Surface enhanced Raman spectroscopy (SERS): A novel reliable technique for rapid detection of common harmful chemical residues

BackgroundThe irrational usage of chemical substances including pesticides and drugs in agricultural and food production is a significant food safety issue due to its residues. Therefore, the detection of harmful residues in foods is an indispensable step for guaranteeing the consumer's health. Conventional methods, such as HPLC, GC-MS and LC-MS are accurate enough, but they fail to meet the requirements of the modern industry for rapid and on-line detection. Novel reliable techniques should thus be developed as alternatives.Scope and approachIn this review, fundamentals of surface-enhanced Raman spectroscopy (SERS) is introduced. Recent advances in its usage for detecting harmful chemical residues in agricultural products including pesticides, antibiotics and β₂-adrenergic agonists are discussed by two typical ways of detection improvement, and the advantages of SERS are addressed. Finally, future trends to routine use of SERS applications in harmful residues are presented.Key findings and conclusionsSERS is a promising detection technique for the detection of common harmful chemical residues with merits of simple sampling, rapid data collection and non-destructiveness. Despite rapid developments in the technology, there is much studies should be done before SERS could be used as a daily tool for the industry.     

Detection and Quantification of Chloramphenicol in Milk and Honey Using Molecularly Imprinted Polymers: Canadian Penny‐Based SERS Nano‐Biosensor

We integrated molecularly imprinted polymers with surface‐enhanced Raman spectroscopy (MIPs‐SERS) to develop an innovative nano‐biosensor for the determination of chloramphenicol (CAP) in milk and honey products. Template molecule (CAP), functional monomer (acrylamide), cross‐linking agent (ethylene glycol dimethacrylate), initiator (2,2’‐azobis(isobutyronitrile)), and porogen (methanol) were employed to form MIPs via “dummy” precipitation polymerization. Static and kinetic studies validated the specific selectivity of MIPs toward CAP over nonimprinted polymers (imprinting factor >4). Canadian penny‐based silver nano‐structure was synthesized as SERS‐active substrate for determination of CAP in food matrices. Collected spectra were processed by principal component analysis to differentiate various concentrations of CAP in foods. Partial least squares regression models showed good prediction values (R > 0.9) of actual spiked contents (0, 0.1, 0.5, 1, 5 ppm) of CAP in milk and honey. This developed nano‐biosensor is low cost, requires little sample pretreatment, and can provide reliable detection of trace level of chemical hazards in food systems within a total of 15 min.     

Recent advances in nanofabrication techniques for SERS substrates and their applications in food safety analysis

ABSTRACT

The ability to analyze food safety and quality in a quick, sensitive, and reliable manner is of high importance in food industry. Surface-enhanced Raman scattering (SERS), which is popular for its significant enhancement, excellent sensitivity, and the fingerprinting ability to identify special molecules, has shown vast potential for rapid detection of chemical constitutes, chemical contaminants, and pathogens in food sample. For SERS, the enhancement of Raman signals is related to not only the SERS-active substrates, but also the interactions between sample and substrates. In the current review, colloidal and solid surface-based substrates are briefly described, fabrication techniques for SERS substrates are presented, and applications of SERS for food matrixes, correlation between substrates and food samples are also introduced. Finally, some outlook on further developments is presented. The current review is therefore intended to provide a comprehensive overview on the nanofabrication of SERS substrates, and the potential of applying SERS as an important food analysis platform.     

Meeting the challenges in the development of risk-benefit assessment of foods

BackgroundRisk-benefit assessment (RBA) of foods aims to assess the combined negative and positive health effects associated with food intake. RBAs integrate chemical and microbiological risk assessment with risk and benefit assessment in nutrition.Scope and ApproachBased on the past experiences and the methodological differences between the underlying research disciplines, this paper aims to describe the recent progress in RBAs, identifying the key challenges that need to be addressed for further development, and making suggestions for meeting these challenges.Key Findings and ConclusionsTen specific challenges are identified and discussed. They include the variety of different definitions and terminologies used in the underlying research disciplines, the differences between the “bottom-up” and the “top-down” approaches and the need for clear risk-benefit questions. The frequent lack of data and knowledge with their consequential uncertainties is considered, as well as the imbalance in the level of scientific evidence associated with health risks and benefits. The challenges that are consequential to the need of considering substitution issues are discussed, as are those related to the inclusion of microbiological hazards. Further challenges include the choice of the integrative health metrics and the potential scope of RBAs, which may go beyond the health effect. Finally, the need for more practical applications of RBA is stressed. Suggestions for meeting the identified challenges include an increased interdisciplinary consensus, reconsideration of methodological approaches and health metrics based on a categorisation of risk-benefit questions, and the performance of case studies to experience the feasibility of the proposed approaches.     

