Volatile flavour components of cooked potato

Extracts of the steam volatiles of cooked potatoes and of a dehydrated, granular potato product have been prepared. High-boiling fatty acids preponderated and were removed prior to concentration and examination of the resulting essences by combined gas chromatography-mass spectrometry-odour assessment. Thirty-five components were identified in potato essences and 20 in a potato granule essence. Chemical and retention data indicated that 2-methoxy-3-ethylpyrazine

1 For clarity in this paper, the methoxy substituent is assigned the 2-position in pyrazines, and is written first, irrespective of the rules of nomenclature.

was present in potato volatiles and mass spectral evidence was obtained of its presence in potato sprout essence. Synthetic work confirmed the known characteristic raw potato odour of 2-methoxy-3-ethylpyrazine and demonstrated that isomers do not possess it. Lack of volatiles rather than off-flavour is believed to account for the differences between the flavour of cooked potatoes and of the potato product examined.     

A comparison of the flavour volatiles from cooked beef and pork meat systems

The headspace volatiles from beef and pork cooked with and without added adipose tissue were entrained on Tenax GC before analysis by gas chromatography (g.c.) and combined gas chromatography-mass spectrometry. Lipid-derived volatiles dominated the headspaces of all samples and the only qualitative difference between beef and pork was an alkene of lipid origin which was peculiar to beef samples. A comparison of the areas of 37 g.c. peaks from replicate analyses of the different meat preparations using canonical variates and stepwise discriminant statistical techniques unambiguously distinguished the lean meats and the lean meats cooked with adipose tissue of either species. Adding adipose tissue to lean meat did not result in proportional increases in lipid-derived volatiles.     

姜味鸡肉糜脯加工技术研究

以鸡脯肉和生姜为主要原料,采用现代工艺,通过感官评定结合质构测定和理化检验,研制营养且具有姜味的鸡肉糜脯。结果表明:生姜汁用量2.8%的产品风味最佳;添加2.4%食盐、10%蔗糖,0～4℃下腌制1.5～2h为最佳腌制条件。     

Effect of packaging and storage conditions on development of warmed-over flavour in sliced, cooked meat

Summary The development of warmed-over flavour (WOF) in a pilot-scale experiment was followed by sensory evaluation and three objective methods (thiobarbituric acid reactive substances, relative hexanal content, and fluorescent lipid oxidation products) during 14 days of chill storage at 4° C of sliced, cooked lean beef using three different packaging conditions: (1) in air in a polyethylene foil (PE); (2) in 99% vacuum in a laminate foil with low oxygen transmission rate (VAC); (3) in a modified atmosphere (30% CO₂/70% N₂) in a laminate foil with low oxygen transmission rate (MAP). Each of the objective methods correlated well with the sensory evaluation. The sensory quality of the meat packed in PE was clearly inferior to the VAC and MAP packed meat, having less meat taste and a perceptible degree of WOF when reheated after only 1 day of storage, increasing to an unacceptable level within 3 days of storage. In contrast, the sensory quality of the VAC and MAP packed meat remained high throughout the storage period. Irrespective of packaging method, no effect of light during the chill storage period on the development of WOF was detected. MAP packaging for precooked beef was tested on a larger scale in a senior citizen food service system. The results showed that in a practical application of MAP the major problem in avoiding WOF was the achievement of a sufficiently low residual oxygen content in the packages.

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Einfluß der Verpackung und Lagerungsverhältnisse auf die Entwicklung des Aufwärmgeschmacks von in Scheiben gekochtem Rindfleisch

