An insight into tapioca and wheat starch gelatinization mechanisms using TD-NMR and complementary techniques

Effect of water content on gelatinization functionality of flour from sprouted sorghum

Sorghum starch granules are encapsulated in a rigid protein matrix that prevents the granules from fully swelling and gelatinizing. Sprouting and subsequent drying treatment can affect the gelatinization properties of sorghum starch. This study aimed to evaluate the gelatinization properties of flours from unsprouted (US) and sprouted (S50, S40) sorghum dried at 50 °C (6h) and 40 °C (12h), respectively. Swelling power (Sp), thermal properties (DSC) and 1H molecular mobility and dynamics were evaluated at different water contents (38-91%). Sp increased with increasing water content, with S40 showing the lowest values, probably due to prolonged amylase activity and thus starch breakdown. Sprouting increased gelatinization temperatures; however, these differences disappeared for high water contents (82 and 91%). From a molecular point of view, sprouted samples showed a decrease in protons associated to the rigid protein matrix and starch structures. 1H CPMG results showed the presence of 4 populations at 38% water content. The evolution of the more mobile population with increasing water content supported the assignment of more mobile water fraction to this population. Sprouting decreased the mobility of populations in unheated samples, suggesting an increase in molecular bonds between flour biopolymers and water. After heating, however, increased molecular mobility in S40 indicated the formation of a weaker network between starch, protein, and water at the molecular level. These results suggest that post-sprouting drying treatment influences sorghum gelatinization, with potential modulation by water content. This study contributes to understanding the application of sprouted sorghum in foods with different moisture content.

Effects of Five Dietary Carbohydrate Sources on Growth, Glucose Metabolism, Antioxidant Capacity and Immunity of Largemouth Bass (Micropterus salmoides)

This study investigated the effects of glucose (GLU), tapioca starch (TS), gelatinized tapioca starch (GTS), potato starch (PS) and gelatinized potato starch (GPS) on growth and physiological responses in juvenile largemouth bass Micropterus salmoides. After 8 weeks, fish fed with starch diets had better weight gain and growth rates. Counts of red blood cells and monocytes were increased in the PS and GPS groups, compared to GLU group. Contents of serum triglyceride and total cholesterol were markedly elevated in the TS, PS and GPS groups. There were lower levels of serum glucose, insulin and cholecystokinin, and higher agouti-related peptide contents in the PS group compared to GLU group. PS and GPS could enhance glycolysis and TCA cycle by increasing their enzyme activities and transcriptional levels. Additionally, starch sources markedly heightened mRNA levels of key genes involved in the respiratory electron transport chain. Additionally, elevated mRNA levels of key antioxidant genes were shown in the TS and GTS groups. Moreover, TS and PS could promote immunity by upregulating transcriptional levels of the complement system, lysozyme and hepcidin. Taken together, starch exhibited better growth via increasing glycolysis and TCA cycle compared with GLU, and PS could improve antioxidant and immune capacities in largemouth bass.

Impact of pre-meal immersion on multi-scale structural changes and starch digestibility of cooked dried noodles

Pre-meal immersion is a common process for both the consumption of dried noodles and development of takeaway noodles, but its impact on the structure and digestibility of dried noodles is still unclear. In this study, dried noodles cooked for the optimal time were immersed at 80 °C for different time durations. Multi-scale structural changes, including texture, molecular structure, microstructure, and in vitro starch digestibility were studied using a combination of kinetic (first-order exponential decay function, the Peleg model, and LOS plots), physicochemical, and microscopic analysis. The relationship between multi-scale structural changes and starch digestibility was derived. As the immersion progressed, the hardness first rapidly decayed and then reached equilibrium. The decay rate in the initial stage depended on the gluten content. In most cases, the immersion process caused depolymerization of gluten proteins and further gelatinization of starch granules, which was observed from an increase in the free -SH content and decrease in the short-range ordered structure, although there were fluctuations over immersion time. Structural changes resulted in the corresponding changes in substance migration. However, a high gluten content (∼15% w/w) imparted a denser microstructure to the noodles, weakening the deterioration effects compared with a low gluten content (∼10% w/w). In vitro digestion experiments proved that samples with higher gluten content had higher starch digestion rates and lower starch digestion extent during immersion. Correlation analysis revealed that there was a negative correlation between k1 and the tightness of the gel. This study helps to reveal the structural mechanisms of starch digestibility in cooked noodles during immersion.

The use of time domain 1 H NMR to study proton dynamics in starch-rich foods: A review

Starch is a major contributor to the carbohydrate portion of our diet. When it is present with water, it undergoes several transformations during heating and/or cooling making it an essential structure-forming component in starch-rich food systems (e.g., bread and cake). Time domain proton nuclear magnetic resonance (TD ¹ H NMR) is a useful technique to study starch-water interactions by evaluation of molecular mobility and water distribution. The data obtained correspond to changes in starch structure and the state of water during or resulting from processing. When this technique was first applied to starch(-rich) foods, significant challenges were encountered during data interpretation of complex food systems (e.g., cake or biscuit) due to the presence of multiple constituents (proteins, carbohydrates, lipids, etc.). This article discusses the principles of TD ¹ H NMR and the tools applied that improved characterization and interpretation of TD NMR data. More in particular, the major differences in proton distribution of various dough and cooked/baked food systems are examined. The application of variable-temperature TD ¹ H NMR is also discussed as it demonstrates exceptional ability to elucidate the molecular dynamics of starch transitions (e.g., gelatinization, gelation) in dough/batter systems during heating/cooling. In conclusion, TD NMR is considered a valuable tool to understand the behavior of starch and water that relate to the characteristics and/or quality of starchy food products. Such insights are crucial for food product optimization and development in response to the needs of the food industry.