Fatty acid and aldehyde composition of individual phospholipid classes of rabbit skeletal muscles is related to the metabolic type of the fibre

The fatty acid composition of individual phospholipid classes as related to metabolic type of fibre in the rabbit was studied. The fatty acid composition of the individual phospholipid classes of five muscles were compared: two glycolytic ones (Longissimus lumborum and Psoas major), two oxidative ones (Soleus and Semimembranosus propriosus,) and an intermediate one (Gastrocnemius laterale). It was shown that except for phosphatidyl inositol (PI), the fatty acid compositions of the main phospholipid classes were strongly related to the metabolic type of the fibres; phosphatidyl ethanolamine (PE) of oxidative muscles contains less 18:2 n-6 and more 18:0 and long chain PUFA of the n-6 and n-3 series than that of glycolytic ones; phosphatidyl choline (PC) of oxidative muscles contains more 18:0 and less 16:0 and 18:2 n-6 than that of glycolytic ones; cardiolipin of the oxidative muscles contains less 18:2 n-6 than those of the glycolytic ones. These differences in fatty acid composition of PE, PC and cardiolipin explain a large part of the differences in fatty acid compositions of the total phospholipids of glycolytic and oxidative muscles.     

Assessment of protein changes in farmed giant catfish (Pangasianodon gigas) muscles during refrigerated storage

Farmed giant catfish (Pangasianodon gigas) muscles (dorsal and ventral sites) were stored in a refrigerator (at 4 °C) for 14 days to determine the effect of refrigerated storage on biochemical and physical changes. The analyses were carried out at 0, 2, 4, 7, 10 and 14 days of storage. At day 14, Ca²⁺ ‐ATPase activity markedly decreased when compared to its value at day 1 (>90%), while a small decrease was observed for surface hydrophobicity and reactive sulfhydryls content. Total volatile basic nitrogen and trichloroacetic‐soluble peptide content gradually increased when the storage period was extended. The myosin heavy chain decreased slightly on SDS‐PAGE for both meat cuts with increased storage time. Expressible drip and cooking loss were highest during the first day of storage and slightly decreased with storage time. Instrumental hardness was significantly higher in the ventral compared to the dorsal muscle, while the toughness was the highest at the second day of storage. The muscle bundles with scanning electron microscopy were less attached, resulting in the observed big gaps over increasing storage time. Results indicated that changes of proteins have detrimental effects on the quality attributes of farmed giant catfish muscles during refrigerated storage, particularly physical and biochemical properties.     

The effect of dietary oregano essential oil on microbial growth of rabbit carcasses during refrigerated storage

The effect of dietary supplementation with oregano essential oil on microbial growth of rabbit carcasses during refrigerated storage was investigated. A total of 45 weaned rabbits were separated into three equal groups with three subgroups each. One group was given the basal diet and served as control and the other two groups were administered diets supplemented with oregano essential oil at levels of 100 and 200 mg/kg diet, respectively (OR100 and OR200 groups). Total viable counts, Pseudomonas spp., lactic acid bacteria, Brochothrix thermosphacta, Enterobacteriaceae and yeast and mould counts, as well as off-odours and appearance of slime were all assessed on rabbit carcasses stored at 3 ± 1 °C for 12 days. The results showed that performance parameters were not affected (p > 0.05) whereas the dietary supplementation with oregano essential oil resulted in lower (p < 0.05) average microbial counts on the carcasses, compared to controls, throughout storage. Dietary supplementation with oregano essential oil at 200 mg/kg was more effective in inhibiting microbial growth compared with 100 mg/kg. Sensory evaluation scores indicated that the carcasses obtained from OR100 and OR200 groups gave a noticeable putrid odour after days 8 and 10, respectively, whereas the control carcasses developed off-odours after the 6th day of storage. Slime formation in the controls was observed after day 6, while the OR100 and OR200 groups were just beginning to show slime after days 8 and 10, respectively.     

