Warmed-over Flavour Development Research Articles

Warmed-over flavour profiles, microbial changes, shelf-life and check-all-that-apply sensory analysis of cooked minced pork treated with varying levels of Moringa oleifera leaf and root powder

This study investigated warmed-over flavour profiles, microbial changes, shelf-life and sensory characteristics of minced cooked pork treated with Moringa oleifera (M. oleifera) root and leaf powder during refrigerated storage at 4 °C. A total of 8 treatments (control = no antioxidant; 0.5ML = 0.5% M. oleifera leaf; 1ML = 1% M. oleifera leaf; 0.5MR = 0.5 % M. oleifera root; 1MR = 1% M. oleifera root; 0.5MLR = 0.5% M. oleifera leaf and root mixed; 1MLR = 1% M. oleifera leaf and root mixed; BHT = 0.02% butylated hydroxytoluene) were evaluated. The minimum inhibitory concentration (MIC) of the plant extracts against the test bacteria was determined using the serial dilution in 96 well microtiter plates technique. Warmed-over flavour profiles were determined using the test for carbonyls assay where hexanal was used as a marker for warmed-over flavour. The check-all-that-apply sensory tool was used to characterise minced cooked pork treated with different antioxidants according to warmed-over flavour taste and odour intensities. The results showed that the antibacterial assay of the extracts exhibited a broad-spectrum of activity against the tested bacteria. The leaf extracts demonstrated better activity against both gram-negative and gram-positive bacteria, with most of the MICs at less than 1 mg/mL, while the root performed better against gram-negative bacteria compared to gram-positive bacteria. There was a significant rapid increase in the warmed-over flavour profiles of the control compared to the M. oleifera and BHT treated pork. The pork samples which had M. oleifera leaf, root, and their combination at inclusion levels of 1% and 0.5% displayed lower warmed-over flavour profiles that fell in the range (1.0–1.46 mg hexanal/100g fat) throughout the storage period. Consumer sensory evaluation revealed that pork samples treated with the highest inclusion level (1%) of the M. oleifera leaf powder received the lowest consumer rating scores for appearance. Based on these results, adding M. oleifera leaf and root powder can decrease warmed-over flavour development and improve the shelf-life of processed pork. Furthermore, the incorporation of M. oleifera root powder can potentially be more acceptable to consumers because of its colour compared to the leaf, which gives the product a green colour that may not be pleasant for some consumers. This suggests that the inclusion of the root powder at 1% may be well accepted for consumption by consumers.

Consumer exposure to warmed-over flavour and their attitudes towards the use of natural antioxidants as preservatives in meat and meat products

PurposeThe objective of the study was to assess consumer exposure to warmed-over flavour, their eating habits with respect to pre-cooked stored meats, awareness of antioxidants and attitudes towards the use of natural antioxidants as preservatives in meat and meat products.Design/methodology/approachA total of 238 Check-All-That-Apply (CATA) design questionnaires were used to gather information from the University of Fort Hare community in the Eastern Cape province of South Africa.FindingsThe majority of the respondents had been exposed to warmed-over flavour before. More than half of the respondents did not know about antioxidants. Respondents were in support of the use of natural antioxidants in meat and meat products.Research limitations/implicationsThe study mainly captured consumer habits based on living arrangements. Age influence could not be extrapolated due to the nature of the population, which was being studied. The population was limited to the University community, which is mainly made up of not so widely spread age groups and more or less similar levels of education. As a result, the findings and conclusions may not be a true reflection of the general public consumers in terms of age, level of education and employment status.Originality/valueThis research presents an original insight into consumer habits concerning the purchasing and storage of pre-cooked meat and meat products. The study revealed that most consumers nowadays prefer ready-to-eat or pre-cooked meat and meat products due to convenience. The warmed-over flavour is common in pre-cooked meats. The findings suggests that the meat industry has to improve the shelf-life of pre-cooked foods such that warmed-over flavour development is delayed to fit into the current consumer habits. In recent years there has been a growing interest in the use of natural antioxidants to improve shelf-life of muscle foods. However, there is a dearth of information on consumer attitudes towards the use of natural antioxidants as preservatives. This study reveals that consumers are willing to try products formulated using natural antioxidants.

