Dennis R. Heldman

Rheological Properties and Textural Attributes of Cooked Brown and White Rice During Gastric Digestion in Vivo

Physical properties of gastric chyme from cooked brown and white rice meals were determined over an 8xa0h 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 (pu2009<u20090.001). Shear stress values were greater in brown rice compared to white rice, and consistently greater in the proximal region compared to the distal region. The gastric chyme behaved as a weak gel, with G’ greater than G”. Rice grain firmness and hardness showed significant differences as a result of rice type, stomach region, and digestion time (pu2009<u20090.001). Rice grains decreased in firmness and hardness over the 8xa0h postprandial period. The median particle diameter was significantly different between stomach regions; the distal region had a smaller median particle diameter compared to the proximal region for both rice types. Our results support the traditional functional description of the stomach, with the main location of breakdown being the distal region. However, our results also suggest that food is not only broken down and immediately emptied; there is a mixing that will occur between the proximal and distal regions, although the full extent of the meal mixing still needs to be quantified. These results help to better understand the physical breakdown processes that food undergoes during gastric digestion, allowing for future optimization of food properties to control their digestive characteristics.

Food Preservation Process Design

Preservation processes for food products have evolved over time as more fundamental information about the factors influencing the processes has become available. Traditionally, thermal processes have been used for the preservation of shelf-stable and refrigerated foods. Recently, ultra-high-pressure and pulsed-electric-field technologies have evolved as alternative preservation processes. The overall objective of this chapter is to assemble information on the design of preservation processes, with specific attention to the kinetics of microbial inactivation, the transport phenomenon within the product structure, and the impacts of the processes on microbial populations and product quality attributes.

Kinetic Models for Food Systems

This chapter discusses the kinetic models for the food systems. Food is a dynamic system. Food component is changing continuously, beginning with changes that occur at the time of the harvest or assembly of raw food materials. These changes continue during handling, processing, and distribution of the product, and ingredients incorporated into the product during formulation of the final food product influence the changes. The changes occur at different rates, depending on the exposure of the product to external environments and the intensity of environmental factors during the chain of events between harvest or assembly and the time of consumption. The changes occurring within the food system have a variety of impacts on the food product, including changes in the microbiological population and modification of some product quality attributes. Kinetic models provide a structural framework for quantitatively describing the changes occurring in a food system. The measurement or availability of appropriate kinetic constants for these changes enable us to estimate the magnitudes of change in a given food component during a process, storage, or other event prior to food consumption.

Kinetics of Food Quality Attribute Retention

This chapter discusses the kinetic parameters available to describe the retention of food quality attributes. In addition, the kinetic parameters are used to demonstrate the quality retention that occurs during a preservation process in a quantitative manner. These illustrations provide quantitative insights into differences in preservation processes and provide a framework for evaluating processes when attempting to determine the process with minimum impact on the quality attributes of the product. Quantifying quality retention during preservation processes for food products has developed over a considerable period of time. The extent to which this information has been used in process design and optimization of processes is limited. The examples presented in this chapter demonstrate the opportunities for predicting the magnitudes of quality retention during preservation processes and potentially minimizing the changes in quality attributes.

Assessment of chicken breast meat quality after freeze/thaw abuse using magnetic resonance imaging techniques: Chicken meat MRI

BACKGROUNDnFreezing/thawing meat can result in quality losses as a result of the formation, melting and reformation of ice. These changes in water state can result in alterations in texture, water holding and other key quality attributes. It was hypothesized that magnetic resonance imaging (MRI) could quantify changes in mobility and localization of water as a function of freezing/thawing, which could be correlated with quality measurements.nnnRESULTSnDrip loss increased significantly for unbrined samples by over 100% after each freeze/thaw cycle (1.5% to 3.3% to 5.3% drip loss). Brine uptake decreased 50% after 2 cycles (from 53% to 28% mass uptake). Drip loss for brined samples increased after 2 cycles; other attributes were not significantly affected. MRI showed brined samples had less change in both proton density and T2 distributions. High-field nuclear magnetic resonance (NMR) imaging showed greater change in T2 distributions.nnnCONCLUSIONnAs freeze/thaw damage increased, meat quality was reduced in both brined and unbrined chicken breasts, with more prominent changes in unbrined meat. These decreases in quality correlated with changes, albeit small, in water mobility and localization as measured by MRI. High-field NMR micro-imaging showed more dramatic changes in T2 distributions in unbrined samples. These MRI techniques are shown to be useful in the assessment of meat quality after freeze/thaw abuse.