Zusammenfassung In einem Modellversuch mit in Scheiben geschnittenem gekochtem Rindfleisch wurde die Entwicklung des Aufwärmgeschmacks mit sensorischer Beurteilung und drei objektiven Methoden (Thiobarbitursäure-reaktive Substanzen, relativer Gehalt von Hexanal und fluorescierenden Fettoxidationsprodukten) während 14tägiger Kühllagerung bei 4 °C untersucht. Das Fleisch wurde auf drei verschiedene Weisen verpackt: (1) mit Luft in Polyäthylenfolie (PE); (2) in 99% Vakuum in laminierter Folie mit niedriger Sauerstoffdurchlässigkeit (VAC); (3) in modifizierter Atmosphäre (30% CO₂/70% N₂) in laminierter Folie mit niedriger Sauerstoffdurchlässigkeit (MAP). Jede objektive Methode korrelierte gut mit der sensorischen Beurteilung. Die sensorische Qualität des PE-Fleisches war merkbar geringer als die des in VAC und MAP verpackten Fleisches. Es hatte nach nur einem Tag Kühllagerung einen geringen Fleischgeschmack und einen merklichen Aufwärmgeschmack, der nach drei Tagen auf ein unakzeptables Niveau zugenommen hatte. Demgegenüber war die sensorische Qualität des in VAC und MAP verpackten Fleischs sehr gut über die ganze Lagerungszeit. Beleuchtung hatte, ungeachtet der Verpackungsmethode, auf die Entwicklung des Aufwärmgeschmacks keinen Einfluß. Bei modifizierter Atmosphärenverpackung von gekochtem Fleisch in größerem Ausmaß in einer Küche zur Verköstigung von älteren Menschen ergab es sich, daß das größte Problem, den Aufwärmgeschmack zu vermeiden, ein ausreichend kleiner Restsauerstoffgehalt in den Verpackungen war.

     

Winery grape-residue extract: Effects on quality and sensory attributes of cooked chicken meat

Sensory analysis, instrumental color, pH, and thiobarbituric acid reactive substances (TBARS) were determined on cooked chicken meat with and without grape seed extract during refrigerated storage. The effectiveness of extracts of winery grape residue from the grape varieties ‘Isabel’ and ‘Niagara’ were tested to evaluate their effectiveness at delaying lipid oxidation in cooked chicken meat and stored under refrigeration (4±1°C). The samples were aerobically and vacuum packaged and stored for 14 days. ‘Isabel’ grape extract (IGE) and ‘Niagara’ grape extract (NGE) proved effective at promoting oxidative stability when applied at concentrations of 40 or 60 mg of gallic acid equivalents (GAE)/kg, with results similar to the synthetic antioxidant butylated hydroxytoluene (BHT). The antioxidant efficiency of the extracts was highly dependent on the concentration used. The addition of grape-residue extracts combined with vacuum packaging proved to be a good method for increasing lipid stability in cooked chicken meat stored under refrigeration.     

Influence of pasture species on the flavour, odour and keeping quality of lamb and mutton

Lambs fed white clover species (Trifolium repens cv. Grasslands Huia or cv. Grasslands 4700) showed a stronger flavour in the fat and lean and a greater intensity of odour in the casseroled 12th rib chop than lambs fed on perennial ryegrass (Lolium perenne). The results for hoggets generally supported those for lambs. Differences in flavour of the lean of the lambs appeared within three weeks from the beginning of the experiment. Differences in intensity of flavour and odour between the shoulder, loin and leg of the hoggets were small. After storage for 8 months at —15°, the thiobarbituric acid (TBA) values of the lean and fat of the 12th rib chop were highly significantly greater in lambs fed white clover than in those fed perennial ryegrass. Similar differences were found in hoggets using carcasses that had been stored for one to two months. In the hoggets, significantly higher TBA values were found in the fatty tissues of the leg than in the loin and shoulder. Differences between the TBA values of the lean were not significant.     

Antimicrobial effect of natural preservatives in a cooked and acidified chicken meat model

