Shelf life and quality of probiotic yogurt produced with Lactobacillus acidophilus and Gobdin

This study evaluated the effect of dry white mulberry and walnut paste (Gobdin, a traditional Turkish food) in probiotic yogurt on the survival of Lactobacillus acidophilus and yogurt properties. Six different yogurts were produced with 0%, 5% and 10% Gobdin using Lactobacillus bulgaricus + Streptococcus thermophilus and with 0%, 5% and 10% Gobdin using L. bulgaricus + S. thermophilus + L. acidophilus. The physical, chemical, microbiological and sensorial properties of the yogurts were evaluated based on storage at 4 ± 1 °C. Probiotic shelf life and the most suitable combinations were determined. The highest L. acidophilus count (8.65 log cfu g^?1) was found in the 5% Gobdin‐supplemented yogurt on the 7th day of storage, while the lowest count (8.11 log cfu g^?1) was found in the probiotic control yogurt on the 21st day. Although the L. acidophilus counts in the probiotic yogurts declined during storage, all values found throughout the 21‐day storage period were >8 log cfu g^?1. This is above the level necessary to provide the desired therapeutic effect in probiotic products (10⁶–10⁷ cfu g^?1). The highest overall acceptability score was obtained on the first day from the yogurt with 5% Gobdin. However, all yogurt samples had general acceptability scores between 7 and 8 points from a 9‐point maximum. Thus, this study determined that a new functional yogurt can be produced using L. acidophilus with 5% Gobdin.     

Preparation and properties of probiotic concentrated yoghurt (labneh) fortified with conjugated linoleic acid

Milk of high conjugated linoleic acid (CLA) level (1.25 g per 100 g milk fat) was produced by inclusion of fish oil and rousted soy bean in the ration of Holstein cows as compared to 0.55 g per 100 g milk fat in the milk of animals receiving control diet. Milk of normal (control) and high CLA content (treatment) was spray‐dried. Labneh was made from 20 g L^?1 reconstituted milk using 3 mL per 100 mL yoghurt starter and 2 mL per 100 mL of probiotic cultures of Lactobacillus casei or Lactobacillus acidophilus. The control (C) and high CLA (T) labneh were analysed chemically and microbiologically, and their viscosities were determined during cold storage for 15 days. The fat content of labneh of high CLA was less than that of the control, but the total solids (TS) were unaffected by the CLA level. Labneh made with Lb. acidophilus had lower TS and higher acidity, exopolysaccharides and acetaldehyde contents and viscosity than that made with the use of Lb. casei. Labneh from the different treatments retained high counts of the added probiotic (>10⁸ cfu g^?1) throughout the storage period. The storage period had significant effects on all parameters determined.     

食品感官货架期确定的一般原则与方法

感官品质是描述和判断食品质量最直观的指标,将此品质作为货架寿命的评价指标而确定的货架期为感官货架期,则对应的感官评价方法是确定感官货架寿命的关键技术之一。由此,结合感官评价方法与货架期预测原理,提出了食品感官货架期确定的一般原则与方法,旨在指导构建我国不同类型食品感官品质的货架期确定指南,完善食品货架期检测标准,为我国食品质量与控制的保障提供标准化支撑。     

食品储存期加速测试及其应用

利用化学动力学的原理,改变储存环境来缩短食品储存期,从而在短时间内可得到长寿食品(一年以上)的储存期,以及应用于食品稳定性的测试,确保食品的商业储存期。     

Short communication: Influence of an aqueous myrrh suspension on yogurt culture bacteria over yogurt shelf life

