Screening of frozen-thawed conditions for keeping nutritive compositions and physicochemical characteristics of goat milk

Frozen milk can help producers overcome the seasonality of goat milk production, low goat production and short lactation periods, and avoid discarding milk during some special periods. We investigated effects of combination between freezing (cryogenic refrigerator of ?16 to ?20°C or ultra-cryogenic refrigerator of ?76 to ?80°C) and thawing (homeothermy of 20 to 25°C or refrigeration of 2 to 4°C) on nutritive compositions and physicochemical characteristics of raw goat milk during storage period (80 d). Compared with fresh goat milk, the frozen-thawed milk decreased contents of fat, protein, and lactose, as well as surface tension and stability coefficient, whereas increased effective diameter and polydispersity index. The average values of color values (L*, a*, and b*) in 4 group samples changed from 83.01 to 82.25, ?1.40 to ?1.54, 3.51 to 3.81, respectively, and the ΔE of most samples did not exceed 2. In contrast to the other 3 frozen-thawed treatments, goat milk treated with ultra-cryogenic freezing-homeothermic thawing (UFHT) possessed higher fat (5.20 g/100 g), smaller effective particle diameter (0.32 µm), and the lowest polydispersity index value (0.26). The color and confocal laser scanning microscopy images of UFHT were similar to those of fresh goat milk, illustrating UFHT was the optimal approach to maintain the natural quality of goat milk. Our finding provides a theoretical basis for producers to freeze surplus milk.     

Antibacterial effect of phenolic compounds from different wines

The antimicrobial properties of pure phenolic compounds and polyphenols of different wines against pathogens were investigated. It was observed that bacterial species exhibited different sensitivities towards the different concentrations of phenolic compounds. Escherichia coli was the most sensitive bacterium and Flavobacterium sp. was resistant against all phenolic compounds tested. All wine samples showed antimicrobial properties and the inhibition increased when the polyphenols concentration of wines increased. Clarified wines were inactive against all bacteria, indicating that polyphenolic compounds present in red wines, are responsible for the antimicrobial effects observed. The different concentrations of polyphenols in wines could have an important impact on consumers with the consequent increase in wine commercialization.     

Joint power control and user scheduling for backbone-assisted industrial wireless networks with successive interference cancellation

In a backbone-assisted industrial wireless network (BAIWN), the technology of successive interference cancellation (SIC) based non-orthogonal multiple access (NOMA) provides potential solutions for improving the delay performance. Previous work emphasizes minimizing the transmission delay by user scheduling without considering power control. However, power control is beneficial for SIC-based NOMA to exploit the power domain and manage co-channel interference to simultaneously serve multiple user nodes with the high spectral and time resource utilization characteristics. In this paper, we consider joint power control and user scheduling to study the scheduling time minimization problem (STMP) with given traffic demands in BAIWNs. Specifically, STMP is formulated as an integer programming problem, which is NP-hard. To tackle the NP-hard problem, we propose a conflict graph-based greedy algorithm, to obtain a sub-optimal solution with low complexity. As a good feature, the decisions of power control and user scheduling can be made by the proposed algorithm only according to the channel state information and traffic demands. The experimental results show that compared with the other methods, the proposed method effectively improves the delay performance regardless of the channel states or the network scales.

     

Effects of Quillaja saponaria extract and Nα-lauroyl-l-arginine ethyl ester on reducing selected foodborne pathogens in vitro and maintaining quality of fresh-cut endive (Cichorium endivia L.) at pilot plant scale

The aim of the present study was to evaluate the applicability of Quillaja saponaria extract (QSE) and N^α-lauroyl-l-arginine ethyl ester (LAE) as antimicrobial wash water additives in fresh-cut lettuce processing. Antibacterial activities of LAE and QSE against selected strains of the foodborne pathogens Salmonella enterica, Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, and Listeria monocytogenes were examined in vitro. Minimum inhibitory concentrations determined by broth microdilution assay demonstrated that LAE exhibited a strong antimicrobial activity with MICs between 4 and 32 μg/mL against all tested strains, whereas QSE showed a weaker antimicrobial activity with MICs >512 μg/mL. On a pilot-plant scale, the effects of warm water washing at 45 °C for 120 s with and without 40 mg/L QSE or 100 mg/L LAE as well as cold water washing at 4 °C for 120 s with QSE or LAE, respectively, of shredded endive (Cichorium endivia L.) were investigated regarding microbiological and sensory quality as well as physiological properties. Samples were analyzed for headspace O₂ and CO₂ levels, phenylalanine-ammonia-lyase activity and contents of nitrite and nitrate during nine days of cold storage at 4 °C. By analogy to its antimicrobial effect against the foodborne pathogens in vitro, LAE allowed up to 4 log₁₀ cfu/mL reduction of the microbial load in the washing water of the pilot plant, and might therefore reduce cross-contamination while saving water. The addition of LAE to warm washing water impaired sensory properties of fresh-cut endive during storage, which was predicted by chlorophyll fluorescence imaging analyses. QSE treatment combined with warm water washing best retained sensory appearance throughout our study, being possibly suitable for the production of premium products.     

