected during ozone processing. Thus, the effects of ozonation on the nutritional properties of tomato juice should be considered by processors prior to its adoption as a preservation technique.     

Rapid Determination of Antioxidant Compounds and Antioxidant Activity of Sudanese Karkade (<Emphasis Type="Italic">Hibiscus sabdariffa</Emphasis> L.) Using Near Infrared Spectroscopy

The extraction conditions applied in destructive analysis of Hibiscus sabdariffa L. (Hs) matrices before the measurement of antioxidant compounds may reduce their activities during isolation and purification due to decomposition. Hence, near infrared spectroscopic system was applied to determine these compounds. The calibration models developed by using partial least squares regression (PLSR) with 48 Hs samples and 24 unknown samples were used to confirm the robustness of the developed model. The results of calibration models effectively allowed the determination of the concentrations of total phenol content (TPC), total flavonoid content (TFC), total antioxidant content (TAC), ferric reducing antioxidant power (FRAP), and 1,1-diphenyl-2-picrylhydrazyl (DPPH) with high correlation coefficients (0.85–0.91) and small standard error of cross-validation (RMSECV) ranged from 0.08 to 0.33. The prediction capacity (RPD) for TPC, TFC, TAC, FRAP, and DPPH ranged from 3.30 to 8.25, thus demonstrating that the near infrared spectroscopic (NIRS) equations developed were applicable to unknown samples. This study demonstrates that NIRS can be considered as a fast tool for the nondestructive determination of antioxidant compounds (phenolics and flavonoids) and antioxidant activity of the Hs.     

RAW MATERIAL pH, PUMP LEVEL AND PUMP COMPOSITION ON QUALITY CHARACTERISTICS OF PORK

ABTRACT
Boneless, paired pork loins (n=120) were selected based on pH at 14 h postmortem. Ultimate pH, drip loss, instrumental color (L*, a*, and b* values), and proximate analysis were determined prior to pumping. Paired loins were cut into four sections and pumped to 100%, 106%, 112% or 118% of original weight to result in a product containing 0.4% sodium tripolyphosphate (STP) for Experiment 1 (Exp. 1) and 0.4% STP plus 0.4% salt for Experiment 2 (Exp. 2). In Exp. I, additional pump level increased (P<0.05) vacuum package purge. Higher raw materials pH reduced purge. A pump level x pH interaction (P<0.05) occurred for cook loss at 70C. In Exp. 2, increased raw materials pH reduced (P<0.05) purge loss and resulted in juicier, more tender pork. Pumped pork had higher (P<0.05) tenderness, juiciness, and saltiness scores than controls.     

Prediction of technological and organoleptic properties of beef Longissimus thoracis from near-infrared reflectance and transmission spectra

Technological and organoleptic properties of beef cuts were predicted by near-infrared (NIR) spectroscopy. Spectra were collected on 189 beef Longissimus thoracis muscle samples using, transmission (NIRT) and reflectance with a probe. Quality assessment and NIR recordings were performed on sliced loin after 2 and 8 days ageing. Partial least squares regression yielded determination coefficients of cross-validation (R(2)(cv)) of 0.12-0.25 for the prediction of Warner-Bratzler Peak Shear Force in reflectance and 0.15-0.41 in transmission. Higher R(2)(cv) were obtained for L* parameter (0.83-0.85), a* (0.39-0.49) and b* (0.73-0.75) with reflectance. Predictions of drip loss and cooking loss were less accurate with a R(2)(cv) range of 0.38 to 0.54 and 0.25 to 0.47, respectively. The NIR spectra collected on fresh meat show good potential to predict CIE L* and b* parameters in reflectance mode.     

