微流控芯片技术在食品领域中的应用

微流控芯片技术是一种全新的微量分析技术。介绍了微流控芯片技术的基本原理、特点及分类,并深入讨论了该技术在食品安全、营养、加工和风味等食品领域中的应用,包括有害化学物质、食品添加剂、转基因食品和食源性致病微生物等的检测,营养物质和功能成分的分析鉴定,食品工艺参数的调控以及食品风味成分的检测,展望了微流控芯片技术在食品领域的广阔应用前景。     

A decade with nucleic acid‐based microbiological methods in safety control of foods

In the last decade, nucleic acid‐based methods gradually started to replace or complement the culture‐based methods and immunochemical assays in routine laboratories involved in food control. In particular, real‐time polymerase chain reaction (PCR) was technically developed to the stage of good speed, sensitivity and reproducibility, at minimized risk of carry‐over contamination. Basic advantages provided by nucleic acid‐based methods are higher speed and added information, such as subspecies identification, information on the presence of genes important for virulence or antibiotic resistance. Nucleic acid‐based methods are attractive also to detect important foodborne pathogens for which no classical counterparts are available, namely foodborne pathogenic viruses. This review briefly summarizes currently available or developing molecular technologies that may be candidates for involvement in microbiological molecular methods in the next decade. Potential of nonamplification as well as amplification methods is discussed, including fluorescent in situ hybridization, alternative PCR chemistries, alternative amplification technologies, digital PCR and nanotechnologies.     

The impact of mineral nutrients in food crops on global human health

Nutrient sufficiency is the basis of good health, productive lives and longevity for everyone. Nutrient availability to people is primarily determined by the output of foods produced from agricultural systems. If agricultural systems fail to provide enough food diversity and quantity to satisfy all the nutrients essential to human life, people will suffer, societies will deteriorate and national development efforts will stagnate. Importantly, plant foods provide most of the nutrients that feed the developing world. Unfortunately, as a result of population pressures, many global food systems are not currently providing enough micronutrients to assure adequate micronutrient intakes for all people. This has resulted in an increasing prevalence of micronutrient deficiencies (e.g., iron deficiency, vitamin A deficiency, and iodine deficiency disorders) that now afflicts over three billion people globally mostly among resource-poor women, infants and children in developing countries. The consequences of micronutrient malnutrition are profound and alarming for human existence. Agricultural approaches to finding sustainable solutions to this problem are urgently needed. This review presents some ways in which plant nutritionists can contribute to preventing micronutrient malnutrition in sustainable ways.     

The development of LENTICULES™ as reference materials for noroviruses

Aims: To investigate the potential for LENTICULES? to act as reference materials (RMs) for noroviruses (NoV) [genogroups I (GI) and II (GII)] by determining their homogeneity and stability characteristics. Methods and Results: NoV used in this study originated from human faecal material, screened for the absence of other faecally transmitted pathogens. The norovirus strains present in the faecal material were characterized by sequencing, and samples containing GI and GII strains representative of genotypes commonly circulating in the community were selected. RMs were produced utilizing modified lenticulating technology. A batch comprising 500 LENTICULES? containing both norovirus genogroups was produced according to ISO Guide 34. The batch was tested and quantified using an ISO 17025 accredited quantitative real‐time RT‐PCR assay. Sufficient homogeneity was established using procedures described by Fearn and Thompson (2010), while stability at less than ?15°C and ambient temperature (17–22°C) was assessed over 52 weeks and 7 days, respectively. Conclusions: Lenticulation was shown to be an effective means of preservation of detectable NoV. LENTICULES? were sufficiently homogeneous and stable throughout medium‐term frozen and short‐term storage at room temperature to serve as RMs. Virus LENTICULES? have the advantages of being easy to manipulate, provide assigned values and do not require the manipulation of high titre clinical material. Significance and Impact of the Study: The results of this study show that norovirus LENTICULES? can be used as stable RMs for quantitative real‐time RT‐PCR assays. They can be utilized as in‐run positive extraction controls and potentially for method calibration and to enable more easy comparison of data generated by the variety of differing norovirus determination methods that have emerged in recent years. LENTICULES? have the potential to provide essential elements of laboratory quality assurance systems for laboratories implementing these new methods for virus testing in foodstuffs and for those running routine analyses.     