Texture changes in fresh cut celery during refrigerated storage

The effect of refrigerated storage temperature (0 or 10 °C) on variations in texture and lignin content of minimally processed celery was assessed. In addition, the evolution of soluble phenols was studied, as well as changes in other quality parameters, namely weight loss, surface colour and contents of chlorophyll and free sugars. To this end, celery cuts were packaged on PVC film‐covered polystyrene trays. The maximum shear force required to cut the strips transversally followed a similar tendency during storage at both temperatures tested. Increases in lignin content were observed which could be related to corresponding texture increases during the first few days in cold storage. There was no evidence that lignification occurred by a cicatrix‐forming process in the wounds caused during cutting. Copyright © 2003 Society of Chemical Industry     

Antioxidant responses in minimally processed celery during refrigerated storage

This work studies the effect of storage temperature (0, 4 and 10 °C) and time on the antioxidant capacity of cut celery packaged in polystyrene trays sealed with PVC film. Samples were taken at 0, 7, 14, 21 and 28 days of storage to determine total phenols, chlorogenic acid and ascorbic acid. The browning potential and antioxidant capacity of the product were also evaluated. The antioxidant power presented similar behaviour for the three temperatures tested, decreasing after the first 7 days and then increasing up to day 14. Such increase coincided with an elevation of the ascorbic acid content, which was stronger for higher temperatures. As a general conclusion, minimally processed celery retained its initial antioxidant capacity for a period of 21 days at 0 °C, showing the lowest levels of browning potential at this temperature.     

New packaging strategies to preserve fresh-cut artichoke quality during refrigerated storage

The influence of both post-harvest treatments and film permeability on the quality loss kinetic of minimally processed artichokes is assessed in this study. In particular, fresh-cut artichoke heads were subjected to dipping in citric acid/calcium chloride water solution, and coating with citric acid loaded sodium alginate, respectively. Three different packaging materials were used: a polyester-based biodegradable film, an aluminum-based multilayer film, and a commercially available oriented polypropylene film. Artichokes quality loss kinetic during storage was determined by monitoring produce appearance, weight loss, pH, and viable cell load of the main spoilage microorganisms. Results suggest that among the selected treatments, coating shows the best performance in terms of artichokes shelf life. As far as the packaging material is concerned, the biodegradable film tested in this work seems to be the most suitable packaging to preserve the quality of the coated fresh-cut produce.Industrial relevance: Fresh-cut vegetables market has grown rapidly in recent years as a result of changes in consumer attitudes. There is a real need to find methods for preservation of minimally processed food products that can gain widespread acceptance by the industry. This paper suggests effective packaging solutions to delay the quality decay kinetic of fresh-cut artichokes. Moreover, the present study proposes a new “green packaging system” that could emphasize the relevance of the obtained results due to the increased attention to the environmental impact.     

Viability of bifidobacteria in commercial dairy products during refrigerated storage

Commercial milk and two brands of yogurt containing bifidobacteria were obtained from retail outlets. All products were evaluated for viability of bifidobacteria and lactic acid bacteria during refrigerated storage at 4 degrees C. Milk was evaluated at 9, 6, and 3 days prior and past its expiration date. The yogurts were evaluated at 3, 2, and 1 week prior and past their expiration. Viability of bifidobacteria and lactic acid bacteria in milk and yogurt remained above 10(6) CFU/ml or g until the expiration date of the respective products. This microbial concentration is the recommended minimum dose to receive the health benefits of these organisms.     

