R. Paul Singh

University of California, Davis | UCD · Department of Biological and Agricultural Engineering

Background: How starch-based food structure can impact the rate and extent of digestion in the small intestine and resulting glycemic response is not properly understood. One possible explanation is that food structure influences gastric digestion, which subsequently determines digestion kinetics in the small intestine and glucose absorption. Howe...

How the stomach can serve as a biochemical environment for starch digestion and the implications on starch emptying are not well-understood. Biochemical changes during gastric digestion of cooked wheat- and rice-based diets of varying particle size and microstructure were investigated using a growing pig model. In larger-particle size diets (rice g...

In vitro gastric digestion studies commonly focus on the acidic environment of the stomach (the distal phase), neglecting that the contact time between food and salivary amylase can be extended during bolus’ temporary storage in the proximal stomach (the proximal phase). Consequently, the role of the proximal phase of gastric digestion on the break...

Correction for ‘Tracking physical breakdown of rice- and wheat-based foods with varying structures during gastric digestion and its influence on gastric emptying in a growing pig model’ by Joanna Nadia et al. , Food Funct. , 2021, DOI: 10.1039/D0FO02917C.

The digestion of starch-based foods in the small intestine as well as factors affecting their digestibility have been previously investigated and reviewed in detail. Starch digestibility has been studied both in vivo and in vitro, with increasing interest in the use of in vitro models. Although previous in vivo studies have indicated the effect of...

There is currently a limited understanding of the effect of food structure on physical breakdown and gastric emptying of solid starch-based foods during gastric digestion. Moisture uptake, pH, particle size, rheological, and textural properties of six solid starch-based diets from different sources (Durum wheat and high amylose white rice) and of d...

The aim of this work was to investigate the role of biochemical digestion on softening and disintegration kinetics of pH 5 and pH 9 egg white gel (EWGs) during in vitro gastric digestion. EWG samples (5 mm length cubes) underwent in vitro digestion by incubation in simulated gastric fluid at different time intervals for up to 240 min. The hardness...

Across many modern industries, as technologies have matured, the use of more complex processes involving multiphase materials has increased. In the food industry, multiphase fluids are now relatively wide-spread, in particular, because of the desire to have faster throughput for large-scale food production. In many cases involving transport, such m...

The role of biochemical and mechanical disintegration on β-carotene release from steamed sweet potatoes (SSP) and fried sweet potatoes (FSP) during in vitro gastric digestion was investigated. Results revealed that, in the absence of mechanical forces generated by the stomach, biochemical digestion did not have a great effect on the breakdown of ce...

The design of a dairy processing plant requires knowledge of the product, process, economics, and hygienic design principles that ensure the production of a safe product. Upon developing a flow sheet of the plant, the required equipment is identified. In dairy processing, certain equipment is common to all plants, such as tanks, heat exchangers, pu...

Buffering capacity is a characteristic of foods to resist changes in pH, which is important to consider in gastric digestion as it will impact physicochemical breakdown of food. A standardized method to measure and quantify buffering capacity in the context of digestion is needed to improve in vitro digestion studies by providing a better estimatio...

Understanding the diffusion of digestive enzymes, particularly pepsin, in different food structures, is a key factorto better control protein digestion and absorption. This study aimed to investigate how protein-based foodmicrostructure impacts pepsin diffusion. Two egg white gels (EWGs) of identical protein concentration (10%)but different structu...

This study investigated the feasibility of using hyperspectral imaging (HSI) to characterize the diffusion of acid and water within food structures during gastric digestion. Two different sweet potatoes (steamed and fried) and egg white gels (pH5 and pH9 EWGs) structures were exposed to in vitro gastric digestion before scanning by HSI. Afterward,...

Digestion behaviour of food protein-based hydrogels is greatly influenced by the gel characteristics and inparticular the microstructure. Using egg white gels (EWGs) as a model food, this study aimed to explore the realtime disintegration by pepsin of different microstructures and subsequent nutrient release kinetics. Usingthermal treatment at 80 °...

Developing a mechanistic understanding of the impact of food structure and composition on human health has increasingly involved simulating digestion in the upper gastrointestinal tract. These simulations have used a wide range of different conditions that often have very little physiological relevance, and this impedes the meaningful comparison of...

Written from the expertise of an agricultural engineering background, this exciting new book presents the most useful numerical methods and their complete program listings.

Gastric protein hydrolysis may influence gastric emptying rate and subsequent protein digestibility in the small intestine. This study examined the gastric hydrolysis of dietary protein from raw and roasted almonds in the growing pig as a model for the adult human. The gastric hydrolysis of almond proteins was quantified by performing tricine-sodiu...

