Active packaging solution to prolong the shelf life of rocket salad

The best packaging conditions for rocket salad were assessed by subsequent experimental trials. In the first step, a preliminary screening of different packaging materials was performed and two micro‐perforated oriented polypropylene films with different micro‐hole diameters (90 and 110 μm) were selected as best packaging solutions. In the subsequent experimental step, modified headspace conditions were applied without any improvement on product quality. In the last step, the effects of an ethylene adsorbent were analysed. Rocket salad packaged in both films with the ethylene adsorbent recorded a shelf life of about 16 days, compared to the control samples that remained acceptable for 13 days. During storage, the microbial quality (mesophilic and psychrotrophic bacteria, pseudomonadaceae, lactic acid bacteria, yeasts, total coliforms and enterobacteriacae), the pH, the colour changes and the main sensory parameters were also monitored.     

碳/碳复合材料在推进系统上的应用

本文介绍了碳 /碳复合材料在固体发动机、液体发动机和涡轮喷气发动机等推进系统上的应用。     

火箭发动机壳体封头形状最优设计的总极值方法

提出了火箭发动机壳体封头形状优化设计的一个新的数学模型，以封头母线函数的系数优化设计变量，封冰的单位容积质量城满足应力及几何等多个约束条件下，采用“积分型总极值”优化方法求解，实例表明，文中提出的数学模型和求解方法是正确和有效的。     

Impact of the synbiotic combination of Lactobacillus casei shirota and oligofructose-enriched inulin on the fecal volatile metabolite profile in healthy subjects

Scope: Hypothesis‐driven approaches have mainly focused on the quantification of SCFAs as mediators of beneficial effects of synbiotics. However, the emergence of metabolite profiling strategies allows to evaluate the colonic metabolism from a top‐down approach. In the present study, we evaluated the impact of a synbiotic combination on fecal metabolite profiles. Methods and results: A synbiotic combination (Lactobacillus casei Shirota cells+oligofructose‐enriched inulin) was evaluated in nine healthy volunteers. Before the start, during and after 4‐wk treatment, fecal samples were obtained. GC‐MS technology was applied to analyze the volatile metabolites. Application of a Type III test revealed that the metabolite profiles from the three conditions were significantly different. We identified three volatile organic compounds, acetate, dimethyl trisulfide and ethyl benzene, which were significantly affected. The acetate levels increased, whereas the dimethyl trisulfide levels decreased during and after the intervention. For ethyl benzene only an effect during the synbiotic intervention period was observed. Conclusion: We report a detailed analysis of the influence of L. casei Shirota combined with oligofructose‐enriched inulin on fermentation metabolites. Our results indicated a stimulation of saccharolytic fermentation and, importantly, a reduction of potentially toxic protein fermentation metabolites dimethyl trisulfide and ethyl benzene attended these effects.     

Polymorphism of the MPR1 gene required for toxic proline analogue resistance in the Saccharomyces cerevisiae complex species

We recently discovered, on the chromosome of Saccharomyces cerevisiae sigma 1278b, novel MPR1 and MPR2 genes required for resistance to a toxic analogue of L-proline, L-azetidine-2-carboxylic acid. The MPR genes, which were absent in the S. cerevisiae genome project strain S288C, encoded a novel acetyltransferase of 229 amino acids that detoxifies the analogue by acetylating it. The MPR1 gene homologue found in Schizosaccharomyces pombe was also shown to encode a similar acetyltransferase. To further analyse the origin and the physiological role of the yeast novel gene, we report here the comparative analysis of the MPR1 gene in the S. cerevisiae complex spp. which belong to the Saccharomyces sensu stricto group. Only the type strain of S. paradoxus exhibited resistance and acetyltransferase activity to L-azetidine-2-carboxylic acid. PCR was then used to isolate the new MPR1 homologue (Spa MPR1) from S. paradoxus with the primers based on the sequence of the MPR1 gene. Gene expression and enzymatic analysis showed that the cloned Spa MPR1 gene encodes an L-azetidine-2-carboxylic acid acetyltransferase of 231 amino acids, which has 87% identity to the MPR1 protein. We also found in the protein databases that S. bayanus contains a DNA fragment that is partly homologous to the MPR1 gene. However, the gene product was considered to lose the enzymatic activity, possibly due to the gene truncation or the base substitution(s) at the important region for catalysis. Further, genomic PCR analysis showed that most of the S. cerevisiae complex spp. have the sequence highly homologous to the MPR1 gene.     

