Derek V. Byrne

The antioxidative activity of plant extracts in cooked pork patties as evaluated by descriptive sensory profiling and chemical analysis

Antioxidative efficiency of extracts of rosemary, green tea, coffee and grape skin in precooked pork patties was investigated during storage under retail conditions (10 days, 4 °C, atmospheric air), using descriptive sensory profiling following reheating and quantitative measurements of hexanal, thiobarbituric acid reactive substances (TBARS) and vitamin E as indicators of lipid oxidation. The initial oxidative status of pork patties (evaluated by ANOVA) showed a significant lower level of secondary oxidation products and higher levels of vitamin E in patties with extracts incorporated, indicating that the extracts retarded lipid oxidation during processing of the meat. Data analysis for the storage study was based on qualitative overview of sensory/chemical variation by principal component analysis (PCA) and quantitative ANOVA-PLSR for determination of the relationship between design variables (days of chill-storage, extract treatment) versus sensory-chemical variables and PLSR for elucidating the predictive ability of the chemical methods for sensory terms. Lipid oxidation was seen to involve a decrease in perception of meat flavour/odour and a concomitant increase in the off-flavour/odours linseed, rancid. TBARS, hexanal and vitamin E were all significant predictive indices (P<0.05) for the majority of the sensory terms, while vitamin E through negative correlation with TBARS and hexanal displayed its antioxidative effect and thus, its ability to preserve sensory fresh meat flavour/odour. The effect of the various extracts incorporated in the product was clearly related to the degree of lipid oxidation and an overall ranking of the antioxidative efficiency of extracts in declining order became apparent: Rosemary>Grape skin>Tea>Coffee>Reference. Furthermore, the relation between extracts and vitamin E indicated that the extracts, to some extent, interacted with the vitamin and prevented it from degrading. In conclusion, the rosemary extract displayed potential for maintaining sensory eating quality in processed pork products.

Influence of chicory roots ( Cichorium intybus L ) on boar taint in entire male and female pigs

Boar taint is an off-flavour of pork caused primarily by a microbial breakdown product, skatole and a testicular steroid, androstenone. As skatole is produced in the large intestine from tryptophan, it is possible that some ‘bioactive’ ingredients could modify protein fermentation and, in the process, diminish boar taint. The aim of this study was to examine the effect of inulin-rich chicory roots (Cichorium intybus L.) on boar taint. In the first of three trials individually penned, entire males and females were given an organic concentrate in which 0·25 of the daily energy intake was replaced with crude chicory roots for 9 or 4 weeks prior to slaughter. In the second trial, entire male pigs were given diets that included, either crude chicory roots, dried chicory roots, or inulin (extracted from chicory roots) for 6 weeks pre-slaughter. In the third trial, intact male pigs were given the dried chicory diet for either 2 or 1 week before slaughter. In all trials the chicory diets were offered on a scale at 0·95 of the Danish recommendation for energy intake, and pig performance was compared with a control group given the organic concentrate at 0·95 of recommended energy intake plus silage ad libitum. In trial 1 an additional control group was offered the organic concentrate at a daily energy intake level of 1·0 of Danish recommendations. The pigs in trials 1, 2, and 3 were slaughtered at an average live weight of 118, 124, and 110kg, respectively, in order to ensure that they had achieved sexual maturity. Overall, skatole concentrations in blood plasma and backfat at slaughter were reduced to almost zero levels by including crude or dried chicory or inulin in the diet. This occurred irrespective of sex and length of feeding period (1 to 9 weeks). In trial 3 a significant effect on blood plasma concentration was observed after 3 days of feeding a diet containing dried chicory. The only significant reduction in plasma androstenone levels was detected in pigs given the crude chicory for a 9 week duration in trial 1. The production and proportion of lean was generally not affected by the addition of either form of chicory to the diets in trials 1 and 2. Therefore, dried chicory may be the most suitable form for commercial use because it: had no initial adverse effects on food intake, consistently reduced skatole without reducing performance, was easy to handle throughout the entire year and is relatively inexpensive.

Perceptual masking of boar taint in Swedish fermented sausages.

