Quantification of resistant starch content in rice after hydrothermal treatments using terahertz spectroscopy.

Since hydrothermal treatments can enhance resistant starch (RS) content in rice and provide health benefits when consumed, a less laborious and non-destructive method to determine RS content is needed. Terahertz (THz) spectroscopy is hypothesized as a suitable method to quantify RS content in rice after hydrothermal treatment with its sensitivity for the intermolecular forces increase in the formation of RS. In this study, we first used the traditional in vitro hydrolysis method to determine the content of RS in rice. Then, the potential of starch absorbance peaks to quantify RS content after three commonly used hydrothermal methods, soaking, mild heat-moisture treatment, and parboiling, was investigated. The second derivative intensities of the peak at 9.0, 10.5, 12.1, and 13.1 THz were confirmed as being correlated with RS content and showed the high accuracy to predict RS content in samples (R2 > 0.96). Our results indicate the RS content of hydrothermally treated rice can be accurately quantified using these peaks.

Structural characteristics and in vitro starch digestibility of oil-modified cooked rice with varied addition manipulations.

Lipid has crucial applications in improving the quality of starchy products during heat processing. Herein, the influence of lipid modification and thermal treatment on the physicochemical properties and starch digestibility of cooked rice prepared with varied addition manipulations was investigated. Rice bran oil (RO) and medium chain triglyceride oil (MO) manipulations were performed either before (BC) or after cooking (AC). GC-MS was applied to determine the fatty acid profiles. Nutritional quality was analyzed by quantifying total phenolics, atherogenic, and thrombogenic indices. All complexes exhibited higher surface firmness, a soft core, and less adhesive. FTIR spectrum demonstrated that the guest component affected some of the dense structural attributes of V-amylose. The kinetic constant was in the range between 0.47 and 0.86 min-1 wherein before mode presented a higher value. The lowest glucose release was observed in the RO_BC sample, whereas the highest complexing index was observed in the RO_AC sample, indicating that the dense molecular configuration of complexes that could resist enzymatic digestion was more critical than the quantity of complex formation. Despite the damage caused by mass and heat transfer, physical barrier, intact granule forms, and strengthened dense structure were the central contributors affecting the digestion characteristics of lipid-starch complexes.

Effects of Matrix Structure on Protein Digestibility and Antioxidant Property of Different Soybean Curds During In Vitro Digestion.

This study compared the three most common types of tofu (soybean curd), which were prepared by using magnesium chloride (MgCl2 tofu), calcium sulfate (CaSO4 tofu), and glucono-δ-lactone (GDL tofu) coagulants. The results showed that GDL tofu had a higher water holding capacity than MgCl2 tofu and CaSO4 tofu, which was attributed to its high surface hydrophobicity and disulfide bond content. GDL tofu possessed the lowest firmness, gumminess, and chewiness, along with a uniform network structure and a thin protein matrix. In contrast, MgCl2 tofu exhibited an inhomogeneous network structure with a thick protein matrix. Combining the results of protein hydrolysis degree, SDS-PAGE, and free amino acids during in vitro digestion, it was indicated that the degree of protein digestion in GDL tofu was the highest. After intestinal digestion, GDL tofu had the highest total phenolic content, ferric reducing antioxidant power, and DPPH value. These results demonstrated the superior protein digestibility and antioxidant property of GDL tofu during in vitro digestion due to its structural characteristics that facilitate enzyme diffusion in the matrix. The findings offer insight into the protein digestibility and antioxidant properties of different types of tofu during digestion from structural characteristic perspective and valuable reference information for consumer dietary nutrition.

Advances in spray-dried probiotic microcapsules for targeted delivery: a review.

Probiotics have gained significant attention owing to their roles in regulating human health. Recently, spray drying has been considered as a promising technique to produce probiotic powders due to its advantages of high efficiency, cost-saving, and good powder properties. However, the severe environmental conditions from drying and digestion can significantly reduce cell viability, resulting in poor bioaccessibility and bioavailability of live cells. Therefore, there is a need to develop effective targeted delivery systems using spray drying to protect bacteria and to maintain their physiological functions in the targeted sites. This review highlights recent studies about spray-dried targeted delivery vehicles for probiotics, focusing on key strategies to protect bacteria when encountering external stresses, the formation mechanism of particles, the targeted release and colonization mechanisms of live cells in particles with different structures. Advances in the targeted delivery of live probiotics via spray-dried vehicles are still in their early stages. To increase the possibilities for industrialization and commercialization, functional improvement of microcapsules in terms of protection, targeted release, and colonization of bacteria, as well as the effect of spray drying on bacterial physiological functions in the host, need to be further investigated.

