Shelf life of Turkish whey cheese (Lor) under modified atmosphere packaging

In this study, the shelf life of Lor cheese stored under different atmosphere compositions was assessed and compared. Lor cheeses were held in four different atmospheres containing: vacuum packaging (VP), 40% CO₂/60% N₂, 60% CO₂/40% N₂ and 70% CO₂/30% N₂ (modified atmosphere packaging). Control cheeses were stored in air. All cheese samples were kept in the refrigerator at 4°C for 45 days and investigated for physicochemical, microbiological and sensory properties. The acidity index value was significantly higher ( P  < 0.05) in the control and vacuum packaged samples than in those stored for the same period under CO₂. Microbiological results showed that modified atmosphere packaging delayed microbial growth compared with air and VP samples. Of the three modified atmospheres, gas mixtures 60% and 70% CO₂ were the most effective for inhibition of growth of micro-organisms. Sensory evaluation (odour and taste) results showed that Lor cheese packaged under modified atmosphere packaging (60% CO₂/40% N₂ and 70% CO₂/30% N₂ ) retained good characteristics for 45 days of storage, while vacuum and control samples were sensorily unacceptable after 10 days of storage.     

Effects of Different Whey Protein Concentrate Coating on Selected Properties of Rainbow Trout (Oncorhynchus mykiss) During Cold Storage (4°C)

In this study, the effect of different whey protein concentrate coating formulations (with or without glycerol) on the storage of fillets over a period of 15 days at 4ºC was investigated. Fillets were conducted to microbiological, chemical, and sensory analyses. Difference in microbiological and chemical changes between samples was found to be significant (p < 0.05) during storage period. The Y and Z were preferred more by the panellists, while C samples received the lowest scores. According to the results of microbiological analyses, shelf life of fillets was estimated at 6, 9, 12, and 15 days for C, X, Y, and Z samples, respectively.     

Influence of storage,brine concentration and in‐container heat treatment on the stability of white brined Nabulsi cheese

Microbial levels were significantly (P < 0.05) affected by the temperature‐time treatments used during in‐container heat treatment of the curd, brine concentration and storage duration. A heat treatment of 115 °C × 2 min, in the absence of NaCl, was sufficient to eliminate Mesophilic micro‐organisms, Coliforms, Staphylococcus aureus and Yeast and Moulds for the duration of 1 year of storage. Sensory scores for colour, appearance and texture increased significantly (P < 0.05) with the increase in the NaCl in brine concentration regardless of the temperature‐time treatment.     

Changes in the microflora of manouri, a traditional Greek whey cheese, during storage

Six batches of manouri cheese were manufactured, and selected microbial groups were counted throughout storage for 20 days at 4°C. The counts of all the microbial groups increased ( P  < 0.05) throughout storage and reached higher levels in cheeses made in summer than in those made in spring. Moreover, the micro-organisms developed better on the cheese surfaces than in the interiors, especially in summer. The pH (6.78–7.33) and salt-in-moisture content (2.53–3.72) of the cheeses did not seem to affect the growth of the bacteria and yeasts present. The isolates of enterobacteriaceae were mainly Hafnia (68.75%), while the isolates from the Baird–Parker medium were mainly staphylococci. There was a great diversity of yeast species, but Debaryomyces hansenii and Pichia membranefasciens predominated. The isolates of enterobacteriaceae, staphylococci and—to a lesser extent—yeasts were proteolytic, but the free amino acid (N-NH2) content of the cheese did not increase significantly during storage (136.4–225.2 mg/kg glycine equivalent). It also seemed that milk fat was not degraded to any great extent (acid degree value 0.09–0.19) by the lipolytic activity of the strains. The main enzymes detected in selected isolates of enterobacteriaceae were leucine aminopeptidase and phosphohydrolase.     

Shelf life of fresh foal meat under MAP, overwrap and vacuum packaging conditions

