大豆分离蛋白-脂质涂层对冷却牛肉品质的影响

研究脂质(硬脂酸、棕榈酸、巴西棕榈蜡和三乙酸甘油脂)与大豆分离蛋白制成的可食性涂层对冷却牛肉品质的影响。考察冷却牛肉在4℃下贮藏108h过程中失重率、颜色、pH值、硫代巴比妥酸值和感官特性的变化。结果表明冷却牛肉在4℃贮藏时的货架期小于108h,而且在4℃贮藏84h后,不同大豆分离蛋白-脂质涂层的优点不同。其中,三乙酸甘油酯蛋白涂层不仅延缓冷却牛肉的氧化,而且有效维持其感官特性,对维持冷却牛肉品质和延长期货架期效果最佳。     

Bunker‐stored silage covered with biodegradable coating. Part I. Laboratory assay

The effect of a hydrophobic biodegradable coating on the conservation of silage was evaluated in comparison with unsealed silage and silage covered with a polyethylene (plastic). Silage samples were subjected to biochemical analysis (pH, dry matter, water‐soluble sugars, ammoniacal nitrogen, lactic acid) and microbiological analysis (total aerobes, lactic acid bacteria, moulds and yeasts) during 135 days of storage. Silage covered with the biodegradable coating had a constant pH value of 4.79 and was preserved against spoilage until day 120, whereas the pH of unsealed silage increased during the first 6 days to a value of 8.22. After 2 months of storage, silage covered with the biodegradable coating had a lower dry matter content, higher water‐soluble sugar content and higher lactic acid concentration than unsealed silage. During storage the population of total aerobes was lower in silage covered with the biodegradable coating than in silage covered with plastic. Furthermore, silage covered with the biodegradable coating had a stable content of aerobic micro‐organisms. The biodegradable‐coated silage showed a growth of lactic acid bacteria similar to that of silage covered with plastic. Only silage covered with the biodegradable coating had a low initial content of moulds and yeasts. Air infiltration was present throughout the storage period in the plastic and biodegradable coating treatments and was linked with the degradation of silage in both cases. However, the biodegradable coating significantly (P ≤ 0.05) increased the period of silage conservation compared with that of uncoated silage. Copyright © 2004 Society of Chemical Industry     

冷鲜牛肉贮藏中菌群结构及优势菌致腐性的分析

为探究牛肉在0?℃冷藏下微生物菌群变化和优势腐败菌,采用培养依赖的16S rRNA结合高通量测序技术分析牛肉样品的微生物多样性变化。通过定期测定接种牛肉汁的生长、感官、蛋白酶活性、pH值和挥发性盐基氮（total volatile basic nitrogen,TVB-N）值,分析分离株的致腐特征。结果表明,牛肉冷藏中感官品质保持良好,15?d出现异味,18?d有腐臭味。而样品中菌落总数第3天快速上升,15?d菌落总数为8.73（lg（CFU/g））,之后呈现稳定,假单胞菌（Pseudomonas spp.）、热死环丝菌（Brochothrix thermosphacta）、肠杆菌（Enterobacter）和乳酸菌4 种分离培养基中细菌与菌落总数增长趋势相似,其中假单胞菌增长最快,肠杆菌数和乳酸菌数生长最慢。两种菌群鉴定结果显示,冷鲜牛肉初始微生物构成复杂,包括热死环丝菌、不动杆菌属（Acinetobacter spp.）、气单胞菌属（Aeromonas spp.）和假单胞菌等多种菌属构成,而腐败末期菌群构成趋于单一,假单胞菌和热死环丝菌为优势腐败菌,特别是莓实假单胞菌（P. fragi）。将腐败分离株10?株假单胞菌、4?株热死环丝菌和1?株蜂房哈夫尼菌（Hafnia alve）接种于冷藏的牛肉汁,发现假单胞菌和蜂房哈夫尼菌的接种组感官评分、pH值和TVB-N值高于热死环丝菌,且假单胞菌有较强的蛋白酶活性。研究表明,结合感官和微生物评价冷鲜牛肉贮藏期为15?d,且菌群多样性下降,假单胞菌和热死环丝菌是优势腐败菌,其中假单胞菌致腐性较强。     

