食品防腐剂的分类、安全性及应用研究

植物精油是一类天然的抑菌剂,能够有效抑制多种肉源腐败菌和致病菌,在肉类工业中应用前景广泛。纳米乳液作为一种纳米级包埋系统,在改善精油的水溶性、稳定性和抑菌活性方面有明显效果,目前已成为肉类防腐保鲜领域的研究热点。因此,本文介绍了植物精油纳米乳液的构建方法（乳化方式、乳化剂）、基本特性（稳定性和生物利用率）,重点探讨了植物精油纳米乳液对肉源腐败菌和致病菌的抑菌活性、影响因素（精油种类、乳化方式、乳化剂、乳液粒径和微生物种类）,及其通过靶向结合、持续释放、被动运输等提高纯精油抑菌活性的内在机制,以期为植物精油纳米乳液在肉制品防腐保鲜中的研究及开发利用提供理论参考。     

Applicability of bacteriocin‐producing Lactobacillus plantarum,Enterococcus faecium and Lactococcus lactis ssp. lactis as adjunct starter in Minas Frescal cheesemaking

The antimicrobial and technological characteristics of three bacteriocinogenic cultures used as adjunct starters in Minas Frescal cheese were investigated. The cheeses were manufactured with 1% commercial lactic starter and 0.5%Lactococcus lactis ssp. lactis ATCC 11454, Lactobacillus plantarum ALC 01 or Enterococcus faecium FAIR‐E 198. The cheeses were then artificially inoculated with Listeria monocytogenes Scott A, Staphylococcus aureus ATCC 27154 and Bacillus cereus K1‐B041 and stored for 21 days at 8°C. The results show that there was no significant difference in the counts of L. monocytogenes and S. aureus between the cheeses made with added bacteriocinogenic cultures and the control cheese. On the other hand, B. cereus exhibited susceptibility to Lb. plantarum ALC 01 and E. faecium FAIR‐E 198 from the seventh day of storage. However, these cultures increased the proteolysis of the Minas Frescal cheese.     

未来食品的发展: 植物蛋白肉与细胞培养肉

豆血红蛋白是一种植物源血红蛋白,在植物蛋白肉加工中可作为重要的风味催化剂和着色剂,大大增加植物蛋白肉的拟真性。为实现豆血红蛋白在食品级微生物中的异源表达,将携带豆血红蛋白LBC2基因的质粒PESC-TRP转入酿酒酵母CEN.PK2-1C中,通过添加kozak序列促进其翻译,并进一步对启动子序列进行选择,以提高豆血红蛋白表达量。对重组菌株进行发酵,用Western blot分析LegH蛋白表达水平。结果显示,诱导型启动子GAL1,10较三种组成型启动子TEF1、ADH1、GAP在表达LegH能力上具有显著优势,较产量最低的ADH1启动子提升了3.93倍。在组成型启动子中,TEF1启动子能力较优,是ADH1启动子的2.91倍,是GAP启动子的1.2倍。最后,利用Ni柱亲和层析对蛋白进行浓缩纯化,测得LegH发酵浓度为2.79 mg/L。本研究成功实现了豆血红蛋白在酿酒酵母中的异源表达,经后续优化有可能成为豆血红蛋白异源表达的又一途径。     

Novel natural food preservatives and applications in seafood preservation: a review

Food preservative additives are natural or synthetic substances which delay degradation in foods caused by microbial growth, enzyme activity, and oxidation. Until recently, the use of synthetic additives in food was more common. However, synthetic additives have not been widely accepted by consumers in recent years due to their assumed adverse effects on their health. Therefore, the tendency of consumers to natural additives is increasing day-by-day. Seafood is an easily perishable food due to its chemical composition. Immediately after harvest, changes in odor, taste, and texture in fishery products can be noticed. For this reason, measures to protect the product must be taken immediately after harvest or catching. Various preservation methods have been developed. In addition to various technological methods, preservative additives are used in fresh or processed seafood as well as in other foods. This review focuses on novel natural preservatives from different sources such as plants, bacteria, fungi, animals and algae, and their use in seafood to protect quality and prolong shelf life. © 2018 Society of Chemical Industry     

Saccharomyces cerevisiae biomass as a source of next-generation food preservatives: Evaluating potential proteins as a source of antimicrobial peptides

