Superchilled,chilled and frozen storage of Atlantic mackerel (Scomber scombrus) – effect on lipids and low molecular weight metabolites

Quality changes in Atlantic mackerel fillets during superchilled, chilled and frozen storage focusing on lipid quality, colour and changes in low molecular weight metabolites relevant for quality and safety were studied. Low formation of oxidation products was observed in chilled (up to 7 days), superchilled (up to 14 days) and frozen storage (up to one year). Only slight formation of TBARS was measured in the samples which correlated with the increasing fillet yellowness. The profile of low molecular weight compounds, analysed by high-resolution NMR, showed clear grouping of the different samples according to both treatment and storage time. The increase in K-value was highest in the chilled samples, reaching a K-value of 93 ± 3% on day 5, exceeding the proposed limit of human consumption (80%) while superchilling reached a K-value of ca 90 % after 14 days. Frozen samples showed acceptable quality in the whole storage period.     

Endotoxin and biogenic amine levels in Atlantic mackerel (Scomber scombrus), sardine (Sardina pilchardus) and Mediterranean hake (Merluccius merluccius) stored at 22 °C

Whole Atlantic mackerel (Scomber scombrus), sardine (Sardina pilchardus) and Mediterranean hake (Merluccius merluccius) from the Croatian Adriatic were stored at 22 °C and changes in histamine, putrescine, tyramine and cadaverine levels were monitored in relation to bacterial endotoxin. After 12 h, histamine levels in sardine were above the legal limit of 50 mg kg^?1, set by the US Food and Drug Administration, and an increase in putrescine content preceded the increase in histamine. After 24 h, histamine contents in mackerel and sardine reached 1090 ± 101 and 577 ± 275 mg kg^?1, respectively, which exceeded the toxic threshold of 500 mg kg^?1. At the same time, the putrescine content was also high in both fish (353–420 mg kg^?1). The time-course of endotoxin production was similar in all fish species stored at 22 °C. A high correlation was found between endotoxin and histamine, and between endotoxin and putrescine in mackerel and sardine. On the other hand, high endotoxin levels in hake, after 24 h, were associated with the low histamine and putrescine content (40–60 mg kg^?1).     

Effect of natural and synthetic antioxidants on protein oxidation and colour and texture changes in refrigerated stored porcine liver pâté

The antioxidant effect of two plant essential oils (sage and rosemary) and one synthetic antioxidant (BHT) on refrigerated stored porcine liver paté (4°C/90 days) was evaluated. Patés with no added antioxidants were used as controls. Liver patés were analysed for protein oxidation, modification of heme (HI) and non-heme iron (NHI) concentrations, and colour and texture characteristics at days 0, 30, 60 and 90 of refrigerated storage. The amount of carbonyls from protein oxidation significantly (p<0.05) increased during refrigerated storage, and this increase was significantly higher in the control patés than in their treated counterparts. Antioxidants successfully protected heme molecules from degradation and significantly inhibited the increase of NHI in refrigerated stored liver patés. Colour changes seemed not to be directly related to oxidative processes since patés with added antioxidants suffered greater colour modifications than the controls. The addition of rosemary essential oil significantly reduced hardness of liver patés. Sage and rosemary essential oils exhibited similar antioxidant properties to BHT denoting their suitability as alternatives to synthetic antioxidants.     

Effect of rosemary extract, chitosan and α-tocopherol on lipid oxidation and colour stability during frozen storage of beef burgers

The effect of rosemary extract, chitosan and α-tocopherol, added individually or in combination, on lipid oxidation and colour stability of frozen (−18 °C) beef burgers stored for 180 days was investigated. The burgers’ lipid oxidation and appearance were evaluated through measurement of primary (conjugated dienes and peroxide value) and secondary (malondialdehyde) oxidation products, together with visual assessment and instrumental measurement of colour. Chitosan alone and in combination with either rosemary or α-tocopherol had the best antioxidative effect (P ? 0.05) compared to individual use of rosemary or α-tocopherol, while the best results were obtained with the combination of chitosan and rosemary. The differences of antioxidative effects, however, between individual use of rosemary or α-tocopherol as compared to the controls were also significant (P ? 0.05). Chitosan added individually or in combination with either rosemary or α-tocopherol had also a noteworthy effect on the burgers’ appearance as it contributed to red colour retention for a much longer period (P ? 0.05) compared all other treatments and the controls. In conclusion, the best antioxidative effects were obtained with the combination of chitosan and rosemary extract.     