Comparison of shelf life of vacuum-packed pork and beef

The relevance of the intrinsic factors of meat to the sensorial shelf life of vacuum-packed, cold-stored minced pork and beef was investigated. The intrinsic factors studied were the pH and the concentrations of glycogen, glucose, glucose-6-phosphate, l-lactate and fat. The initial bacterial loading was the same on all the meat. High correlations were found between the initial values of pH, fat and l-lactate, respectively, and the rate of spoilage. Using partial least square regression, it was shown that changes in the pH and the concentrations of l-lactate and glucose-6-phosphate during storage were able to explain 68% of the variation observed in the rate of spoilage. No relationship was found between spoilage and the origin of the meat (pork or beef).     

Evaluation of fermentation and aerobic stability of wet brewers' grains ensiled alone or in combination with various feeds as a total mixed ration

Wet brewer's grains (BG; 200 g kg^?1 dry matter(DM)) were ensiled alone or in combination with various dry feeds as a total mixed ration (TMR; 540 g kg^?1 DM) in laboratory silos. Ensilage was stopped at 40 days (experiment 1) or at 5, 20, 40 and 60 days (experiment 2) after storage. The composition of soluble sugars and the profiles of fermentation products were determined. The 60 day silages were subjected to aerobic deterioration and changes in silage temperature were recorded for 7 days. A rapid pH fall coupled with accelerated lactic acid production was observed in BG silage; soluble sugars, mainly composed of maltose and raffinose, completely disappeared within 5 days of ensiling. Prolonged storage, however, decreased lactic acid concentration and increased acetic acid greatly. Appreciable amounts of propionic acid and 1‐propanol were also produced in BG silage in the late stages of fermentation. When TMR silage was made, the decline in pH and the increase in lactic acid were delayed due to the low moisture content. Acetic acid production was enhanced from the beginning of storage, and mannitol accumulated in TMR silage. Yeast numbers were lower in TMR than in BG silage, but the changes were limited in the late stages of fermentation. When exposed to air, the temperature of BG silage increased after 3 days, whereas that of TMR silage appeared stable during the 7 days test. The results indicate that BG is a suitable by‐product for ensiling and, when ensiled with various feeds as a TMR, improved stability against aerobic deterioration can be expected. Copyright © 2003 Society of Chemical Industry     

Determination of volatile compounds of precooked prawn (Penaeus vannamei) and cultured gilthead sea bream (Sparus aurata) stored in ice as possible spoilage markers using solid phase microextraction and gas chromatography/mass spectrometry

BACKGROUND: Solid phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) have been reported as useful techniques for analysing volatile compounds to monitor fish freshness. In this study, SPME/GC/MS was applied to cultured gilthead sea bream and precooked prawn stored in ice for 6 days in order to find possible markers of spoilage. Total volatile basic nitrogen (TVB‐N) was also determined as a common index of spoilage. RESULTS: The TVB‐N value at the end of the storage period for cultured gilthead sea bream (302.40 ± 8.50 mg kg^?1) was within the range of acceptability for edible fish (300–400 mg kg^?1) but could be considered at the beginning of spoilage. For precooked prawn the TVB‐N value at day 6 (863.04 ± 7.84 mg kg^?1) was not acceptable for human consumption. SPME/GC/MS identified 30 compounds in cultured gilthead sea bream and 49 compounds in precooked prawn. In particular, 3‐methyl‐1‐butanol, 2‐methylbutanal, 3‐methylbutanal and 3‐hydroxy‐2‐butanone increased during refrigerated storage both in the two species investigated here and in other species reported elsewhere and could be considered as markers of spoilage. CONCLUSION: This study confirmed that SPME/GC/MS can be considered an efficient method suitable for analysing the volatile compounds of both raw fish and fishery products in order to monitor loss of freshness. Copyright © 2008 Society of Chemical Industry     

Effects of sodium caseinate‐ and milk protein concentrate‐based edible coatings on the postharvest quality of Bing cherries