Cereals, legumes, oilseeds, fruits, and vegetables are the most important food crops in the world, with cereal grains contributing the bulk of food calories and proteins worldwide. Generally, the supply of grains and other food can be enhanced by increasing production and by reducing postharvest losses. While food production has increased significa...

Knowledge of the physicochemical conditions to which foods are exposed during gastric digestion is important to facilitate the design and development of novel foods with enhanced functionalities. While in-vivo and in-vitro trial have provided an increased understanding of the functional activity of the gastric wall and the outcomes of digestion, li...

The pharmaceutical industry has implemented the Biopharmaceutics Classification System (BCS), which is used to classify drug products based on their solubility and intestinal permeability. The BCS can help predict drug behavior in vivo, the rate-limiting mechanism of absorption, and the likelihood of an in vitro-in vivo correlation. Based on this a...

Breakdown of rice during gastric digestion may be influenced by rice structure, presence of salivary α‐amylase, and hydrolysis by gastric acid. During mastication, saliva is mixed with rice, allowing α‐amylase to begin starch hydrolysis. This hydrolysis may continue in the gastric environment depending on the rate at which gastric acid penetrates i...

An in vitro ‘dynamic’ model for food digestion diagnosis, the Human Gastric Simulator (HGS), has been designed to reproduce the fluid mechanical conditions driving the disintegration and mixing of gastric contents during digestion. The HGS simulates the stomach as a flexible compartment, and mimics its contractive motility by a series of rollers th...

In food processing it is not uncommon to require specialized processes to achieve desired objectives. Separation of solid particles from liquid streams is accomplished using filtration. Mathematical expressions are used to describe constant rate or constant pressure filtration. These expressions are also useful in designing filtration systems. When...

Packaging is necessary for protecting foods during shipment and storage. Packaging provides protection to the food from various environmental factors such as oxygen, carbon dioxide, water vapor, aroma, and light. Mass transfer through the packaging wall must be well understood to design an appropriate package. Since packaging also provides a means...

Drying or dehydration of foods is an extremely important food processing operation used to preserve foods for extended periods of time. The distinguishing features between drying and concentration are the final level of water and nature of the product. Concentration leaves a liquid food, whereas drying typically produces product with water content...

Mass transfer is an important phenomenon with numerous applications in food processing. Concentration gradients of a substance in a food cause diffusion of that substance from high to low concentration. The magnitude of diffusion coefficient provides an indication of the rate at which the diffusing substance moves from one location to another. Conv...

Underpinned by the delivery of better human health and well-being through food innovation, a new generation of food products aimed at improving bioavailability through the controlled release of nutrients and bioactive compounds has become a leading trend for the global food sector. The efficient design of these novel functional foods requires a bet...

Food processing operations are carried out by using energy in the form of steam, electricity and natural gas. Steam is usually generated at the processing plant sites using boilers. Conversion of water into steam involves phase change that is described by the application of thermodynamics. Upon generation, steam must be transported using pipes to p...

In a food processing plant, it is common to transport food from one operation to another using a wide range of product handling equipment. For liquid foods, various types of pumps are used, whereas, solid foods are often handled using conveyors. To design a pumping system, the first step is to know the properties of the foods such as density and vi...

The mixing performance of gastric contents during digestion is expected to have a major role on the rate and final bioavailability of nutrients within the body. The aim of this study was to characterize the ability of the human stomach to advect gastric contents with different rheological properties. The flow behavior of two Newtonian fluids (10−3...

Mixing of a particle-laden material during peristaltic flow in the stomach has not been quantified in vivo. Gastric mixing plays a key role in the digestion process; it determines the availability of acid and enzymes to individual food particles and controls the length of time particles will spend in the antral region, where they are subjected to m...

Engineered metal/mineral, lipid and biochemical macromolecule nanomaterials (NMs) have potential applications in food. Methodologies for the assessment of NM digestion and bioavailability in the gastrointestinal tract are nascent and require refinement. A working group was tasked by the International Life Sciences Institute NanoRelease Food Additiv...

Simulated gastro-intestinal digestion is widely employed in many fields of food and nutritional sciences, as conducting human trials are often costly, resource intensive, and ethically disputable. As a consequence, in vitro alternatives allowing for the determination of a variety of endpoints such as bioaccessibility of nutrients and non-nutrients,...

The rate of almond breakdown during gastric digestion may be influenced by structural changes that occur during roasting. The primary objective of this study was to investigate in vivo physical property changes of raw and roasted almonds during gastric digestion, using the growing pig as a model for an adult human. Seventy two male pigs were fed a...

During mastication, starch hydrolysis caused by salivary α-amylase may influence food bolus formation and subsequent breakdown during gastric digestion. The objective of this study was to examine texture changes of rice boluses after simulated mastication. Boluses were prepared with three varieties each of brown and white rice (short, medium, and l...