Dehydration of salmon (Atlantic salmon), beef,and apple (Granny Smith) using Refractance window™: Effect on diffusion behavior,texture, and color changes

The aim of this research was to study the use of Refractance window™ (RW™) in the dehydration of salmon (Atlantic salmon), beef (lean), and apples (Granny Smith) through the analysis of the effective diffusivity determined through the Fick's model and the anomalous model.Salmon, beef, and apple slices were dried at 55 and 95 °C, using either a conventional drying process or RW™. Water activity (a_w) was measured periodically by drying, and the effective diffusion (D_eff) was measured using Fick's second law and an anomalous model. Color changes (∆E) and firmness were also measured.The results showed that mass transfer in salmon and beef was not improved by RW™. In contrast, in apple slices dehydrated using RW™, the D_eff and processing times were significantly (p < 0.05) affected, reflecting a reduced drying time required to attain an a_w of 0.6.RW™ is a powerful tool that allows for the dehydration of fruit using temperatures of 95 °C and provides a 50% reduction in drying time.     

Effects of red beet extracts on protein and lipid oxidation,colour, microbial,sensory properties and storage stability of Turkish pastırma

Lipid oxidation and discoloration are two important problems in the storage of pastırma, a meat product. In this research, the usability of lyophilized red beet water extract (LRBWE) in cemen paste and its effects on the pastırma quality (especially colour, protein and lipid oxidation, microbial and sensory properties) were investigated during storage. Two trials were conducted; in trial 1, LRBWE was obtained, its various properties were designated and effects on the cemen paste of these extracts (0.0%, 0.4%, 0.6%, 0.8% 1.0% and 1.2%) were determined. In trial 2, pastırma with cemen paste containing 0.8%, 1.0% and 1.2% LRBWE were produced and stored at 4 ± 1 °C for 150 days. The LRBWE did not influence protein oxidation of pastırma, whereas increasing LRBWE level led to a decrease in lipid oxidation (P < 0.01), and an increase in redness (a1) value (P < 0.01) and sensory properties (P < 0.01) of sliced pastırma compared with control pastırma. These results revealed that the addition of 1.0% or 1.2% LRBWE to cemen paste was effective to improve the colour stability, lipid oxidation, microbial and sensory quality of pastırma during storage.     

Lipid and protein oxidation, release of iron from heme molecule and colour deterioration during refrigerated storage of liver pâté

In the present work, lipid and protein oxidation, increase of non-heme iron (NHI) content and colour changes occurring during refrigerated storage (90 days/4 °C) of liver pâtés from Iberian and white pigs were studied. Iberian pigs were reared outdoors and fed on natural resources (grass, acorns) while white pigs were intensively reared and fed on a mixed diet. Lipid and protein oxidation were, respectively, measured by determining TBA reactive substances (TBARS) and protein carbonyl groups. Pâtés from Iberian pigs had better oxidative stability at all stages of storage, having lower amounts of TBARS and carbonyls compared to those from white pigs (p<0.05). NHI increased during refrigerated storage of liver pâtés, with those from white pigs having a higher amount of NHI at all stages of storage (p<0.05). During refrigerated storage, L^*-values tended to increase while the evolution of a^* and b^* depended on the group and did not seem to be related to the oxidative processes.     