The effect of natural and synthetic antioxidants and packaging type on the quality of cooked poultry products during frozen storage.

The effect of oil-soluble rosemary extract, sodium erythorbate and their mixture, and the influence of packaging method (air and vacuum packaging) on the quality of cooked turkey meatballs stored at -20 ℃ was determined. The smallest changes in malondialdehyde content were observed in samples with the addition of the natural antioxidant regardless of the packaging method. The mixture of synthetic and natural antioxidants was more effective in retarding lipid oxidation than the synthetic antioxidant, and more desirable results were observed in vacuum-packaged samples than in air-packaged samples. The samples with the addition of oil-soluble rosemary extract were characterised by lower intensity of red colour, but this parameter was more stable during frozen storage. The results of a sensory analysis revealed that the application of oil-soluble rosemary extract with or without sodium erythorbate significantly inhibited the development of warmed-over flavour in cooked poultry products.

Prediction of warmed-over flavour development in cooked chicken by colorimetric sensor array

The aim of this study was to develop a simple and rapid method based on colorimetric sensor array (CSA) for evaluation of warmed-over flavour (WOF) in cooked chicken. All samples were classified according to storage time by CSA coupled with principle component analysis (PCA) or hierarchical cluster analysis (HCA). The CSA data were used to establish prediction models with thiobarbituric acid reactive substances (TBARS), pentanal, hexanal, or heptanal associated with WOF by partial least square regression (PLSR). For the TBARS model, the coefficient of determination (rp2) was 0.9997 in the prediction range of 0.28–0.69mg/kg. In each of the models for pentanal, hexanal, and heptanal, all rp2 were higher than 0.960 in the range of 0.58–2.10mg/kg, 5.50–11.69mg/kg, and 0.09–0.16mg/kg, respectively. These results demonstrate that the CSA was able to predict WOF development and to distinguish between each storage time.

Desenvolvimento de terminologia descritiva para warmed-over flavor em carne assada bovina

Foi avaliado o desenvolvimento de warmed-over flavor (WOF) em carne assada bovina através da análise sensorial descritiva utilizando-se os músculos longo dorsal, semitendinoso e supra-espinhoso de novilhos da raça Nelore. Houve uma pré-seleção para recrutamento dos provadores, de 45 indivíduos inscritos, 35 foram pré-selecionados, destes, 24 foram avaliados com testes de diferença (quatro testes triangulares) para determinar a habilidade em discriminar diferenças de WOF em amostras de carne assada. Após os testes, 13 indivíduos foram selecionados para determinar o Perfil Sensorial de cada amostra. Inicialmente, 70 termos foram propostos pela equipe sensorial para a análise descritiva quantitativa, mas foram eliminados os termos que não apresentaram relevância para o produto, que não contribuíram para a discriminação de WOF na carne assada e os que apresentaram dificuldade de ser detectados pelos provadores. Restaram ao final 18 termos, sendo todos utilizados nos três tipos de músculos analisados. A análise descritiva quantitativa pode ser realizada para a obtenção de resultados satisfatórios para a pesquisa de warmed-over flavor em carne assada em experimentos científicos e para o desenvolvimento de produtos.

Monitoring of warmed-over flavour in pork using the electronic nose – correlation to sensory attributes and secondary lipid oxidation products

