Water transport in starchy foods: Experimental and mathematical aspects

BackgroundThe availability and movement of water inside the food materials play essential roles for food stability by affecting their physical and chemical properties, and microbiological activity. Understanding the moisture sorption behavior is a necessary step to control food properties. Food processing unit operations like drying and cooking influence the behavior of starch since such systems trigger swelling or shrinkage as a result of moisture sorption or desorption mechanisms. Also, these processes alter many aspects of starch-containing foods such as acceptability, nutritional value, quality, and shelf-life.Scope and approachTherefore, understanding the water transport in starchy foods and the changes occurring in functional properties of starch has a great importance to describe and model their sorption and drying behavior. First, the primary mechanisms occurring during water transport such as moisture sorption, swelling, gelatinization, and glass transition are discussed using experimental results presented in the literature. Additionally, the hybrid mixture theory (HMT) and its potential for predicting transport mechanisms in starchy foods is discussed.Key findings and conclusionsIn addition to experimental considerations, the mathematical modeling provides complementary information to predict the heat and fluid transfer. The hybrid mixture theory based multiscale models are able to describe the physico-chemical changes and general transport mechanisms occurring within a porous food matrix. This theory can also be used to predict the quality changes in food products during processing.     

Molecular thermodynamics modeling of equilibrium moisture in foods

Moisture content in foods affects many aspects of processing and storage, as well as quality and pathological activity. Understanding its behavior is very important in the food industry for designing effective long-term food management strategies, in particular transportation and storage. Most approaches found in the literature dealing with moisture in foods consist of measuring it as a function of relative humidity and temperature and then fitting the data to empirical or semi-empirical models for interpolation or correlation purposes. Most semi-empirical models are modifications of early gas adsorption models on hard surfaces, which fundamentally are not well suited to describe water in softer materials such as foods. In this work, we propose and use a more general framework based on equilibrium molecular thermodynamics to model and correlate equilibrium moisture content (EMC) in foods that takes into account other non-adsorption phenomena such as mixing and swelling of the biopolymers in foods. The framework is general, and the current model shows very good results correlating and modeling EMC. The model parameters provide insight into the nature of the water activity in food products, providing potentially useful information for food processing and modeling.     

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.     

Multispectral Imaging for Plant Food Quality Analysis and Visualization

The multispectral imaging technique is considered a reformation of hyperspectral imaging. It can be employed to noninvasively and rapidly evaluate food quality. Even though several imaging or sensor‐based techniques have been conducted for the quality assessment of various food products, the rise of multispectral imaging has been more promising. This paper presents a comprehensive review of the use of the multispectral sensor in the quality assessment of plant foods (such as cereals, legumes, tubers, fruits, and vegetables). Different quality parameters (such as physicochemical and microbiological aspects) of plant‐based foods that were determined and visualized by the combination of modeling methods and feature wavelength selection approaches are summarized. Based on the literature, the most frequently used wavelength selection methods are the successive projection algorithm (SPA) and the regression coefficient (RC). The most effective models developed for analyzing plant food products are the partial least squares regression (PLSR), least square support vector machine (LS‐SVM), support vector machine (SVM), partial least squares discriminant analysis (PLSDA), and multiple linear regression (MLR). This article concludes with a discussion of challenges, potential uses, and future trends of this flourishing technique that is now also being applied to plant foods.     

Pulsed Light Treatments for Food Preservation. A Review

Consumers demand high-quality processed foods with minimal changes in nutritional and sensory properties. Nonthermal methods are considered to keep food quality attributes better than traditional thermal processing. Pulsed light (PL) is an emerging nonthermal technology for decontamination of food surfaces and food packages, consisting of short time high-peak pulses of broad spectrum white light. It is considered an alternative to continuous ultraviolet light treatments for solid and liquid foods. This paper provides a general review of the principles, mechanisms of microbial inactivation, and applications of PL treatments on foods. Critical process parameters that are needed to be optimized for a better efficiency of PL treatments are also discussed. PL has considerable potential to be implemented in the food industry. However, technological problems need to be solved in order to avoid food overheating as well as to achieve better penetration and treatment homogeneity. In addition, a more extensive research is needed to understand how PL affects quality food attributes.     

Reaction Kinetics at High Pressure and Temperature: Effects on Milk Flavor Volatiles and on Chemical Compounds with Nutritional and Safety Importance in Several Foods

Consumers demand, in addition to excellent eating quality, high standards of safety and nutrition in ready-to-eat food. This requires a continuous improvement in conventional processing technologies and the development of new alternatives. Prevailing technologies such as thermal processing can cause extensive and undesirable chemical changes in food composition while minimal processing strategies cannot eliminate all microbial pathogens. This review focuses on pressure-assisted thermal processing, a new alternative for shelf-stable foods. Its implementation requires an analysis of reaction kinetics at high pressure and elevated temperature. Acceleration of the inactivation of bacterial spores by the synergistic effect of pressure and temperature is expected to allow processing at lower temperature, shorter process time, or a combination of both. Therefore, thermal degradation of quality is expected to be lower than that of conventional thermal processes. However, few studies have focused on the effect of the conditions required for the inactivation of bacterial spores on the kinetics of chemical reactions degrading food quality, particularly at the high temperatures required for the processing of low-acid foods.     

