Annual Review of Food Science and Technology - Volume 6, 2015

This article describes my early life and the chance events leading to my becoming a microbiologist and then my embarking on a career developing the plasmid biology and genetics of lactococci used in milk fermentations.

Because, in general, native starches do not have properties that make them ideally suited for applications in food products, most starch is modified by dervatization to improve its functionality before use in processed food formulations, and because food processors would prefer not to have to use the modified food starch label designation required when chemically modified starches are used, there is considerable interest in providing starches with desired functionalities that have not been chemically modified. One investigated approach is property modification via physical treatments, that is, modifications of starches imparted by physical treatments that do not result in any chemical modification of the starch. Physical treatments are divided into thermal and nonthermal treatments. Thermal treatments include those that produce pregelatinized and granular cold-water-swelling starches, heat-moisture treatments, annealing, microwave heating, so-called osmotic pressure treatment, and heating of dry starch. Nonthermal treatments include ultrahigh-pressure treatments, instantaneous controlled pressure drop, use of high-pressure homogenizers, dynamic pulsed pressure, pulsed electric field, and freezing and thawing.

A new understanding of the nature and organization of fat crystalline supramolecular structure, in particular at the nanoscale, has arisen in the past three years. These new findings have helped establish that the first step in the formation of a triacylglycerol network is the creation of nanocrystalline platelets that aggregate into polycrystalline clusters in the micrometer range, ultimately forming a three-dimensional network. This review explains how fat nanostructure can be characterized and highlights recent findings on how crystallization parameters influence the formation of fat nanocrystals. For instance, shear has been shown to modify not only nanoplatelet size but also their aggregation, affecting some macroscopic properties such as porosity and, therefore, the ability of the network to effectively bind liquid oil. This new information on fat nanostructure is relevant from scientific and technological standpoints and has opened up the possibility of nanoengineering material properties as well as developing new products and processes.

Emerging technologies in antimicrobial coatings can help improve the quality and safety of our food supply. The goal of this review is to survey the major classes of antimicrobial agents explored for use in coatings and to describe the principles behind coating processes. Technologies from a range of fields, including biomedical and textiles research, as well as current applications in food contact materials, are addressed, and the technical hurdles that must be overcome to enable commercial adaptation to food processing equipment are critically evaluated.

Non-nutritive sweeteners (NNSs) provide sweetness to foods and beverages without adding calories. They have thus been found useful in minimizing the dietary sugar content of diabetics and the dietary energy content of individuals attempting to lose or maintain body weight. Their usefulness in weight reduction has recently been questioned, however, based on the notion that they can actually increase hunger and food intake and thereby promote weight gain. The evidence offered in support of this idea comes principally from the fields of taste physiology, metabolic endocrinology, human behavior, and epidemiology. This review evaluates this evidence and does not find it compelling. Indeed, the most straightforward findings to the contrary derive from several intervention studies in both children and adults showing that the chronic, covert replacement of dietary sugar with NNSs does not increase, and can in fact reduce, energy intake and body weight.

Recent insights into the relationship between the human gut and its resident microbiota have revolutionized our appreciation of this symbiosis and its impact on health and disease development. Accumulating evidence on probiotic and prebiotic interventions has demonstrated promising effects on promoting gastrointestinal health by modulating the microbiota toward the enrichment of beneficial microorganisms. However, the precise mechanisms of how prebiotic nondigestible oligosaccharides are metabolized by these beneficial microbes in vivo remain largely unknown. Genome sequencing of probiotic lactobacilli and bifidobacteria has revealed versatile carbohydrate metabolic gene repertoires dedicated to the catabolism of various oligosaccharides. In this review, we highlight recent findings on the genetic mechanisms involved in the utilization of prebiotic fructooligosaccharides, β-galactooligosaccharides, human milk oligosaccharides, and other prebiotic candidates by these probiotic microbes.

The application of electrostatics in both powder and liquid coating can improve the quality of food, such as its appearance, aroma, taste, and shelf life. Coatings can be found most commonly in the snack food industry, as well as in confectionery, bakery, meat and cheese processing. In electrostatic powder coating, the most important factors influencing coating quality are powder particle size, density, flowability, charge, and resistivity, as well as the surface properties and characteristics of the target. The most important factors during electrostatic liquid coating, also known as electrohydrodynamic coating, include applied voltage and electrical resistivity and viscosity of the liquid. A good understanding of these factors is needed for the design of optimal coating systems for food processing.