Sensory analysis of meatballs was carried out to monitor the warmed-over flavour (WOF) development in cooked, cold-stored (at 4 °C for 0, 2 and 4 days) and reheated meatballs derived from M. longissimus dorsi (LD) and M. semimembranosus (SM) of pigs fed a standard diet supplemented with either 3% of rapeseed oil or 3% of palm oil. This was performed in combination with measurement of volatile compounds using a solid-state-based gas sensor array system (electronic nose) and gas chromatography/mass spectrometry together with measurement of thiobarbitoric acid reactive substances (TBARS). Subsequently, to elucidate the relations and predictability between the obtained data, the gas sensor responses were correlated with chemical (volatile and non-volatile secondary lipid oxidation products) and sensory data (flavour and odour attributes), using partial least squares regression modelling (PLSR). The TBARS, hexanal, pentanal, pentanol and nonanal all correlated to the sensory attributes associated to WOF formation. Moreover, the responses from eight of the MOS (metal oxide semiconductor) sensors within the electronic nose proved to be significantly related to WOF characteristics detected by both sensory and chemical analysis, while six of the MOSFET (metal oxide semiconductor field effect transistor) sensors were related to freshly cooked meat attributes determined by sensory analysis. The obtained results show the potential of the present gas sensor technology to monitor WOF formation in pork.

Effects of EDTA and a combined use of nitrite and ascorbate on lipid oxidation in cooked Japanese sardine ( Sardinops melanostictus) during refrigerated storage

To elucidate the effects of EDTA and a combined use of nitrite and ascorbate on oxidative rancidity of cooked Japanese sardine ( Sardinops melanostictus) stored at refrigeration temperature (2 °C), changes in peroxide values (PV), thiobarbituric acid (TBA) value and fatty acid composition were monitored. The PV and TBA values of the meat with and without EDTA (250 mg/100 g meat) increased gradually, while they remained unchanged when a mixture of sodium nitrite (10 mg NO 2/100 g meat) and sodium ascorbate (200 mg/100 g meat) was added. Total polyenoic acids in the nitrite and ascorbate mixture-treated meat decreased at a slower rate than in the control group. These changes in PUFA composition were due to differences in oxidative stability between the meats containing different antioxidants. In conclusion, a combined use of nitrite and ascorbate showed a greater antioxidativity in terms of the lower PV and TBA values than did EDTA and resulted in preventing the development of warmed-over flavour in cooked sardine during of 14 day refrigerated storage.

Synergism between dietary vitamin E and exogenous phytic acid in prevention of warmed-over flavour development in chicken breast meat, Pectoralis major M.

The effect of alpha-tocopheryl acetate (AT) supplementation and exogenous application of this vitamin E associated with phytic acid (PA) on chicken breast meat WOF development was assessed. Control group was fed with 7.7IU of AT/kg of ration and supplemented group was fed with 200.0IU of AT/kg of ration. Dietary vitamin E as measured by TBARS inhibited WOF development by 78.9; 69.0; 60.7 and 46.5% (p<0.05) during storage at 6° C for 0, 1, 3 and 5 days, respectively. This inhibition was significantly increased (p<0.05) by 86.1; 91.6; 92.9 and 95.3% during storage at 6° C for 0, 1, 3 and 5 days, respectively, when 2mM PA was added in supplemented breast meat. In the exogenous experiment, through Response Surface Methodology design it was found out AT did not have a significant role towards oxidation inhibition whereas PA inhibited partially in samples stored for 48h at 6° C. The results showed that dietary AT inhibited at initial stage, subsequently PA would act at propagation phase occurring synergetic reaction between both antioxidants.

Effect of salt on color and warmed over flavor in charqui meat processing

A combination of salt (NaCl) high concentration and curing salt was investigated for their role in warmed-over flavor (WOF) and color changes during charqui meats processing. WOF was measured by TBARS method in uncured charqui meat (CH) and in cured charqui known in Brazil as Jerked beef (JB). WOF occurred substantially in CH and sodium nitrite was able to inhibit 40-45% (p<0.05) in JB samples stored for 30 days. Color parameters also changed as evaluated by CIELAB system. The a*/b* ratio showed that CH samples presented brown color indicating the formation of metmyoglobin (Fe3+) whilst JB samples presented deep red color an indication of nitrosylmyoglobin (Fe2+) formation. Under cooking, a*/b* ratio indicated the presence of denatured metmyoglobin (Fe3+) in CH and formation of nitrosylmyochromogen (Fe2+) in JB samples. The actual iron state influenced the color of charqui meat and apparently nitrite was able to chelate Fe ions, thus inhibiting development of WOF.