Functionalization techniques for improving SERS substrates and their applications in food safety evaluation: A review of recent research trends

BackgroundFood safety and quality have gained much attention in recent years and the capability to evaluate food quality and safety in a sensitive, rapid, and reliable manner is of great importance in the food industry. Therefore, surface-enhanced Raman scattering (SERS) with the advantages of excellent sensitivity, high selectivity, non-destructive nature and significant enhancement to identify the target has demonstrated a great potential for quick detection of chemical contaminants, chemical constitutes, and pathogens in food samples.Scope and approachThe enhancement of Raman signals for SERS is not only related to the interactions between substrates and samples but also the functionalization of substrates to gain SERS active substrates. In the present review, different types of substrates are briefly discussed, functionalization techniques for SERS active substrates are discussed, and applications of functionalized SERS substrate in food samples are presented.Conclusions and key findingsIt is evident that functionalization techniques for improving SERS substrates have given encouraging outcomes, which provides possibility for identifying multiple target analytes within a complex matrix, and thus could be used as a powerful analytical tool in real-world applications in food safety analysis as well as for enhancing food quality surveillance.     

Non-dairy probiotic food products: An emerging group of functional foods

ABSTRACT

The functional food sector has shown tremendous growth in recent years with the application of probiotic bacteria as “food additives”. The utilization of probiotic bacteria in food presents many challenges related to their growth, survival, viability, stability and functionality in food processing, storage and consumption as well as changes of sensory characteristics of probiotic foods. Although dairy foods are currently the most common food carrier to deliver probiotics, an increasing number of non-dairy food matrices exhibit potential for delivery of probiotics. This review provides more recent insight into the emergence of non-dairy probiotics products, the interactions between probiotics and different food matrices and the challenges in developing such products. Some of the technical issues are also reviewed and discussed. These issues include the efficacy of probiotic bacteria in non-chilled, low pH or high water activity foods; the potential loss of bacterial viability, additionally unwanted fermentation and changes of the sensory characteristics of food products which may result in poor microbiological quality and low acceptability to consumers.     

Fabrication of SERS‐Active Substrates using Silver Nanofilm‐Coated Porous Anodic Aluminum Oxide for Detection of Antibiotics

We have developed a silver nanofilm‐coated porous anodic aluminum oxide (AAO) as a surface‐enhanced Raman scattering (SERS)‐active substrate for the detection of trace level of chloramphenicol, a representative antibiotic in food systems. The ordered aluminum template generated during the synthesis of AAO serves as a patterned matrix on which a coated silver film replicates the patterned AAO matrix to form a 2‐dimensional ordered nanostructure. We used atomic force microscopy and scanning electron microscopy images to determine the morphology of this nanosubstrate, and characterized its localized surface plasmon resonance by ultraviolet‐visible reflection. We gauged the SERS effect of this nanosubstrate by confocal micro‐Raman spectroscopy (782‐nm laser), finding a satisfactory and consistent performance with enhancement factors of approximately 2 × 10⁴ and a limit of detection for chloramphenicol of 7.5 ppb. We applied principal component analysis to determine the limit of quantification for chloramphenicol of 10 ppb. Using electromagnetic field theory, we developed a detailed mathematical model to explain the mechanism of Raman signal enhancement of this nanosubstrate. With simple sample pretreatment and separation steps, this silver nanofilm‐coated AAO substrate could detect 50 ppb chloramphenicol in milk, indicating good potential as a reliable SERS‐active substrate for rapid detection of chemical contaminants in agricultural and food products.     