Simulated In Vitro Digestive Characteristics of Raw Yam Tubers in Japanese Diet: Changes in Protein Profile, Starch Digestibility, Antioxidant Capacity and Microstructure.

The consumption of raw yam tuber through grated yam "tororo" is a major and popular diet in Japan. However, few studies have been undertaken to evaluate the digestive characteristics of raw yam tubers. This study aimed to fill this gap by investigating the changes in the protein profile, protein and starch digestibility, antioxidant capacity and microstructure of two typical yam tubers (Nagaimo N-10 and Nebaristar) in the Japanese diet, applying a simulated in vitro digestion method. Results showed that both samples contained a considerable protein content of about 11% (dry basis) and a protein digestibility of 43-49%. The electrophoretic patterns confirmed that dioscorin was the main protein of the yam tuber, and it could be digested into peptides and free amino acids with low molecular weight during in vitro digestion. The starch hydrolysis results suggested that eating raw yam tuber cannot induce a fast glycemic increase for consumers due to a low starch digestibility of 4.4-6.1%. In addition, Nebaristar showed a higher bioaccessibility in some key amino acids and total phenolic content than the Nagaimo N-10. This study provides some essential nutritional information and simulated digestion behaviours of the raw yam tubers, which could be useful for consumers and industries when buying and processing yam tubers from the perspective of changes in the nutritional profile during digestion.

Changes in bioactive compounds and antioxidant activity of plant-based foods by gastrointestinal digestion: a review.

Phenolic compounds, omnipresent in plants, are a crucial part of the human diet and are of considerable interest due to their antioxidant properties and other potential beneficial health effects, for instance, antidiabetic, antihypertensive, anti-inflammatory, and anticancer properties. The consumption of a variety of plant-based foods containing various phenolic compounds has increased due to published scientific verification of several health benefits. The release of phenolic compounds and change in their bioactivities examined through in vitro simulated gastrointestinal digestion could provide information on the biological potency of bioactive components, which will allow us to elucidate their metabolic pathways and bioactivities at target sites. This review reports on the recent research results focused on changes during the gastro and/or intestinal phase. The effect of digestive enzymes and digestive pH conditions during simulated digestion accounted for the variations in bioaccessibility and bioavailability of phenolic antioxidants as well as the corresponding antioxidant activities were also summarized and presented in the review.

In vitro protein digestibility and biochemical characteristics of soaked, boiled and fermented soybeans.

Protein digestibility of soybean obtained from the main manufacturing steps for natto, such as soaking (soaked soybeans 'S'), boiling (boiled soybeans 'B'), and fermentation (fermented soybeans 'F'), was examined in this study. Biochemical indices for the processed soybeans from each manufacturing step and those digested fractions by simulated in vitro gastrointestinal digestion were also evaluated. The result showed a significant (P < 0.05) increase in the protein digestibility of B (48.71 ± 0.04%) and F (50.21 ± 0.45%) compared to that of S (20.58 ± 0.25%), accompanying the accumulation of small protein sub-fractions and essential amino acids. Besides, antioxidant activity indices of all digested fractions increased around two to fourfold at the end of the simulated digestion. F showed a consistently increasing trend when the digestion stage progressed and maximum values overall at the final digestion stage.  Soybeans from fermentation step showed higher protein digestibility and indispensable amino acids as well as potential bioactivities than those from boiling and soaking step. The results demonstrated that manufacturing steps improved nutritional values of soybean protein, such as bioavailability of amino acids and certain bioactivities.

Effect of in vitro digestion on bioactive compounds, antioxidant and antimicrobial activities of coffee (Coffea arabica L.) pulp aqueous extract.

Effect of in vitro digestion on bioactive compounds, biological activities of coffee pulp extract (CPE) against pathogens and a probiotic (Lactobacillus acidophilus TISTR 1338) was investigated. Total phenolic compound (TPC), chlorogenic acid (CGA), caffeine (CF), total monomeric anthocyanin (TMA), antioxidant and antimicrobial activities of the CPE were determined before and after digestion. After the digestion, the TPC, CGA and CF decreased 7.9, 31.7 and 50.0%, dry weight (dw), respectively. The antioxidant activity decreased 22.6% (DPPH) and 12.4% (FRAP). The CPE inhibited Escherichia coli TISTR 780 and Staphylococcus aureus TISTR 1466 at 150 and 200 mg/mL, respectively. Both CPE and the digested CPE had no effect on the tested probiotics. These results suggest that bioactive compounds of CPE may degrade during in vitro digestion, consequently the antioxidant and antimicrobial properties. Therefore, CPE could be a potential natural antimicrobial for food industry with no effect on the probiotics.