A comparison of warmed-over flavour in pork by sensory analysis, GC/MS and the electronic nose

Pork muscle samples ( M. longissimus dorsi and M. psoas major) were obtained from pigs given one of 4 dietary treatments, (i) control diet, (ii) supplemental iron (300 mg iron (II) sulphate/kg feed), (iii) supplemental vitamin E (200 mg dl-α-tocopheryl acetate/kg of feed) and (iv) supplemental vitamin E+supplemental iron. Warmed-over flavour (WOF) was evaluated by a trained sensory panel ( n=8) for the four treatments cooked and refrigerated at 4 °C for up to 5 days. Gas chromatography mass spectrometry (GC/MS) and Electronic nose analysis was performed on a subset of the full design which included samples of M. longissimus dorsi, treatments (ii) and (iii) and M. psoas major with treatment (i) for 0 days of WOF development. Day 5 of WOF development was included in the subset and represented by samples of M. longissimus dorsi, treatment (iv) and M. psoas major, treatments (ii) and (iii). Bi-linear modeling was used to determine the correlation of GC/MS and electronic nose data to sensory data. Also, the reproducibility and reliability of electronic nose data was evaluated by repeating the analysis of samples in a different laboratory and with a time difference of approximately 11 months. Mean-centring was used to normalise the data from these two different electronic noise data sets. GC/MS data correlated to sensory data with specific compounds (e.g., pentanal, 2-pentylfuran, octanal, nonanal, 1-octen-3-ol and hexanal), proving to be good indices of oxidation in cooked samples of M. longissimus dorsi and M. psoas major. Electronic nose data correlated to sensory data and separated the sensory variation. The reproducibility of this data was high with the second set of samples being predictive of the first set.

Sensory and chemical assessment of pork supplemented with iron and vitamin E

Pork muscle samples ( M. longissimus dorsi and M. psoas major) were obtained from pigs given one of four dietary treatments, (1) control diet, (2) supplemental iron (7g 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. Vitamin C was supplemented to all dietary treatments to facilitate iron uptake. Vitamin E and iron tissue levels were determined for each treatment. Warmed-over flavour (WOF) was evaluated by a trained sensory panel ( n=8) for the four treatments which were cooked and refrigerated at 4 °C for up to 5 days. Thawing loss, driploss and thiobarbituric acid reactive substances (TBARS) were also determined. Vitamin E muscle tissue levels were greatest in the Iron/vitamin E-treated group followed by the vitamin E group, control and iron treated groups, respectively for M. longissimus dorsi. Whereas, for M. psoas major vitamin E tissue levels were in order of magnitude, vitamin E>iron/vitamin E>iron>control group. Iron tissue levels were in the order vitamin E>iron/vitamin E>control>iron for M. longissimus dorsi and iron>vitamin E>control>iron/vitamin E for M. psoas major. Thus, vitamin E and vitamin C promoted non-supplemental iron absorption in the vitamin E-treated group for M. longissimus dorsi and to a lesser extent for M. psoas major. M. psoas major was more susceptible to warmed-over flavour development than M. longissimus dorsi for all treatments as determined by sensory profiling, due to higher tissue iron levels. From sensory profiling, WOF development in M. longissimus dorsi and M. psoas major was highest in the iron-supplemented groups followed by the control and vitamin E-supplemented groups.