Potential of SERS for rapid detection of melamine and cyanuric acid extracted from milk

Melamine, a nitrogen-rich chemical, was implicated in the pet and human food recalls in 2007 and in the global food safety scares in 2008 involving milk and other milk-derived products. In this study, we investigated the feasibility of using surface-enhanced Raman spectroscopy (SERS) coupled with SERS-active gold substrates for rapid detection of trace amounts of melamine and its analogue (that is, cyanuric acid) in liquid milk. Raman signals of tested samples were significantly enhanced by SERS. The identification limit for SERS using gold substrate can reach 2 ppm of melamine in liquid milk. Partial least squares (PLS) models were established for the quantification of melamine in liquid milk by SERS: R = 0.90, RMSEP = 1.48 × 10⁻⁵. Our results demonstrate that rapid detection of melamine in milk can be achieved by SERS; while detection of cyanuric acid in milk remains a challenging task due to rapid enol-keto tautomerism of cyanuric acid. The SERS method is faster and simpler than other traditional methods, and requires minimum sample preparation. These results demonstrate that SERS could be used to detect food contaminants such as melamine in foods and food ingredients quickly and accurately.     

CRISPR-Cas-based detection for food safety problems: Current status,challenges, and opportunities

Food safety is one of the biggest public issues occurring around the world. Microbiological, chemical, and physical hazards can lead to food safety issues, which may occur at all stages of the supply chain. In order to tackle food safety issues and safeguard consumer health, rapid, accurate, specific, and field-deployable detection methods meeting diverse requirements are one of the imperative measures for food safety assurance. CRISPR-Cas system, a newly emerging technology, has been successfully repurposed in biosensing and has demonstrated huge potential to establish conceptually novel detection methods with high sensitivity and specificity. This review focuses on CRISPR-Cas–based detection and its current status and huge potential specifically for food safety inspection. We firstly illustrate the pending problems in food safety and summarize the popular detection methods. We then describe the potential applications of CRISPR-Cas–based detection in food safety inspection. Finally, the challenges and futuristic opportunities are proposed and discussed. Generally speaking, the current food safety detection methods are still unsatisfactory in some ways such as being time-consuming, displaying unmet sensitivity and specificity standards, and there is a comparative paucity of multiplexed testing and POCT. Recent studies have shown that CRISPR-Cas–based biosensing is an innovative and fast-expanding technology, which could make up for the shortcomings of the existing methods or even replace them. To sum up, the implementation of CRISPR-Cas and the integration of CRISPR-Cas with other techniques is promising and desirable, which is expected to provide “customized” and “smart” detection methods for food safety inspection in the coming future.     

Texture of Japanese foods

Abstract

Texture of some traditional Japanese foods made from rice, vegetables, fish, and soybeans are discussed, as well as some accepted Western foods and some new fabricated foods. Universally accepted qualities seem to be crispness, crunchiness, hardness, softness, pliability, etc. It seems that a texture uniquely accepted by the Japanese is “stickiness.” Textures of newly developed Japanese food products will probably have to be modified to suit the dietary cultures of each country for international acceptance.     

Organic food

“Organic” or “organically grown” foods are commonly represented as “food grown without pesticides; grown without artificial fertilizers; grown in soil whose humus content is increased by the additions of organic matter; grown in soil whose mineral content is increased with applications of natural mineral fertilizers; which has not been treated with preservatives, hormones, antibiotics, etc.” The substitution of “organic” for “chemical” fertilizers during the growth of plants produces no change in the nutritional or chemical properties of foods. All foods are made of “chemicals.” Traces of pesticides have been reported to be present in about 20 to 30% of both “organic” and conventional foods. These traces are usually within the official tolerance levels. Such levels are set low enough to protect consumers adequately. Indeed, there is no record of a single case of injury to a consumer resulting from the application of pesticides to food crops at permitted levels. There is no method for distinguishing between “organic” and conventional foods. The use of the term “organic” is a promotional device. Prices of “organic” foods tend to be higher than those of their conventional counterparts. A series of controlled tests showed that conventional foods were superior to corresponding “health foods” in terms of odor, color, texture, and flavor.     