The objective of this study was to investigate the physico-chemical properties, the microbial counts and the sensory properties' changes of foal steaks packed under various conditions. The experimental packaging systems were: (i) vacuum packaging (VP), (ii) overwrap packaging and (iii) two modified atmosphere packaging methods (MAP): high O(2) MAP (80% O(2)+20% CO(2)) and low O(2) MAP (30% O(2)+70% CO(2)). The meat was stored at 2°C during 14days and tested for pH, colour, lipid and protein oxidation, microbial counts and sensory assessment of odour, colour and appearance. Of the two MAP, overwrap and VP, both MAP were the most effective treatments for the inhibition of the total viable counts (TVC), Pseudomonas spp., psychrotrophic aerobic bacteria, lactic acid bacteria, Enterobacteriaceae as well as moulds and yeast. According to the sensory evaluation, foal steaks packed under overwrap and MAP treatments resulted unacceptable after 7days of storage, whereas the vacuum-packed meat was still acceptable. Moreover, the redness value decreased significantly (P<0.001) with all treatments during the storage time, except for the vacuum packs, which increased significantly (P<0.001). Finally, foal steaks from overwrap packaging and MAP conditions had a greater increase of TBAR'S values and carbonyl content during the storage time. High O(2) levels affected foal meat quality negatively, while anaerobic conditions extended the meat's shelf life up to 14days.     

Viability of probiotic micro-organisms during storage, postacidification and sensory analysis of fat-free yogurts with added whey protein concentrate

The aim of this research was to evaluate the effect of the addition of whey protein concentrate (WPC) on the viability of Lactobacillus acidophilus and Bifidobacterium longum and on postacidification throughout the shelf life of fat-free yogurts, and also to analyse the sensory characteristics of the products. Postacidification was not significantly changed by the addition of WPC, but was decreased by Lactobacillus bulgaricus inoculation. WPC did not influence the viability of the lactic acid bacteria ( L. bulgaricus and Streptococcus thermophilus ), but it improved the growth and survival of the micro-organisms L. acidophilus and B. longum , especially the former. The panellists did not identify significant differences ( P <  0.05) of the yogurts due to the addition of WPC.     

Occurrence of moulds associated with ovine raw milk and cheeses of the Spanish region of Castilla La Mancha

The distribution of mould species was examined at several points of the processing chain in a Manchego cheese plant and associated dairy farms. Geotrichum and Fusarium were the genera most frequently isolated from milk samples as well as in cheeses ripened for one month, evidencing a direct transfer from raw milk. Conversely, the mycobiota of long‐ripened cheeses consisted mainly of Penicillium species, which gained entry to the cheese through the air of ripening rooms. This study contributes to the understanding of the dynamics of fungal populations in semihard and hard cheeses, highlighting that airborne transfer from the stables could have a direct impact on their quality.     

微生物法测定乳清蛋白粉类样品中的叶酸含量

目的 建立微生物法测定乳清蛋白粉类样品中叶酸含量的分析方法。方法 利用叶酸标准品制作叶酸标准曲线。将样品进行超声处理得到样品溶液。向试管中加入等体积的培养基和不同体积的样液,稀释至10mL,得到样品待测液。样品待测液和叶酸标准曲线溶液灭菌后,加入鼠李糖乳杆菌(Lactobacillus casei spp.rhamnosus)CICC 6224菌悬液进行培养,将培养物混匀后测其吸光度值,根据标准曲线计算相应的叶酸含量,并进行方法的空白试验、检出限、精密度、重复性、稳定性及回收率试验。结果 在0.1010~1.0103ng/mL范围内,叶酸标准曲线呈现良好的线性,相关系数R_²=0.99373,符合GB/T27404-2008《实验室质量控制规范》的要求,该方法的相对标准偏差(relative standard deviation,RSD)为3.8%(n=6),平均回收率为102.5%(n=9)。结论 该方法稳定准确,适合用于测定乳清蛋白粉类样品中的叶酸含量。     

The use of carbon dioxide in the processing and packaging of milk and dairy products: A review

The upswing in consumer demand for fresh and high quality preservative‐free foods has led to the development of modified atmosphere packaging (MAP). Increasingly, MAP is being used with high carbon dioxide (CO₂) concentration as well as CO₂/N₂ gas mixes. Modified atmosphere packaging or ‘gas flushing’ as it is also known is an increasingly popular technique used to extend the shelf life (both quality and safety) of a number of dairy products. Carbon dioxide is an active constituent of MAP, naturally present in freshly drawn raw milk. Addition of CO₂ to raw milk or flushing the package headspace has proved to be a simple and cost‐effective method, depending upon the initial microbiological quality of the food product. Carbon dioxide addition through MAP or direct injection as an economically affordable shelf life extension strategy is used commercially worldwide for some dairy products. The development of food packaging machines with integrated gas flushing capabilities and the supply of ‘food grade’ gases allow dairy foods manufacturers to enhance the quality of their products. This review presents a broad spectrum of current research and the current trends with respect to CO₂ as a natural microbial hurdle with special focus on its precise mechanism and its role in quality improvement of dairy products.     