DATA ANALYTICAL METHODOLOGIES IN THE DEVELOPMENT OF A VOCABULARY FOR EVALUATION OF MEAT QUALITY

ABSTRACTPork patties from M. longissimus dorsi and M. psoas major were used by a sensory panel to develop a descriptive vocabulary to describe warmed‐over flavor development. The patties were made from meat from animals supplemented with one of four dietary treatments, (I) control diet, (II) supplemental iron (7 g iron (II) sulfate/kg feed), (III) supplemental vitamin E (200 mg dl‐α‐tocopherol acetate/kg of feed) and (IV) supplemental vitamin E + supplemental iron. The sample set used for training reflected the variation in muscle type and degree of warmed‐over flavor development (day 1 and 5). The sensory terms selected had to be relevant to the samples, discriminate between the samples, have cognitive clarity and be nonredundant. Based on these selection criteria an initial training list of 36 sensory terms consisting of odors, flavors, basic tastes and aftertastes was developed in a pretrial using experts with product knowledge. This list constituted the start of training the panel. Principle Component Analysis (PCA) and assessor suggestions were used for reducing the number of terms and after 5 days of training this list was reduced to 21 sensory terms. The discriminative ability of the sensory panel improved over the course of sensory training and was quantified by using the mean assessor signal to noise ratios (S/N) for the sensory terms for each training session. This signal to noise ratio is essentially the total initial variance divided by the residual cross‐validated variance. Subsequent detailed multivariate analysis found that the bilinear descriptor leverage was a particularly efficient method for term reduction.

Warmed‐Over Flavor and Lipid Stability of Beef: Effects of Prior Nutrition

ABSTRACT: Development of lipid oxidation and warmed‐over flavor (WOF) in cooked meats during refrigerated storage was investigated in beef from pasture‐fed cattle or grain‐fed cattle supplemented with 0, 500, or 2500 IU vitamin E/head/d for 105 d. Meat from pasture‐fed cattle contained as much α‐tocopherol as grain‐fed cattle supplemented with 2500 IU vitamin E, but it was found to be less prone to lipid oxidation and development of WOF. It also contained a higher percentage of linolenic acid and lower content of linoleic acid than grain‐fed beef.

Descriptive sensory profiling and physical/chemical analyses of warmed-over flavour in pork patties from carriers and non-carriers of the RN − allele

Descriptive sensory profiling was carried out to evaluate warmed-over flavour (WOF) development in cooked, chill-stored and reheated pork patties derived from the meat ( Musculus longissimus dorsi) of carriers (RN −/rn +) and non-carriers (rn +/rn +) of the RN − gene. Patties were oven-cooked at 150 and 170 °C and chill-stored for up to 5 days to facilitate warmed-over flavour (WOF) development. In addition, thawing losses, cooking losses, pH and TBARS were measured in the cooked pork patties. Analysis of variance (ANOVA) was used to investigate changes in the physical/chemical measurements due to the experimental design variables (storage days, cooking temperature and genotype) and multivariate ANOVA-partial least squares regression (APLSR) was used to determine relationships between the design variables and the sensory and physical/chemical data. WOF was found to involve the development of lipid oxidation derived nuance off-flavour and odour notes, e.g. rancid-like flavour and linseed oil-like odour, in association with a concurrent decrease in ‘meatiness’ as described by, e.g. cooked pork meat-like flavour. Cooking temperature was described by roasted-like and caramel-like odours and samples from carriers of the RN − gene were described as more ‘sour’ and ‘metallic’. Thawing and cooking losses were found to be significantly ( P <0.05) higher in meat from carriers of the RN − gene versus non-carriers. pH was negatively related to samples from carriers of the RN − gene. However, the measured pH in RN − carriers could not be significantly ascribed as lower in non-carriers in the freshly cooked meat samples. TBARS were found to be significant ( P <0.05) predictors of the sensory terms related to the lipid oxidation aspect of WOF. Moreover, TBARS were significantly ( P <0.05) higher in meat from RN − gene carriers but, significantly ( P <0.05) lower in meat cooked at high oven temperatures (170 °C). The former effect was postulated as related to pH and the latter as related to the antioxidant effects of Maillard reaction products developed at higher cooking temperatures. Overall, WOF, cooking temperature and genotype were differentiated as individual dimensions through sensory profiling of the meat samples and each source of variation was characterised by specific groups of sensory descriptors. Moreover, the predictive nature of thawing losses, cooking losses and TBARS was established for the effects of RN − gene, cooking temperature and WOF, respectively.