Review: Enzyme inactivation during heat processing of food-stuffs

Enzyme inactivation during heat processing is reviewed with regard to fundamental aspects (structure, thermodynamics and kinetics), mathematical models and the relationship between enzyme activity and food quality. Enzyme stability is related to enzyme structure and to factors in the microenvironment. Kinetics of inactivation are categorized with respect to reaction order and two models are briefly discussed which describe the variation of inactivation rates with temperature. The determination of accurate kinetic parameters is emphasized where the objective is to develop mathematical models of enzyme inactivation in real foods. The value of modelling inactivation is assessed. Enzymes having effects on sensory quality are reviewed with particular emphasis on those enzymes which influence flavour, through lipid degradation, and those which affect texture by catalysing the breakdown of starch, pectin or protein.     

Formation risk of toxic and other unwanted compounds in pressure-assisted thermally processed foods

Consumers demand, in addition to excellent eating quality, high standards of microbial and chemical safety in shelf-stable foods. This requires improving conventional processing technologies and developing new alternatives such as pressure-assisted thermal processing (PATP). Studies in PATP foods on the kinetics of chemical reactions at temperatures (approximately 100 to 120 °C) inactivating bacterial spores in low-acid foods are severely lacking. This review focuses on a specific chemical safety risk in PATP foods: models predicting if the activation volume value (V(a) ) of a chemical reaction is positive or negative, and indicating if the reaction rate constant will decrease or increase with pressure, respectively, are not available. Therefore, the pressure effect on reactions producing toxic compounds must be determined experimentally. A recent model solution study showed that acrylamide formation, a potential risk in PATP foods, is actually inhibited by pressure (that is, its V(a) value must be positive). This favorable finding was not predictable and still needs to be confirmed in food systems. Similar studies are required for other reactions producing toxic compounds including polycyclic aromatic hydrocarbons, heterocyclic amines, N-nitroso compounds, and hormone like-peptides. Studies on PATP inactivation of prions, and screening methods to detect the presence of other toxicity risks of PATP foods, are also reviewed.     

Recent Advances in Food Thawing Technologies

Serious quality deterioration can occur with suboptimal thawing, and thus innovative thawing technologies may have an important role in improving the final quality of frozen foods. In recent years, although several new thawing technologies have been extensively studied, such as ultra‐high pressure assisted thawing, ultrasound‐assisted thawing, high‐voltage electrostatic field thawing, ohmic thawing, and radio frequency thawing, more research is needed to make them more applicable to thawing of food industrially. A better evaluation of the impact of thawing is needed to help move new thawing technologies forward. This review discusses the principles involved, the applications to different types of foods, modeling of the various processes, new evaluation techniques, and patents obtained for the different systems. The benefits and weaknesses of these systems are also discussed to provide a more complete review of these new thawing techniques. This review will, hopefully, encourage additional work that may help reach the goal of having better food thawing systems.     

Physical Aging of Amorphous Starches (A Review)

In recent years, physical behaviors of glassy foods are greatly focused as many processed foods are consumed in their glassy states. Physical aging is one of the important phenomena for glassy foods, which is responsible for quality changes vs. retention of freshness during storage. The aging phenomenon can be predicted on the basis of a process of thermodynamic relaxation, induced by structural rearrangements in amorphous matrices. Thus, it can be evaluated by using calorimetric, volumetric, and mechanical analyses. Starch is one of the principal components in most cereal‐based glassy foods, and its aging is thus relevant to the overall changes in quality and freshness of various cereal‐based food products. The polymeric theory for the physical aging of glassy starch is reviewed on the basis of the existing literature, and the aging kinetics based on the changes in various physical and thermal properties are discussed.     

DETERMINATION OF STABLE ISOTOPE RATIOS IN FOOD ANALYSIS

Within the last few years, stable isotope analysis has gained increasing importance in authenticity control of food and food ingredients. The development of the methodology from its start in the geological sciences is reviewed, the requirements and the specific features of the technique in the area of food quality assessment are outlined, and the progress in instrumentation during the last few decades is described. Scope and limits of the analysis of stable isotope ratios to assess the quality and to determine the origin are demonstrated for foods, such as fruit juice, wine, spirits, or beer. The classical approaches investigating hydrogen, carbon and oxygen isotopes as well as strategies including elements, such as nitrogen and sulfur, are reviewed. The present state of the art and future possibilities of the methodology are discussed.     

Carotene Degradation and Isomerization during Thermal Processing: A Review on the Kinetic Aspects

Kinetic models are important tools for process design and optimization to balance desired and undesired reactions taking place in complex food systems during food processing and preservation. This review covers the state of the art on kinetic models available to describe heat-induced conversion of carotenoids, in particular lycopene and β-carotene. First, relevant properties of these carotenoids are discussed. Second, some general aspects of kinetic modeling are introduced, including both empirical single-response modeling and mechanism-based multi-response modeling. The merits of multi-response modeling to simultaneously describe carotene degradation and isomerization are demonstrated. The future challenge in this research field lies in the extension of the current multi-response models to better approach the real reaction pathway and in the integration of kinetic models with mass transfer models in case of reaction in multi-phase food systems.     

