Combination of heat treatment and chitosan coating to improve postharvest quality of wolfberry (Lycium barbarum)

The synergistic application of hot water dip at 42 °C for 30 min and 1% chitosan coating on differentiation in postharvest quality traits, microstructure as well as microbiological evolution of wolfberry fruits was investigated. Fresh wolfberry fruits were stored at 2 ± 0.5 °C and 90% relative humidity (RH) for 28 days. Results indicated the combination of prestorage heat treatment and chitosan coating maintained higher levels of ascorbic acid, total phenolic contents and antioxidant capacity as well as lower decay, compared with untreated wolfberry fruits. The possible mechanism was that the heat treatment almost sealed open stomata to limit the sites of pathogen penetration into fruits independently, followed by the biofilm formed by chitosan which controlled secondary infections as well as slowed changes in fruit respiration and metabolic activity in wolfberries. The synergistically treated fruit also exhibited a higher acceptability obtained by sensory analysis after cold storage. In this sense, the integrated application of heat treatment and chitosan coating could be regarded as an effective strategy to extend storage life and maintain the postharvest quality of wolfberry fruits.     

Prevalence,enumeration, and characterization of Salmonella isolated from aquatic food products from retail markets in China

This study aimed to estimate the extent and level of Salmonella contamination of aquatic food products in China, and to determine serotype, virulotype, and the antimicrobial resistance profiles of recovered Salmonella isolates. Out of 554 samples collected from July 2011 to May 2014, 86 (15.5%) tested positive for Salmonella. The highest contamination rate occurred in oysters (23.1%, 6/26), followed by freshwater fish (18.6%, 43/231), shrimp (13.0%, 13/100), and saltwater fish (12.2%, 24/197). The contamination levels generally corresponded to a most probable number (MPN)/g of 0.3–10, although one sample exceeded 110 MPN/g. Among the 103 isolates, S. Typhimurium, S. Wandsworth, S. Thompson, and S. Derby were the most prevalent serovars. Sixty-eight isolates (66.0%) were resistant to at least one antimicrobial, and 35 (34.0%) were resistant to more than three. High rates of resistance were observed for tetracycline (35.9%), ampicillin (28.2%), nalidixic acid (26.2%), trimethoprim-sulfamethoxazole (25.2%), chloramphenicol (20.4%) and streptomycin (18.4%). Of note, S. Thompson isolates exhibited resistance to multiple extended-spectrum cephalosporins, ciprofloxacin, and other antimicrobials. PCR analysis of 15 virulence genes showed that ssaQ, mgtC, siiD, sopB, and bcfC were present in all 103 isolates, whereas the remaining loci were variably distributed. S. Typhimurium, S. Enteritidis, and S. Weltevreden isolates exhibited a wider range of pathogenicity determinants compared with the other strains. Our study provides a comprehensive surveillance on prevalence of Salmonella in aquatic food products from China and indicates its potential risk to public health. These data are valuable for epidemiological studies, risk management, and public health strategies.     

A QM/MM study of the catalytic mechanism of aspartate ammonia lyase

Aspartate ammonia lyase (Asp) is one of three types of ammonia lyases specific for aspartate or its derivatives as substrates, which catalyzes the reversible reaction of l-aspartate to yield fumarate and ammonia. In this paper, the catalytic mechanism of Asp has been studied by using combined quantum-mechanical/molecular-mechanical (QM/MM) approach. The calculation results indicate that the overall reaction only contains two elementary steps. The first step is the abstraction of C_β proton of l-aspartate by Ser318, which is calculated to be rate limiting. The second step is the cleavage of C_αN bond of l-aspartate to form fumarate and ammonia. Ser318 functions as the catalytic base, whereas His188 is a dispensable residue, but its protonation state can influence the active site structure and the existing form of leaving amino group, thereby influences the activity of the enzyme, which can well explain the pH dependence of enzymatic activity. Mutation of His188 to Ala only changes the active site structure and slightly elongates the distance of C_β proton of substrate with Ser318, causing the enzyme to remain significant but reduced activity.     

Floral origin markers for authenticating Lavandin honey (Lavandula angustifolia x latifolia). Discrimination from Lavender honey (Lavandula latifolia)

The aim of this study was to identify the botanical origin of Lavandin honey, a monofloral product of recent proliferation obtained from a hybrid of the species Lavandula angustifolia and Lavandula latifolia. Lavandin was authenticated here in chemical, palynological and sensory terms, and discriminated from the more common Lavender honey (L. latifolia).A total of 14 physico–chemical parameters, 26 pollen types, 13 sensory attributes and 80 volatile compounds were identified and/or quantified for this purpose.High concentrations of γ-nonalactone, farnesol and acetovanillone, which were for the first time identified as components of honey aroma in this study, together with several lactones, dehydrovomifoliol, 4-methoxyacetophenone and decanal are proposed as chemical markers for authenticating Lavandin monofloral honey. In sensory terms, increased scores for “caramel” and “peach compote” sensations, together with an increased Rubus pollen content, provide additional useful information for the accurate authentication of Lavandin honey and its discrimination from Lavender honey (L. latifolia).Results showed enough floral markers to authenticate the botanical origin of Lavandin honey allowing its marketing as monofloral rather than generic honey.     