Freezing-induced changes in goat cheese: Effect of freezing rate,storage and freeze–thaw cycles

This study compared the effect of various freezing set-ups [freezing in the walk-in freezer (WF), blast freezing and liquid nitrogen freezing (LNF)] on the textural properties of goat cheeses. The influences of freeze–thaw cycles (1, 3 and 5) and storage time (1, 7 and 14 days) at 4°C on the hardness and visual appearance were investigated. The results showed that freezing damaged the cheese structure, particularly for WF. Frozen samples were not suitable for 4°C storage. Freeze–thaw cycles further damaged the texture of both cheese logs and crumbles, resulting in increased dryness. The development of the dry structure was faster for the LNF-treated sample.     

Cholesterol oxidation in frozen dark chicken meat: influence of dietary fat source, and α-tocopherol and ascorbic acid supplementation

A factorial design assessed the effect of dietary fat source (beef tallow, fresh and oxidized sunflower oils, and linseed oil), and α-tocopheryl acetate (α-TA) and ascorbic acid (AA) supplementation (225 and 110 mg/kg feed, respectively) on the cholesterol oxidation product (COP) content and 2-thiobarbituric acid (TBA) values in raw and cooked dark chicken meat vacuum packaged and stored at -20°C for 7 months. COP determination showed good linearity, recovery and precision. Dietary α-TA was highly effective in protecting raw or cooked meat from cholesterol and fatty acid oxidation, regardless of its degree of unsaturation. In contrast, AA supplementation was ineffective and even promoted oxidation in raw meat from broilers fed unsaturated fat diets that had not been supplemented with α-TA. Oxidation values (raw or cooked meat) from α-TA or α-TA+AA supplemented diets were not statistically different (P>0.05). TBA and COP values were significantly correlated in raw samples (r=0.6466, P=0.0001).     

Determination of protein in foods: comparison of net protein and crude protein (N × 6.25) values

The purpose of the present study was: (1) to determine net (true) protein (NP) values as sums of amino acid residues and to compare them with crude protein (PA) values; and (2) to calculate the nitrogen-to-NP conversion factors by means of linear regression analyses between the NP values and nitrogen content. The differences between NP and PA values varied between food groups. The NP values in milk and milk products were, on average, 5.5% smaller than the corresponding PA values. The corresponding figures for other foods were: meat and meat products 15.4%, fish and fish products 20.6%, cereals and bakery products 12.2%, vegetables, fruits and berries 13.9% and miscellaneous processed foods 16.1%. In the present study the nitrogen-to-NP conversion factor for milk and milk products was 5.94, meat and meat products 5.17, fish and fish products 4.94, cereals and bakery products 5.40, vegetables, fruits and berries 5.36 and miscellaneous processed foods 5.51; the general conversion factor for all foods was 5.33. The above respective factors were 5.0, 17.3,21.0, 13.6, 14.2, 11.8 and 14.7% smaller than the official factor of 6.25. We conclude that the traditional PA values (N × 6.25) deviate significantly from the NP values. We recommend that protein definitions and methods of determination should be re-evaluated in the appropriate international organizations and updated in line with current knowledge and analytical capabilities for both scientific and other purposes.     

Impact of selected factors – Cultivar,storage, cooking and baking on the content of anthocyanins in coloured-flesh potatoes

The impact of selected factors – cultivar, storage, cooking and baking on the content of total anthocyanins (TAC) in coloured-flesh potato cultivars has been studied. TAC ranged from 248.5 to 2257.8 mg kg⁻¹ dry matter (DM). TAC difference between cultivars was statistically significant. Cold storage (4 °C) influenced TAC differentially. In the Violette and Highland Burgundy Red cultivars TAC increased by 18.5% and 12.1% respectively, and in the Valfi cultivar it decreased by 33.9%. Baking increased TAC 3.34 times whereas cooking in boiled water increased it 4.22 times. Correlation between antioxidant activity (AOA) and TAC (r² = 0.659) has been found. The Violette, Vitelotte and Highland Burgundy Red cultivars with the highest TAC showed high AOA and the Shetland Black cultivar and the cultivars Salad Blue and Blue Congo with a “marbled” texture showed the lowest TAC and AOA. Individual anthocyanidins are fingerprints of colour-fleshed potato cultivars.     