Prediction of Liquid Specific Heat Capacity of Food Lipids: Oil specific heat modeling…

Specific heat capacity (cp ) is a temperature dependent physical property of foods. Lipid-being a macromolecular component of food-provides some fraction of the foods overall heat capacity. Fats/oils are complex chemicals that are generally defined by carbon length and degree of unsaturation. The objective of this investigation was to use advanced specific heat capacity measurement to determine the effect of fatty acid chemical structure on specific heat capacity of food lipids. In this investigation, the specific heat capacity of a series of triacylglycerols were measured to quantify the influence of fatty acid composition on specific heat capacity based on two parameters; the -average carbon number (C) and the average number of double bonds (U). A prediction model for specific heat capacity of food lipids as a function of C, U and temperature (T) has been developed. A multiple linear regression to the three-parameter model (R2 = 0.87) provided a good fit to the experimental data. The prediction model was evaluated by comparison with previously published specific heat capacity values of vegetable oils. It was found that the model provided a 0.53% error, while three other models from the literature predicted cp values with 0.85% to 1.83% average relative deviation from experimental data. The outcomes from this research confirm that the thermophysical properties of fat present in foods are directly related to the physical chemical properties.nnnPRACTICAL APPLICATIONnThe specific heat capacity of food products is widely used in process design. Improvements of current models to predict specific heat capacity of food products will assist in the development of efficient processes and in the control of food quality and safety. Furthermore, the understanding of how changes in chemical structure of macromolecular components of foods effect thermophysical properties may begin to allude to models that are not just empirical, but represent portions of the differences in chemistry.

Correction: Analysis of moisture diffusion mechanism in structured lipids using magnetic resonance imaging

Correction for ‘Analysis of moisture diffusion mechanism in structured lipids using magnetic resonance imaging’ by Sravanti Paluri et al., RSC Adv., 2015, 5, 76904–76911.

Process Design Models

This chapter illustrates the influence of preservation processes on other product components and quality attributes. The research literature for food preservation processes provides numerous approaches to accommodate the mathematics of integration. The quantitative guidance for development of process time for preservation processes has been derived from the design of thermal processes (commercial sterilization) for shelf-stable foods. The process time is important for the operator of the process and the specific process conditions associated with ensuring that the thermal process reduces the target microbial population to the target level. The process design parameter can be applied for any type of preservation process, including continuous flow systems and alternative technology systems. The general approach is applied to alternative preservation technologies; the concepts are illustrated using the traditional thermal process. The impact of a preservation process on any individual component of a food can be evaluated by time-step computation.

Physical Transport Models

This chapter focuses on the significant base of information on thermal energy transport models, as well as the more limited number of models for transport phenomenon occurring during the use of alternative technologies for food preservation. The transport models for processes involving thermal energy provide an excellent basis for developing and applying transport models for alternative processes. The information to be developed and presented includes physical properties of foods, as influenced by temperature, pressure, and other variables associated with the preservation process. The appropriate and available transport models are presented and illustrated in this chapter. The models referenced are for thermal energy transport, but information on pressure distribution and electric field distribution are also explored. Applying models to predict temperature distribution histories within a food product structure depend on access to reliable physical properties data.

Process Validation and Evaluation

This chapter discusses the process validation and evaluation. Validation is very important. The primary purpose of many preservation processes is to ensure microbiological safety of the food product. As indicated during the development of process design, the microbial population of concern is a pathogen, and the process is designed to reduce the risk of a food safety hazard to some negligible level. To ensure that the process design is appropriate to prevent the manufacturing of product causing a food-borne illness outbreak, the process design must be validated. The conditions of the validation should consider as many of the process variables as possible. There are four factors that emphasize the need for process validation: the acceptability of kinetic constants, physical properties of product, shape and size of product container or package, and quality considerations.