Quercetagetin loaded in soy protein isolate–κ-carrageenan complex: Fabrication mechanism and protective effect

In the present study, the potential of soy protein isolate (SPI)–κ-carrageenan (κ-CG) complex as a protective carrier for quercetagetin was investigated at different pH values (pH 2.3 and 6.5). The particle size of the ternary aggregates was slightly increased at pH 2.3, yet dramatically decreased at pH 6.5 with increasing quercetagetin concentration. Moreover, the negative ζ-potential of the ternary aggregates was increased significantly (p < 0.05) at pH 6.5. The addition of quercetagetin to the SPI–κ-CG complex could highly quench the intrinsic fluorescence of SPI. Circular dichroism spectra further suggested that the bound quercetagetin could induce the rise of β-sheet and β-turn contents at the cost of α-helix and unordered coil fractions of SPI. In addition, quercetagetin could increase the viscoelasticity of the ternary aggregates at both pH. Furthermore, the SPI–κ-CG complex was found to be superior to single SPI or κ-CG in terms of improving light stability and radical scavenging ability of quercetagetin.     

Thermal markers arising from changes in the protein component of milk

Classification of heat load applied to milk requires the detection of parameters appropriately related to the intensity of the heat treatment. Current analytical methods based on heat-induced changes in the protein component of milk have been directed either to determine the amount of protein-derived products arised from heat treatments or to evaluate the extent of thermal denaturation of milk proteins. Lately, a new analytical strategy has been developed according to the occurrence of three major whey proteins, namely bovine serum albumin (BSA), beta-lactoglobulin (βlg) and alfa-lactalbumin (αla), normally soluble at pH 4.6 in raw milk, in the pH 4.6 insoluble protein fraction recovered from heat-treated milk. The results have shown that pH 4.6 insoluble BSA, βlg and αla, as detected by ELISA in milk, can be regarded as thermal markers suited for either dairy process control or regulation purposes.     

Bioactive compounds from Cudrania tricuspidata: A natural anticancer source

Abstract

The tumor is becoming a critical threat to our lives in these years. Searching for antitumor substances from natural products is a great interest of scientists. Cudrania tricuspidata (C. tricuspidata) is a regional plant containing 158 flavonoids and 99 xanthones, and others ingredients with favorable bioactivity. This review comprehensively analyzes the antitumor compounds from C. tricuspidata against different tumors, and 78 flavonoids plus xanthones are considered as underlying antineoplastic. Importantly, the structure of preylation groups is the primary source of antitumor activity among 45 flavonoids plus xanthones, which could be a direction of structural modification for a better antitumor ability. Additionally, the fruits are also preferable sources of antitumor compounds compared to the roots and barks due to the abundant isoflavones and sustainability. However, many studies only focused on the cells viability inhibition of the compounds, the underlying molecular mechanisms, and the intracellular targets remain ambiguous. In conclusion, C. tricuspidata has a great potential for anti-tumor prevention or therapy, but more attention should be paid to deeper research in vitro and in vivo models.     

Profiles and concentrations of heterocyclic aromatic amines formed in beef during various heat treatments depend on the time of ripening and muscle type

Heterocyclic Aromatic Amine (HAA) profiles and concentrations depended on several factors. The largest changes in the HAA profile were observed in meat ripened (chill stored) for 5–10 days. Amines whos concentration varied most prominently included: Phe-P 1, harmane, AαC, IQ, IQx, PhIP, MeAαC, and MeIQx. HAA concentrations were strongly correlated with concentrations of the above compounds. Time of storage significantly affected the HAA profile and concentration. The profile changed dynamically for storage times up to 10 days. For longer times the profile stabilized, only the HAA content increased.A novel, highly precise and accurate HAA analytical method was developed for this study. Results may help to optimize meat processing technology from the point of view of reducing concentration of HAA formed during heat treatment, including the most carcinogenic; IQ, IQx, MeIQx and PhIP amines.     

花色苷递送系统研究进展

花色苷作为植物中常见的功能色素物质,具有广泛的生理功能。然而,花色苷在加工和贮存过程中稳定性较差,容易发生降解。许多研究报道递送系统可应用于提高花色苷稳定性,进而提高其在体内的生物利用度。本文介绍了花色苷在人体内消化吸收的过程,并综述了目前用于提高花色苷肠道稳定性的几种递送系统,包括蛋白质递送系统、多糖递送系统、脂质体递送系统、复乳体系递送系统以及复合递送系统,以期为功能因子在食物中的进一步开发和利用提供理论依据。     

广东省水生动物中的维氏气单胞菌和无乳链球菌的耐药性评估

为研究广东省水生动物中的维氏气单胞菌(Aeromonas veronii)和无乳链球菌(Streptococcus agalactiae)对不同种类抗生素的药物敏感性,从广东省9个地区人工养殖的水生动物体内分离维氏气单胞菌及无乳链球菌。其中分离出32株维氏气单胞菌和16株无乳链球菌。利用药敏纸片法检测分离菌株对14种抗生素的药物感受性,发现两种病菌对其中的7种抗菌药物有明显的敏感性。利用最小抑菌浓度法检测分离菌株对7种敏感抗生素的耐药性,发现32株维氏气单胞菌对甲砜霉素(29%)部分耐药,盐酸土霉素(41%)和交沙霉素(38%)部分敏感,对盐酸环丙沙星(82%)、强力霉素(82%)、氟苯尼考(75%)和磺胺二甲嘧啶(100%)都敏感。16株链球菌对甲砜霉素(100%)全部耐药,对交沙霉素(25%)部分敏感,对盐酸环丙沙星(100%)、强力霉素(100%)、盐酸土霉素(100%)、氟苯尼考(100%)和磺胺二甲嘧啶(88%)都敏感。本论文的研究可以对今后抗生素在维氏气单胞菌与无乳链球菌的使用中提供一定的参考,促进抗生素的合理使用。