Surgical castration of male piglets has traditionally been practiced to avoid development of boar taint in pork meat which can occur if entire male pigs are raised. Boar taint is commonly characterised as exhibiting the odour and flavour of urine and manure. This study involves sensory characterisation of the possibilities to mask boar taint in meat from entire male pigs by fermentation and smoking to maintain high sensory quality in meat products if castration is prohibited. Model and commercial type Swedish fermented sausage products based on low or high levels of boar tainted fat, three different starter cultures and two different levels of smoking were studied. In the model sausages, liquid smoke masked the perception of boar taint. In contrast, the smoking procedure of the commercial sausages was insufficient to totally mask the perception of boar taint. In both the model and commercial sausages, the aroma development from the starter cultures lowered the perception of boar taint but was insufficient for total perceptual masking. Due to the total masking effect of smoking in the model sausages, it was clear that smoke may present a potential solution to remove the perception of boar taint in fermented sausages if the smoking procedure is optimised.

Application of an electronic nose for measurements of boar taint in entire male pigs

An electronic nose based on ion mobility spectrometry was used for boar taint measurements of entire male pig samples varying in androstenone and skatole levels (0.09-0.88μg/g fat and 0.01-0.26μg/g fat, respectively). Sensory perceptible boar taint (especially boar odour) was found to be more related to androstenone than to skatole, whereas a rancid note was determined more related to skatole than to androstenone. Multivariate models implementing some generally prescribed cut-off limits for androstenone (0.50μg/g) and skatole (0.21μg/g) indicated that the e-nose could be used for ordering samples with respect to low and high levels of androstenone and skatole. Studying the direct relationships between e-nose data, sensory data, androstenone and skatole showed better predictivity of the chemical compounds (androstenone: r=-0.948, RMSEP=0.309; skatole: r=-0.629, RMSEP=0.069) than for single sensory descriptors (boar odour r=0.409, RMSEP=0.789). The results thus suggest that the e-nose technology based on ion mobility spectrometry as in the MGD-1 may have a potential for future rapid sorting of boars at the slaughter line. The study provides new knowledge of the applicability of ion mobility spectrometry for measuring boar taint and also confirms the challenge of measuring boar taint using chemically determined cut-off limits for a sensory perceptible phenomenon. Thus, future development should be more devoted to developing holistic approaches rather than focusing on the influence of single variables on boar taint.

Sensory based quality control utilising an electronic nose and GC-MS analyses to predict end-product quality from raw materials

The objective of the present study was to investigate if an electronic nose, comprising six metal oxide sensors (MOS) could predict the sensory quality of porcine meat loaf, based on measuring the volatiles in either the raw materials or the meat loaf produced from those raw materials. A multivariate data analysis strategy involving analysis of variance partial least squares regression (APLSR) and principal component analysis (PCA) was used to determine causal and predictive relationships between the raw material and meat loaf samples, sensory analysis, electronic nose, and GC-MS measurements. The results showed that the six MOS sensors in the Danish odour sensor system (DOSS) could detect the raw materials that led to unacceptable products, as determined by sensory profiling and in-house sensory quality control (QC), and separate those raw materials from each other, based on the volatile composition, as determined by GC-MS. However, the electronic nose was unable to detect all the sensory unacceptable meat loaf samples themselves due to changes in the volatile composition after cooking. Analysis of the GC-MS compounds identified from raw materials and meat loaf samples indicate that two MOS sensors mainly responded to alcohols and to a lesser degree to aldehydes and alkanes, whereas two other sensors most likely responded to low molecular weight sulphur compounds. Thus, the results indicate that measuring volatiles with the MOS sensors in the DOSS system, on raw materials for processed meat products, may be a feasible strategy in sensory based quality control, and may also have potential in predicting the sensory quality of the end product.

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.

Feeding strategy for improving tenderness has opposite effects in two different muscles

Compensatory growth has been shown to affect rate of muscle protein turnover and may potentially improve tenderness of beef. Thus, a study of tenderness in relation to feeding regime and slaughtering at a time with maximal muscle protein degradation was performed. Friesian bull calves (5-month-old) were fed either ad libitum (n=6) (AA) or restrictively for 3 months followed by re-alimentation for 6 weeks (n=6) (RA) before slaughter at 10 months. At slaughter the fractional breakdown rate of muscle protein was 2.4% in RA compared with 1.6% in AA (P<0.06). Sensory profiling revealed superior texture of M. semimembranosus from RA compared with AA, whereas M. longissimus was superior in texture from AA compared with RA, with no difference in proteolysis and shear force. In conclusion it was clear that different muscles in terms of tenderness responded very differently to the nutritional manipulation.