Gold nanoparticles: From synthesis,properties to their potential application as colorimetric sensors in food safety screening

BackgroundFood safety management and guarantee are the basic requirement during food processing, circulation, storage, and marketing. Elevating the ability to evaluate food quality and safety in a rapid, sensitive and reliable manner is of great importance in food industry. Recently, gold nanoparticles due to unique optical property, ease of functionalization and preparation, and high selectivity and sensitivity have received considerable attention in the field of food safety.Scope and approachGold nanoparticles exhibit distinguishable optical characteristic in different aggregated states and thus have been developed into simple colorimetric sensors for the quick detection of chemical contaminants in food samples. Herein, we reviewed the current methods for synthesis and functionalization of gold nanoparticles, strategies for fabrication of gold nanoparticle based colorimetric sensors and their applications in rapid analysis of food contaminant. Moreover, the inherent optical property of gold nanoparticles and their detecting principle have been highlighted. Finally, the main challenges and future efforts in developing such colorimetric sensors for food contaminants detection were discussed.Key findings and conclusionsGold nanoparticles as smart colorimetric sensors conform to the requirement of modern analysis, such as high selectivity, sensitivity, simplicity, celerity, and portability. Thus, they have great potential to be applied as power sensing tools for food safety screening.     

Food irradiation‐chemistry and applications∗

Abstract

Food irradiation is one of the most extensively and thoroughly studied methods of food preservation. Despite voluminous data on safety and wholesomeness of irradiated foods, food irradiation is still a “process in waiting.” Although some countries are allowing the use of irradiation technology on certain foods, its full potential is not recognized. Only 37 countries worldwide permit the use of this technology. If used to its full potential, food irradiation can save millions of human lives being lost annually due to food‐borne diseases or starvation and can add billions of dollars to the world economy. This paper briefly reviews the history and chemistry of food irradiation along with its main applications, impediments to its adoption, and its role in improving food availability and health situation, particularly in developing countries of the world.     

纤维基表面增强拉曼基底的研究进展

为解决传统纤维表面拉曼增强(SERS)基底所存在的稳定性差、操作不便等问题。介绍了柔性SERS基底的优势,总结了目前各类纤维基SERS基底的研究进展及其在痕量检测领域的应用,简述了电磁增强和化学增强2种表面增强拉曼现象的基本原理。综述了纤维纸基SERS、织物基SERS、散纤维及纳米纤维膜SERS基底的制备方法及其应用,并着重介绍了织物基SERS材料的研究现状及其在在线检测应用方面的挑战与机遇。基于织物基SERS材料高度灵敏及灵活检测的特点,展望了其作为可穿戴传感器件用于即时检测和周身环境监测的前景,为拓展智能纺织品的应用领域开辟了新的思路。     

纸上微型实验室在食品检测领域的研究进展

“纸上微型实验室”是以纸为基底的微型分析系统,其因高灵敏、低成本、便携化、可批量生产等独特优势突破了传统检测技术的局限,在食品现场快速检测领域展现出巨大应用潜力。本文梳理了典型的“纸上微型实验室”,分别对纸层析法、化学试纸、侧流层析试纸条、纸基微流控分析装置和合成生物学纸进行全面综述,并重点介绍了“纸上微型实验室”在食品检测领域中的应用,最后讨论了纸基分析方法的优势、挑战和发展趋势,以期为“纸上微型实验室”更全面地应用于食品检测领域提供理论支撑。     

Ultrasensitive Detection of Enrofloxacin in Chicken Muscles by Surface-Enhanced Raman Spectroscopy Using Amino-Modified Glycidyl Methacrylate-Ethylene Dimethacrylate (GMA-EDMA) Powdered Porous Material

Illegally use of enrofloxacin in chicken has raised serious concerns due to its negative effects on public health. In this study, surface-enhanced Raman spectroscopy (SERS) using amino-modified glycidyl methacrylate-ethylene dimethacrylate (GMA-EDMA) powdered porous material was developed and validated to detect enrofloxacin in chicken muscles. By this method, enrofloxacin in chicken muscles was successfully detected at a concentration of 0.01 mg kg^?1, which was lower than the legal maximum residue limit. And the unique “fingerprint-like” spectral patterns of enrofloxacin obtained from SERS spectra could be used for identification and characterization. Compared with high-performance liquid chromatography, the assay of six samples with SERS was rapid in less than 40 min, and the detection was highly sensitive. The results demonstrate that SERS using GMA-EDMA powdered porous material can be potentially employed as a screening tool for rapid detection of residual drugs in a large amount of food samples.     