Survival of probiotic microflora in Argentinian yoghurts during refrigerated storage

The survival of Bifidobacterium bifidum BBI and Lactobacillus acidophilus LAI in reduced-fat (liquid) and full-fat (set) yoghurts produced with two commercial lactic starter cultures (SID and SISD) was investigated. The viability of the probiotic bacteria was also assayed in milk acidified with lactic acid at different pH values. Samples were stored at 5°C for up to 4 weeks. There was a great variability in the survival ability of the probiotic cultures in the two yoghurt types. L. acidophilus LAI demonstrated, in general, a lower resistance to the yoghurt environment than B. bifidum BBI. On the other hand, the full-fat yoghurt was a more inhibitory medium than the reduced-fat one, especially for B. bifidum BBI. Regarding the lactic starters used, the results showed that the culture SISD was clearly more inhibitory for both probiotic organisms than the culture SID. The loss of cell viability in yoghurt samples was different (higher in some cases and lower in others) from that due to lactic acid only. In general, pH values of 4.5 or lower jeopardised the cell viability of the probiotic organisms in yoghurt stored at 5°C. This work shows the importance of selecting a suitable combination of probiotic strains and starter cultures when different yoghurt types are formulated.     

Viability of microencapsulated bifidobacteria in set yogurt during refrigerated storage

Bifidobacteria are probiotic organisms that improve the microbial balance in the human gut. They can be incorporated as live cultures in fermented dairy foods, including yogurt, for transmission to humans. Because bifidobacteria are sensitive to high acidity, their viability in yogurt is limited. The objective of the present study was to investigate the effect of microencapsulation on the viability of bifidobacteria in yogurt during refrigerated storage for 30 d. Live bifidobacterial cells were encapsulated in kappa-carrageenan. Cell enumeration, determination of titratable acidity and pH, quantitation of lactic and acetic acids, and sensory evaluation (consumer test) were carried out on the yogurt samples. Microbiological results showed a decline of 78 and 70.5% in the population of Bifidobacterium longum B6 and B. longum ATCC 15708, respectively, for the treatments containing nonencapsulated cells. No difference in bifidobacterial population was observed in the encapsulated treatments. The acetic acid content in the yogurt with nonencapsulated bifidobacteria was higher than that in the plain yogurt (control) and encapsulated treatments. The increase in lactic acid content during storage was not different among the various treatments for B. longum B6, but was greater for nonencapsulated than encapsulated B. longum 15708 and the control. Consumers judged the nonencapsulated treatment as the most sour, which was likely due to the higher acetic acid content. Consumers preferred the control and nonencapsulated treatments over the encapsulated treatment. Microencapsulation appears to increase the viability of bifidobacteria in yogurt. This technique can be used to transmit bifidobacteria via fermented products provided that sensory characteristics of the product are improved or maintained.     

Lipid composition of pork muscle in relation to the metabolic type of the fibres

The aim of this study was to investigate the relationships between lipid composition and metabolic type of the muscles in pork. Five muscles (Longissimus dorsi, Biceps femoris, Psoas major, Trapezius and Masseter) were chosen in order to cover a broad range of metabolic type. The results showed that:     

Lipid characteristics associated with oxidative and glycolytic fibres in rabbit muscles

The purpose of this study was to specify the intramuscular lipid characteristics which are related to the metabolic type of muscles. Two glycolytic muscles (Longissimus lumborum and Psoas major), two oxidative ones (Soleus and Semimembranosus propriosus) and an intermediate one (Gastrocnemius laterale) were dissected from rabbit carcasses. The results showed that:

1. (a) The glycolytic muscles contain less total lipids, triglycerides and cholesterol than the oxidative ones.

2. (b) Phospholipid content, cardiolipin and PE proportions were lower and PI proportion was higher in the glycolytic muscles than in the oxidative ones.

3. (c) The phospholipids of the glycolytic muscles contain more 16:0 and 18:2 n−6 but less 18:0 and long chain polyunsaturated fatty acids (20:4 n−6, 22:5 n−6 and n−3) than those of the oxidative muscles.