Bing cherries were coated with sodium caseinate‐ or milk protein concentrate‐based edible coatings. Besides the proteins (100 g kg^?1), the coating formulations also included glycerol (about 300 g kg^?1 protein) and either beeswax or a stearic–palmitic acid blend at a concentration of 0, 100 or 300 g lipid phase kg^?1 of protein. All coatings, especially those containing 300 g kg^?1 stearic–palmitic acid blend, successfully reduced water loss of the fruits. The edible coatings had a beneficial effect on the sensory quality of the cherries, and there were significant (p < 0.05) effects of the coating treatments on soluble solids, titratable acidity and pH. Copyright © 2004 Society of Chemical Industry     

Influence of storage temperature on the quality of beef liver; pH as a reliable indicator of beef liver spoilage

The development of the microbial flora specifically involved in the spoilage of sliced beef livers packaged and stored under aerobic conditions at 0 and 3 °C for 14 days was studied. Changes in the pH value of the product were also determined. The possibility that pH value could be considered as a quick and reliable indicator of incipient spoilage was particularly considered. All microbial groups (except micrococci) showed differences in their rates of growth between 0 and 3 °C. Pseudomonads and lactic acid bacteria were the main components of the spoilage flora. When the 37 °C aerobic plate counts (APCs) reached 10⁵–10⁶ CFU g⁻¹ and the 20 °C APCs and pseudomonad counts reached 10⁶–10⁷ CFU g⁻¹, visible surface colonies (VSCs) were observed. The presence of VSCs is the most important criterion to determine organoleptic beef liver spoilage and has hence enabled us to establish a shelf-life of up to 8–10 and 5.5–6.5 days for samples stored at 0 and 3 °C respectively. Our study shows that the determination of pH, which is simple, economical and rapid, is capable of giving a reliable estimate of the spoilage status of beef livers. pH values lower than 6.15 may be considered as indicative of beef liver spoilage. © 1999 Society of Chemical Industry     

杀菌和贮藏方式对酱牛肉的微生物和品质的影响

为探究杀菌和贮藏方式对酱牛肉贮藏期间微生物与品质的影响,对低温贮藏不杀菌(4N)、常温贮藏不杀菌(25N)和常温贮藏杀菌(25S)的真空包装酱牛肉进行了研究。对酱牛肉16S rRNA基因的V4~V5区域进行高通量测序,并测定其质构、色泽、pH、TVB-N和TBARs等指标。高通量测序结果显示,属水平上丰度较大的有沉积小杆菌属(Sediminibacterium)、魏斯氏菌属(Weissella)、芽孢杆菌属(Bacillus)等,其在酱牛肉的贮藏过程中作为不同时期的优势腐败菌大量生长,魏斯氏菌属和芽孢杆菌属分别是未杀菌处理和杀菌处理后酱牛肉中的优势腐败菌。微生物结果表明25N组在第3天微生物超标,4N组保质期可延长至21 d,25℃贮藏杀菌组保质期可达35 d。杀菌和贮藏温度不同的酱牛肉随着贮藏期延长,质构稳定性、pH值和a~*值显著下降(P<0.05),L~*值先下降后上升。3组酱牛肉的TVB-N值和TBARs值在贮藏期均显著增加(P<0.05)。     

Evaluation of two biodegradable coatings on corn silage quality

This experiment was performed to assess two different biodegradable coating formulations for the preservation of corn silage quality. Soy‐ and casein‐based biodegradable coatings were evaluated for their ability to exclude oxygen and preserve corn silage. Experiments were conducted under natural conditions outdoors. The effect of the coating composition on silage quality was compared with the quality of silage covered with a plastic (0.15 mm) (positive control) and uncovered (negative control) after 4 and 8 week periods. The results showed that the two biodegradable coatings offered the same level of silage protection during the overall experiment (8 weeks). As compared with the negative control, the two formulations prevented deterioration associated with air infiltration (heating, mold growth and dry matter losses) and limited the decrease in nutritive value. Also, the pH of the coated silage was significantly lower (P ≤ 0.05) than the negative control after 4 weeks of storage. Silage coated with the biodegradable coatings was able to maintain the pH below 4.5 during the first 4 weeks of storage. The decline in lactic acid concentration seems to have been initiated by the lactate‐utilizing yeasts, responsible for the increase in the silage pH. No visual growth of mold was observed in silage sealed with biodegradable coatings. This study showed that biodegradable coatings were able to protect the quality of silage during 4 weeks but the biodegradable coatings were not as good as plastic at preserving silage after 8 weeks of storage. Copyright © 2005 Society of Chemical Industry     

