Study of molecular interaction and texture characteristics of hydrocolloid-mixed alginate microspheres: As a shell to encapsulate multiphase oil cores.

This work investigates the molecular interaction of hydrocolloids (xanthan gum (XG), hydroxyethyl cellulose (HEC), carbomer (CBM) and hymagic™-4D (HA)) with sodium alginate (SA) in microspheres in detail. The molecular interaction of hydrocolloids with SA are demonstrated by the rheological property analysis of the mixed solutions as well as the morphology structure and texture characteristics studies of the microspheres. It is found that the hydrocolloids (XG, HEC and CBM) with branches or capable to coil are able to form complex networks with SA through molecular interactions which hinders the free diffusion of calcium ions and changes the texture characteristics of microspheres. In addition, the mixed solutions (SA-XG and SA-HEC) with complex networks and do not have a chelating effect on calcium ions are used to form the shell of the microcapsules through droplet microfluidic technology, and stable with soft microcapsules encapsulating multiphase oil cores have been successfully prepared. At the same time, the textural properties of microcapsules are quantized, which are related to human sensory properties. The developed stable and soft microcapsules which have the properties of sensory comfort are expected to be applied in the personal care industry and a variety of fields.

The swallowing threshold and starch hydrolysis of cooked rice with different moisture contents for human mastication.

Swallowing threshold is a critical parameter that marks the condition of food after mastication in the human mouth being ready to be swallowed. In the current study, a new aspect was investigated in which the food boluses from cooked rice with three moisture contents (52%, 63% and 73% on a wet basis) were masticated and collected just before swallowing by a group of twelve voluntary participants. Both mechanical/textural properties and physicochemical characteristics of the cooked rice and their boluses were investigated. The results show that the oral duration of the cooked rice was positively associated with rice hardness, but negatively correlated with the moisture content of rice boluses. After chewing, the textural properties except cohesiveness and adhesiveness varied little among the rice bolus samples. A significant decrease in the textural parameters was shown for the cooked rice with a low (52%) and middle (63%) moisture content after mastication. In contrast, the decrease was insignificant for the cooked rice having the highest moisture content (73%). Consistently, a negative correlation between the hardness of cooked rice and the amount of soluble reducing sugar in the rice boluses was presented. The salivary impregnation and the particle size distribution of the rice boluses at the swallowing threshold were independent on rice physics (i.e., initial moisture content, texture) and oral physiology. In addition, due to the high efficiency of salivary α-amylase, the starch in cooked rice could be hydrolyzed as much as one-third during oral digestion. The present study suggests that the initial moisture content of cooked rice and mastication conditions such as the presence of α-amylase and salivary impregnation could influence the physicochemical properties of rice boluses at the swallowing threshold. These factors should be carefully considered in future in vitro digestion studies of carbohydrate-based food products.

The surface mechanics of cooked rice as influenced by gastric fluids measured using a micro texture analyzer.

In this study, a micro texture analyzer (MTA) was employed to explore the texture characteristics of the surface of an individual steamed rice (SR) and fried rice (FR) grain exhibited in four simulated digestion environments in vitro. The elastic modulus, hardness and elastic index of the single cooked rice particle were measured using the MTA. The hardness of SR particles decreased by 66, 81, 89.1, and 95% after simulated digestion in distilled water, HCl, simulated gastric fluid (SGF), and simulated salivary and gastric fluid (SSF + SGF), respectively. This is in line with the most significant volume expansion and structure ruptures when digested in SSF + SGF. Similar mechanical and structural behaviors were shown for FR, but the hardness and elastic modulus decreased less than those of SR under the same digestion conditions. The different surface mechanics are consistent with the reduced expansion and more compact structure with smaller voids in FR during in vitro digestion. This could be attributed to the encapsulation by frying oil on the surface that would retard the diffusion of digestive fluids into the rice kernels. A weak negative correlation was found between the elastic modulus and the moisture content of the cooked rice. The present study has quantitatively assessed the surface mechanics of cooked rice as influenced by gastric fluids using the MTA. This is practically meaningful for gaining an in-depth understanding of the influence of textural modifications on disintegration of solid foods and release of nutrients during digestion.