Sensory shelf life determination of a processed meat product ‘rullepølse’ and microbial metabolites as potential indicators

Sensory profiling was performed for a Danish lightly fermented heat-processed cold cut pork product termed ‘rullepølse’. Product samples were stored under modified atmosphere (MAP, 30% CO₂/70% N₂) for 0, 28 and 34 days and with subsequent aerobic storage for 4 days (MAP–OPEN) at temperatures of 4 °C and 8 °C. Microbial growth and metabolism was also measured with a focus on lactic acid bacteria (LAB) and their organic acid metabolites including lactic acid, acetic acid and α-ketoisocaproic acid. These acids were examined for sensory shelf life indexing potential for the ‘rullepølse’. Storage temperature exerted distinct impacts on the sensory characterised shelf life of ‘rullepølse’ stored under MAP and MAP–OPEN conditions. The MAP stored ‘rullepølse’ with subsequent 4 days storage in air (MAP–OPEN) could be stored for at least 28 days at 4 °C without a decrease in the sensory quality when opened. Whilst MAP stored ‘rullepølse’ at 8 °C with subsequent open storage (MAP–OPEN), compared to the lower temperature displayed a reduced shelf life of less than 28 days if sensory quality of the ‘rullepølse’ was to be maintained. The stage of sensory deterioration was correlated with high bacterial counts exceeding 10⁶ CFU g⁻¹. With respect to indexing ability of the examined organic acids none were found to have clear potential for prediction of the sensory deterioration.     

Optimization of modified atmosphere packaging with respect to physicochemical characteristics of Requeijão

The effects of modified atmosphere packaging on physicochemical and sensorial characteristics (contents of free fatty acids, lactose, lactic acid and moisture, as well as pH and rigidity) in Portuguese whey cheese (Requeijão) were studied following a response surface methodology using storage time, storage temperature and fraction of CO₂ in the flushing gas as manipulated variables. Inspection of the sensorial optima in terms of the different parameters indicated that it is convenient to set the storage temperature equal to 4°C because no significant lipolysis takes place, irrespective of overhead atmosphere. Plain CO₂ as flushing gas will in general ensure more constant composition until 15 days and will provide protection against extensive lipolysis. In terms of overall visual aspect, all packaged cheeses were preferred to their unpackaged counterparts; however, in terms of acidic smell, only whey cheeses stored at 4°C exhibited significant differences relative to those stored at higher temperatures.     

Influence of different content of cheese whey and oligofructose on the properties of fermented lactic beverages: Study using response surface methodology

Lactic beverages have been used as an important vehicle for probiotics, and the utilization of cheese whey and oligofructose would contribute even more to the functional properties of this product. However, because of the short lifespan of probiotics, studies have been carried out aiming at the evaluation of the contribution of the prebiotics in the improvement of the viability of these microorganisms. The technological properties (fermentation time, acidity and syneresis index) and the population of probiotic bacteria in fermented lactic beverages manufactured with different content of cheese whey and oligofructose were evaluated. The results showed that oligofructose, at the concentrations evaluated in this study, did not show any significant influence on the response variables, whereas the content of cheese whey only influenced the syneresis index of lactic beverages.     

Effect of rosemary extract, chitosan and α-tocopherol on microbiological parameters and lipid oxidation of fresh pork sausages stored at 4°C

The effect of rosemary extract, chitosan and α-tocopherol, added individually or in combination, on microbiological parameters and lipid oxidation of fresh pork sausages stored for 20 days at 4 °C was investigated. Microbiological determinations included the enumeration of Enterobacteriaceae, Pseudomonas spp., total viable count, yeasts and moulds and lactic acid bacteria, while pH values were also determined. Lipid oxidation was evaluated through measurement of primary (peroxide value) and secondary (malondialdehyde concentration) oxidation products. Chitosan addition resulted in significant (P ? 0.05) inhibition of microbial growth, while the lowest microbial counts were obtained in the samples containing both chitosan and rosemary, indicating a possible synergistic effect. Chitosan and its combinations with either α-tocopherol or rosemary, and especially the latter combination, showed also the most intense antioxidative effect (P ? 0.05), at least when compared to α-tocopherol alone or the controls, while use of rosemary extract alone had a comparable (P > 0.05) antioxidative effect with chitosan and its combinations. Shelf life of samples containing chitosan was almost doubled compared to the remaining samples. In conclusion, the best antimicrobial and antioxidative effects were obtained from the combination of chitosan with the rosemary extract.