Lack of an association between single nucleotide polymorphisms in the bovine leptin gene and intramuscular fat in Bos taurus cattle

Leptin contributes to the regulation of adiposity and metabolism, and single nucleotide polymorphisms (SNPs) in the leptin gene have been associated with intramuscular fat (IMF) levels in beef. Our objectives were to estimate the frequency of four SNPs in the leptin gene in nine purebred cattle (n = 430), to test for linkage disequilibrium and infer haplotypes, and to determine if individual genotypes or estimated haplotypes were associated with IMF values in crossbred cattle (n = 244). The four SNP loci were found to be in linkage disequilibrium and thus, the frequencies of each of the 16 possible haplotypes were inferred by maximum likelihood. No significant association between any individual SNP and haplotype was found with the divergent IMF values. Our results suggest that these SNPs are not influential on the divergent IMF levels in the crossbred population tested.     

Ohmic heating of meats: Electrical conductivities of whole meats and processed meat ingredients

The ohmic heating rate of a food is highly influenced by its electrical conductivity (σ). A survey of σ values of commonly used meat ingredients when dispersed as 5% (w/w) aqueous solutions/suspensions was undertaken. A subset was further investigated at typical usage levels in solution/suspension, and/or when incorporated into beef blends, while σ of selected cuts from five meat species (beef, pork, lamb, chicken and turkey) was also measured. Measurements were made from 5 to 85 °C and showed a linear increase in σ values with increasing temperature. In processed beef, addition of sodium chloride and phosphate (P22) caused a significant increase in σ which in turn would lead to an increase in ohmic heating rates. Furthermore, whole meats with lower endogenous fat or processed meats with the least added fat displayed higher σ and reduced ohmic heating times. In beef maximum σ was observed when fibres were aligned with the current flow.     

Predictive model of Vibrio parahaemolyticus growth and survival on salmon meat as a function of temperature

The growth and survival curves of a strain of pandemic Vibrio parahaemolyticus TGqx01 (serotype O3:K6) on salmon meat at different storage temperatures (range from 0 °C to 35 °C) were determined. In order to model the growth or inactivation kinetics of this pathogen during storage, the modified Gompertz and Weibull equations were chosen to regress growth and survival curves, respectively, and both equations produced good fit to the observed data (the average R² value equals to 0.990 for modified Gompertz and 0.920 for Weibull equation). The effect of storage temperature on the specific growth rate (μ) was modeled by square root type equation, and the relationship between μ and lag time (λ) was described by a rule of μ × λ = constant. The shape factor (n) and scale factor (b) values of the Weibull equations versus the temperature (°C) were plotted and the temperature effects on these parameters were described by two linear empirical equations. The predicted growth and survival curves from the model were compared to real enumeration results, using the correlation coefficient (R²), bias factor (B_f) and accuracy factor (A_f), to assess the performance of the established model. The results showed that the overall predictions for V. parahaemolyticus TGqx01 growth or inactivation on salmon at tested temperatures agreed well with observed plate counts, and the average R², B_f and A_f values were 0.958, 1.019 and 1.035, respectively.     

Hyperspectral imaging for the investigation of quality deterioration in sliced mushrooms (Agaricus bisporus) during storage

In this study, the potential application of hyperspectral imaging (HSI) for quality prediction of white mushroom slices during storage at 4 °C and 15 °C was investigated. Mushroom slice quality was measured in terms of moisture content, colour (CIE Lightness, L* and yellowness, b*) and texture (hardness, H and chewiness, Ch). Hyperspectral images were obtained using a pushbroom line-scanning HSI instrument, operating in the wavelength range of 400–1,000 nm with spectroscopic resolution of 5 nm. Multiple linear regression (MLR) and Principal Component Regression (PCR) models were developed to investigate the relationship between reflectance and the various quality parameters measured. 20 optimal wavelengths for quality prediction were selected after performing an exhaustive search for the best subsets of predictor variables on a calibration set of 84 samples. PCR applied to the set of optimal wavelengths gave the best performance as compared to MLR and PCR on the entire wavelength range. When applied to an independent validation set of samples, PCR models developed on the calibration set were capable of predicting moisture content with RMSEP of 0.74% w.b. and R ² of 0.75, L* with RMSEP of 0.47 and R ² of 0.95, b* with RMSEP of 0.66 and R ² of 0.75, H with RMSEP of 0.49 N and R ² of 0.77 and Ch with RMSEP of 0.27 N and R ² of 0.72. Virtual images showing the distribution of moisture content on the mushroom surface were generated from the estimated PCR model. Results from this study could be used for the development of a non-destructive monitoring system for prediction of sliced mushroom quality.     