Saccharomyces cerevisiae is the main biotechnological tool for the production of Baker's or Brewer's biomasses, largely applied in beverage and fermented-food production. Through its gene expression reprogramming and production of compounds that inactivate the growth of other microorganisms, S. cerevisiae is able to grow in adverse environments and in complex microbial consortia, as in fruit pulps and root flour fermentations. The distinct set of up-regulated genes throughout yeast biomass propagation includes those involved in sugar fermentation, ethanol metabolization, and in protective responses against abiotic stresses. These high abundant proteins are precursors of several peptides with promising health-beneficial activities such as antihypertensive, antioxidant, antimicrobial, immunomodulatory, anti-obesity, antidiabetes, and mitogenic properties. An in silico investigation of these S. cerevisiae derived peptides produced during yeast biomass propagation or induced by physicochemical treatments were performed using four algorithms to predict antimicrobial candidates encrypted in abundantly expressed stress-related proteins encoded by different genes like AHP1, TSA1, HSP26, SOD1, HSP10, and UTR2, or metabolic enzymes involved in carbon source utilization, like ENO1/2, TDH1/2/3, ADH1/2, FBA1, and PDC1. Glyceraldehyde-3-phosphate dehydrogenase and enolase II are noteworthy precursor proteins, since they exhibited the highest scores concerning the release of antimicrobial peptide candidates. Considering the set of genes upregulated during biomass propagation, we conclude that S. cerevisiae biomass, a food-grade product consumed and marketed worldwide, should be considered a safe and nonseasonal source for designing next-generation bioactive agents, especially protein encrypting antimicrobial peptides that display broad spectra activity and could reduce the emergence of microbial resistance while also avoiding cytotoxicity.     

Food colors: Existing and emerging food safety concerns

Food colors are added to different types of commodities to increase their visual attractiveness or to compensate for natural color variations. The use of these additives is strictly regulated in the European Union, the United States, and many other countries worldwide. There is a growing concern about the safety of some commonly used legal food colorants and there is a trend to replace the synthetic forms with natural products. Additionally, a number of dyes with known or suspected genotoxic or carcinogenic properties have been shown to be added illegally to foods. Robust monitoring programs based on reliable detection methods are required to assure the food is free from harmful colors. The aim of this review is to present an up to date status of the various concerns arising from use of color additives in food. The most important food safety concerns in the field of food colors are lack of uniform regulation concerning legal food colors worldwide, possible link of artificial colors to hyperactive behavior, replacement of synthetic colors with natural ones, and the presence of harmful illegal dyes—both known but also new, emerging ones in food. The legal status of food color additives in the EU, United States, and worldwide is summarized. The reported negative health effects of both legal and illegal colors are presented. The European Rapid Alert System for Food and Feed notifications and US import alerts concerning food colors are analyzed and trends in fraudulent use of color additives identified. The detection methods for synthetic colors are also reviewed.     

Short communication: Improving the activity of bile salt hydrolases in Lactobacillus casei based on in silico molecular docking and heterologous expression

Bile salt hydrolase (BSH) plays an essential role in the cholesterol-removing effect of lactic acid bacteria, which hydrolyze conjugated bile salts to amino acid and deconjugated bile salts. However, Lactobacillus casei lacks the bsh gene, which may make it highly sensitive to bile salt stress. We wanted to improve the BSH activity of L. casei for various food-industry applications (e.g., milk fermentation). Plate assay testing indicated that Lactobacillus plantarum AR113 has the highest BSH activity. We cloned and sequenced 4 bsh genes from the genome of L. plantarum AR113. Structure modeling and molecular docking of BSH indicated that BSH1 and BSH3 could react efficiently with bile salts, so we selected BSH1 and BSH3 for heterologous expression in L. casei. Compared with single expression of BSH1 or BSH3, co-expression of both protein sequences showed the highest hydrolysis activity by HPLC analysis. Our results suggested that heterologous expression of BSH in L. casei can significantly improve host activity against bile salts, and in silico molecular docking could be an efficient method of rapid screening for BSH with high activity.     