Food digestion is crucial to sustain life. Although it has been examined for more than 300 years, the basic principles are not entirely understood. Antral motility is well characterized, and current research is seeking to determine flow patterns generated by the stomach's peristaltic contractions. The rate of gastric emptying for solid and liquid m...

Long recognized as the bestselling textbook for teaching food engineering to food science students, this 5e transitions with today's students from traditional textbook learning to integrated presentation of the key concepts of food engineering. Using carefully selected examples, Singh and Heldman demonstrate the relationship of engineering to the c...

Food engineering (FE) was identified as a promising field in the mid-20th century. In the succeeding years, demand for food engineers in industry has continued unabated, but the field, in an academic sense, has not quite lived up to its potential. Yet, the coming challenges of the 21st century offer many opportunities for persons with FE training....

Almonds are an important dietary source of lipids, protein, and α-tocopherol. It has been demonstrated that the physical form of almond kernels influences their digestion and absorption, but the role of thermal processes on the digestion of almonds has received little attention. The objectives of this study were to examine the gastric emptying and...

The textural properties of almonds may be assessed using a predictive model consisting of the moisture adsorption isotherms, Fick’s second law of water diffusion, and Fermi’s distribution function. The experimental data of moisture adsorption and the mechanical properties of almonds were measured and fitted into the preceding three models, respecti...

Background: Rice structure is important to rice grain and starch breakdown during digestion. The objective of this study was to determine the gastric emptying and rice composition during gastric digestion of cooked brown and white medium-grain (Calrose variety) rice using the growing pig as a model for the adult human. Results: Brown and white r...

The particle size distribution of foods during gastric digestion indicates the amount of physical breakdown that occurred due to the peristaltic movement of the stomach walls in addition to the breakdown that initially occurred during oral processing. The objective of this study was to present an image analysis technique that was rapid, simple, and...

Knowledge of the fluid dynamic behavior of gastrointestinal (GI) contents during digestion is essential to further understand and model the bioavailability of nutrients and pharmaceuticals in health and disease. The dynamics that develop within the GI tract are the result of a complex and self-regulated interplay between the physical properties of...

Physical properties of gastric chyme from cooked brown and white rice meals were determined over an 8 h postprandial period in the proximal and distal stomach regions of pigs. Rice gastric chyme behaved as a Herschel-Bulkely fluid; the shear stress values were significantly different as a result of rice type, stomach region, and digestion time (p <...

The rate of bolus disintegration in the stomach plays an important role in gastric emptying, which has been shown to be directly correlated with post-food consumption blood glucose levels and satiety. This study examined the effect of various oral and gastric factors on bread bolus disintegration, including flour type, hydrodynamic forces, saliva l...

The equilibrium moisture content of raw and blanched almonds of California grown “Carmel” variety was determined by using static gravimetric method at 25, 35 and 45C over a range of water activities (Aw) from 0.11 to 0.97. The sorption data were fitted to the Guggenheim–Anderson–de Boer (GAB) model. The goodness of fit of the model was evaluated by...

This paper, based on the symposium "Real-World Nutritional Translation Blended With Food Science," describes how an integrated "farm-to-cell" approach would create the framework necessary to address pressing public health issues. The paper describes current research that examines chemical reactions that may influence food flavor (and ultimately foo...

The objective of this study was to determine the release and bioaccessibility of β-carotene from fortified almond butter using in vitro digestion models. Two types of fortifiers were investigated: β-carotene oil (oil) and whey protein isolate (WPI)-alginate-chitosan capsules containing β-carotene oil (capsule). Shaking water bath and Human Gastric...

Moisture adsorption characteristics of California grown almonds (Nonpareil: pasteurized and unpasteurized almonds; Monterey: pasteurized, unpasteurized and blanched almonds) were obtained using the gravimetric method over a range of water activities from 0.11 to 0.98 at 7-50ºC. The weights of almonds were measured until samples reached a constant w...

Specific effects of food processing on food digestion remain to be clearly established. The objective of this study was to determine the effect of rice processing (cooked brown and white rice) on the rheological properties, chemical composition (water, starch, fiber, protein) and pH of gastric chyme in pigs over a two hour post-ingestion period in...

The first step in the digestion process is mastication, or chewing, when food is broken down, lubricated with saliva, and formed into a cohesive mass known as the food bolus. Upon swallowing, the bolus moves to the stomach and undergoes further breakdown during gastric digestion. The subject of this review is the formation of the food bolus and its...

The objective of this study was to investigate the influence of boiling, roasting and frying on the digestion of peanuts in simulated gastric environment. Raw and processed peanuts were tested for disintegration in a model stomach system. The differences in disintegration rate were explained with respect to the changes in moisture absorption and te...

