Annual Review of Food Science and Technology - Volume 9, 2018

Caenorhabditis elegans is a small free-living nematode that lives in temperate soil environments. It has been widely employed as an animal model in research involving obesity, aging, and neurodegenerative diseases, including Alzheimer's disease, because of its various advantages, such as small size, large number of progeny, completely sequenced genome, and short life span, over traditional animal models of vertebrates. These benefits contribute to an ideal research model organism. In this review, we provide an introduction to C. elegans and its applications in obesity, aging, and Alzheimer's disease studies, with the aim of stimulating scientists to use C. elegans as an experimental model in various fields of research.

There has been considerable concern related to Cronobacter spp. in foods, especially due to their highlighted association with neonatal infections through the ingestion of reconstituted powdered infant formula (PIF). This concern resulted in improved microbiological criteria recommendations by the Codex Alimentarius Commission and revised WHO advice on the preparation of infant feeds. In recent years, the diversity of the genus has been well described, and various detection and typing methods have been developed. This review considers our current knowledge of the genus and how DNA-sequence-based methods have contributed considerably to research into improved detection methods and more reliable identification procedures, genotyping schemes, and genomic analysis. The broader occurrence of Cronobacter in food ingredients, finished products, and food manufacturing environments is covered. This review also highlights the significance of clonal lineages in microbial source tracking and the use of CRISPR-cas array profiling.

Foam is a high-volume fraction dispersion of gas into a liquid or a solid. It is important to understand the effect of formulation on shelf life and texture of food foams. The objective of this review is to elucidate mechanisms of formation and stability of foams and relate them to the formulations. Emulsifiers are important in foam formation, whereas proteins are generally preferred to provide long-term stability. Syneresis in foams is a precursor to their collapse in many instances. Intermolecular forces, conformation, and flexibility of proteins play an important role in foam stabilization. An adsorbed protein layer at air/water interfaces imparts interfacial rheology that is necessary to improve the shelf life of foam products. Wettability and spreading of food particles at the interface can stabilize or destabilize foams, depending on their properties. More studies are needed to fully understand the complex interplay of various mechanisms of destabilization in a real-food formulation.

The intestinal microbiota have emerged as a central regulator of host metabolism and immune function, mediating the effects of diet on host health. However, the large diversity and individuality of the gut microbiota have made it difficult to draw conclusions about microbiota responses to dietary interventions. In the light of recent research, certain general patterns are emerging, revealing how the ecology of the gut microbiota profoundly depends on the quality and quantity of dietary carbohydrates and proteins. In this review, I provide an overview of the dependence of microbial ecology in the human colon on diet and how the effects of diet on host health depend partially on the microbiota. Understanding how the individual-specific microbiota respond to short- and long-term dietary changes and how they influence host energy homeostasis will enable targeted interventions to achieve specific outcomes, such as weight loss in obesity or weight gain in malnutrition.

This article reviews the application of enzymes in lipid modification. Lipases are the most established biocatalysts used for the synthesis of structured triacylglycerols, fats, and margarine and for the release of flavoring fatty acids for food applications. In addition, the various enzymes, such as P450 monooxygenases, hydratases, lipoxygenases, and certain lyases, used for oxyfunctionalization and the phospholipases used for degumming are covered. Basic aspects of enzyme catalysis and the modern tools used for their discovery and improvement by protein engineering provide insight into how suitable biocatalysts can be identified and optimized for an application. In addition to isolated enzymes, whole-cell engineered microorganisms are also used for lipid modification. Thus, the polyunsaturated fatty acid EPA (eicosapentaenoic acid) can be produced in a yeast using sugar as a renewable resource.

Radio-frequency (RF) heating, as a thermal-processing technology, has been extending its applications in the food industry. Although RF has shown some unique advantages over conventional methods in industrial drying and frozen food thawing, more research is needed to make it applicable for food safety applications because of its complex heating mechanism. This review provides comprehensive information regarding RF-heating history, mechanism, fundamentals, and applications that have already been fully developed or are still under research. The application of mathematical modeling as a useful tool in RF food processing is also reviewed in detail. At the end of the review, we summarize the active research groups in the RF food thermal-processing field, and address the current problems that still need to be overcome.

With the rapidly increasing demand for and use of engineered nanoparticles (NPs) in agriculture and related sectors, concerns over the risks to agricultural systems and to crop safety have been the focus of a number of investigations. Significant evidence exists for NP accumulation in soils, including potential particle transformation in the rhizosphere and within terrestrial plants, resulting in subsequent uptake by plants that can yield physiological deficits and molecular alterations that directly undermine crop quality and food safety. In this review, we document in vitro and in vivo characterization of NPs in both growth media and biological matrices; discuss NP uptake patterns, biotransformation, and the underlying mechanisms of nanotoxicity; and summarize the environmental implications of the presence of NPs in agricultural ecosystems. A clear understanding of nano-impacts, including the advantages and disadvantages, on crop plants will help to optimize the safe and sustainable application of nanotechnology in agriculture for the purposes of enhanced yield production, disease suppression, and food quality.