Cholesterol and lipid oxidation in raw and pan‐fried minced beef stored under aerobic packaging

BACKGROUND: The type of packaging atmosphere has been reported as a technological factor that consistently affects the quality of lipid fraction in meat. Oxidation of cholesterol and lipids was evaluated before and after pan frying in commercial refrigerated minced beef stored under aerobic atmosphere for 1 and 8 days. RESULTS: In raw beef, cholesterol and lipid oxidation developed at a slow rate. Cholesterol oxidation products (COPs) did not significantly vary (～8 µg COPs g^?1 of fat) over 8 days, while in the same period thiobarbituric acid reactive substances (TBARS) less than doubled (from 0.7 to 1.2 malondialdehyde equivalents kg^?1 of muscle). Pan frying did not influence the oxidative degree in the fresh product but consistently catalyzed cholesterol oxidation in stored beef. A significant increase was assessed in beef at the end of storage: from 8.6 to 30.0 µg COPs g^?1 of fat in raw and cooked beef, respectively. CONCLUSION: Aerobic packaging did not appear as a pro‐oxidant factor in fresh minced beef with a good oxidative quality during a short period of refrigerated storage. Copyright © 2010 Society of Chemical Industry     

Colour of fat,and colour,fatty acid composition and sensory characteristics of muscle from heifers offered alternative forages to grass silage in a finishing ration

The effect of type of silage offered to beef heifers during the finishing period on aspects of beef quality was determined. In two experiments, a diet based on grass silage (GS) was compared with a diet based on maize silage (MS) or whole-crop wheat silage (WCW). Compared to the GS-based diet, increasing the amount of MS linearly increased fat whiteness while the increase in fat whiteness due to WCW was dependent on the stage of crop maturity at harvesting. There was no effect of diet on muscle colour or on muscle pH measured at 48 h post-mortem, drip loss, taste panel traits after 14 days ageing or shear force values at 2, 7 or 14 days ageing. The alternative silages decreased the n − 3 polyunsaturated fatty acid proportion and increased the linoleic:linolenic acid ratio in intramuscular lipid. It is concluded that type of silage affects fat colour and fatty acid composition of muscle but not the other muscle characteristics examined.     

壳聚糖协同生物源保鲜剂对冷鲜牛肉的保鲜效果

为延长冷鲜牛肉的保鲜期并减少贮藏期间的汁液流失,以菌落总数、总挥发性盐基氮值、pH值和汁液流 失率等作为评价指标,选用壳聚糖与前期实验筛选的复配生物源保鲜剂（乳酸链球菌素质量浓度2.5 g/L、ε-聚赖氨 酸3.0 g/L、纳他霉素1.5 g/L）对冷鲜牛肉进行涂膜保鲜,并与商业保鲜剂的保鲜效果进行对比。结果表明：复配 生物源保鲜剂结合壳聚糖涂膜保鲜的冷鲜牛肉4 ℃贮藏8 d时的汁液流失率较对照组降低2.13%;贮藏16 d时,复配 生物源保鲜剂结合壳聚糖涂膜保鲜冷鲜牛肉的菌落总数为4.75 （lg（CFU/g））,属于二级鲜肉,较对照组降低了 4 个数量级。可见,复配生物源保鲜剂、商业保鲜剂、复配生物源保鲜剂结合壳聚糖涂膜处理均可延长冷鲜牛肉的 保鲜期。复配生物源保鲜剂结合壳聚糖涂膜的保鲜效果最好,可将冷鲜牛肉的保鲜期延长至16 d。     