Preparation of phosphorus and carbohydrate microcapsules for manipulating dietary C : P ratio for aquatic suspension-feeders

SUMMARY 1. Dietary phosphorus can be limiting for aquatic animals such as suspension-feeders. However, our understanding has been limited by the difficulty of manipulating dietary P without altering other aspects of food quality. We microencapsulated various forms of bioavailable P with carbohydrate to manipulate dietary C : P ratio for suspension-feeders.
2. Calcium phosphate, sodium hexametaphosphate, sodium tripolyphosphate and tetrasodium pyrophosphate were each mixed with a concentrated solution of a carbohydrate base (either maltodextrin or potato starch) and microencapsulated using an interfacial polymerisation technique. Each of the 10 types of capsules produced had a particle size ideal for suspension-feeders (3–10 μm).
3. Leakage rates were low (<12% of capsule weight per day). Relative enzymatic breakdown in vitro by carbohydrases (amylase or cellulase) was similar among the 10 capsule types and was always at least 15 times the comparable leakage rate.
4. Release of dissolved P from enzyme-treated capsules varied depending on capsule P content. Liberation of P from capsules prepared from 20% w/w sodium hexametaphosphate in maltodextrin (molar C : P = 1.8) was three times greater than all other types, and this combination appears most suitable as a dietary supplement for zooplankton.
5. Although P content and capsule integrity were greatly influenced by choice of carbohydrate, choice of P compound, and the mixing ratio of the two, P-rich artificial microparticles can be produced that have low leakiness, high digestibility, and a physical size suitable for aquatic suspension-feeders. Therefore, microcapsules represent promising tools for manipulating dietary C : P for suspension feeders.     

生物钟信号调控的营养学

近日节律是生物界普遍存在的一种生理现象,而内源性生物钟是产生近日节律的物质基础,它能使生物体感知并适应环境中的光、温度和食物等周期信号,从而使生物体与外界环境保持周期同步。研究表明,葡萄糖、胆固醇、腺苷、咖啡因、维生素A和视黄酸等营养物质能通过各自不同的方式调控哺乳动物的生物钟,影响其近日节律的信号输出。本文概述了至今为止研究发现的各类与生物钟信号调控相关的营养物质及功能的相关研究进展。     

Recent developments in the use of viability dyes and quantitative PCR in the food microbiology field

The increase in foodborne outbreaks highlights the need for rapid, sensitive and specific methods for food safety monitoring, enabling specific detection and quantification of viable foodborne pathogens. Real‐time PCR (qPCR) combined with the use of viability dyes, recently introduced, fulfils all these requirements. The strategy relies on the use of DNA‐binding molecules such as propidium monoazide (PMA) or ethidium monoazide (EMA) as sample pretreatment previous to the qPCR. These molecules permeate only membrane‐compromised cells and have successfully been applied for different types of foodborne pathogens, including bacteria and viruses. Moreover, those dyes have been explored to monitor different food manufacturing processes as an alternative to classical cultural methods. In this review, state‐of‐the‐art information regarding viability PCR (v‐PCR) is compiled.     

A role for proline synthesis and transport in Listeria monocytogenes barotolerance

Aims: To assess the contribution of proline biosynthesis to listerial barotolerance. Methods and Results: Using a Listeria monocytogenes proBA deletion mutant, incapable of synthesizing proline, together with a proline‐overproducing strain, the contribution of proline synthesis to listerial barotolerance was determined. The ΔproBA strain does not survive as well as the wild type when subjected to treatment of 500 MPa in rich media and 400 MPa in minimal media (c. 1 log lower survival in both conditions). Betaine and carnitine decrease the ability of the wild type to survive at low pressures (300 MPa), but confer normal or slightly increased levels of protection at higher pressures (350 and 400 MPa). Conclusions: A functional proline synthesis system is required for optimal survival of Listeria following treatment at high‐pressure (HP) levels (500 MPa in brain heart infusion and 400 MPa in defined medium), particularly where other compatible solutes are absent or limiting. Significance and Impact of the Study: Given the potential of HP processing as an effective food processing/safety strategy, understanding how pathogens such as Listeria have evolved to cope with such stresses is an important food safety consideration. In this context, the work presented here may help to develop safer and more effective processing regimens.