Exopolysaccharides produced by lactic acid bacteria are a diverse group of polysaccharides produced by many species. They vary widely in their molecular, compositional, and structural characteristics, including mechanisms of synthesis. The physiochemical properties of these polymers mean that they can be exploited for the sensorial and textural enhancement of a variety of food and beverage products. Traditionally, lactic acid bacteria exopolysaccharides have an important role in fermented dairy products and more recently are being applied for the improvement of bakery products. The health benefits that are continually being associated with these polysaccharides enable the development of dual function, added-value, and clean-label products. To fully exploit and understand the functionality of these exopolysaccharides, their isolation, purification, and thorough characterization are of great importance. This review considers each of the above factors and presents the current knowledge on the importance of lactic acid bacteria exopolysaccharides in the food and beverage industry.

Low-moisture foods (LMFs) have been defined as those food products with a water activity (aw) less than 0.85 and are generally considered less susceptible to microbial spoilage and the growth of foodborne pathogens. However, in recent years, outbreaks linked to LMFs have increased, with Salmonella spp., Bacillus cereus, Cronobacter sakazakii, Clostridium spp., Escherichia coli O157:H7, non-O157 E. coli, and Staphylococcus aureus being the principal pathogens involved. Because of the new concerns raised as a result of recent outbreaks, new approaches need to be developed to control foodborne pathogens in LMFs. This review summarizes the recent research on novel inactivation methods suitable for use on LMFs. Among the methods discussed are the nonthermal inactivation methods as well as other novel methods such as radio-frequency and microwave heating. Additional research is needed to evaluate older technologies and develop new technologies, either alone or in combination, to understand the mechanisms of inactivation.

Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), both abundant in fish oil, are known to have significant biochemical and physiological effects primarily linked to the improvement of human health, especially cardiovascular and brain health. However, the incorporation of fish oil into foods and beverages is often challenging, as fish oil is very easily oxidized and can cause undesirable flavors. This review discusses this rapid formation of the fishy and metallic off-flavors, focusing especially on an early stage of fish oil oxidation. Although oxidative stability and quality of commercialized fish oil have improved over the past few years, there is a still a problem with its application: Flavor deterioration can be found even at very low oxidation levels. This review also notes the effective way to inhibit the formation of the volatile compounds responsible for the flavor deterioration.

Increasingly, studies showing the protective effects of the Mediterranean diet (MedDiet) on different diseases (cardiovascular, diabetes, some cancers, and even total mortality and aging indicators) are being published. The scientific evidence level for each outcome is variable, and new studies are needed to better understand the molecular mechanisms whereby the MedDiet may exercise its effects. Here, we present recent advances in understanding the molecular basis of MedDiet effects, mainly focusing on cardiovascular diseases but also discussing other related diseases. There is heterogeneity in defining the MedDiet, and it can, owing to its complexity, be considered as an exposome with thousands of nutrients and phytochemicals. We review MedDiet composition and assessment as well as the latest advances in the genomic, epigenomic (DNA methylation, histone modifications, microRNAs, and other emerging regulators), transcriptomic (selected genes and whole transcriptome), and metabolomic and metagenomic aspects of the MedDiet effects (as a whole and for its most typical food components). We also present a critical review of the limitations of the studies undertaken and propose new analyses and greater bioinformatic integration to better understand the most important molecular mechanisms whereby the MedDiet as a whole, or its main food components, may exercise their protective effects.

The labels currently used on food and beverage products only provide consumers with a rough guide to their expected shelf lives because they assume that a product only experiences a limited range of predefined handling and storage conditions. These static labels do not take into consideration conditions that might shorten a product's shelf life (such as temperature abuse), which can lead to problems associated with food safety and waste. Advances in shelf-life estimation have the potential to improve the safety, reliability, and sustainability of the food supply. Selection of appropriate kinetic models and data-analysis techniques is essential to predict shelf life, to account for variability in environmental conditions, and to allow real-time monitoring. Novel analytical tools to determine safety and quality attributes in situ coupled with modern tracking technologies and appropriate predictive tools have the potential to provide accurate estimations of the remaining shelf life of a food product in real time. This review summarizes the necessary steps to attain a transition from open labeling to real-time shelf-life measurements.

The main purpose of this review is to clarify whether the consumption of food rich in melanoidins and dietary advanced glycosylation end-products (dAGEs) is harmful or beneficial for human health. There are conflicting results on their harmful effects in the literature, partly due to a methodological issue in how dAGEs are determined in food. Melanoidins have positive functions particularly within the gastrointestinal tract, whereas the intake of dAGEs has controversial physiological consequences. Most of the in vivo intervention trials were done comparing boiled versus roasted diet (low and high dAGE, respectively). However, these studies can be biased by different lipid oxidation and by different calorie density of foods in the two conditions. The attraction that humans have to cooked foods is linked to the benefits they have had during mankind's evolution. The goal for food technologists is to design low-energy-dense products that can satisfy humans’ attraction to rewarding cooked foods.