Ageing of large cuts of beef loin in vacuum or high oxygen modified atmosphere – Effect on shear force,calpain activity,desmin degradation and protein oxidation

The aim was to investigate the effect of ageing large beef cuts directly in high oxygen modified atmosphere (MA) and how ageing time in vacuum influence meat quality when followed by retail packaging in high oxygen MA. Large cuts (10 cm long) of beef loin (LD) were aged for up to 25 days postmortem in different ageing systems at 4 °C. Ageing solely in high oxygen modified atmosphere (MA, 80% O₂ + 20% CO₂) for 5 or 10 days and ageing in vacuum for 5 or 15 days followed by high oxygen MA for 5 or 10 days were compared with ageing in vacuum for 5, 15 and 25 days. Warner–Bratzler shear force, purge and cooking losses, calpain activity and desmin and carbonyl contents were measured. Shear force decreased to the same level when ageing this large beef cut solely in high oxygen MA for 5 or 10 days as when ageing in vacuum. The activity of μ-calpain disappeared, the activity of m-calpain decreased and purge loss increased between 5 and 10 days, but cooking loss and the contents of desmin and carbonyls were unaffected. The ageing time in vacuum before packaging of this large beef cut in high oxygen MA did not affect the ultimate shear force. The m-calpain activity decreased and the content of carbonyls increased compared with solely in vacuum after 15 days of total ageing, but there was no difference in the content of desmin or cooking loss between these ageing systems at the same ageing time.     

Mechanical and microstructural properties of soy protein – high amylose corn starch extrudates in relation to physiochemical changes of starch during extrusion

Mechanical and microstructural properties of expanded extrudates prepared from blends of high amylose corn (Zeamays L. ssp. Mays) starch (HACS) and soy protein concentrate (SPC) were studied in relation to the physicochemical changes in starch. Effects of screw speed (230 and 330 rpm) and SPC level (10%, 20%, 30% and 50%) on expansion and mechanical properties were determined. Compared with 230 rpm, screw speed at 330 rpm resulted in increased specific mechanical energy, expansion ratio, water absorption and water solubility indices and decreased bulk density and piece density. Varying screw speeds did not significantly affect the mechanical strength of extrudates or starch molecular weight distribution. Bulk and piece densities, and water absorption index (WAI) only slightly increased or exhibited no significant trends as SPC level increased to 20%. A substantial increase in bulk and piece densities and decrease in expansion ratio and WAI were observed as SPC level increased from 20% to 30%. The trends were either reversed or moderated as SPC increased to 50%. These results in combination with average crushing force and water solubility index data provided a significant insight into the interactions between HACS and SPC during extrusion processing. As compared to an earlier baseline study by our research group on normal corn starch – SPC extrudates, results from the current study indicated that the expansion of extrudate containing HACS alone was lower than that of extrudates containing normal corn starch. However, expansion of the HACS–SPC blends was not significantly impacted at 10–20% SPC levels, whereas the expansion of normal corn starch was significantly reduced.     

Aroma-volatile profile and its changes in Australian grown black Périgord truffle (Tuber melanosporum) during storage

Black Périgord truffle (Tuber melanosporum) is one of the most expensive fungi in the world that appreciated by gourmets. Studies have indicated the impact of growing location and soil microorganisms on the aroma profile of truffle. The aroma profile of West Australian black Périgord truffle (Tuber melanosporum) has not been previously reported, which was studied over a 14 day storage period. Sixty-four compounds were identified in all truffle samples. Significant changes (P > 0.05) were observed in 11 key volatiles (carbon dioxide, acetaldehyde, 2-butanone, 3-methyl-1-butanal, toluene, 2-butenal, formic acid 2-methyl butyl ester, 3-methyl-1-butanol, 6-methyl-2-heptanol, 3-octanol and dimethyl sulfoxide) over time. Comparison of these results against published aroma profile of European grown black Périgord truffle identified number of significant similarities and differences were also detected. Dimethyl sulfoxide, a compound previously identified in European grown white truffle (Tuber magnatum), was detected. Principle component analysis (PCA) showed that the major changes in the truffle aroma profile took place in the first 7 days of storage.     