降血糖类保健食品市场质量状况与监管

糖尿病是一种常见的慢性内分泌代谢性疾病,与生活习惯息息相关。由于生活水平的提高及饮食习惯的改变,目前糖尿病患病率持续增长。我国具有悠久的药食同源传统,糖尿病人不仅可以通过服用降糖药物控制过高的血糖,而且摄食某些特殊食品同样能起到控制高血糖的效果,因此很多具有辅助降血糖功能的保健食品应运而生。本文从市场概况、检验标准、质量现状以及存在的问题等4个维度来论述我国降血糖类保健食品市场的质量状况,并提出加快建立补充检验方法和审批速度、加大快筛技术研发力度、加强宣传教育合理引导消费以及加强网络销售监管等建议。     

Nutrition-based health: cell-based bioassays for food antioxidant activity evaluation

Food science has progressively evolved and now there are wide evidences that foods have biological activities that are beyond their classical nutritional value. In this field, the antioxidant activity of pure compounds, food, feed, and dietary supplements has been extensively studied and numerous analytical approaches and assay models have been developed, involving various systems from simple chemical assays to animal models and human studies. This article is an overview of different cell-based models that have been used for testing the antioxidant properties of food, feed, and dietary supplements. Advantages, drawbacks, and technical problems to develop and validate suitable, robust, and high-throughput cell-based bioassays for screening food antioxidant activity will be discussed.     

A user-friendly general-purpose predictive software package for food safety

Computer-aided engineering tools can help speed up food product, process and equipment design by making it easier to check “what if” scenarios, much as such tools have improved productivity in other industries. In particular, food safety is a critical area where such predictive tools can have great impact. A realistic, integrated and comprehensive software has been developed that can simulate a food process and its safety by combining a fundamental, physics-based model of the process with the kinetics of microbiological and chemical changes during processing to provide needed information at any time and at any location in the food during processing. Compositions for a large number of foods are integrated into the software, and therefore, composition-based prediction of thermophysical properties, needed for the model, can be obtained. Microbiological and chemical kinetic databases that are also built-in can cover many practical situations, based on the grouping of foods. An intuitive graphical user interface has been built with those in the food sector in mind.     

Relating Food Engineering to Cooking and Gastronomy

Modern consumers are increasingly eating meals away from home and are concerned about food quality, taste, and health aspects. Food engineering (FE) has traditionally been associated with the industrial processing of foods; however, most underlying phenomena related to FE also take place in the kitchen during meal preparation. Although chemists have positively interacted with acclaimed chefs and physicists have used foods as materials to demonstrate some of their theories, this has not been always the case with food engineers. This review addresses areas that may broaden the vision of FE by interfacing with cooking and gastronomy. Examples are presented where food materials science may shed light on otherwise empirical gastronomic formulations and cooking techniques. A review of contributions in modeling of food processing reveals that they can also be adapted to events going on in pots and ovens, and that results can be made available in simple terms to cooks. Industrial technologies, traditional and emerging, may be adapted to expand the collection of culinary transformations, while novel equipment, digital technologies, and laboratory instruments are equipping the 21st‐century kitchens. FE should become a part of food innovation and entrepreneurship now being led by chefs. Finally, it is suggested that food engineers become integrated into gastronomy's concerns about safety, sustainability, nutrition, and a better food use.     

Acrylamide Formation in Foods during Thermal Processing with a Focus on Frying

This paper summarizes the current state of knowledge on acrylamide formation in foods during thermal processing. The main pathway of acrylamide formation in foods is linked to the Maillard reaction, and in particular, the amino acid asparagine. Effects of several factors related to food composition and processing conditions on the formation levels of acrylamide, and also, other quality characteristics in thermally processed foods are discussed in detail. From a process control point of view, it is also addressed that there is a need to develop viable models for the estimation of acrylamide contents in heated foods during the stages of process design and optimization. Fried potato products, as one of the most encountered category of thermally processed foods, are specifically emphasized for acrylamide formation, potential ways of mitigation, and modeling its formation during frying.     

A review of kinetic models for inactivating microorganisms and enzymes by pulsed electric field processing

As a non-thermal technology, pulsed electric field (PEF) treatment can be utilized in food processing and bioengineering for the inactivation of microorganisms and quality-degrading enzymes, as well as the retention of health-related compounds and the extension of shelf-life. Development of kinetic models that fit the degree of microbial inactivation and the loss of food quality is important to improve the efficiency of PEF treatment. The current review aims to provide an overview of the kinetic models used by PEF for microbial inactivation in liquid foods. Kinetics modeling for the destruction of microorganisms, inactivation of enzymes, retention of health-related compounds, and extension of shelf-life are discussed. Additionally, the fitting accuracy of several models, as well as issues that need further investigation, are discussed to promote further understanding and the deployment of PEF technology.