Mining,heterologous expression,purification, antibactericidal mechanism,and application of bacteriocins: A review

Bacteriocins are generally considered as low-molecular-weight ribosomal peptides or proteins synthesized by G⁺ and G⁻ bacteria that inhibit or kill other related or unrelated microorganisms. However, low yield is an important factor restricting the application of bacteriocins. This paper reviews mining methods, heterologous expression in different systems, the purification technologies applied to bacteriocins, and identification methods, as well as the antibacterial mechanism and applications in three different food systems. Bioinformatics improves the efficiency of bacteriocins mining. Bacteriocins can be heterologously expressed in different expression systems (e.g., Escherichia coli, Lactobacillus, and yeast). Ammonium sulfate precipitation, dialysis membrane, pH-mediated cell adsorption/desorption, solvent extraction, macroporous resin column, and chromatography are always used as purification methods for bacteriocins. The bacteriocins are identified through electrophoresis and mass spectrum. Cell envelope (e.g., cell permeabilization and pore formation) and inhibition of gene expression are common antibacterial mechanisms of bacteriocins. Bacteriocins can be added to protect meat products (e.g., beef and sausages), dairy products (e.g., cheese, milk, and yogurt), and vegetables and fruits (e.g., salad, apple juice, and soybean sprouts). The future research directions are also prospected.     

我国新资源食品食用情况的社会文化影响因素分析

目的 调查新资源食品的食用情况, 并对其社会文化影响因素进行研究探讨。方法 对776 名消费者的问卷调查、6 家北京新资源食品生产厂家实地调研和卫生部新资源食品专家访谈, 采用Excel、SPSS17.0专业统计软件对收集到的数据进行统计分析。结果 影响新资源食品食用人群、食用量的社会文化影响因素有消费者自身因素、生产厂家因素、政府政策因素、舆论导向。结论 提出目前新资源食品发展中存在的问题和解决方式, 推动新资源食品的健康稳定发展。     

Short communication: Naturally sensitive Bacillus thuringiensis EG10368 produces thurincin H and acquires immunity after heterologous expression of the one-step-amplified thurincin H gene cluster

Heterologous expression of bacteriocin genetic determinants (or operons) has long been a research interest for the functional analysis of genes involved in bacteriocin biosynthesis, regulation, modification, and immunity. Previously, construction of genomic libraries of the bacteriocin producer strains was usually required to identify new bacteriocin operons, a method that is tedious and time consuming. For the first time, we directly amplified an 8.14-kb bioinformatically identified thurincin H gene cluster using a one-step PCR method with 100% accuracy. This amplified gene cluster was cloned into plasmid pHT315, resulting in plasmid pGW139, and subsequently transformed to Bacillus thuringiensis EG10368, a strain naturally sensitive to thurincin H. Heterologous expression of the gene cluster makes the sensitive B. thuringiensis EG10368 produce thurincin H at a higher level compared with the wild-type producer, B. thuringiensis SF361. Moreover, B. thuringiensis EG10368pGW139 acquired complete immunity to thurincin H. The results indicated that one-step PCR is a promising tool to accurately amplify long bacteriocin gene clusters used in bacteriocin functional analysis studies and it is an effective way to produce bacteriocins at a higher level, without the need to clone large chromosomal fragments.     

Multilayer packaging: Advances in preparation techniques and emerging food applications

In recent years, with advantages of versatility, functionality, and convenience, multilayer food packaging has gained significant interest. As a single entity, multilayer packaging combines the benefits of each monolayer in terms of enhanced barrier properties, mechanical integrity, and functional properties. Of late, apart from conventional approaches such as coextrusion and lamination, concepts of nanotechnology have been used in the preparation of composite multilayer films with improved physical, chemical, and functional characteristics. Further, emerging techniques such as ultraviolet and cold plasma treatments have been used in manufacturing films with enhanced performance through surface modifications. This work provides an up‐to‐date review on advancements in the preparation of multilayer films for food packaging applications. This includes critical considerations in design, risk of interaction between the package and the food, mathematical modeling and simulation, potential for scale‐up, and costs involved. The impact of in‐package processing is also explained considering cases of nonthermal processing and advanced thermal processing. Importantly, challenges associated with degradability and recycling multilayer packages and associated implications on sustainability have been discussed.     

Modeling food matrix effects on chemical reactivity: Challenges and perspectives

ABSTRACT

The same chemical reaction may be different in terms of its position of the equilibrium (i.e., thermodynamics) and its kinetics when studied in different foods. The diversity in the chemical composition of food and in its structural organization at macro-, meso-, and microscopic levels, that is, the food matrix, is responsible for this difference. In this viewpoint paper, the multiple, and interconnected ways the food matrix can affect chemical reactivity are summarized. Moreover, mechanistic and empirical approaches to explain and predict the effect of food matrix on chemical reactivity are described. Mechanistic models aim to quantify the effect of food matrix based on a detailed understanding of the chemical and physical phenomena occurring in food. Their applicability is limited at the moment to very simple food systems. Empirical modeling based on machine learning combined with data-mining techniques may represent an alternative, useful option to predict the effect of the food matrix on chemical reactivity and to identify chemical and physical properties to be further tested. In such a way the mechanistic understanding of the effect of the food matrix on chemical reactions can be improved.     