Physicochemical and microbiological changes of “Souvlaki” – A Greek delicacy lamb meat product: Evaluation of shelf-life using microbial,colour and lipid oxidation parameters

Fresh Souvlaki-type lamb meat was packaged under vacuum (VP) and modified atmospheres (MAs) and stored under refrigeration (4 °C) for a period of 13 days. The following gas mixtures were used: M1: 30%/70% (CO₂/N₂) and M2: 70%/30% (CO₂/N₂). Identical samples were aerobically-packaged and used as control samples. Quality evaluation of product stored under the above packaging conditions was conducted using physicochemical and microbiological analyses. Of the chemical parameters determined, pH values of product showed no significant differences for all packaging treatments as a function of storage time. Lipid oxidation of lamb meat was enhanced by aerobic storage and gas mixture M1, whereas VP and gas mixture M2 controlled lipid oxidation to a greater extent. Souvlaki colour stability (as determined by a^∗, b^∗ and L^∗ values) was not negatively affected by either VP or MA conditions during the 13 days of storage. Of the two MAs and VP used, gas mixture M2 and VP were the most effective treatments for the inhibition of total viable counts (TVC), Pseudomonas spp., yeasts and Brochothrix thermosphacta in Souvlaki meat. Lactic acid bacteria (LAB) and Enterobacteriaceae were also found in the microbial flora of Souvlaki and increased during storage under all packaging conditions used. Based on microbiological analysis data and on the proposed a^∗ values, the use of VP and MAP (M2: 70%CO₂/30N₂) extended the shelf-life of “Souvlaki” meat stored at 4 °C by approximately 4–5 days compared to aerobic packaging.     

Performance, muscle composition and meat texture in veal calves administered a β-agonist (clenbuterol)

The effect of clenbuterol administration on performance, muscle composition and meat texture was studied in veal calves. Three groups, of ten animals each, were assigned to the three following treatments for 27 days: control, administration of 0·3 and 1·0 ppm in the feed (dry matter basis). After a 14-day withdrawal period, the animals were slaughtered, and three muscles were sampled (M. longissumus thoracis; M. triceps brachii caput longum; M. rectus abdominis). During the period of clenbuterol administration, the treated calves exhibited a higher daily liveweight gain (DLWG) and a higher feed conversion efficiency (FCE) compared to those of the control calves, but these effects were reversed during the subsequent withdrawal period. At slaughter, the overall DLWG, FCE and carcass weight were similar in the three treatments, but the dressing percentage in the clenbuterol-treated calves was up to 5·7 points higher than that of the control calves. In the muscles studied, the clenbuterol had little effect on pH, sarcomere length, dry matter and nitrogen contents, collagen heat stability (solubility, isometric tension) or cooking loss; but it markedly reduced the content of lipids, collagen and haem pigments. The clenbuterol also affected myofibrillar strength after ageing, measured either on raw meat or on cooked meat. This was particularly evident in cooked meat which showed up to a two-fold increase in mechanical parameters (maximum stress, compression modulus) after the clenbuterol treatment. No dose effect was detected except for the mechanical parameters. It was concluded that clenbuterol administration affects, meat in two opposite ways, viz. a marked toughening effects, due to a reduction in the muscle ageing rate, that is not compensated by a concomitant tenderizing effect (through a decrease in the intramuscular collagen content).