Modified Extraction Method for Determining 2‐Thiobarbituric Acid Values in Meat with Increased Specificity and Simplicity

ABSTRACT: Monitoring the development of warmed‐over flavor (WOF) is critical for the quality control of meat products. This study was to modify the acid‐extraction method for analyzing thiobarbituric acid‐reactive substances (TBARS) as an indicator of WOF in cooked meats. After centrifuging the extract of cooked beef, the supernatant of the extract was reacted with 80 mM TBA solution at 40 °C. The reaction between TBA and malonaldehyde was completed within 90 min, and interfering agents such as sucrose did not form any detectable color interference. The TBARS values in cooked beef samples after storage at 4 °C for zero and 7 d were 2.1 and 10.8 mg/kg, respectively. The recovery rate was between 92 and 102%. This method could be used to measure TBARS in cooked beef.

Sensory and chemical investigations on the effect of oven cooking on warmed-over flavour development in chicken meat

Descriptive sensory profiling was carried out to evaluate the effect of oven-cooking temperature (160, 170, 180, 190 °C) on warmed-over flavour (WOF) development in cooked, chill-stored (at 4 °C for 0, 1, 2 and 4 days) and reheated chicken patties, derived from M. pectoralis major. In addition, gas chromatography–mass spectrometry (GC–MS) was carried out on a representative sub-set (160, 180, 190 oC, stored at 4 °C for 0, 1, 4 days) of the meat samples used in sensory profiling. The effects of cooking and WOF in the sensory and chemical data were analysed using multivariate ANOVA-Partial Least Squares Regression (APLSR). Descriptive profiling indicated that WOF development was described by an increase of ‘rancid’ and ‘sulphur/rubber’ sensory notes and a concurrent decrease of chicken ‘meaty’ characteristics. Increasing cooking temperature resulted in meat samples with a more ‘roasted’, ‘toasted’ and ‘bitter’ sensory nature. Moreover, the ‘roasted’ character of the meat samples was also related to WOF development. Analysis of the volatile compounds from the chicken patties showed a rapid development of lipid oxidation derived compounds with chill-storage. Such compounds most likely contributed to the ‘rancid’ aspect of WOF development. Moreover, changes in sulphur-containing compounds were also related to WOF development and were proposed as additional participants in the lipid oxidation reactions. The sensory effects of these compounds were mainly described by the ‘sulphur/rubber’ note associated with WOF development. Overall, cooking temperature was found to increase the formation of Maillard-derived compounds, however, these did not appear to inhibit WOF development in the chicken patties.

Sensory and chemical analysis of cooked porcine meat patties in relation to warmed-over flavour and pre-slaughter stress

Two independent sensory profiles were carried out to evaluate warmed-over flavour (WOF) development in cooked, chill-stored and reheated pork patties. The patties were derived from the Musculus semimembranosus of animals subjected to different pre-slaughter stress treatments. All patties were stored in oxygen permeable bags at 4°C for 0, 1, 2, 3 and 5 days to facilitate WOF development. In addition, thiobarbituric acid reactive substances (TBARS), conjugated dienes, pH, water content, total lipids and the fatty acid compositions of phosphatidyl choline (PC), phosphatidyl ethanolamine (PE) and total lipids, were measured in the cooked meat patties. A data analytical strategy involving Analysis of Variance–Partial Least Squares Regression (ANOVA–PLSR), to determine relationships between the design variables (WOF and pre-slaughter stress) and the sensory-chemical data, and PLSR to elucidate predictive links between the sensory and chemical data was utilised. WOF was found to involve the development of lipid oxidation derived nuance off-flavour and odour notes, e.g. rancid-like flavour and linseed oil-like odour, in association with a concurrent decrease in cooked pork meat-like flavour. The reduction in “meatiness”, over the initial days, 0–2 of WOF development was attributed to the degradation of both, unstable sulfur-containing amino acids in meat proteins and sulfur-containing “meaty” aroma compounds. Whereas, at the later days, 3–5 of WOF development the “meaty” loss was ascribed to perceptual masking by lipid oxidation products. TBARS and conjugated dienes were found to be significant ( P<0.05) predictors of the sensory terms related to the lipid oxidation aspect of WOF. Whilst the polyunsaturated fatty acid (PUFAs) contents of PE, PC and the total lipids were found to decrease with WOF development, reflecting their loss in lipid oxidation reactions. The sensory variation related to pre-slaughter stress appeared to be distinct from WOF variation and was described by a sour to sweet taste continuum. However, interactions were noted that indicated increasing pre-slaughter stress resulted in a decreased sensory perception of WOF. Moreover, pH and water content were found to significantly ( P<0.05) predict the sensory effects resulting from pre-slaughter stress.