Fifty-five years have passed and more than 100,000 articles have been published since the first report of an electrochemical enzyme biosensor. However, very few biosensors have reached practical application and commercialization. The bulk of the research effort has been on increasing sensitivity and selectivity. In contrast, the number of publications dealing with stability or stabilization of enzyme biosensors is very small. Here, we critically review enzyme stabilization strategies as well as the progress that has been done in the past 20 years with respect to enzyme biosensor stabilization. Glucose oxidase, lactate oxidase, alcohol oxidase, and xanthine oxidase are the focus of this review because of their potential applications in food. The inconsistency in reporting biosensor stability was identified as a critical hurdle to research progress in this area. Fundamental questions that remain unanswered are outlined.

X-ray micro–computed tomography (micro-CT) provides the unique ability to capture intact internal microstructure data without significant preparation of the sample. The fundamentals of micro-CT technology are briefly described along with a short introduction to basic image processing, quantitative analysis, and derivative computational modeling. The applications and limitations of micro-CT in industries such as meat, dairy, postharvest, and bread/confectionary are discussed to serve as a guideline to the plausibility of utilizing the technique for detecting features of interest. Component volume fractions, their respective size/shape distributions, and connectivity, for example, can be utilized for product development, manufacturing process tuning and/or troubleshooting. In addition to determining structure-function relations, micro-CT can be used for foreign material detection to further ensure product quality and safety. In most usage scenarios, micro-CT in its current form is perfectly adequate for determining microstructure in a wide variety of food products. However, in low-contrast and low-stability samples, emphasis is placed on the shortcomings of the current systems to set realistic expectations for the intended users.

Omega-3 polyunsaturated fatty acids (PUFAs) include α-linolenic acid (ALA; 18:3 ω-3), stearidonic acid (SDA; 18:4 ω-3), eicosapentaenoic acid (EPA; 20:5 ω-3), docosapentaenoic acid (DPA; 22:5 ω-3), and docosahexaenoic acid (DHA; 22:6 ω-3). In the past few decades, many epidemiological studies have been conducted on the myriad health benefits of omega-3 PUFAs. In this review, we summarized the structural features, properties, dietary sources, metabolism, and bioavailability of omega-3 PUFAs and their effects on cardiovascular disease, diabetes, cancer, Alzheimer's disease, dementia, depression, visual and neurological development, and maternal and child health. Even though many health benefits of omega-3 PUFAs have been reported in the literature, there are also some controversies about their efficacy and certain benefits to human health.

Heat treatments are widely used in food processing often with the aim of reducing or eliminating spoilage microorganisms and pathogens in food products. The efficacy of applying heat to control microorganisms is challenged by the natural diversity of microorganisms with respect to their heat robustness. This review gives an overview of the variations in heat resistances of various species and strains, describes modeling approaches to quantify heat robustness, and addresses the relevance and impact of the natural diversity of microorganisms when assessing heat inactivation. This comparison of heat resistances of microorganisms facilitates the evaluation of which (groups of) organisms might be troublesome in a production process in which heat treatment is critical to reducing the microbial contaminants, and also allows fine-tuning of the process parameters. Various sources of microbiological variability are discussed and compared for a range of species, including spore-forming and non-spore-forming pathogens and spoilage organisms. This benchmarking of variability factors gives crucial information about the most important factors that should be included in risk assessments to realistically predict heat inactivation of bacteria and spores as part of the measures for controlling shelf life and safety of food products.

The fermented foods industry is constantly seeking new starter cultures to deal with changing consumer preferences and new fermentation processes. New cultures can either be composed of strains isolated from nature or improved derivatives of existing isolates. A variety of techniques involving natural selection and evolution are available to enhance the performance of existing strains, including the isolation of mutants with desired properties, adaptive laboratory evolution, genome shuffling, and genome editing. Numerous examples of traits that can be improved are provided. These include resistance to bacteriophages; the secretion of glucose to increase sweetness; the production of vitamins, antifungal compounds, bacteriocins, texture, or aroma; enhancement of acidification rates and acid tolerance; and elimination of biofilm formation. Careful consideration is required to ensure the developed strains are suitable for the desired purpose, as some approaches may lead to regulatory concerns.

Human milk is a unique and complex fluid that provides infant nutrition and delivers an array of bioactive molecules that serve various functions. Glycans, abundant in milk, can be found as free oligosaccharides or as glycoconjugates. Milk glycans are increasingly linked to beneficial outcomes in neonates through protection from pathogens and modulation of the immune system. Indeed, these glycans influence the development of the infant and the infant-gut microbiota. Bifidobacterium species commonly are enriched in breastfed infants and are among a limited group of bacteria that readily consume human milk oligosaccharides (HMOs) and milk glycoconjugates. Given the importance of bifidobacteria in infant health, numerous studies have examined the molecular mechanisms they employ to consume HMOs and milk glycans, thus providing insight into this unique enrichment and shedding light on a range of translational opportunities to benefit at-risk infants.

Research on combining pro- and prebiotics as synbiotics to enhance human and animal health has accelerated in the past 10 years, including many clinical trials that have assessed a diverse range of synbiotic formulations. In this review, we summarize these studies as well as the commercial applications of synbiotics that are available. In particular, we critically assess the claimed health benefits of synbiotic applications and the ecological and therapeutic factors to consider when designing synbiotics and discuss the implications of these concepts for future research in this field.