The impact of the various chemical and physical factors on the degradation rate of bronopol

Bronopol (2‐bromo‐2‐nitropropane‐1,3‐diol) is used as preservative in cosmetic industry. Its main role in commercial products consists in protection of the cosmetic composition stability by inhibiting the development of micro‐organisms. Unfortunately, preservatives can also undergo the degradation processes. The aim of examinations was to prove that bronopol decomposes in aqueous solutions and storage conditions have a significance influence on its degradation rate. High‐performance liquid chromatography method (methanol/water with hydrochloric acid 5:95 v/v) with spectrophotometric detection (210 nm) was used for examining the decomposition rate of bronopol. The impact of chemical (addition of cosmetics components: citric acid and/or sodium dodecylsulfate) and physical (elevated and ambient temperature, sunlight or ultraviolet radiation and air access) factors has been elaborated. Bronopol decomposes most rapidly (independently on the sample surrounding conditions) when it is in solution with sodium dodecylsulfate, the inverse dependence is observed in the presence of two compounds – citric acid and sodium dodecylsulfate. Additionally, the elevated temperature causes the acceleration of decomposition. Bronopol degradation by‐products were also identified as methanol, formic acid, tris(hydroxymethyl)methane and 2‐bromo‐2‐nitroethanol.     

Exploring new potential health‐promoting vegetables: glucosinolates and sensory attributes of rocket salads and related Diplotaxis and Eruca species

BACKGROUND: Rocket salads (Diplotaxis tenuifolia and Eruca vesicaria) are presently highly appreciated salad vegetables. Related species are consumed as food plants in several regions, and may contribute to differentiation in the fresh food supply chain. Glucosinolates are well‐known healthy phytochemicals and responsible for positive and negative sensory properties of edible Brassicaceae. To investigate the potential for exploitation of new crops, Diplotaxis and Eruca germplasm was subject to sensory evaluation and glucosinolate analysis. RESULTS: Typical rocket salad flavour and pungency were perceived as positive sensory traits. Bitter, and especially herbaceous notes, characterised the groups of less accepted accessions. The groups classified as significantly unpleasant were characterised by high glucosinolate content, with either sinigrin (strong perceived pungency, flavour and several other additional sensory notes), or sinalbin/gluconapin (strong herbaceous note, low flavour perceived), as the dominant components. CONCLUSIONS: Low glucosinolate content, and a composition rich in recognised health‐promoting components (glucoerucin, glucoraphanin) were associated with higher acceptance. In relation to food uses, moderate glucosinolate content and high acceptance may be a better option to enhance the intake of healthy phytochemicals than high glucosinolates and potential rejection. High glucosinolate types may find better perspectives in the field of food integrators. Copyright © 2009 Society of Chemical Industry     

Proteomic analysis of the distribution of the major seed allergens in wild,landrace, ancestral,and modern soybean genotypes

BACKGROUND: A comparative analysis of seed allergens from various soybean genotypes is crucial for identifying and eliminating potential allergens. We have investigated the distribution of three major allergens (Gly m Bd 60K, Gly m Bd 30K and Gly m Bd 28K) in wild, landrace, ancestral and modern soybean genotypes. RESULTS: Gly m Bd 60K allergens consist of α subunits of β‐conglycinin and G2 subunits of glycinin. In wild genotypes, α subunits of β‐conglycinin separated into six to seven protein spots whereas five to seven spots were observed in the landraces. All genotypes of modern and ancestral groups showed 3–5 protein spots of α subunits of β‐conglycinin. All genotypes showed eight spots of glycinin G2 subunits except one ancestral genotype which had seven spots. Two protein spots were detected for Gly m Bd 30K in 14 genotypes but one spot was detected in two wild genotypes. Two protein spots were detected for Gly m Bd 28K in all genotypes. CONCLUSION: Considerable heterogeneity of the α subunit of β‐conglycinin distribution exists among these 16 soybean genotypes. Significant proteomic variation was observed between different soybean groups rather than among genotypes in the same group. This investigation would be valuable to researchers working with soybean and nutrition. Copyright © 2007 Society of Chemical Industry     

Mutational study of the role of tyrosine-49 in the Saccharomyces cerevisiae xylose reductase

The xyl1 gene encoding xylose reductase was cloned from Saccharomyces cerevisiae and expressed in Escherichia coli. The purified enzyme readily carried out xylose reduction in vitro. It prefers NADPH as the co-enzyme by about 80-fold over NADH. Compared to the native enzyme purified from S. cerevisiae (Kuhn et al., 1995), the recombinant xylose reductase displayed slightly higher (about two-fold) affinities (K(m)) for the substrate (xylose) and co-factor (NADPH), as well as a 3.9-fold faster turnover number (K(cat)) and 7.4-fold greater catalytic efficiency (K(cat)/K(m)). The reason for the apparent discrepancies in kinetic constants between the recombinant and native S. cerevisiae xylose reductases is not known. Replacement of Tyr49 by Phe in the recombinant enzyme led to greater than 98% loss of activity, suggesting that this residue plays a critical role in catalysis. Intrinsic enzyme fluorescence spectroscopic analysis showed that the wild-type and the Y49F variant both bound the co-enzyme NADPH with similar affinity. This supports the view that Tyr49 is involved in interaction with the substrate and not the co-factor during catalysis.     