The susceptibility of food oil to quality loss is largely determined by the presence of oxygen. This article reviews the current understanding concerning the effect of oxygen types, location, and concentration on the oxidative stability of foods. It also discusses the major factors that influence the interaction between oxygen and lipids such as antioxidants, prooxidants, reactive oxygen species (ROS), environmental conditions, and oxygen scavengers. Research has shown that the amount of oxygen needed to cause oxidation is generally very small and that by reducing oxygen concentration in containers to less than 2%, oxidative stability can be greatly enhanced. However, very few studies have systematically examined the oxygen levels needed to reduce, or inhibit, lipid oxidation processes. Thus, a more comprehensive understanding of the relationship between oxygen levels and lipid oxidation is necessary for the development of innovative antioxidant solutions and package designs that prolong the quality of foods containing lipids.

Foodborne bacterial pathogens encounter many environmental insults or stresses during food production, processing, storage, distribution, and preparation. However, these pathogens can sense changes in their surroundings and can respond by altering gene expression. A protective response may follow that increases tolerance to one or more stresses. This phenomenon is referred to as stress adaptation and has been shown to aid in the survival of pathogens in food products and in the food processing environment. Furthermore, stress adaptation may alter the virulence properties of pathogens and can contribute to survival in vivo during infection. Elucidating the molecular mechanisms underlying stress adaptation in bacterial food pathogens is essential for the development and implementation of more effective control measures and will permit the design of optimal processing regimes that combine maximum safety with consumer demands for more fresh-like, minimally processed foods.

This article reviews progress in the field of food colloids with particular emphasis on advances in novel functional ingredients and nanoscale structuring. Specific aspects of ingredient development described here are the stabilization of bubbles and foams by the protein hydrophobin, the emulsifying characteristics of Maillard-type protein–polysaccharide conjugates, the structural and functional properties of protein fibrils, and the Pickering stabilization of dispersed droplets by food-grade nanoparticles and microparticles. Building on advances in the nanoscience of biological materials, the application of structural design principles to the fabrication of edible colloids is leading to progress in the fabrication of functional dispersed systems—multilayer interfaces, multiple emulsions, and gel-like emulsions. The associated physicochemical insight is contributing to our mechanistic understanding of oral processing and textural perception of food systems and to the development of colloid-based strategies to control delivery of nutrients during food digestion within the human gastrointestinal tract.

Bioactive peptides are encrypted within the primary structure of food proteins where they remain inactive until released by enzymatic hydrolysis. Once released from the parent protein, certain peptides have the ability to modulate the renin-angiotensin system (RAS) because they decrease activities of renin or angiotensin-converting enzyme (ACE), the two main enzymes that regulate mammalian blood pressure. These antihypertensive peptides can also enhance the endothelial nitric oxide synthase (eNOS) pathway to increase nitric oxide (NO) levels within vascular walls and promote vasodilation. The peptides can block the interactions between angiotensin II (vasoconstrictor) and angiotensin receptors, which can contribute to reduced blood pressure. This review focuses on the methods that are involved in antihypertensive peptide production from food sources, including fractionation protocols that are used to enrich bioactive peptide content and enhance peptide activity. It also discusses mechanisms that are believed to be involved in the antihypertensive activity of these peptides.

Particle-stabilized emulsions, also referred to as Pickering emulsions, have garnered exponentially increasing interest in recent years. This has also led to the first food applications, although the number of related publications is still rather low. The involved stabilization mechanisms are fundamentally different as compared to conventional emulsifiers, which can be an asset in terms of emulsion stability. Even though most of the research on Pickering emulsions has been conducted on model systems, with inorganic solid particles, recent progress has been made on the utilization of food-grade or food-compatible organic particles for this purpose. This review reports the latest advances in that respect, including technical challenges, and discusses the potential benefits and drawbacks of using Pickering emulsions for food applications, as an alternative to conventional emulsifier-based systems.

The oral bioavailability of a health-promoting dietary component (nutraceutical) may be limited by various physicochemical and physiological phenomena: liberation from food matrices, solubility in gastrointestinal fluids, interaction with gastrointestinal components, chemical degradation or metabolism, and epithelium cell permeability. Nutraceutical bioavailability can therefore be improved by designing food matrices that control their bioaccessibility (B*), absorption (A*), and transformation (T*) within the gastrointestinal tract (GIT). This article reviews the major factors influencing the gastrointestinal fate of nutraceuticals, and then uses this information to develop a new scheme to classify the major factors limiting nutraceutical bioavailability: the nutraceutical bioavailability classification scheme (NuBACS). This new scheme is analogous to the biopharmaceutical classification scheme (BCS) used by the pharmaceutical industry to classify drug bioavailability, but it contains additional factors important for understanding nutraceutical bioavailability in foods. The article also highlights potential strategies for increasing the oral bioavailability of nutraceuticals based on their NuBACS designation (B*A*T*).