Myrrh is an essential oil and natural flavoring approved by the US Food and Drug Administration, and it has antibacterial and antifungal activity against pathogens. Our objective was to determine the effect of an aqueous myrrh suspension on Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus counts in peptone solution and yogurt, as well as pH and titratable acidity of yogurt during 5 wk of storage at 1 to 4°C. The myrrh suspension (10% wt/vol) was prepared and incorporated into a pure culture dilution in peptone and into yogurt mix at a 1% (vol/vol) level. A control with no myrrh was also prepared, and 3 replications were conducted. Streptococcus thermophilus were enumerated using Streptococcus thermophilus agar with aerobic incubation at 37°C for 24 h, and Lactobacillus delbrueckii ssp. bulgaricus were enumerated using de Man, Rogosa, and Sharpe agar adjusted to pH 5.2, with anaerobic incubation at 43°C for 72 h. During the 8-h period after inoculation, S. thermophilus and L. delbrueckii ssp. bulgaricus counts in peptone solution at 37°C and 43°C, respectively, were not significantly different in the presence or absence of the aqueous myrrh suspension. Counts of S. thermophilus in yogurt containing myrrh (mean ± SD; 4.96 ± 0.58 log cfu/mL) were not significantly different from those in the control yogurt (4.87 ± 0.39 log cfu/mL). The log counts for L. delbrueckii ssp. bulgaricus in yogurt containing myrrh (5.04 ± 1.44 log cfu/mL) and those of the control (5.52 ± 1.81 log cfu/mL) did not differ, and the counts remained within 1 log of each other throughout 5 wk of storage. The pH of the yogurts containing the aqueous myrrh suspension was not significantly different from that of the control yogurts, and their pH values were within 0.1 pH unit of each other in any given week. Titratable acidity values remained steady around 1.1 to 1.2% lactic acid for both yogurt types throughout the storage period, with no significant differences between them. Yogurt culture bacteria can survive in the presence of a myrrh suspension in yogurt with no significant change in pH or titratable acidity. Therefore, it may be beneficial to add an aqueous myrrh suspension to yogurt.     

Manufacturing, properties and shelf life of labneh: a review

Labneh is a concentrated yogurt widely produced and consumed in the Middle Eastern countries and Balkans.
This review focuses attention on the different manufacturing methods of labneh and its quality in terms of microbiology, rheology, sensory and nutrition. The shelf life of this healthy milk-derived product is also discussed in this review.     

Increasing the shelf life of pikeperch (Sander lucioperca) fillets affected by low-density polyethylene/Ag/TiO2 nanocomposites experimentally produced by sol-gel and melt-mixing methods

Sol-gel and melt-mixing processes, which are used for the synthesis of low-density polyethylene/silver/titanium dioxide nanocomposites, can inactivate pathogens. In the sol-gel method, the nanocomposites were used to treat four selected microorganisms using the disk-diffusion method. In the melt-mixing method, fish coverage films were used to examine the shelf life of fish. TiO₂ along with different concentrations of Ag (0%, 1%, 3%, and 5%) generated the nanocomposites. The maximum inhibition zone diameters (mm) for Staphylococcus aureus, Escherichia coli, Candida albicans, and Aspergillus niger in 3% Ag were measured. It was concluded that applying the LDPE/Ag/TiO₂ nanocomposites produced could be beneficial for inactivation of pathogens.     

Effectiveness of active and modified atmosphere packaging on shelf life extension of a cheese tart

This study evaluated the shelf life extension of a cheese cake subjected to modified atmosphere (MAP) and active packaging (AP). Cheese cakes were packaged under different N₂/CO₂ ratios (70/30 and 20/80) (MAP batches), by placing a sachet of an iron oxide-based oxygen absorber inside trays (AP batch) and with air (air batch). Changes in microbial growth, in-package gas composition, chemical–physical parameters including texture and sensory attributes were monitored for 48 days at 20 °C. AP allowed a mould-free cheese cake shelf life of 48 days, MAP extended the shelf life of samples packaged under 30% and 80% CO₂ up to 14 and 34 days, respectively, whereas tarts stored with air spoiled after 7 days. MAP resulted in a significant increase in hardness after 14 days of storage, whereas AP tarts recovered the initial texture after 48 days. Panellists judged AP tarts over the acceptability threshold during the whole shelf life of cheese tarts.     

探寻白酒在货架期感官和理化指标的变化规律

酒体在长时间的存放过程中,受温度和光线照射等因素的影响,会发生酸增酯减的现象,从而造成酒体的感官甚至酯类指标达不到国家标准的要求。通过对灌装入瓶的不同贮存时间(相当于货架期)成品酒样品和在模拟货架期环境中不同酒精度、不同酒体、不同盛酒容器等产品的指标变化的跟踪,进行白酒货架期的感官和呈味物质成分测定。探寻白酒在货架期内感官和理化指标变化规律,为白酒行业先期的酒体设计提供科学依据。     

不同发酵剂生产的酸奶感官评定和TPA质构分析

质构剖面分析法(Texture Profile Analysis,TPA)是食品质构分析的重要方法。该文通过质构剖面分析法研究了不同发酵剂对酸奶质构的影响,并和感观评价方法进行了比较。结果表明,不同发酵剂对酸奶的硬度和胶粘性影响很大,单一保加利亚乳杆菌和嗜热链球菌生产的酸奶硬度和胶粘性最高。两菌混合硬度和胶粘性明显降低,但内聚性最高。嗜热链球菌可明显增加产品粘度。TPA分析和感观评价中硬度参数值非常吻合,TPA分析中的胶粘性和感观评价中的喉咙口滞留度有较好的关联性。两菌混合后提高杆菌比例生产的酸奶综合感观评价值最高。     