Effects of ripening, 1-methylcyclopropene and ultra-high-pressure pasteurisation on the change of volatiles in Chinese pear cultivars

BACKGROUND: Aroma is one important fruit sensory attribute influenced by the volatile constituents related to species, variety and technological treatments. We analysed the variations of volatile compounds in five pear cultivars and investigated their changes related to different pear organs, different ripening stages, 1‐MCP treatment and ultra‐high‐pressure pasteurisation. RESULTS: Considerable variations exist in the quantity of 10 volatile compounds among five pear cultivars. Their levels generally showed an increasing trend when collected at later harvest time in Ya pear. In Whangkeumbae pear, most volatile compounds reached their maximum levels in skin and pulp. After treating pears with 42 µmol L^?1 1‐methylcyclopropene (1‐MCP), the levels of volatiles remained basically unchanged or only slightly increased in Ya pear during a shelf life of 21 days. When Huangguan pear juice was pasteurised by using ultra‐high pressure, the levels of volatiles significantly changed during the shelf life. CONCLUSION: The volatile compositions of five different Chinese pear cultivars differ considerably. The levels of these volatiles vary along with ripening stages and pear tissues. A moderate concentration of 1‐MCP could keep the levels of volatile compounds basically unchanged during storage and ultra‐high‐pressure pasteurisation could change the levels of volatiles significantly during the following shelf life. Copyright © 2011 Society of Chemical Industry     

Analysis of the mould microbiome and exogenous enzyme production in Moutai‐flavor Daqu

The objective of this study was to isolate and screen the mould microbiome of five Moutai‐flavor Daqu samples and to characterize and quantify the associated exogenous enzymes. In all, 11 and 18 mould genera were identified in the samples by, respectively, a culture‐dependent method and a culture‐independent high throughput sequencing method. Species of Aspergillus and Rhizopus were the dominant mould genera in the Moutai‐flavor Daqu samples. Analysis of enzyme production showed that Aspergillus versicolor in Daqu ZX01 exhibited the highest neutral proteinase activity (2671.0 ± 73.9 U/g) and Rhizomucor pusillus in Daqu DYT01 exhibited the highest saccharifying amylase production ability (1724.6 ± 11.0 U/g). Copyright © 2017 The Institute of Brewing & Distilling     

Absorption of N-phenylpropenoyl-L-amino acids in healthy humans by oral administration of cocoa (Theobroma cacao)

Besides flavan-3-ols, a family of N-phenylpropenoyl-L-amino acids (NPAs) has been recently identified as polyphenol/amino acid conjugates in the seeds of Theobroma cacao as well as in a variety of herbal drugs. Stimulated by reports on their biological activity, the purpose of this study was to investigate if these amides are absorbed by healthy volunteers after administration of a cocoa drink. For the first time, 12 NPAs were quantified in human urine by means of a stable isotope dilution analysis with LC-MS/MS (MRM) detection. A maximum amount was found in the urine taken 2 h after the cocoa consumption. The highest absolute amount of NPAs excreted with the urine was found for N-[4'-hydroxy-(E)-cinnamoyl]-L-aspartic acid (5), but the highest recovery rate (57.3 and 22.8%), that means the percentage amount of ingested amides excreted with the urine, were determined for N-[4'-hydroxy-(E)-cinnamoyl]-L-glutamic acid (6) and N-[4'-hydroxy-3'-methoxy-(E)-cinnamoyl]-L-tyrosine (13). In order to gain first insights into the NPA metabolism in vivo, urine samples were analyzed by LC-MS/MS before and after beta-glucuronidase/sulfatase treatment. As independent of the enzyme treatment the same NPA amounts were found in urine, there is strong evidence that these amides are metabolized neither via their O-glucuronides nor their O-sulfates. In order to screen for caffeic acid O-glucuronides as potential NPA metabolites, urine samples were screened by means of LC-MS/MS for caffeic acid 3-O-beta-D-glucuronide and 4-O-beta-D-glucuronide. But not even trace amounts of one of these glucuronides were detectable, thus excluding them as major NPA metabolites and underlining the importance of future investigations on a potential O-methylation or reduction of the N-phenylpropenoyl moiety in NPAs.