The inhibitory effect of Microgard 100, Microgard 300, nisin, Alta 2002, Perlac 1902, sodium lactate and essential oil of mustard on microorganisms experimentally inoculated was screened in an acidified chicken meat model (pH = 5.0) and stored for 2 weeks at a none restrictive growth temperature of 22 degrees C. All antimicrobials tested were used at the highest concentration recommended by their manufacturer. Sausage batter made with mechanically deboned chicken was inoculated with a mixed culture of Escherichia coli ATCC 25922, Brochothrix thermosphacta CRDAV452, and a protective culture Lactobacillus alimentarius BJ33 (FloraCan L-2). A final cell concentration of 3-4 log CFU g (-1) was targeted after cooking at a core temperature of 55 degrees C for each microorganism in order to assess cell count variation effectively. Composition, water activity (a(w)), pH and redox potential of the sausage model was also evaluated. The E. coli population decreased steadily during storage and was close or below detection level (< 1 log CFU g (-1)) for all treatments, including the control, after 14 days. Sodium lactate was most effective against B. thermosphacta; population was 4 log lower than the control after 14 days of storage. When essential oil of mustard was used, aerobic mesophilic bacteria and lactic acid bacteria were significantly lower than the control after 2 days of storage (P < or = 0.05). The other antimicrobial agents tested had no significant effect on the aerobic mesophilic bacteria, E. coli, B. thermosphacta and lactic acid bacteria counts, when compared to the control.     

The effects of antioxidative treatments on mutton flavour/odour intensity and species flavour differentiation

This study examined the effects of curing and oxygen exclusion on the odour and flavour of sheepmeats. One series of experiments examined the effect of curing on the ability of panellists to distinguish between the flavours of lean mince from various species (mutton, beef, pork, chicken). Other experiments examined the effects of curing and of maintaining an anoxic storage/cooking environment on the intensity of mutton flavour and odour, particularly adipose tissue odour. Curing had no effect on panellists' abilities to distinguish between the flavour of mince from different species. Storage and cooking of uncured mutton adipose tissue samples under anoxic conditions limited lipid oxidation but enhanced mutton odour intensity. Nitride had a pro-oxidant effect on mutton adipose tissue stored in air. There was no corresponding effect on mutton odour intensity. These findings suggest that lipid oxidation products contribute very little to mutton odour from adipose tissue, and possibly also to species flavour differences in lean meats.     

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.     

Use of molecular sieve 5A in the analysis of the flavour volatiles of cooked chicken

A short column of molecular sieve 5A has been used to simplify the complex pattern of flavour volatiles extracted by isopentane from cooked meat, prior to analysis by gas-liquid chromatography and identification by mass spectrometry. The molecular sieve removed all components from the mixture except aromatic hydrocarbons, branched cyclic compounds and some halogenated derivatives. Recovery experiments showed no loss of aromatics on the sieve and there was complete removal of n-alkanes, n-alkanals, n-alkanones, n-alkanols and fatty acid methyl esters. Some n-alkanes were recovered from the molecular sieve by displacement with hexadecane.     

Influence of post-mortem treatments on turkey and chicken meat texture

Toughness of poultry breast muscle was influenced by the rate of rigor onset, the rate of cooling and chilled storage time. The pH of the breast muscle at 20 min after stunning (pH₂₀) in 52-day-old chickens varied from 5.9 to 6.9, and in 70-day-old turkeys from 6.2 to 6.8. In turkey meat with pH₂₀ > 6.4, toughening was induced by immersion chilling to 7°C within 65 min post mortem and subsequent 'tanking' in iced water. Unaged, thawed meat from chicken carcasses, in which freezing commenced about 2 h after stunning was tougher than that from carcasses chilled for 16 h before freezing. Both were tender after 7 days chilled storage. Electrical stimulation of carcasses using 94 V decreased pH₂₀ by an average of 0.3 unit in turkey, with no overall increase in tenderness. In chicken, it decreased the pH₂₀ by 0.5 unit, but caused an overall toughening due to increased rigor shortening in carcasses with pH₂₀ < 5.8.     