Fabrication of Spray-Dried Microcapsules Containing Noni Juice Using Blends of Maltodextrin and Gum Acacia: Physicochemical Properties of Powders and Bioaccessibility of Bioactives during In Vitro Digestion.

Microencapsulation of fermented noni juice (FNJ) into powder format could protect bioactive compounds, reduce the unpleasant odour and improve the acceptability for consumers. Blends of maltodextrin (MD) and gum acacia (GA) were used to achieve spray-drying microencapsulation of noni juice at different blending ratios. The physicochemical properties including microstructure, moisture content, water activity, particle size, bulk/tapped density, dissolution rate, ATR-FTIR and the bioaccessibility of bioactive compounds in powders during in vitro digestion were examined. Results showed that blends produced with more GA produced microcapsules with lower moisture content, water activity and bulk/tapped density, but slower powder dissolution. The ATR-FTIR results suggested that there were no significant chemical interactions between the core material and carrier or between the MD and GA in the blend powders. The spray-dried noni juice powder produced using the blends with higher ratio of GA to MD showed a better protection on the bioactive compounds, resulting in a higher bioaccessibility of powders during in vitro digestion. This study provides insights into microencapsulation of noni juice using blends of MD and GA and examines the physicochemical properties and bioaccessibilities of spray-dried powders as affected by the selected carriers.

Bio-properties of Saba banana (Musa 'saba', ABB Group): Influence of maturity and changes during simulated in vitro gastrointestinal digestion.

Saba banana, a popular fruit crop grown in Southeast Asia, is an economical source of a variety of beneficial agents. This study examined the variations in total phenolic, flavonoid, and antioxidant activities of five maturity stages of Saba banana, and their changes during simulated in vitro gastrointestinal digestion as affected by varying structural compositions. Antioxidant activities were evaluated using ferric reducing antioxidant power (FRAP), metal ion chelating (MIC) activity, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays. Results of DPPH and ABTS were compared in terms of TEAC (Trolox Equivalent Antioxidant Capacity) and VCEAC (Vitamin C Equivalent Antioxidant Capacity) values. Bio-properties were found to be highest in mature green stage with values slightly decreased as ripening proceeded. Simulated digestion showed a continuous increase in total phenolic with comparatively faster release in structure-less state (slurry) than samples with intact structure (cut). The trend of antioxidant activities was increased in the gastric phase and then decreased at the onset of intestinal phase, except for MIC which showed a reverse effect. Our study indicated that the bio-properties of Saba banana were affected by maturity and modifications in its physical structure and composition could influence the release behaviors of food components during simulated digestion.

Comparative study of conventional steam cooking and microwave cooking on cooked pigmented rice texture and their phenolic antioxidant.

The impact of two different cooking processes (microwave and steaming) on cooked rice quality (i.e., texture), and changes in the bioactive compounds (total phenolic content [TPC] and total anthocyanin content [TAC]) and antioxidant activities (DPPH and FRAP assays) of black and red (nonwaxy) and purple (waxy) pigmented rice were investigated. No significant difference in the firmness between microwave-cooked rice and steam-cooked rice was found, except for cooked purple rice. However, microwave cooking promoted an increase in the cooked rice adhesiveness, which approximately higher 2- ~ 3-fold than that of steam cooking with varying among rice cultivars. Microwave cooking also exhibited significantly higher TPC (1.2- ~ 2.0-fold), TAC (2.0- ~ 3.2-fold), DPPH (1.3- ~ 2.5-fold), and FRAP (1.5- ~ 2.4-fold) than steam cooking for black and purple rice cultivars. There was a strong positive correlation among these bioactive compounds and the antioxidant activities (p < .01). Our study indicated that the TPC, TAC, DPPH, and FRAP of all rice examined were remarkably decreased after cooking, and the extent of the decrease depended on the rice cultivar and cooking method.

In vitro examination of starch digestibility of Saba banana [Musa 'saba'(Musa acuminata × Musa balbisiana)]: impact of maturity and physical properties of digesta.