Proteomic analysis of differentially expressed proteins in bovine milk during experimentally induced Escherichia coli mastitis

The objectives of the current study were to profile changes in protein composition using 2-dimensional gel electrophoresis on whey samples from a group of 8 cows before and 18 h after infection with Escherichia coli and to identify differentially expressed milk proteins by peptide sequencing using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry post source decay. Only proteins present in whey fractions of all 8 cows were sequenced to avoid reporting a protein response unique to only a subset of infected cows. Despite the overwhelming presence of casein and β-lactoglobulin, the low abundance proteins transthyretin, lactadherin, β-2-microglobulin precursor, α-1-acid glycoprotein, and complement C3 precursor could be identified in whey samples from healthy cows. Whey samples at 18 h postinfection were characterized by an abundance of serum albumin, in spots of varying mass and isoelectric point, as well as increased transthyretin and complement C3 precursor levels. Also detected at 18 h postinoculation were the antimicrobial peptides cathelicidin, indolicidin, and bactenecin 5 and 7, and the proteins β-fibrinogen, α-2-HS-glycoprotein, S100-A12, and α-1-antiproteinase. Most notable was the detection of the acute phase protein α-1-acid glycoprotein in mastitic whey samples, a result not previously reported. In contrast to methods used in previous proteomic analyses of bovine milk, the methods used in the current study enabled the rapid identification of milk proteins with minimal sample preparation. Use of a larger sample size than previous analyses also allowed for more robust protein identification. Results indicate that examination of the protein profile of whey samples from cows after inoculation with E. coli could provide a rapid survey of milk protein modulation during coliform mastitis and aid in the identification of biomarkers of this disease.     

Effects of cutting intensity and stirring speed on syneresis and curd losses during cheese manufacture

Recombined whole milk was renneted under constant conditions of pH, temperature, and added calcium, and the gel was cut at a constant firmness. The effects of cutting and stirring on syneresis and curd losses to whey were investigated during cheese making using a factorial design with 3 cutting modes designed to provide 3 different cutting intensity levels (i.e., total cutting revolutions), 3 levels of stirring speed, and 3 replications. These cutting intensities and stirring speeds were selected to give a wide range of curd grain sizes and curd shattering, respectively. Both factors affected curd losses, and correct selection of these factors is important in the cheesemaking industry. Decreased cutting intensity and increased stirring speed significantly increased the losses of fines and fat from the curd to the whey. Cutting intensities and stirring speeds in this study did not show significant effects on curd moisture content over the course of syneresis. Levels of total solids, fines, and fat in whey were shown to change significantly during syneresis. It is believed that larger curd particles resulting from low cutting intensities coupled with faster stirring speeds resulted in a higher degree of curd shattering during stirring, which caused significant curd losses.     

拉曼光谱技术在注射剂快检中的应用研究

从注射剂药品快检的角度出发,运用拉曼光谱技术对注射用头孢拉定、头孢唑林钠、苯巴比妥钠、头孢呋辛钠4种针剂进行快速鉴别、检查。通过与原料药的拉曼光谱进行对比,对特征拉曼信号进行了定性分析,得到了四种样品的拉曼光谱图,为这些药品的鉴定提供了重要的参考数据。本方法操作简便、快速并且对测试样品无损,可成为注射剂快速检测的分析方法。     