Development of spoilage microbiota in beef stored in nisin activated packaging

The aim of this study was to assess the microbial populations causing the spoilage of chilled beef during storage and to evaluate the effect of the use of an antimicrobial packaging for the meat storage. A nisin activated antimicrobial packaging was developed by using a nisin, HCL and EDTA solution and used for the storage of beef cuts at 1 °C. The common spoilage related microbial groups were monitored during the storage of beef in activated and non activated plastic bags by using selective media. The use of the antimicrobial packaging caused an overall significant reduction of viable counts of Gram positive bacteria such as carnobacteria, lactic acid bacteria and Brochotrix thermosphacta whose development was inhibited for at least 11 days of storage compared to the control. Moreover, a 1–3 log cycles reduction of enterobacteria was also registered between 22 and 32 days of storage. The microbiota was assessed at species level by using Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis of 16S rRNA gene of DNA extracted directly from meat and from bulk cells from selective media plates and showed that the species occurring within the targeted microbial groups did not change according to storage conditions. In conclusion, the use of the nisin activated packaging reduced the number of spoilage populations but did not affect the species diversity. Improved antimicrobial packaging is needed, possibly coupled with vacuum storage, to possibly achieve a simultaneous inhibition of more spoilage microbial groups and to preserve the microbiological quality of beef during chilled storage.     

Chemical properties and sensory quality of ice cream fortified with fish protein

BACKGROUND: Fish protein powder is a functional ingredient that can be used for enhancing the nutritional value of food products. In this study the effect of fortification with different levels of fish protein powder (FP) on chemical properties and sensory quality of Persian ice cream with 0, 30 and 50 g kg^?1 FP during storage at ? 18 °C for 4 months was investigated. RESULTS: Ice creams fortified with 50 and 30 g kg^?1 FP had significantly higher protein and solid‐non‐fat content than ice cream with 0% FP or 83, 69 and 51 g kg^?1 protein and 215, 204 and 181 g kg^?1 solid non‐fat, respectively. All products had the same levels of fat, lactose, acidity and pH. They had similar sensory quality after production except for colour, but sensory properties of fortified samples changed significantly after 2 months of storage. Colour faded, cohesiveness decreased, sandiness/coarseness increased, sweetness decreased and fish flavour and off‐odour increased. The control ice cream scored highest for additives odour and flavour. CONCLUSION: Development of ice cream fortified with fish protein powder could be an effective way to enhance nutritional and functional value of ice cream. But studies on storage stability, consumers' acceptance and attitudes are recommended if companies are planning to do so. Copyright © 2011 Society of Chemical Industry     

Effect of kafirin protein coating on sensory quality and shelf-life of 'Packham's Triumph' pears during ripening

BACKGROUND: Pears are exported in large quantities from South Africa, resulting in large revenues. Minimisation of quality losses once the fruit has reached the export destination is as important as following strict export and distribution protocols. Kafirin can form edible films. In this study an edible coating made from 20 g kg^?1 kafirin coating solution was applied as a postharvest treatment to retard quality deterioration of ‘Packham's Triumph’ pears during storage at the typical ripening temperature (20 °C). Changes in physicochemical and sensory quality were monitored over a period of 24 days. RESULTS: The kafirin coating was unable to retard the onset of ripening but decreased the respiration rate and retarded the progression of senescence. However, moisture loss was exacerbated in the kafirin‐coated fruit during ripening at 20 °C, especially towards the end of the shelf‐life. CONCLUSION: The kafirin coating extended the eat‐ripe quality of the pears by 1–2 weeks. However, the appearance of the fruit was unacceptable after 14 days of storage in terms of wrinkled skin. Further work is needed to improve the water barrier properties of the kafirin coating by incorporating a wax or triglyceride into the coating formulation or more simply by applying a kafirin coating to waxed fruit. Copyright © 2011 Society of Chemical Industry     

洋葱皮乙醇提取物对冷却牛肉颜色、脂质和蛋白质氧化稳定性的影响

将牛肉切片在3种浓度（0.5 %、1.0%、2.0%）的洋葱皮乙醇提取物（Ethanol Extract of Onion Skin,EEOS）溶液中浸渍后在4 ℃条件下冷藏12 d,并与空白对照组和添加了抗坏血酸（ascorbic acid,V_C）的处理组进行比较,分析EEOS对牛肉在冷藏期间的颜色褐变、脂肪和蛋白质氧化以及腐败程度的影响。结果表明:EEOS总酚含量较高,具有很强的自由基清除活性;添加EEOS可延缓牛肉pH上升,提高颜色稳定性,减少高铁肌红蛋白的生成,同时延缓脂肪和蛋白的氧化进程。2% EEOS有效降低了牛肉样品硫代巴比妥酸反应物（Thiobarbituric acid reactive substances,TBARS）和蛋白质羰基含量,与空白对照组相比分别降低56.9%和17.6%。此外,2% EEOS还可显著降低挥发性盐基氮（Total Volatile Basic Nitrogen,TVB-N）的含量（P<0.05）。因此,添加2% EEOS可抑制牛肉冷藏期间的颜色褐变和脂肪、蛋白质的氧化,可在牛肉冷藏保鲜中作为天然抗氧化剂。     