     

Investigation of molecular changes in wine during storage in refrigerated cabinets

Wine is a complex chemical mixture that is bound to change over time. Most wines are produced for consumption within months. Some premium wines are meant to be maturated for several years or even decades after bottling. The post-bottling evolution and the longevity of a wine depends on its initial chemical composition and the storage conditions. Temperature, exposure to light and the closure type are often mentioned as the most important storage influences. Especially elevated temperature is known to cause accelerated aging reactions in wine. Refrigerated wine storage cabinets promise to be the best storage option without the need of a wine cellar. They are available in different sizes and fit in every household. However, the influence of vibrations and low-interval temperature fluctuations caused by compressors are parameters that have been neglected in literature. The aim of this thesis was to investigate if vibrations and low-interval temperature fluctuations, which occur in refrigerated wine storage cabinets, have an influence on the post-bottling evolution of a wine. The influence of both parameters was studied separately from each other. The impact of vibration on oxidation and gas uptake from the headspace of a wine bottle into the wine was investigated using a model wine with saturated O2 and different headspace volumes. The study revealed that vibration promotes the dissolution of O2 from the headspace of bottle into the wine resulting in a faster SO2 consumption. Furthermore, it was shown that horizontal bottle position accelerated the O2 uptake significantly. It was concluded that the increased surface size between headspace and wine accelerates the O2 dissolution in wine. Also, bigger headspace volumes caused an accelerated O2 uptake into the wine. An experiment without any headspace volume revealed that the factors vibration and bottle position did not accelerate the O2 consumption in wine. This proves that vibration and bottle position accelerate only the dissolution of O2 in wine, but not the chemical reaction of O2 with wine constituents. The influence of vibration on the volatile profile of wine was investigated using Riesling sparkling and still wines sealed with different closures that were subjected to vibration for six months. Vibration caused no CO2 losses, SO2 and color changes in all wines indicating that vibration caused by compressors has no impact on the gas permeability of the used closures. However, vibration affected the volatile profile of sparkling wine and Riesling still wine sealed with a screw cap. Similar to the model wine study described earlier, it was shown that the equilibrium of volatile substances between the wine and the headspace in a bottle was influenced by vibration. The gas-liquid-equilibrium of some volatile compounds was shifted towards wine, while others were shifted towards headspace. As a result of this, the concentration of volatile compounds in wine is changed. Besides this indirect influence of vibration, the results of this study also suggested that specific degradation and formation reactions of volatile compounds are directly influenced by vibration. These multiple effects of vibration most likely explain why increasing vibration intensities could not be proportionally related to the observed volatile changes. The investigation of different wine styles revealed that the impact of vibration depends strongly on the initial composition of wine, age, and packaging conditions. Especially, headspace volume, closure type and CO2 pressure are likely to influence the equilibrium of volatile substances between the wine and the headspace in a bottle. Another study investigated the impact of low-interval temperature fluctuations on the volatile profile of wine. For this purpose, a Riesling wine was stored for two years under different temperature fluctuation patterns caused by compressors. Additionally, a model wine with nine volatile substances with known concentrations was stored for eight months under the same fluctuation patterns. The low- interval temperature fluctuations were compared to the mean value of the temperature fluctuations. Chemical and sensory analysis revealed that that low-interval temperature fluctuations accelerate wine aging reactions like ester hydrolysis and monoterpene degradation. Even small temperature amplitudes showed a significant impact on wine aging. The observed effect was explained by the Arrhenius equation which states that reaction rates exponentially increase with rising temperatures. A pump effect of air through the closure was initially assumed but not observed in this study. Small deviations in wine temperature, such as those caused by door openings of a refrigerator were found to be negligible. It was concluded that low-interval temperature fluctuations can accelerate wine aging reactions. The amplitude of the temperature fluctuations should be as small as possible during bottle storage of wine. This thesis showed that both parameters, vibration, and low-interval temperature fluctuations, have been proven to influence the evolution of wine during bottle storage. Regarding storage conditions in a refrigerated wine storage cabinet, those parameters should be monitored. Wine connoisseurs should therefore consider good wine cabinets, since some manufacturers emphasize on the importance to minimize vibrations and temperature fluctuations in their devices. The development of technology should be advanced to reduce both vibration and temperature fluctuations in refrigerated wine storage cabinets. Future research should focus on specific wine compounds in model systems and realistic vibration conditions to reveal the relationship between vibration intensities and reaction rates. The impact of low-interval temperature fluctuations on wine compositional changes should be investigated considering horizontal and vertical bottle positions. The calculated acceleration factors due to temperature fluctuations have to be verified by isotherm storage conditions at higher temperatures.     