Effect of laccase and transglutaminase on the textural and water-binding properties of cooked chicken breast meat gels

The effects of laccase and transglutaminase (TG) on the firmness and weight loss of cooked chicken meat homogenate gels were investigated at laboratory scale. The salt, trisodium pyrophosphate and meat contents were also used as variables. Laccase decreased firmness and increased weight loss of phosphate-free, low-meat (65%) and low-salt (1%) gels, although it modified myosin and troponin T and reacted with isolated myofibrils. By applying both low-salt (1%) and low-phosphate (0.17%) amounts, gel firmness decreased and weight loss increased (p<0.05) greatly. A high dosage of TG significantly improved (p<0.05) the strength of phosphate-free, low-meat and low-salt homogenate gels compared to the corresponding no-enzyme controls. TG improved gel firmness of the low-meat homogenate to the level of the homogenate containing 75% meat. Weight loss was increased significantly (p<0.05) in all cases when the high-TG dosage was used. Enzymes were not capable of improving either texture or water-holding capacity in the low-salt–low-phosphate system. The firmness and cooking loss of the chicken meat products containing different amounts of meat, salt and TG were investigated at pilot scale. Under the conditions and dosages used, TG was capable of improving (p<0.05) firmness of the products without a significant reduction in water-holding capacity.     

Effect of natural antioxidant combinations on lipid oxidation in cooked chicken meat during refrigerated storage

The effect of combinations of sage, oregano and honey on lipid oxidation in cooked chicken meat during refrigeration at 4°C for 96h was determined. Chicken samples (thigh and breast) were then separated into five groups: control; butylated hydroxytoluene; oregano+sage; oregano+sage+5%honey and oregano+sage+10%honey. Quantitative measurements of thiobarbituric acid reactive substances, conjugated dienes, hexanal, fatty acids, cholesterol and cholesterol oxides were used as indicators of lipid oxidation. Acceptability and preference were also evaluated. The effectiveness of the natural antioxidants for reducing the velocity of lipid oxidation in cooked chicken thigh and breast was demonstrated after 48 and 96h of refrigeration at 4°C. The treatments that presented the lowest hexanal values after 96h of refrigeration were oregano+sage+5%honey and oregano+sage+10%honey. Only traces of free cholesterol oxides were found (25-OH, 7-k, 7α-OH and 7β-OH). The natural antioxidants protected cooked chicken meat from oxidation processes and resulted in great acceptability.     

Effect of refrigerated and frozen storage on the survival of Campylobacter jejuni in cooked chicken meat breast

This experimental work aimed to examine the survivability of Campylobacter jejuni in cooked chicken breast under several conditions: storage for 1, 3, and 7 d at refrigerated temperatures (4 °C) and for 20 d at frozen temperatures (-18 °C). In addition, storage at ambient temperature (26 to 28 °C) was involved. Chicken samples were inoculated with a mixed culture of C. jejuni strains (ATCC: 29428 and 33219) of known concentrations (50 and 500 CFU/g). Bacterial cells were recovered and enumerated using standard procedure (Preston method). Bacteria were not detected in the majority of samples stored at ambient temperature. Refrigeration reduced survivals in 95, 90, and 77.5% for samples inoculated with 500 CFU/g and kept for 1, 3, and 7 d, respectively. The maximum reduction reached 1 log(10) cycle for all refrigeration durations. It was observed that bacteria died in 17.5% of samples kept for 7 d at 4 °C. However, survivors in samples inoculated with 50 CFU/g were not detected in 50, 65, and 55% of samples kept for 1, 3, and 7 d, respectively. Freezing rendered survivors not detectable in 70% of samples inoculated with 50 CFU/g, while survived viable counts were reduced in 92.5% of samples inoculated with 500 CFU/g. These findings suggested that C. jejuni could be killed or just sublethally injured with or without reduction in viable counts under the investigated storage temperatures, which may indicate the ability of this bacterium to survive in chicken meat stored under refrigerated and frozen conditions.     