猕猴桃多酚在羊肉反复冻融过程中的改善肉质和延缓氧化作用

反复冻融会造成羊肉品质下降,为明确猕猴桃疏果多酚在羊肉反复冻融中的作用,从而达到保持羊肉品质、延缓羊肉氧化、延长冻融羊肉货架期的目的。本研究用猕猴桃疏果多酚、表儿茶素、叔丁基对苯二酚（tertbutylhydroquinone,TBHQ）对羊肉浸泡,进行1、3、5次冻融处理,测定羊肉汁液流失率、显微结构、物性指标、pH值、色泽及肌红蛋白氧化状态、硫代巴比妥酸反应物（thiobarbituric acid reactive substances,TBARS）值、挥发性盐基氮（total volatile base nitrogen,TVB-N）值及羊肉脂肪酸相对含量。结果发现,随着冻融次数的增加汁液流失值呈增加趋势,在冻融结束时,疏果多酚组的汁液流失率较表儿茶素、TBHQ及空白组分别降低了17.57%、16.83%和40.10%(P<0.05);在冻融期间,羊肉在疏果多酚处理下有利于维持其肌纤维结构的完整性,可以减缓冻融羊肉硬度过度降低（P<0.05）;pH值随冻融次数的增加而降低,冻融5次结束后,疏果多酚组的pH值最高且比表儿茶素组显著升高了4.55%(P<0.05)...     

Measurement of 4He-p recoil cross sections

The recoil cross sections of protons induced by ⁴He⁺ particles were experimentally determined in an energy range of 1.3–2.1 MeV at recoil angles of 20° and 30 ° . The angular dependence of the recoil cross section at 2.0 MeV was also measured. By using the principle of detailed balance, a calculation of ⁴He-p recoil cross sections were calculated from p-⁴He phase shift data. Good agreement between the experimental data and theoretical values was found. The results show that recoil cross sections at low energies are non-Rutherford and are larger than the Rutherford value by approximately a factor of 2 at 2.0 MeV.     

基于主成分分析法评价两种餐饮用油的煎炸性能

目的 分析两种常见餐饮用油(餐饮调和油A和餐饮调和油B)煎炸性能的差异,并对餐饮用油煎炸品质进行综合评估。方法 在模拟西式快餐实际油炸条件下进行煎炸薯条实验,考察了餐饮用油在油炸过程中十项品质指标,并利用主成分分析法(PCA)对两种餐饮用油在油炸过程中的煎炸性能进行综合评价。结果 餐饮用油品质指标间存在不同程度的相关性,PCA将10个品质指标缩减成2个综合性评价指标,累计贡献率达87.920%,反映了餐饮用油煎炸品质的大部分信息,并进一步提取出评估餐饮用油煎炸性能的5个关键指标,即过氧化值、极性组分、碘价、羰基值以及亚油酸/棕榈酸比值。主成分分析综合得分表明,在油炸过程中,餐饮调和油A得分较高,具有较好的煎炸性能。结论 本研究建立的餐饮用油煎炸性能评价体系为煎炸油的筛选和质量控制提供借鉴。     

Qualitative and quantitative identification of adulteration of milk powder using DNA extracted with a novel method

The extraction of high-quality DNA from processed dairy products is often the crucial step in an authentication process by PCR-based methods. In this study, we optimized a novel DNA extraction method for milk powder and used the extracted DNA for identification of milk powder based on PCR analysis. The DNA quality was assessed by amplifying target sequences from mitochondrial genes, as well as by monitoring the yield, purity, and integrity of the extracted DNA. In addition, a laboratory adulteration model of milk powder was detected by PCR-based methods (PCR and real-time PCR) using primers targeting the mitochondrial 12S rRNA gene. Results showed that a sufficient amount and quality of DNA could be isolated from milk powder with this method. Both PCR and real-time PCR detection of cow milk compositions in goat milk powder further confirmed the DNA extracted with this extraction method could be widely used in addressing milk powder adulterant by a PCR-based method.     

不同脱乙酰度蚕蛹壳聚糖结构分析及其清除自由基能力的比较研究

首次采用无水乙醇浸泡辅助脱乙酰基与间歇式碱处理相结合的方法,通过控制反应时间制备不同脱乙酰度的蚕蛹壳聚糖。同时对其脱乙酰度、表观黏度和分子量等理化指标进行测定,用红外光谱对其基本结构进行表征,并分别采用邻二氮菲-Fe2＋氧化法、核黄素-光-氮蓝四唑法和DPPH法对其清除羟自由基（·OH）、超氧阴离子自由基（O2-·）和DPPH自由基能力进行了测定。结果表明：当反应时间为5、7、9h时,蚕蛹壳聚糖的脱乙酰度分别为：78.12%、86.45%、95.96%;蚕蛹甲壳素和不同脱乙酰度壳聚糖的红外光谱图的不同说明其结构上的差异,可为进一步研究其性质提供理论参考;蚕蛹壳聚糖对羟自由基和超氧阴离子自由基的清除率均较低,但均高于虾蟹壳来源的壳聚糖;对DPPH·的清除率较高。三种壳聚糖对三种自由基清除率的大小顺序均为：脱乙酰度为95.96%的壳聚糖〉脱乙酰度为86.45%的壳聚糖〉脱乙酰度为78.12%的壳聚糖。     

苹果疏除幼果与成熟果多糖成分分析及抗氧化活性研究

为了探究苹果疏除幼果与成熟果多糖组成成分及抗氧化活性的的差异,采用热水浸提法从苹果幼果与成熟果果渣中分别提取多糖,通过PMP柱前衍生化高效液相色谱法(HPLC)分析两种多糖的单糖组成,并通过体外抗氧化评价体系对二者的抗氧化活性进行比较研究。结果表明:苹果疏除幼果与成熟果多糖均由10种单糖构成,但单糖比例存在较大差异,抗氧化结果表明:苹果疏除幼果与成熟果多糖均具有一定的还原能力,并对O-2·、DPPH·和·OH具有清除能力,但在相同浓度水平下,苹果疏除幼果多糖的抗氧化能力显著高于成熟果多糖。