Seed coats of pulses as a food ingredient: Characterization,processing, and applications

BackgroundIn recognition of their multiple benefits on environment, food security, and human health, pulses are attracting worldwide attention. The seed coat is a major by-product of pulse processing, and its only markets are as low value ruminant feed and very limited use in high fibre foods. Recently, accumulating studies have suggested that this underutilised by-product has greater potential as a novel natural “nutritious dietary fibre” which can be used as a functional food ingredient.Scope and approachThis review discusses biochemical and physicochemical functionalities of seed coats of six globally important pulses: chickpea, field pea, faba/broad bean, lentil and mung bean with a special emphasis on the emerging food pulse lupin. Food process modification and recent human food applications of the seed coats are summarized. Bio-availability of the seed coat compounds, and phomopsins contaminated lupin seed coats as a typical example of safety issue are discussed.Key findings and conclusionsHigh levels of dietary fibre, minerals and potential health-promoting phytochemicals in the seed coats indicate their great potential to be used as a natural “nutritious dietary fibre”. However, further in-depth studies are required to improve their desirable nutritional, physiological and techno-functional properties whilst minimizing any undesirable ones.     

表面增强拉曼光谱技术在食品安全检测中的最新研究进展

食品种类繁多,食品中存在的污染物问题也越来越复杂。因此,探究快速、灵敏、简单地检测食品中痕量污染物的检测技术对保障食品安全具有重要的意义,也是食品安全中非常重要的一环。近几十年来,表面增强拉曼散射(surface-enhanced Raman scattering, SERS)检测技术凭借其检测快速、无损、灵敏度高等优点,已成为食品安全检测的可靠工具。目前缺乏近几年关于SERS检测技术最新研究进展的概述。因此,本文简要综述了SERS的增强机制、增强底物及其检测技术;总结了近3年来关于表面增强拉曼光谱在食品安全检测方面的实际应用。为了更好地将SERS检测技术应用于今后食品安全的常规检测中,应研发更加低成本的技术,更简单的操作方法,开发新的SERS增强底物,将SERS检测与其他检测方法更好的结合。     

Hazard analysis critical control point: A review

Abstract

Hazard analysis critical control point (HACCP) is a food process control system developed in the early 1970s to ensure the safety of foods for the United States space program. Since the 1970s HACCP has evolved into a recognized means to assure the safety of foods throughout the food industry both within the United States and elsewhere. Based on the principle of prevention rather than detection, HACCP has been extensively and successfully used in the low‐acid canned food industry since the early 1970s. Since that time, HACCP has achieved greater prominence with a refinement of the HACCP principles and the application of HACCP to other processes and products. The purpose of this review is to trace the evolution of HACCP to its present‐day applications in the food industry and discuss its importance for the production of a safer food supply.     

Development and evaluation of a surface-enhanced Raman scattering (SERS) method for the detection of the antioxidant butylated hydroxyanisole

Butylated hydroxyanisole (BHA) is a common antioxidant used in foods and food packaging materials, and it can migrate into the food during its supply chain. BHA has been shown to be carcinogenic, which has gained substantial attention in recent years. In this study, the feasibility of using surface-enhanced Raman scattering (SERS) coupled with SERS-active gold substrates for rapid detection of trace amounts of BHA was investigated. Raman signals of tested samples were enhanced significantly by SERS. The detection limit of the BHA solution can reach 10 μg/mL by SERS enhanced with 50 nm gold nanoparticles and in a 1.0 pH solution system. The Raman peak at 480 cm⁻¹ was used as the index of quantitative analysis, the line correlation was R ² = 0.9803. The results showed that the SERS method is useful for sensitive and selective detection of BHA. By comparing the enhanced peak features, the adsorption behavior of BHA on the surface of gold nanoparticles was analyzed in detail and it was determined that the molecule was adsorbed on the gold surface by “Ph-O(H) (Ph = phenyl)”. The benzene ring vibration increased significantly, inferring that the benzene ring is perpendicular to the surface of the gold nanoparticles.