The human gut is a complex ecosystem occupied by a diverse microbial community. Modulation of this microbiota impacts health and disease. The definitive way to investigate the impact of dietary intervention on the gut microbiota is a human trial. However, human trials are expensive and can be difficult to control; thus, initial screening is desirable. Utilization of a range of in vitro and in vivo models means that useful information can be gathered prior to the necessity for human intervention. This review discusses the benefits and limitations of these approaches.

The ubiquity of Bacilli endospores in soils facilitates their easy transfer routes to other environments, including cleanrooms and low-biomass sites required by many industries such as food production and processing. A bacterial endospore is a metabolically dormant form of life that is much more resistant to heat, desiccation, lack of nutrients, exposure to UV and gamma radiation, organic chemicals, and oxidizing agents than is a vegetative cell. For example, the heat tolerance of endospores depends on multiple factors such as sporulation temperature, core dehydration, and the presence of minerals and small, acid-soluble proteins (SASPs) in the core. This review describes our current understanding of the persistence mechanisms related to sporeformers' biochemical properties and discusses in detail spores' heat, radiation, and reactive chemical resistance. In addition, it discusses the impact of contamination with spores on many areas of human activity, spore adhesive properties, and biofilm contribution to resistance.

The sensory perception of texture is an important contributor of our general appreciation of foods. Food texture is mainly described in terms of mouthfeel and afterfeel attributes. The role of oral processing in the perception of texture and the role of microstructure therein have been reviewed regularly over recent years (Chen & Engelen 2012, Foegeding et al. 2011, Stieger & van de Velde 2013) and are not, therefore, addressed in this review. The scope of this review relates to the molecules that underlay the texture of foods. Protein, carbohydrate, and fat are the major structuring components in foods. In this review we focus on the physical interactions between proteins and polysaccharides that form the basis for the microstructure and texture of these foods. In general, food products are classified in four categories by their sensory and rheological properties: liquids, semisolids, soft solids, and hard solids (van Vliet et al. 2009). These four categories provide a useful classification framework, although they are not precisely defined by specific rheological properties. The current review focuses on semisolid and soft-solid foods.

Foodborne outbreaks of viral origin have become increasingly a serious public health concern. High-pressure processing (HPP), a nonthermal technology, has come to the forefront for food processing given its minimal effects on food quality. Recent studies have revealed encouraging results for the inactivation of several human viruses by HPP. This review provides comprehensive information on the use of HPP to eliminate viruses in model systems and foods. We address the influences of various parameters, including pressure level, holding time, pH, temperature, and food matrix on the efficacy of pressure inactivation of viruses, as well as insight into the mechanisms for inactivation of enveloped and nonenveloped viruses. HPP is a promising technology for mitigating virus contamination of foods, thus it is essential to identify the optimal parameters for enhancing virus inactivation while ensuring sensory and nutritional quality retention of foods.

Human noroviruses (NoVs) are the leading cause of foodborne illness in the United States, and they exact a considerable human and economic burden worldwide. In fact, the many challenging aspects of human NoV have caused some to call it the nearly perfect foodborne pathogen. In this review, a brief overview of NoVs and their genetic structure is provided. Additionally, the challenges and recent developments related to human NoVs regarding viral evolution, transmission, epidemiology, outbreak identification, cultivation, animal and human models, and detection are presented.

High pressure processing (HPP) has emerged as a commercially viable food manufacturing tool that satisfies consumers' demand for mildly processed, convenient, fresh-tasting foods with minimal to no preservatives. Pressure treatment, with or without heat, inactivates pathogenic and spoilage bacteria, yeast, mold, viruses, and also spores and extends shelf life. Pressure treatment at ambient or chilled temperatures has minimal impact on product chemistry. The product quality and shelf life are often influenced more by storage conditions and packaging material barrier properties than the treatment itself. Application of pressure reduces the thermal exposure of the food during processing, thereby protecting a variety of bioactive compounds. This review discusses recent scientific advances of high pressure technology for food processing and preservation applications such as pasteurization, sterilization, blanching, freezing, and thawing. We highlight the importance of in situ engineering and thermodynamic properties of food and packaging materials in process design. Current and potential future promising applications of pressure technology are summarized.

Manufacturers often cannot simply add a nutraceutical to a food when formulating functional foods that have acceptable sensory appeal as well as the desired health benefits. The appropriate application of microencapsulation for stabilizing nutraceuticals enables their effective delivery through food. Careful design of the delivery system helps protect sensitive nutraceuticals from the environment and processing stresses encountered during food manufacture, and prevents undesirable interactions of the nutraceutical with components in the food matrix. Microencapsulation technologies overcome hurdles associated with the successful delivery of nutraceuticals in healthy foods if due consideration is given to challenges at all stages throughout the supply chain. This encompasses stabilizing and protecting nutraceuticals from degradation in ingredient formats, during processing, in the final food product, and during intestinal transit until they are released at the desired site in the gastrointestinal tract to impart their targeted health effects.