鲟鱼肉冷藏期间腥味及品质变化

为探明鲟鱼肉冷藏过程腥味形成规律及其影响因素,文中研究分析了鲟鱼背部、腹部和尾部肌肉组织品质指标和鱼腥味变化情况。结果表明:冷藏前期3个部位的鱼肉挥发性盐基氮(TVB-N)值增加缓慢,5 d后TVB-N呈现快速增长,表明鱼肉开始出现微生物腐败迹象。表征脂肪氧化程度的硫代巴比妥酸值(TBARS)冷藏前期增幅缓慢,第3天后增幅加速,脂肪氧化速度加快;冷藏期间脂肪氧化酶(LOX)活性呈先升高后降低的趋势;冷藏2 d后鱼体主要不饱和脂肪酸下降幅度加快,挥发性物质总量增加明显。对鱼肉冷藏期间挥发性物质风味特征进行分类分析表明,鱼肉冷藏过程中以鱼腥味、青草味及脂肪氧化气味变化为主,其中以鱼腥味变化最为突出。将贮藏过程中鱼肉品质指标与鱼腥味变化规律进行分析发现,鱼腥味等异味的产生主要是由脂肪氧化所致,后期微生物腐败对鲟鱼肉风味变化起协同作用。     

Effects of sunflower honey on the physicochemical,microbiological and sensory characteristics in set type yoghurt during refrigerated storage

The primary purpose of this research was to monitor the influence of sunflower honey addition (2%, 4% and 6% w/v) to yoghurt milk on survival of the microbial flora of yoghurt and the physicochemical and sensory characteristics during refrigerated storage for 4 weeks. The water activity decreased according to the addition of honey with higher concentrations in the storage period (4°C). At the end of fermentation, pH values of yoghurt samples ranged between 4.33 (without honey) and 4.52 (addition of honey with 6%). The highest water holding capacity, consistency and the lowest brightness values were determined in the groups produced with 6% honey addition. The water holding capacity and a* (redness) values of the honey incorporated yoghurt samples increased during storage. Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus values of the yoghurt with honey increased compared with the control group samples (P < 0.01). Addition of honey to yoghurt milk has affected the vitality of the characteristics starters in the incubation and storage time of the yoghurt samples (P < 0.01). Optimum sweetness was obtained with the samples containing 4% honey level.     

Quantitative changes in anthocyanin pigments of lychee fruit during refrigerated storage

Changes in cyanidin-3-glucoside, cyanidin-3-rutinoside, malvidin-3-acetylglucoside, total anthocyanins, percent polymeric color and browning indexes in stored lychee (Litchi chinensis Sonn.) fruits were determined. Total anthocyanin content declined from 1·77 to 0·73 mg/g fresh weight, and individual anthocyanins also decreased throughout the 48-day storage period. Decline in anthocyanins was accompanied by an increase in browning. Polymeric pigments also gradually increased from 20·9 to 53%.     

Role of yeast proliferation in the quality degradation of strawberries during refrigerated storage