Heterocyclic aromatic amines in cooked hamburgers and chicken obtained from local fast food outlets in the Ottawa region

Heterocyclic aromatic amines (HAAs) are formed in protein-rich foods during high temperature cooking such as frying and grilling. Since most HAAs are potent mutagens and almost all are carcinogenic to laboratory animals, their formation in cooked foods is a health concern. In the present study, 31 cooked hamburgers and six chicken preparations were obtained from various fast food outlets in the Ottawa area and analyzed for HAAs. In the developed procedure, ground-up samples were extracted under both acidic and alkaline conditions, cleaned on SPE cartridges, and the concentrations of various HAAs determined using electrospray ionization LC/MS/MS. Deuterium-labelled internal standards of the three most commonly found HAAs (IQ, MeIQx, and PhIP) in such foods were used for quantitation and recovery correction. Varying levels of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) (0.2–6 μg/kg), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) (0.1–3.5 μg/kg), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) (0.3–6.9 μg/kg), and 7,8-dimethyl-IQx (2-amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline) (0.1–2.9 μg/kg) were detected in most hamburgers, whereas our limited data on the chicken samples (wings, drumsticks, and nuggets) indicated the presence of mainly PhIP (0.1–2.1 μg/kg) and MeIQx (0.1–1.8 μg/kg). Traces of 4,7,8-trimethyl-IQx (<0.1 μg/kg), 3-amino-1,4-dimethyl-5H-pyrido[3,4-b]indole (Trp-P-1) (<0.1–0.3 μg/kg), and 3-amino-1-methyl-5H-pyrido[3,4-b]indole (Trp-P-2) (<0.1–0.8 μg/kg) were also detected in some samples of hamburgers but not in any of the chicken analyzed thus far. Since hamburger is a popular meal among Canadians, regular consumption of such items may contribute substantially to one's dietary intake of HAAs.     

Modelling the effect of fatty acids in odour development of cooked meat in vitro: part I-sensory perception

We have investigated the contribution of muscle components to the development of cooked meat odour in an aqueous model system using trained taste panels. Reaction mixtures were prepared with oleic, linoleic and linolenic acids with or without cysteine and ribose in a buffer with or without ferrous sulphate. Odour profiles were assessed and triangular tests were used to determine the ability of panellists to discriminate between mixtures. The presence of sugar and amino acid was highly detectable by panellists independently of the fatty acid considered (P<0.001). However, the presence of C18:3 made differences more obvious between mixtures than the presence of C18:1 or C18:2. 'Meaty' notes were only associated with cysteine and ribose. 'Fishy' notes were only apparent in C18:3 mixtures with or without sugar and amino acid, although the presence of cysteine and ribose decreased the perception. The addition of Fe(++), a pro-oxidant present in the muscle, produced a reduction in the score of the attributes although the pattern was the same as when Fe was not used in the mixtures. Only 'fishy' notes that were exclusively perceived in C18:3 mixtures showed a higher score in the presence of iron. Iron also produced a better discrimination in C18:3 mixtures, which were closely related to 'grassy' notes in the presence of cysteine and ribose.     

Potent odorants formed by lipid peroxidation as indicators of the warmed-over flavour (WOF) of cooked meat

Hexanal (I), 1-octen-3-one (II), (E,E)-2,4-nonadienal (III), (E,E)-2,4-decadienal (IV) andtrans-4,5-epoxy-(E)-2-decenal (V) were quantified in cooked meat (beef, pork, chicken) in which the warmed-over flavour (WOF) was observed after storage for 2 days at 4°C. Odour activity values of the compounds on the basis of odour threshold values in water revealed that compounds I and V contributed most strongly to WOF. During the storage, free iron but not metmyoglobin catalysed the increase of compounds I, II, IV and V in models containing the lipids of beef meat.     

Contributions of non-volatile and volatile compounds to the umami taste and overall flavour of shiitake mushroom extracts and their application as flavour enhancers in cooked minced meat

Aqueous extracts of dried shiitake mushrooms (Lentinus edodes) were prepared as taste and flavour enhancers for meat formulations. Effects of time and temperature on the chemical and sensory properties of the extracts were examined. Extracts prepared at 70 °C had significantly higher concentrations (p < 0.001) of the savoury tasting 5′-ribonucleotides than those prepared at 22 °C but increasing the extraction time from 30 to 360 min only increased their recovery slightly (p = 0.053). In contrast, higher temperature extracts had considerably smaller concentrations of the major volatile compounds, such as lenthionine, 1-octen-3-ol, 1,3-dithiethane and dimethyl disulfide, because of loss through volatilisation.