Application of shellac for the development of probiotic formulations

In this study, we have improved the enteric properties of shellac and developed probiotic formulations comprising this natural polymer. The effects of plasticizers such as glycerol and glyceryl triacetate, as well as water-soluble polymers such as sodium alginate, hydroxypropyl methylcellulose and polyvinylpyrrolidone on thermodynamic characteristics and coating properties of shellac were evaluated. The data indicate that glycerol showed the best plasticization effect. Hydroxypropyl methylcellulose and polyvinylpyrrolidone had superior miscibility with shellac compared to sodium alginate. Then, three fluid-bed dried bacterial species i.e., Enterococcus faecium, Bifidobacterium bifidum and Lactobacillus reuteri, were coated with formulations comprising different concentrations of shellac and additives. Coatings with shellac containing 5% glycerol or 5% sodium alginate or up to 20% [w/w] polyvinylpyrrolidone protected the microorganisms against acidic pH and provided the best release profile in simulated intestinal fluid. Moreover, these formulations maintained promising cell survival rates after four months of storage at 5 °C. E. faecium and B. bifidum showed more resistance to manufacturing process than L. reuteri.     

The effects of sorbates on the ensilage of chopped whole-plant maize and lucerne

The incorporation of (a) sorbic acid (0.18 and 0.90 g kg^?1, fresh weight basis) and potassium sorbate (0.90 g kg^?1) with chopped lucerne, and (b) sorbic acid (0.90 g kg^?1) and potassium sorbate (0.90 g kg^?1) with chopped maize (whole-plant) at the time of ensiling, led to a reduction in the surface spoilage associated with the ensilage of these two forages. Use of sorbic acid (0.90 g kg^?1) and potassium sorbate (0.90 g kg^?1) led to (a) a reduction of volatile nitrogen (VN), higher levels of residual water-soluble carbohydrates (WSC) in lucerne silage and more aerobically stable lucerne silage and (b) a reduction in weight loss, population of yeasts and moulds, and VN, higher levels of WSC in maize silage and more aerobically stable maize silage when compared to the untreated forages or forages treated with sorbic acid and potssium sorbate at 0.045 and 0.18 g kg^?1 (fresh weight basis), respectively.     

Effects of Fish Gelatin and Tea Polyphenol Coating on the Spoilage and Degradation of Myofibril in Fish Fillet During Cold Storage

Fish fillet is easily spoiled during storage. Antimicrobial edible coating of gelatin extracted from fish skins and bones and tea polyphenol (TP) was developed to inhibit the spoilage of fish fillet during cold storage. For coating containing 0.4 % TP and 1.2 % gelatin, the pH only slightly increased from 6.17 at day 0 to 6.32 at day 17 of cold storage, while the pH of control coating increased to 6.87 at day 17. Atomic force spectrometry was used to analyse the nanostructure of myofibril, which is the major component of fish muscle. The results showed that the length of myofibril from 0.4 % TP and 1.2 % gelatin group was greater than 15 μm, while the diameter and height were 3.38 and 0.59 μm, respectively, which exhibited the most intact nanostructure after 17 days of cold storage. Meanwhile, matrix-assisted laser desorption–ionisation–time-of-flight mass spectrometry result showed that TP delayed the degradation of myosin light chain 3 and troponin T in myofibril. Gas chromatography–mass spectrometry of volatile organic compounds (VOCs) also showed that 0.4 % TP and 1.2 % gelatin coating group had minimal production of spoilage markers, such as 1-octen-3-ol, 2-methyl propanoic acid and dimethyl sulfide. The microbial analysis showed that the aerobic mesophilic/psychrotrophic count, yeasts and moulds of 0.4 % TP and 1.2 % gelatin group were significantly lower than the control group. Therefore, 0.4 % TP and 1.2 % gelatin coating showed the best antimicrobial effect and can be used to maintain the nanostructure of fish fillet and prevent the spoilage during cold storage.