Starch digestion kinetics of extruded reformed rice is changed in different ways with added protein or fiber

Mechanisms of rice protein hydrolysate regulating the in vitro digestibility of rice starch under extrusion treatment in terms of structure, physicochemical properties and interactions

The effect of protein hydrolysates on starch digestibility has been observed in other heat treatments but has yet to be extensively researched under extrusion. This study aimed to analyze the physicochemical properties, structure, and starch digestibility of extruded rice starch-protein hydrolysate (ERS-RPH) complexes prepared by extrusion treatment. The resistant starch contents of ERS-RPH (12.30 %-19.36 %) were higher than those of extruded starch alone (6.33 %). The interaction forces, physical barrier effects, and enzyme inhibition indicated that RPHs at varying hydrolysis degrees hindered starch digestibility by reducing its contact with enzyme and via adhesion and hydrogen bonding with starch. RPHs with higher hydrolysis exhibited greater inhibition of starch digestibility, limiting the swelling power of starch and the leaching of amylose, thereby improving the thermal stability of starch. Fourier transform infrared spectroscopy results revealed the presence of hydrogen bonding interactions between RPHs and starch in complexes, intensifying the ordered structure of starch. Extrusion caused an increase of 6.8 %-10.8 % in the relative crystallinity of ERS-RPH compared to extruded starch alone. Moreover, the strength of V-type structure was reinforced after extrusion. These results enhanced comprehension of how PRHs regulate starch digestibility under extrusion, and offer direction for producing slow-digesting foods.

Modulating the glycemic response of starch-based foods using organic nanomaterials: strategies and opportunities

Traditionally, diverse natural bioactive compounds (polyphenols, proteins, fatty acids, dietary fibers) are used as inhibitors of starch digestive enzymes for lowering glycemic index (GI) and preventing type 2 diabetes mellitus (T2DM). In recent years, organic nanomaterials (ONMs) have drawn a great attention because of their ability to overcome the stability and solubility issues of bioactive. This review aimed to elucidate the implications of ONMs in lowering GI and as encapsulating agents of enzymes inhibitors. The major ONMs are presented. The mechanisms underlying the inhibition of enzymes, the stability within the gastrointestinal tract (GIT) and safety of ONMs are also provided. As a result of encapsulation of bioactive in ONMs, a more pronounced inhibition of enzymes was observed compared to un-encapsulated bioactive. More importantly, the lower the size of ONMs, the higher their inhibitory effects due to facile binding with enzymes. Additionally, in vivo studies exhibited the potentiality of ONMs for protection and sustained release of insulin for GI management. Overall, regulating the GI using ONMs could be a safe, robust and viable alternative compared to synthetic drugs (acarbose and voglibose) and un-encapsulated bioactive. Future researches should prioritize ONMs in real food products and evaluate their safety on a case-by-case basis.

The Microstructure, Rheological Characteristics, and Digestibility Properties of Binary or Ternary Mixture Systems of Gelatinized Potato Starch/Milk Protein/Soybean Oil during the In Vitro Digestion Process

The in vitro digestibility of potato starch-based foods interacting with milk protein and soybean oil was investigated. Microstructures and rheological changes upon digestion were determined. The results showed that the addition of milk proteins (casein and whey protein) promoted gelatinized potato starch digestion, while soybean oil slowed down gelatinized potato starch digestion. A mixture of soybean oil and milk protein promoted the digestion of milk protein, while a mixture of gelatinized potato starch and milk protein inhibited the digestion of milk protein. The mixture of milk protein and/or gelatinized potato starch with soybean oil promoted the release of free fatty acids in soybean oil. The highest release rate of free fatty acids was attained by a mix of milk protein and soybean oil. The mixed samples were digested and observed with a confocal laser scanning microscope. The viscosity of the digestates was determined by a rheometer. Overall, the results demonstrated that the addition of milk protein and soybean oil had an effect on the in vitro digestibility of gelatinized potato starch and its microstructure.