The difficulty in experimentally characterizing the dynamics of gastric contents during digestion has limited the knowledge required to understand and model the kinetics of food disintegration. The goal of this work was to experimentally characterize, in a closed system, the peristaltic flow of fluids with different rheological properties. An exper...

The aim of this work was to develop and validate a computational fluid dynamic model of the forced-air cooling process of fresh strawberries, and use it as a design tool to develop a cooling system aimed at promoting a rapid, uniform and more energy efficient process. The improved performance of the new design was experimentally confirmed. It not o...

In this work a 3-D computational fluid dynamic (CFD) model of the stomach geometry and motility during digestion was developed, and to use it to analyze the flow behavior of gastric fluids with different rheological properties, and their effect on the motion of discrete food particles. The results were in good agreement with experimental data previ...

To fully characterize and model food digestion, an underpinning knowledge of the relationship between the disintegration rate of food structures and the dynamics of gastric contents during digestion needs to be developed. Under the scope of this paper, the possibility of using computational fluid dynamic techniques to obtain a unique insight and qu...

Previous studies have shown that brown rice generates lower glycemic responses than white rice, a trait that may be beneficial in the dietary management of chronic diseases such as diabetes and hyperlipidemia. The objective of this study was to investigate influence of rice digestion on the physical properties of the gastric digesta that may furthe...

The package system designs currently used by the strawberry industry are largely based on empirical techniques and have limited the efficiency of forced-air cooling applications. In this study, a new system capable of promoting a more uniform and energy-efficient cooling was developed. The design of this new system was based on a series of numerica...

Food deterioration and spoilage during storage and distribution are a result of a variety of chemical, biochemical, and/or physical changes. These changes are often the result of product composition, environmental factors, and processing conditions. A variety of measures are available to a food technologist to obviate the deteriorative effects of e...

Instrumental techniques are widely used to assess the changes in quality attributes and evaluate remaining shelf life of the foods. This chapter presents some of the major instrumental techniques for evaluating shelf life of food, including determination of color, appearance, texture, rheological properties, lipid oxidation, and microbiological ana...

The knowledge of solid loss kinetics of foods during digestion is crucial for understanding the factors that constrain the release of nutrients from the food matrix and their fate of digestion. The objective of this study was to investigate the solid loss of carrots during simulated gastric digestion as affected by pH, temperature, viscosity of gas...

Targeted delivery of drugs in different parts of the human gastrointestinal (GI) tract is well studied and applied in the pharmaceutical industry. This chapter includes results from research undertaken to bring the technique of targeted delivery into the food area. In order to predict the fate of a food particle in the GI tract, some important fact...

The rate of bolus disintegration in the stomach is important in determining gastric emptying, which is correlated with post-food consumption blood glucose levels and satiety. This study examined the effect of various factors on bread bolus disintegration rate, including flour type, gastric juice components, saliva level, and presence of α-amylase i...

The objective of this study was to develop an in vitro stomach model, the Human Gastric Simulator (HGS), for studying gastric digestion of foods. The HGS is designed in such a way as to simulate the continuous peristaltic movement of stomach walls, with similar amplitude and frequency of contraction forces as reported in vivo. The HGS mainly consis...

Unlabelled: During gastric digestion, food is disintegrated by a complex interaction of chemical and mechanical effects. Although the mechanisms of chemical digestion are usually characterized by using in vitro analysis, the difficulty in reproducing the stomach geometry and motility has prevented a good understanding of the local fluid dynamics o...

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The complex structure of the package systems currently used by the strawberry industry has prevented an efficient design of the forced-air cooling process. In this study, we investigated the mechanisms through which different design parameters affect the rate and uniformity of cooling, using a previously validated computational fluid dynamics model...

Knowledge of digestion kinetics of solid foods in human stomach, as affected by food processing methods, is critical in establishing processing conditions at the manufacturing stage to achieve desirable release of nutrients in the gastrointestinal tract. The objective of this study was to investigate how roasting affected disintegration and solid r...

A model stomach system was used to investigate disintegration of various foods in simulated gastric environment. Food disintegration modes and typical disintegration profiles are summarized in this paper. Mechanisms contributing to the disintegration kinetics of different foods were investigated as related to acidity, temperature, and enzymatic eff...

The behaviour of β-lactoglobulin (β-lg)-stabilized emulsions (1.0wt% protein and 20.0wt% soy oil) using pepsin digestion under simulated gastric conditions (37°C, pH 1.2 and 34mM NaCl ionic strength, with continuous shaking at approximately 95rev/min for 2h) was investigated. Changes in particle size, ζ-potential and microstructure were monitored a...

The aim of this study was to validate a previously developed mathematical model for predicting the airflow behavior within individual packages of strawberries (clamshells) during forced-air cooling applications. The model was validated by using a non-intrusive flow measurement technique (PIV). The use of PIV required the development of a simplified...