The digestibility of starch in Saba banana as affected by maturity and physical properties of digesta was investigated. Five maturity stages were identified based on peel color index which also showed significant differences in physicochemical properties and starch granule morphology. The effect of physical properties of digesta was evaluated by monitoring the viscosity throughout the simulated digestion process and comparing two different physical structures of banana: (1) unhomogenized cut samples which have intact tissue structure and (2) homogenized slurry representing disrupted cellular structure. During ripening process, a decrease in starch content was noted with a concomitant formation of sugars and increasing concentration of acids. Green unripe stages showed the highest rate of starch hydrolysis in both physical structures and a decreasing trend was observed as ripening proceeded. The high digesta viscosity values of ripe stages was found to have an inhibitory effect on starch hydrolysis. Similarly, the differences in physical structure of food affected the digestive enzymes efficiency in breaking down starch. These results suggested that the physicochemical changes accompanying maturation and the physical properties (i.e. high viscosity and presence of intact cell structure) of food could significantly impact the rate of starch digestion.

In vitro gastrointestinal digestion of crisphead lettuce: Changes in bioactive compounds and antioxidant potential.

In this study, the potential health benefits of crisphead lettuce (Lactuca sativa L.) before and after digestion were represented by the recovery, bioaccessibility, and change of bioactive compounds including total phenolic (TPC) and total flavonoids content (TFC), and bioactivities [in vitro antioxidant activities including 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2, 2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activities, ferric reducing antioxidant power (FRAP) and metal ion chelating activity (MIC)]. The release of bioactive compounds as well as bioactivities increased during gastric and intestinal digestion for 1 h and subsequently decreased when digestion was completed. The bioaccessibility of TPC and TFC at after digestion was 56-73 and 75-79%, respectively. Among all bioactivities, crisphead lettuce showed a residual activity of ABTS (61-95%) followed by FRAP (70-86%), DPPH (24-52%) and MIC (32-73%) during the digestion. Our study suggested that crisphead lettuce maintains stability in both bioactive compounds and bioactivities during the digestion.

Starch digestibility of various Japanese commercial noodles made from different starch sources.

To examine the effect of starch variety and structure-related attributes on noodle starch digestibility, cooked Japanese commercial noodles, such as Harusame (mung bean starch), Malony (potato starch) and Udon (wheat flour), were kinetically analyzed during simulated in vitro digestion. The kinetic constant of the homogenized noodle slurry (10.8 × 10-2-22.9 × 10-2) was 10-20 times higher than that of the intact one (0.9 × 10-2-1.5 × 10-2), whereas the equilibrium starch hydrolysis (%) was equivalent. Therefore, the noodle microstructure, which is influenced by the present of binding agent and enhancer, should relate to the starch digestibility. Also, the starch digestibility at the early small intestine phase was associated with the cohesiveness and water retention ability of the cooked noodles. These results indicate that the internal microstructures of cooked noodles and the binding agent properties play an important role in the starch digestibility of noodles.

The microstructure of starchy food modulates its digestibility.

Starch is the main carbohydrate in human nutrition and shows a range of desired food properties. It has been demonstrated that fast digestion of starchy food can induce many health issues (e.g., hyperglycaemia, diabetes, etc.); therefore, how to modulate its digestion is an interesting topic. Previous studies have revealed that the microstructure and digestibility of starchy food of different botanical origin or from multiple processes are quite different; modulating starch digestion by retaining or altering its microstructure may be effective. In the present review, the current knowledge of the relationship between microstructural changes to starchy food and its digestibility at molecular, cell and tissue, and food processing levels is summarized. New technologies focused on microstructure studies and ways to manipulate food microstructure to modulate starch digestibility are also reviewed. In particular, some insights focusing on the future study of microstructure and the digestibility of starchy food are also suggested.

Parboiling reduced the crystallinity and in vitro digestibility of non-waxy short grain rice.

The impact of parboiling on starch digestibility of cooked rice was examined through an in vitro digestion model. Results indicated that the equilibrium starch hydrolysis of polished rice was the highest (86.55%), followed by that of parboiled-polished (83.94%), brown (80.59%) and parboiled rice (76.95%). X-ray diffraction analysis indicated that A-type crystals were predominant in brown rice and polished rice, while A-, B- and V-type crystalline structures coexisted in parboiled rice and parboiled-polished rice. Thin and compact layers were observed on the surfaces of parboiled rice and were considered to be physical barriers that reduce the starch digestibility. The study demonstrates that parboiling could change the crystallinity and reduce the starch digestion of rice significantly.