Sensory panel consistency during development of a vocabulary for warmed-over flavour

A sensory vocabulary of 20 terms each with a corresponding reference material was developed over 7 sessions using pork patties derived from the meat of carriers and non-carriers of the RN − gene. Patties were oven-cooked at 150 and 170°C and chill-stored for up to 5 days to facilitate warmed-over flavour development. Generalised Procrustes Analysis (GPA) was used to investigate sensory terms and their individual use by panellists over the sessions. GPA explained variance indicated that the final vocabulary displayed a similar amount of information to that of the initial vocabulary of 42 terms. Individual panellists scale use was found to converge over the sessions. Panel agreement on many odour and flavour terms appeared to be enhanced as term synonyms were removed in vocabulary development. Sample discriminability decreased from sessions 1–4, where term concepts were verbally communicated to the panel. Term reference introduction in session 5 caused a levelling in sample discriminability and a reduction in agreement, most likely related to perceptual confusion. Subsequently, references enhanced both discriminability and agreement. Thus, it may be more useful to introduce reference materials earlier, if not in the first session, of the vocabulary development process.

Power of experimental designs, estimated by Monte Carlo simulation

What is the optimal size of an experiment? How should the practical experimenter determine this optimal experimental size? The paper presents a conceptually simple method for estimating the statistical power of experimental designs, based on Monte Carlo simulation. In the planning stage of a project, several alternative experimental designs may thereby be compared with respect to their ability to balance the risk of committing Type I and Type II errors against the cost. The Monte Carlo power estimation of a design is based on the following main steps: generate artificial data in a number of (say 5000) hypothetical experiments, based on the design and on certain assumptions; analyse each artificial data set in the same way that the future, real data set is intended to be analysed; from the distributions of the obtained parameter estimates, study the risks associated with the given experimental design. The method is illustrated for a factorial design in sensory analysis concerning warmed-over flavour development in meat. Here the Monte Carlo simulations indicated that four replicates were needed, given certain assumptions. The real experiment was performed independently twice, each time in four replicates. The resulting analysis of effects gave satisfactory results, indicating that four replicates had given the necessary and sufficient power in each of the two experiments. Copyright © 2000 John Wiley & Sons, Ltd.

Warmed-over flavour in porcine meat — a combined spectroscopic, sensory and chemometric study

The effectiveness of applying rapid spectral techniques in the prediction of meat quality in relation to pre-slaughter stress and warmed-over flavour (WOF) was investigated. The effect of pre-slaughter stress on the development of WOF is a relatively new area of interest in WOF research. The present study investigated the relationship between pre-slaughter stress and WOF characteristics (after 0 to 5 days' storage) in porcine meat as evaluated by chemical, sensory and spectroscopic methods. Sensory evaluation, visual reflectance spectroscopy (VIS) and low-field 1H NMR (LF-NMR) proved efficient in describing the different stress groups and the storage period, whereas fluorescence spectroscopy and the TBARS test were only able to follow WOF during storage. Near Infrared Reflectance (NIR) and Raman scatter showed a very weak relationship to pre-slaughter stress and levels of WOF during storage. Good correlations (up to r=0.93) of sensory terms were achieved with VIS and fluorescence spectroscopy and LF-NMR.