Quality changes of strawberries during storage can be caused both by microbiological and physiological processes. There is little known about the possible contribution of microbiological processes to the quality degradation of strawberries. In this study, quality of strawberries during storage was evaluated by analytical and sensorial analyses. It was the aim to investigate the influence of microbiological activity on the changes of different quality factors of strawberries during storage. During storage at 7 degrees C, quality was mainly determined by the odor and by visual defects. Regarding the odor, highly microbiologically contaminated late-season strawberries packaged in air at 7 degrees C became sensorially unacceptable due to the presence of high amounts of ethyl acetate. This could be attributed to the yeast proliferation: at yeast concentrations above 5.0 log cfu/g, an increase in ethanol was detected in the headspace of the strawberries. It was shown that ethanol was converted to ethyl acetate by strawberries resulting in an unacceptable odor. In an experiment with low microbiologically contaminated early-season strawberries, not reaching the above mentioned yeast counts, less ethyl acetate was detected which resulted in strawberries that were sensorially acceptable during the whole storage period (12 days). Strawberries packaged in modified atmosphere conditions showed a different quality pattern due to the effect of decreased O2-concentrations on both microbiological and physiological processes. This paper demonstrates that also microbiological processes on strawberries should be considered as they could play an important role in the sensorial quality when interacting with physiological processes.     

Proteolysis of ultra-high pressure homogenised treated milk during refrigerated storage

Plasmin residual activity and its relation to proteolysis of milk subjected to ultra-high pressure homogenisation (UHPH; 200–300 MPa, inlet temperature = 30 °C and 40 °C) and to a high-pasteurisation treatment (90 °C, 15 s) were studied during refrigerated storage. Proteolysis was examined by capillary electrophoresis, HPLC peptide profiles, pH 4.6-soluble nitrogen and free amino acids. Inactivation of plasmin increased as homogenisation pressure did. Extensive proteolysis, was observed in 200 MPa 40 °C milk, due to its higher native and microbial enzyme contents, compared with the other samples. In general, hydrolysis of β-casein, hydrophobic peptide and pH 4.6-soluble nitrogen levels increased with higher residual plasmin activity, while hydrophilic peptides were not affected by the different treatments applied. β-Lactoglobulin was denatured to a greater extent by thermal treatment than by UHPH treatments. This study provides further insight into how UHPH treatments influence milk properties.     

冷藏中低聚果糖对发酵乳中微生物的影响

对添加低聚果糖的原料奶，使用嗜酸乳杆菌、双歧杆菌和嗜热链球菌作为快速发酵剂进行发酵后．在4℃条件下储存42d。每周对发酵乳进行微生物分析和酸度测试。结果表明，低聚果糖质量浓度在10—50g／L时对嗜酸乳杆菌和嗜热链球菌的存活都没有太大影响。双歧杆菌活菌数下降幅度比嗜酸乳酸杆菌和嗜热链球菌要快。但添加低聚果糖对双歧杆菌的存活起到重要作用。结论是低聚果糖产品对双歧杆菌有益生作用，因此在冷藏发酵乳制品中有助于提高双歧杆菌活菌数。     

Changes of soybean quality during storage as related to soymilk and tofu making

ABSTRACT:  Soybeans are stored and transported under various humidity and temperature conditions. Soymilk and tofu are two of the most important foods made from whole soybeans. The objective of this study was to investigate the influence of storage conditions on soybean quality as related to soymilk and tofu-making properties. Soybeans of 3 different genotypes (Proto, IA2032, and Vinton 81) were stored in varying conditions: temperature ranging from 4 to 50 °C, relative humidity from 55% to 80%, initial moisture content from 6% to14%, and storage time up to 15 mo depending upon storage conditions. The effects of different storage conditions on soybean color, solids and protein extractability, soymilk pH, tofu yield, tofu solids and protein contents, tofu color, and texture were investigated. While no significant changes occurred for the soybeans stored at 4 °C, the soybeans stored at high temperatures (30 to 50 °C) exhibited significant quality loss ( P < 0.05). The degradation of soybean lightness (Hunter L ), color difference (Δ E ), and solid extractability exhibited a linear relationship with time. Soak weight decreased at high temperature and relative humidity, but increased at mild storage conditions. Several combinations of storage conditions at temperatures exceeding 30 °C produced a drastic loss in tofu yield. Storage also affected the tofu making process by reducing optimum mixing time to produce the highest tofu yield. Varietal difference in soybean storability was observed. The results provided useful information for the soybean processing industry to store soybeans using the optimal storage conditions and to estimate soybean quality after storage.