基于电子鼻判别富士苹果货架期的研究

利用电子鼻对不同货架期内的富士苹果挥发性成分进行检测。通过雷达图和负荷加载(Loadings)分析研究主要传感器响应值的变化,利用主成分分析(PCA)、线性判别分析(LDA)模式判别方法进行数据分析。结果表明,第7、8号传感器在苹果常温货架期判别中起主要作用,而第2、7号传感器在苹果贮后货架期的判别中起主要作用。PCA、LDA方法均可准确判别常温不同货架期的苹果;与PCA相比,LDA方法可以更准确对不同贮后货架寿命苹果进行判别,并呈现出良好的集中性和单向趋势。因此,电子鼻快速判别不同货架期的苹果具有可行性。      

复合调味品的灭菌工艺及保质期确定

复合调味品在研发阶段就必须充分考虑到该产品的保质期要求.选择适当的杀菌及灌装方式,确保产品质量在保质期内的基本一致.文中针对目前业内复合调味品产品质量控制上存在的主要问题,详细分析了复合调味品生产中灭菌工艺的选择,以及产品的保质期认定方法.     

糕点的保质期研究

阐述了糕点在贮存过程中发生的品质变化,分析了水分活度在糕点贮存中的作用并介绍了水分活度在国内外的发展现状,提出了几种可以应用在糕点中的亲水性物质,可以使糕点在贮存过程中延缓老化,延长保质期,从而达到保鲜的目的。     

Estimation of storage time of yogurt with artificial neural network modeling

Changes in the physical, chemical, and microbiological structure of yogurt determine the storage and shelf life of the product. In this study, microbial counts and pH values of yogurt during storage were determined at d 1, 7, and 14. Simultaneously, image processing of yogurt was digitized by using a machine vision system (MVS) to determine color changes during storage, and the obtained data were modeled with an artificial neural network (ANN) for prediction of shelf life of set-type whole-fat and low-fat yogurts. The ANN models were developed using back-propagation networks with a single hidden layer and sigmoid activation functions. The input variables of the network were pH; total aerobic, yeast, mold, and coliform counts; and color analysis values measured by the machine vision system. The output variable was the storage time of the yogurt. The modeling results showed that there was excellent agreement between the experimental data and predicted values, with a high determination coefficient (R² = 0.9996) showing that the developed model was able to analyze nonlinear multivariant data with very good performance, fewer parameters, and shorter calculation time. The model might be an alternative method to control the expiration date of yogurt shown in labeling and provide consumers with a safer food supply.     

棕榈油品质对饼干保质期的影响

本文通过饼干的虐待储藏实验及风味品评实验，研究了棕榈油不同色泽及抗氧化剂TBHQ含量对饼干保质期的影响，并提出了饼干保质期达到12个月所要求的棕榈油质量指标。     

延长鲜切面货架期的研究

研究了酒精,脱氢乙酸,二丁基羟基甲苯,对羟基苯甲酸丙酯,山梨酸钾,过氧化苯甲酰,叔丁基对苯二酚,鹿蹄草8种防腐剂在恒温冷藏下（4℃～8℃）对鲜切面保藏期的影响,得出了有效延长鲜切面保藏期的防腐剂组合：脱氢乙酸0．06％,山梨酸钾0．06％,酒精4％（均以面粉添加量计）,可延长鲜切面保存时间24～48h。     

迷迭香提取物对大黄鱼货架期的影响

研究了迷迭香提取物作为生物保鲜剂对大黄鱼4℃贮藏过程中其品质变化和货架期的影响。实验将碎冰处死的整条大黄鱼分别置于4℃的迷迭香溶液（0、0.1%、0.2%、0.3%）中浸泡60min,沥干后所有样品采用蒸煮袋包装于4℃的冰箱中贮藏。通过测定鱼体贮藏过程中的菌落总数、pH、TVB-N、TBA、K值、感官评分等鲜度指标的变化规律,探讨了迷迭香提取物对大黄鱼低温贮藏过程中货架期的影响。结果表明,经过迷迭香提取物处理的大黄鱼细菌总数、TVB-N、TBA、K值在储藏期20d内显著低于对照组（p<0.05）,且具有较好的感官评分;其中迷迭香浓度为0.2%时,保鲜效果最佳,能够抑制大黄鱼低温贮藏过程中的微生物繁殖,有效减缓蛋白质的降解及脂肪的氧化,有效延长大黄鱼的货架期。