Many existing food manufacturing processes rely on empirical knowledge and are not often designed or performed with a thorough understanding of the underlying phenomena. Drying and rehydration processes are one example of this. The water transfer behavior within foods during these processes varies depending on the manufacturing and cooking conditions, significantly influencing food quality. Based on the observation that the brightness of food changes in response to its moisture content, a novel method for measuring water transfer within foods was developed. Using this approach, new mechanisms of water transfer in pasta were proposed. In addition, a new framework for understanding these complex phenomena, referred to as the artificial intelligence comprehensive and reverse analysis method, was suggested. The effectiveness of this method was demonstrated by elucidating the complex mechanisms by which the gluten structure in noodles affects food texture. This review provides an overview of our findings.

Freezing wheat dough has great benefits in reducing baking costs and time, but bread baked from frozen dough has a smaller loaf, coarser crumb, and harder crust than bread baked from fresh dough. In addition to the preservation process, the ingredients added to frozen dough have a substantial positive impact on the quality of frozen dough. In this study, the effects of the addition of oil on the physical properties of frozen dough and the quality of the bread baked after freezing and thawing were examined. Quality change was investigated for four types of frozen dough made from four different fats with different triacylglycerol constituent fatty acids. Frozen dough with added soybean oil and grapeseed oil had a thicker crumb skeleton after baking. In addition, the frozen dough with soybean oil showed less stretchiness and more protein conglutination. The ratio of unsaturated fatty acids in the oil tended to adjust the extensibility of the frozen dough and alter the crumb skeleton of the baked bread.

The primary physicochemical aspects of freezing are the substantial reduction of water activity and the increase of osmotic pressure by freeze-induced concentration. The temperature-dependent ice fraction subsequently affects the changes in thermal properties and specific chemical reaction processes. In frozen food, the ice structure is strongly determined by the moving ice-front through the balance of water mass transfer and heat transfer. By controlling the ice structure, progressive freeze-concentration could be applied to concentrate liquid food with high quality. In some living organisms, freeze-related biosubstances are produced and accumulated for freeze-tolerance. The cell structure also plays an important role in the freeze-tolerance of cells in microorganisms, plants, and animals.

Solid food products are typically in an amorphous state, and their physical properties change dramatically at the glass to rubber transition temperature (T_g). T_g decreases with increasing water content because of water plasticizing effects. When T_g becomes lower than the ambient temperature, a glass to rubber transition occurs at the ambient temperature. The water content at T_g＝25°Cis usually described as the critical water content (w_c). In this review, the effect of glass to rubber transition on the texture of cookies, the caking of mango powder and the compressibility of soup powder is explained. T_g of the food samples was evaluated by differential scanning calorimetry or thermal rheological analysis. w_c was determined from the relationship between T_g and water content. Fracture properties of the cookie samples changed from brittle to ductile at w_c. Caking of mango powder occurred at water contents above w_c. Hardness of soup powder compressed at temperatures above T_g was much higher than when compressed at temperatures below T_g.

Water often controls the processability and preservability of foods, especially those of the low-water content, by means of mobilities of water and food polymer molecules. Glass transition is a concept of dynamics governs the mobilities and physical properties of foods as well. An explanatory address with a focus on the glass transition in foods was then presented in this workshop.

The thermal behaviors of pore water were studied by adiabatic calorimetry between 50 and 300K. We utilized pore water in 1) silica MCM-41 with pore diameters of 1.5 to 5.0nm, 2) sephadex G10 of a cross-linked dextran gel, and 3) bovine serum albumin (BSA) of a globular protein. The three pore walls differed in hydrophilic/hydrophobic properties, pore size and shape, and flexibility. The hydration levels for G10 and BSA were h=0.273 and 0.321, as evaluated by the mass ratio of water to anhydride. Pore water in MCM-41 revealed glass transitions at around 115, 165, and 210K; the first was attributed to the freezing-in of interfacial water molecules neighboring the pore walls. The temperatures, which increased discretely with pore size, were interpreted to correspond, respectively, with the situations where 2, 3 and 4 hydrogen bonds are broken simultaneously in the activation for rearrangement of water molecule. The glass transitions in hydrated G10 and BSA displayed some similar behaviors as those in MCM-41. It was found that the number of accessible microscopic states of pore water in G10 was small with regard to the configurational degree of freedom below 273K, as compared with those of bulk water and pore water in MCM-41. The number of pore water in BSA was further small, even at 300K, suggesting that the structure of BSA with h=0.321 is determined by BSA itself and most water molecules are confined to narrow spaces.

Bioencapsulation of food additives or functional ingredients aims to protect sensitive core materials during storage and consumption, transport them to designated positions in the gastrointestinal tract, and release them at appropriate rates to maximize bioavailability. Bioencapsulation systems need to be designed with GRAS (generally recognized as safe) materials, and the physicochemical processes involved in matrix formation are crucial for realizing expected functionality. From an engineering perspective, it is important to develop a processing method for obtaining products with desirable features. The author has previously reported that a freezing step represents an interesting processing tool for controlling the properties of an encapsulation system. During freezing, the growth of ice crystals in an aqueous solution results in a cryoconcentrated (freeze-concentrated) phase that is controlled by phase equilibrium. The author’s idea is to control matrix formation in the cryoconcentrated phase for optimizing encapsulation systems. This review summarizes this concept and future scope.

Microencapsulation of flavor is an important technology whereby liquid flavor is enclosed in a carrier matrix by spray drying. In this review, the flavor release from spray-dried powder is discussed. Flavor release from the spray-dried powder could be correlated using the Avrami (Weibull) equation. In the analysis of flavor release from the powder, the unknown parameters were: the diffusion coefficient of flavor in the matrix, D_out, diffusion coefficient of flavor in the flavor droplet, D_in, and mass transfer coefficient from the powder, κ_L, which were estimated to fit d-limonene release behavior by using the partial differential equation model. First, the parameters were determined by fitting with the experimental database, assuming that the release in the matrix was the rate limiting step (D_in»D_out). The diffusion model could explain well the release characteristics of encapsulated d-limonene. For the release of encapsulated d-limonene from the spray-dried powder at 51% RH and 50°C, diffusion of flavor inside the matrix was the rate-limiting step. The encapsulated flavor powder with vacuoles showed greater release than powder without vacuole formation.

The quality control of frying oil and the management of cooking processes are critical to the taste of fried foods, and to the safety and economic efficiency of the commercial production of fried foods. The authors conducted research to assess the degradation of frying oil by studying its electrical properties and observed peculiar behavior of the dielectric constant believed to be caused by water present in the frying oil. An analysis of the dielectric constant suggested that water remains in high-temperature frying oil for a relatively long period of time. It is generally thought that water promptly reaches its boiling point of 100°C when added to high-temperature frying oil and is immediately discharged from the oil and into the atmosphere as steam. Verification that water indeed remains in frying oil at elevated temperature for long periods of time would indicate that there is a mechanism that hinders the discharge of water from high-temperature oil. Accordingly, in this paper we reproduce the conditions in which water remains in the frying oil and consider the factors causing this retention. We also discuss methods for extending the life of frying oils by controlling and managing the degradation of oil caused by hydrolysis when used frying oil is stored.