非精神活性药用大麻的应用及开发

为了实现大麻二酚酸合成酶（CBDAS）的微生物底盘高效表达,为体外合成大麻二酚（CBD）提供重组酶。首先从高CBD含量大麻叶片中克隆CBDAS基因,利用生物信息学方法分析其蛋白的基本理化性质,构建重组质粒pPIC9K-CBDAS后转化毕赤酵母菌,筛选重组蛋白CBDAS高表达的培养条件,并分析CBDAS的催化活性。结果表明,构建的pPIC9K-CBDAS融合蛋白表达系统能在毕赤酵母中表达;在甲醇添加量为1%、培养基pH6.0和培养48 h的诱导条件下表达量最大;重组酶CBDAS催化底物大麻萜酚酸（CBGA）反应4 h后大麻二酚酸（CBDA）含量显著增加（P<0.05）,在8 h后CBD含量显著增加（P<0.05）,在12 h时合成CBDA和CBD量达到最大值;CBDAS在大麻叶片大麻萜酚酸（CBGA）粗提液和CBGA标品中反应12 h后分别生成CBDA 60.64和20.12 ng/mL,CBD 128.01和207.87 ng/mL,具有较强的催化活性。通过酵母异源表达实现了大麻CBDAS的重组表达,为经济高效地合成CBDA和CBD提供活性酶。     

Dietary fibre: Challenges in production and use of food composition data

Dietary fibre is a heterogeneous group of components for which several definitions and analytical methods were developed over the past decades, causing confusion among users and producers of dietary fibre data in food composition databases. An overview is given of current definitions and analytical methods. Some of the issues related to maintaining dietary fibre values in food composition databases are discussed.     

Precision cellular agriculture: The future role of recombinantly expressed protein as food

Cellular agriculture is a rapidly emerging field, within which cultured meat has attracted the majority of media attention in recent years. An equally promising area of cellular agriculture, and one that has produced far more actual food ingredients that have been incorporated into commercially available products, is the use of cellular hosts to produce soluble proteins, herein referred to as precision cellular agriculture (PCAg). In PCAg, specific animal- or plant-sourced proteins are expressed recombinantly in unicellular hosts—the majority of which are yeast—and harvested for food use. The numerous advantages of PCAg over traditional agriculture, including a smaller carbon footprint and more consistent products, have led to extensive research on its utility. This review is the first to survey proteins currently being expressed using PCAg for food purposes. A growing number of viable expression hosts and recent advances for increased protein yields and process optimization have led to its application for producing milk, egg, and muscle proteins; plant hemoglobin; sweet-tasting plant proteins; and ice-binding proteins. Current knowledge gaps present research opportunities for optimizing expression hosts, tailoring posttranslational modifications, and expanding the scope of proteins produced. Considerations for the expansion of PCAg and its implications on food regulation, society, ethics, and the environment are also discussed. Considering the current trajectory of PCAg, food proteins from any biological source can likely be expressed recombinantly and used as purified food ingredients to create novel and tailored food products.     

Conventional and emerging detection techniques for pathogenic bacteria in food science: A review

BackgroundContinuous transformation and development of new detection tools for bacteria has converted the laborious scientific work into smart apparatus in recent years. The journey had begun with the culture-based plate enumeration, and now it has evolved into several culture-independent techniques. Polymerase chain reaction (PCR) is on the top of the list that is now a routinely used biological approach to detect bacterial cells. Instrumental techniques are also helpful in this regard, as they are more sensitive for detection of various microbes.Scope and approachIn this review, we described new trends and their practical application in the fields of detection microbiology and food technology. This study provides a brief overview of conventional and modern detection techniques which includes nucleic-acid sequence based techniques to non-destructive imaging techniques.Key findings and conclusionsBesides the availability of antibiotics and clinical treatments, bacterial infections significantly increase the mortality rate. It is necessary to detect apparent infectious agents beforehand. Therefore, the detection methods for microorganisms should be more rapid, smart and reliable in response to the need. Conventional detection techniques are slow and time-consuming but more accurate and reliable than the modern detection techniques. By combing the mentioned techniques, scientists can achieve better results.