两种不同产地诺丽果的主要营养成分与抗氧化活性评价

目的 研究不同产地诺丽果的主要营养成分与抗氧化活性的异同。方法 通过国标法、分光光度法和色谱法对比分析海南和斐济诺丽果中主要矿物质和微量元素、挥发性成分、多酚组成与抗氧化活性。结果 两种诺丽果中K、Ca、Mg、P、S元素含量较高,而斐济诺丽果的矿物质与微量元素的总量高于海南诺丽果。诺丽果挥发性成分主要由酯类和酸类化合物组成,并且斐济诺丽果果实中酯类和酸类成分含量较高。海南诺丽果中总酚的含量显著高于斐济诺丽果（P<0.05）,而总黄酮含量则低于斐济诺丽果（P>0.05）。从两种诺丽果中共检测出20种酚类物质,其中6种酚酸和14种类黄酮物质,主要以没食子酸、槲皮素-3-鼠李糖苷和芦丁含量最高。海南诺丽果对2,2’-联氮-双(3-乙基苯并噻唑啉-6-磺酸)二铵盐自由基清除能力要强于斐济诺丽果,而对1,1-二苯基-2-三硝基苯肼自由基清除能力和铁离子还原能力则弱于斐济诺丽果,并与主要酚类物质组成相关。结论 两种诺丽果具有较高的营养价值和良好的抗氧化活性,且斐济诺丽果的综合品质略优于海南诺丽果。     

Dietary polyphenols and type 2 diabetes: Human Study and Clinical Trial

Abstract

Significant evidence from epidemiological investigations showed that dietary polyphenols might manage and prevent type 2 diabetes (T2D). This review summarizes human studies and clinical trials of polyphenols as anti-diabetic agents. Polyphenols from coffee, guava tea, whortleberry, olive oil, propolis, chocolate, red wine, grape seed, and cocoa have been reported to show anti-diabetic effects in T2D patients through increasing glucose metabolism, improving vascular function as well as reducing insulin resistance and HbA1c level. However, individual flavonoid or isoflavonoid compounds appear to have no therapeutic effect on diabetes, based on the limited clinical data. Preliminary clinical trials provided evidence that resveratrol had anti-diabetic activity in humans by improving glycemic control in subjects with insulin resistance. Besides, anthocyanins exhibited anti-diabetic properties by reducing blood glucose and HbA1c levels or the improvement of insulin secretion and resistance. The structure-activity relationship of polyphenols as anti-diabetic agents in humans has been rarely reported.     

Electric field effects on β-lactoglobulin thermal unfolding as a function of pH – Impact on protein functionality

The presence of moderate electric fields (MEF) during ohmic heating (OH) treatment of whey protein systems have demonstrated potential to change physicochemical and functional properties, like aggregation rate and extension or viscoelastic behaviour. However, the specific action of MEF upon the molecular structure of proteins, particularly during thermal processing has yet to be clarified. The effects of MEF in pure fractions of β-lactoglobulin (β-lg) under non-aggregating conditions (low concentration and ionic strength), were investigated in this work. Protein samples were identically heat-treated through conventional and OH methods and at different pH values. β-lg's structural features were characterized by evaluation of secondary structure distribution and local conformational changes using techniques such as circular dichroism, intrinsic and extrinsic fluorescence and free thiol groups reactivity. It was confirmed that MEF affects β-lg upon thermal unfolding, resulting in distinctive structural features, surface hydrophobicity and SH reactivity. The mechanism of action is probably related with the molecular motion induced by the oscillating electric field and is more pronounced at neutral pH, where β-lg is more susceptible to thermal structural changes. These results contribute to a better understanding of OH processing and its effects in food matrices reinforce the possibility of using MEF as a toll to change protein functionality.Industrial relevanceOhmic heating is an emerging technology and is being established as reference method for processing protein-rich food such as dairy and egg products. Non-thermal effects of the applied electric fields during ohmic heating have been addressed but few works deal with their real impact in structural and molecular properties of food proteins with high biological value.In this work demonstrated that the presence of an electric field during ohmic heating processing influences structural aspects of beta-lactoglobulin. This knowledge plays an important role on process design (i.e. pasteurization binomials and fouling control) and product quality because these proteins play an essential role in food's nutritional and organoleptic properties, as well as on functionality, allergenicity and stability aspects.