Influence of instant rice characteristics and processing conditions on starch digestibility-A review

Instant rice is increasingly popular around the world due to its convenience, but it commonly has a high glycemic index, and a frequent consumption might contribute to the occurrence of many chronic diseases. In this review, the main factors determining starch digestibility of instant rice were comprehensively evaluated, aiming to help the rice industry develop instant rice with slow starch digestibility. Starch digestibility in instant rice can be reduced by manipulating its intrinsic and extrinsic nutrients. Processing conditions, including pre-gelatinization, storage, and reheating are also important for the starch digestibility of instant rice. Individual differences in terms of glycemic response to the same carbohydrate-based diet should be considered when knowledge is transformed from in vitro method to human conditions. This review contains important information that has the potential to reduce the starch digestibility of instant rice and improve public health.

Understanding effects of glutelin on physicochemical and structural properties of extruded starch and the underlying mechanism

This work studied effects of different amounts of rice glutelin (RG) on physicochemical and structural properties of extruded rice starch (ERS) and explored the underlying mechanism of interaction between rice starch and RG upon extrusion processing. The results showed that the addition of RG altered the pasting properties, improved the viscoelastic, and increased the water mobility of ERS. The weight loss of ERS decreased from 71.40 % to 62.61 %, while the degradation temperature increased from 290.48 °C to 296.25 °C as the RG content increased from 0 % to 12 %. The complex index of extruded starch-glutelin complexes significantly elevated from 10.40 % to 35.81 % when RG content increased from 6 % to 12 %. Fourier-transform infrared spectra confirmed that RG interacted with starch via Maillard reactions, and the binding strength between RG and starch was enhanced at a higher RG content. Furthermore, results of rheological property and chemical interactions demonstrated that hydrogen bonding, hydrophobic, and electrostatic interaction were formed between RG and starch during extrusion. In summary, the obtained results of this study can further enrich the theory of starch-protein interactions and show the possibility of RG applied in the extruded starchy foods.

Pre-fermentation of rice flour for improving the cooking quality of extruded instant rice

Extruded instant rice (EIR) could not maintain an intact grain morphology during cooking, which seriously affected its cooking quality. The problem was solved by pre-fermentation of rice flour for 5-10 days. Consequently, the cooking loss was significantly reduced, while the hardness, stickiness and water absorption of EIR were significantly increased. The mechanism was that the gel network of EIR was strengthened by the following ways: (1) pre-fermentation significantly increased the total starch and amylose contents of rice flour due to the dissolution or leaching of lipids, ash and soluble proteins into the fermentation broth; (2) pre-fermentation degraded the amorphous region of starch granules by enzymes and organic acids, resulting in a molecular structure with lower polydispersity index and molecular weight, and higher proportion of long- and ultra-long branched chains of amylopectin. This kind of molecular structure was conducive to the formation of ordered double helix structures and strong gel network.

Effects of soy protein isolate hydrolysates on cholecystokinin released by rat intestinal mucosal cells and food intake in rats

Soy protein isolate hydrolysates (SPIH) were prepared from soy protein isolate (SPI). Effects of SPIH on a satiety signal cholecystokinin (CCK) and feeding behavior in rats were investigated. SPIH induced more CCK release (164.66 ± 2.40 pg/mL) by rat intestinal mucosal cells than SPI (143.33 ± 3.71 pg/mL). Meal size (MS), intermeal interval (IMI), and satiety ratio (SR = MS/IMI) of rats received different daily doses of SPIH or dietary fiber were detected for 40 days. A 100 mg/kg dose of SPIH resulted in a greater SR than an identical dose of dietary fiber, while a 300 mg/kg dose resulted in a less MS and IMI. A 500 mg/kg dose of SPIH had similar effects to the same dose of dietary fiber on reducing MS, extending IMI, and increasing SR, but resulted in a significantly less body weight at the end of the experiment (318.15 ± 17.83 g) than the dietary fiber group (340.28 ± 6.15 g).