Lipid droplet-associated gene expression and chromatin remodelling in LIPASE 5'-upstream region from beginning- to mid-endodormant bud in 'Fuji' apple.

KEY MESSAGE: We found that lipid accumulation in the meristem region and the expression of MdLIP2A, which appears to be regulated by chromatin remodeling, coincided with endodormancy induction in the 'Fuji' apple. In deciduous trees, including apples (Malus × domestica Borkh.), lipid accumulation in the meristem region towards endodormancy induction has been thought to be an important process for the acquisition of cold tolerance. In this study, we conducted histological staining of crude lipids in the meristem region of 'Fuji' apples and found that lipid accumulation coincided with endodormancy induction. Since a major component of lipid bodies (triacylglycerol) is esterified fatty acids, we analysed fatty acid-derived volatile compounds and genes encoding fatty acid-modifying enzymes (MdLOX1A and MdHPL2A); the reduction of lipid breakdown also coincided with endodormancy induction. We then characterised the expression patterns of lipid body-regulatory genes MdOLE1 and MdLIP2A during endodormancy induction and found that the expression of MdLIP2A correlated well with lipid accumulation towards endodormancy induction. Based on these results, we conducted chromatin remodelling studies and localized the cis-element in the 5'-upstream region of MdLIP2A to clarify its regulatory mechanism. Finally, we revealed that chromatin was concentrated - 764 to - 862 bp of the 5'-upstream region of MdLIP2A, which harbours the GARE [gibberellin responsive MYB transcription factor binding site] and CArG [MADS-box transcription factor binding site] motifs-meristem development-related protein-binding sites.

The importance of an oral digestion step in evaluating simulated in vitro digestibility of starch from cooked rice grain.

To examine the effect of oral digestion step in a simulated in vitro starch digestion model, the digestibility of intact, homogenized and actual chewed cooked rice grains was investigated and analyzed. The kinetics of starch digestibility were calculated from changes in the hydrolysis percent of starch that were achieved during simulated small intestinal digestion stage. Morphological and histological microscopic tissue structures were also examined. Compared with the trend of starch hydrolysis changes of the actual chewed grain, 1.3U/ml of salivary α-amylase concentration treated for 60min was regarded as a mimicked condition to the simulate in vitro oral digestion step in this study. The results showed that the equilibrium percent of starch hydrolysis for all of the samples ranged from 84.2% to 95.9% with no significant differences observed regardless of whether the oral digestion step was included (p>0.05). In contrast, the kinetic constant, which is one of the measure of starch digestion rate during small intestinal stage, significantly increased with the degree of grain homogenization increased: 120s>actual chewed ≥1s>intact, for both the gastrointestinal and oral plus gastrointestinal processes. These results indicated that the kinetic constant was influenced by the change of cooked rice grain structure in oral digestion step that would be related to increase in enzyme accessibility to rice starch. Thus, rice grain digestibility was affected by grain-scale structural changes, including grain tissue damages which were normally observed during the oral digestion step.

Impact of postharvest drying conditions on in vitro starch digestibility and estimated glycemic index of cooked non-waxy long-grain rice (Oryza sativa L.).

BACKGROUND: Wet paddy needs to be dried to reduce its moisture content after harvesting. In this study, effects of postharvest drying condition on in vitro starch digestibility and estimated glycemic index of cooked rice (Oryza sativa L.) were investigated. Varying drying conditions, i.e. hot-air drying at 40, 65, 90 and 115 °C, and sun drying were applied to raw paddy. After husking and polishing, polished grains were cooked using an electric rice cooker. Cooked samples were analyzed for their moisture content and amount of resistant and total starch. Five samples in both intact grain and slurry were digested under simulated in vitro gastrointestinal digestion process. The in vitro starch digestion rate was measured and the hydrolysis index (HI) and estimated glycemic index (eGI) were calculated. RESULTS: Cooked rice obtained from hot-air drying showed relatively lower HI and eGI than that obtained from sun-drying. Among samples from hot-air drying treatment, eGI of cooked rice decreased with increasing drying temperature, except for the drying temperature of 115 °C. As a result, cooked rice from the hot-air drying at 90 °C showed lowest eGI. CONCLUSION: The results indicated that cooked rice digestibility was affected by postharvest drying conditions. © 2016 Society of Chemical Industry.