荧光假单胞菌和热杀索丝菌对低温贮藏期间猪肉品质变化的影响

为研究荧光假单胞菌和热杀索丝菌与猪肉品质变化的相关性,测定了在4 ℃下贮藏猪肉的微生物菌落数、pH值、色泽（L*、a*、b*值）、质构特性、总糖含量、总挥发性盐基氮（total volatile basic nitrogen,TVB-N）值和硫代巴比妥酸反应物（thiobarbituric acid reactive substances,TBARS）值以及通过扫描电子显微镜观察猪肉肌纤维微观结构的变化。结果表明,在冷藏期间,微生物菌落数、pH值、TVB-N值、TBARS值等随着猪肉冷藏时间延长而上升,而总糖含量、L*值、a*值、硬度、咀嚼性均呈降低趋势。同时,研究发现猪肉冷藏过程中微生物的生长繁殖使其肌纤维结构发生明显变化。猪肉理化品质变化与微生物的种类和生长速率相关,热杀索丝菌的致腐败能力高于假单胞菌。相关性分析结果表明,菌落数、pH值、总糖含量、TVB-N值、TBARS值与冷藏时间密切相关,其中微生物菌落数与冷藏时间的相关性最高,可作为冷藏猪肉品质评价和货架期预测的监测指标。     

Sensory colour assessment of fresh meat from pigs supplemented with iron and vitamin E

Pork muscle samples (M. longissimus dorsi) were obtained from pigs given one of four dietary treatments: (1) control diet; (2) supplemental iron [7-g iron (II) sulphate/kg feed]; (3) supplemental vitamin E (200-mg dl-α-tocopheryl acetate/kg of feed); and (4) supplemental vitamin E+supplemental iron. Muscle cores were packaged in polythene bags and placed in a retail refrigerated display cabinet at 5±1°C, under fluorescent light (1000 LUX) for up to 5 days. Samples were subjected to visual colour evaluation by a trained sensory panel (n=12) at 0, 1, 3 and 5 days. In addition instrumental L*, a* and b* values and drip loss were measured on each day of analysis. All samples became less red and browner over storage time in the refrigerated display cabinet. The vitamin E treated samples were more red and less brown compared with the other samples on successive days in the cabinet followed by the control, iron/vitamin E and iron treatments. The iron/vitamin E treatment was positioned midway between the vitamin E and iron treatments indicating that the vitamin E in the samples was effective in reducing the pro-oxidative effect of iron in inducing the brown metmyoglobin pigment development. Iron supplementation did not significantly (P<0.05) increase M. longissimus dorsi iron tissue levels, but had a detrimental effect on the visual sensory properties of the iron and iron/vitamin E treatment groups with greater metmyoglobin formation. Vitamin E appears to have promoted non-supplemental iron absorption in the vitamin E treated group without the detrimental sensory colour characteristics associated with ferrous sulphate supplementation. Drip loss increased in all samples during the course of the experiment with no significant (P<0.05) differences between the experimental groups. The panellists were able to differentiate the four experimental groups on each day of the study and were more effective in evaluating the colour quality of samples than instrumental assessment, i.e. the Hunter L* a* b* method.     

Muscle pH(60), colour (L, a, b) and water-holding capacity and the influence of post-mortem meat temperature

The use of the pH(60) and colour parameters (L, a, b) as chilled pork drip loss predictors 24 h post-mortem as well as the influence on this meat characteristic of an early blast cooling regime (90 min post-mortem) were investigated. Despite the best correlation found with pH(60) (-0·647), both indicators were found to be poor for this purpose, it being impossible to use them alone for pork quality classification (PSE/DFD status). Comparing the evolution between the drip losses on chilled and early deep frozen (-60°C) longissimus dorsi pork cuts, the results indicate that both the thawing regime and the time the samples stay in refrigeration, influence the observed trends significantly. The general drip loss enhancement seen after thawing as well as the increasing meat toughness, judged subjectively, must be due to cold-shortening and/or thaw rigor phenomena.     

蔬菜提取物对猪肉脯品质的影响

选取芹菜、韭菜和胡萝卜3 种蔬菜的提取物代替亚硝酸盐添加到猪肉脯中,对肉脯的硫代巴比妥酸（thiobarbituric acid-reactive substance,TBARS）值、色差L*、a*、b*值、感官评定及亚硝酸盐残留量进行测定。结果表明：芹菜提取物作为发色剂代替硝酸盐和亚硝酸盐作用于猪肉脯中,能够产生理想的色泽、风味和口感,同时能够控制肉脯的氧化速率,延长货架期,并且亚硝酸盐残留量与不添加亚硝酸盐的空白组相当。