Sensory and instrumental analysis of longitudinal and transverse textural variation in pork longissimus dorsi

In the present study sensory and instrumental analysis of the textural properties of pork longissimus dorsi were performed and analysed using multivariate data analytical methodologies. The aims were to determine how textural properties of musculus longissimus dorsi varied transversely, longitudinally, between left and right muscles, and as a function of ageing. By training the panel in the descriptive texture profile method the panellists were able to clearly detect, discriminate and describe the textural variation in the samples, except for the transverse variation. Sensory evaluation revealed a non-significant trend (P>0.05) of decreasing tenderness from dorsal (nearest the spinal column) to medial sampling position. When analysed instrumentally, using a modified Warner-Bratzler shear force apparatus, the transverse muscle variation was found to increase in force (N) required for deformation from dorsal to lateral sampling position. Overall, these two methods agreed in that the dorsal position was the more tender of the three positions investigated. Lengthwise muscle variation was highly defined when assessed using sensory analysis, whereas instrumental analysis was unable to detect this variation. The sensory analysis revealed that tenderness decreased and hardness increased as the sample position approached the caudal end of the muscle. Additionally, sensory analysis revealed a major turnover point in textural properties at the end of the ribcage area in that tenderness showed a marked decrease in this area and hardness and juiciness increased correspondingly in the same area. Both sensory and instrumental analysis showed that muscles from left and right side of the carcass differed significantly (P<0.05) in their textural properties. The right side muscle was clearly defined into stages more so than the left side muscle. In addition, the right loin was found to be harder per se than the left loin, which was postulated to be caused by a greater amount of work performed by right muscles compared to left muscles. Significant differences (P<0.05) in sensory textural attributes were observed overall with increased ageing. The variation within muscles, which contributed to the overall change in texture with ageing, was found to be due to changes in the longitudinal variation, in that the individual chop variation observed at the cranial end became less pronounced when the meat was aged. Differences observed between the cranial and caudal end remained, regardless of ageing for 4 or 7 days. No changes could be seen in the transverse texture during ageing. In general, sensory and instrumental analyses were found largely to be predictive indexes of each other. However, these two methods could not be said to be causally predictive in that they did not measure the same physical properties of the meat. For instance sensory determined tenderness is a result of the type and rate of deformation and the heterogeneity of the sample assessed, whereas instrumental measurement is a result of resistance to shearing. The present study showed significant variation between longitudinal locations and this variation is critical when designing sensory texture profiling experiments of meat from loins. Moreover, the textural differences between left and right loin muscles must be considered when texture prediction is the objective if an applicable conclusion is to be drawn.

Sensory profiling of textural properties of meat from dairy cows exposed to a compensatory finishing strategy

A compensatory finishing strategy was evaluated to improve the quality of meat from dairy cows. The experiment included ten pairs of Holstein Friesian dairy cows. Each pair was the progeny of the same sire, in the same parity, and approximately at the same number of days in lactation before entering the experiment. Within each pair, one cow was allocated to a compensatory finishing strategy, dried off for 4 days, and further restricted in energy intake for another 17 days followed by 6 weeks of ad libitum feeding. The strategy improved the sensory texture and flavour of both M. longissimus dorsi (LD) and M. semimembranosus (SM). This was supported by lower shear force in both muscles (P<0.02). The effect can be ascribed to various factors; in LD an increased amount of IMF plays a significant role, whereas in SM an increased protein turnover is suggested to be the dominating factor.

Compensatory growth response as a strategy to enhance tenderness in entire male and female pork M. longissimus thoracis.

The effects of restrictive feeding strategies aimed at promoting a compensatory growth response were investigated with respect to tenderness improvement in pork M. longissimus thoracis. Compensatory growth response is defined by increased weight in pigs fed ad libitum after a period with restricted feeding compared to pigs fed ad libitum the entire fattening period. Specifically, the aim was to study the sensory textural characteristics after female and entire male pigs have been exposed to restrictions in either energy, protein or both in specific growth periods. It was found that textural differences were caused by feeding strategies and not related to variation in intramuscular fat, which did not vary significantly between genders. The female pigs demonstrated compensatory growth response and the texture was significantly (P<0.001) improved by low dietary level of energy from day 50 to 90 and normal dietary level of protein during the entire feeding period. For the entire male pigs, low level of protein in the late feeding period significantly (P<0.05) improved the texture. Also, low level of protein and normal level of energy in the early feeding period resulted in improved tenderness. However, these texture improvements were deemed not to be an effect of compensatory growth since the entire male pigs did not compensate for the feeding restriction in the early feeding period. The tenderness enhancement for the entire male pigs compromised the production results in terms of 7-15% lower carcass weight.