Four phenolic acids from purple sweet potato and their effects on physicochemical,digestive and structural characteristics of starch

Liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS) was employed to investigate free phenols that were released from purple sweet potato (PSP) by alkaline, acid and enzymatic hydrolysis. Four phenolic acids, including ferulic, isoferulic, 4-hydroxybenzoic and caffeic acids, were identified. Based on their effects on the characteristics of purple sweet potato starch (PSPS), the four phenolic acids were studied. Furthermore, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT–IR) and X-ray diffraction (XRD) techniques were employed to explore the microstructures of the complexes of the phenolic acids and PSPS. The obtained results demonstrated that the pasting, thermal, retrogradation, as well as digestive properties of PSPS were all influenced by the phenolic acids which interacted with PSPS through noncovalent hydrogen bonds. The influence of the four phenolic acids on the properties of PSPS was in the descending order: 4-hydroxybenzoic acid > ferulic acid > caffeic acid > isoferulic acid.     

In vitro potential of flavonoids from tartary buckwheat on antioxidants activity and starch digestibility

The effects of various flavonoids of Tartary buckwheat (rutin-enhanced flavonoid extract [REFE and quercetin-enhanced flavonoid extract [QEFE]) and individual flavonoids (rutin, quercetin and kaempferol) on the antioxidant activity, inhibition of α-glucosidases and α-amylase and starch digestibility were evaluated. Quercetin possessed the highest antioxidant activity and inhibition of α-glucosidases and α-amylase activity followed by kaempferol and rutin. REFE and QEFE have similar antioxidant and inhibition of α-amylase activities, but QEFE has much higher α-glucosidases inhibition than REFE. Tartary buckwheat flour has the lowest content of rapidly digestible starch and predicted glycaemic index (pGI) compared to maize flour, wheat flour and rice flour. Addition of rutin and quercetin to wheat flour showed a weak or no effect on digestion inhibition, but they inhibited starch digestion under solid complex conditions. Our results may help explain the benefits of supplementing the diet with food rich in flavonoids.     

Understanding the structural characteristics,pasting and rheological behaviours of pregelatinised cassava starch

The structural characteristics, pasting and rheological behaviours of cassava starch before and after pregelatinisation were determined by various modern analysis techniques. Pregelatinisation, especially in an ultrasonic environment, can disrupt the granule structure, crystalline structure and short‐range ordered molecular structure of cassava starch. Compared with native starch, pregelatinisation had significantly decreased viscosities and weakened gel structures of starch pastes. Not only did native and pregelatinised starch pastes exhibit shear‐thinning behaviours but also the pregelatinised treatment resulted in the formation of weak gel structures. This study enabled us to acquire the desired pasting and rheological properties of pregelatinised starch by modulating its hierarchical structural changes.     

The effects of blackcurrant and strawberry powder on the physicochemical and in vitro glycaemic response of starches derived from sweet potato (Ipomoea batatas) and potato (Solanum tuberosum)

Phenolic compounds have been shown to deliver numerous health benefits. Research has also shown that starch and phenolic compounds interact. This study aimed to investigate the effects of blackcurrant and strawberry powder on the physicochemical and in vitro predicted glycaemic response of sweet potato and potato starches. Sweet potato, or potato, starches were mixed with 0%, 5%, 10% and 15% (w/w) of blackcurrant, or strawberry, powder, to form blackcurrant and strawberry-enriched starch pastes. The results showed that enrichment with 5%, 10% and 15% blackcurrant or strawberry powder for sweet potato and potato starch significantly altered the pasting viscosity and colour profiles (P < 0.05), increased the phenolic content and antioxidant activities of starch pastes (P < 0.05). Blackcurrant or strawberry powders mixed with sweet potato or potato starches reduced amount of reducing sugar released during in vitro digestion. Addition of 15% blackcurrant powder for the starch exerted stronger in vitro antioxidant and hypoglycaemic properties than that of 15% strawberry powder. Collectively, these findings suggested that addition of blackcurrant or strawberry powder into sweet potato and potato starches manipulated the hypoglycaemic property of pastes.     

Automatic segmentation on multiple starch granules from microscopic images

Starch is the most important carbohydrate in the human diet and contained in many staple foods such as rice, wheat, corn, potatoes and cassava, etc. Currently, microscopic imaging technology is one of the most effective ways to investigate and analyze the structure of starches. Segmentation of starch granules is a necessary step for starch granule structure analysis such as starch granules detection, shape recognition, and size computation. This article investigates a new method based on GVF (gradient vector flow) snake deformable model for starch granules segmentation. The proposed method focuses on full automatic segmentation on granules, especially on separation of adjacent and contacted starch granules, which occur widely in microscopic images. A novel energy function based on position and intensity is introduced into the directional gradient computation, thus the directional gradient is used to obtain the directional GVF snake, which drives the deforming contours to the real contours of multiple granules. To demonstrate the good ability of the proposed method, we segment 30 starch granule images and compare it with the level set method, experimental results show that the new method can separate multiple starch granules successfully; especially it works much better on overlapping objects segmentation than the level set method.     

Surface imaging of thermally sensitive particulate and fibrous materials with the atomic force microscope: a novel sample preparation method

High-resolution surface imaging by atomic force microscopy (AFM) of particulate materials is often problematic, principally as a result of the large height (z) variations in sample topography that either prevent the probe scanning over the particle or cause probe self-imaging. This paper reports a novel method of embedding thermally sensitive particulate and fibrous materials which overcomes many of these problems and facilitates AFM imaging of these difficult materials. The process involves partial embedding of the sample in a cyanoacrylate film polymerized at room temperature. The sample heating required in currently used methods of particulate embedding is avoided and the method is therefore suitable for thermolabile materials. The cyanoacrylate film provides a flat hard surface which is ideal for AFM imaging, and the method has allowed successful imaging of relatively large particulate and fibrous samples such as starch granules and cellulose fibres. The cyanoacrylate has the added benefit that shrinkage holes in the film allow easy visual identification of areas where the film may have partially covered the sample.     

粉状淀粉粘合剂的制备工艺流程和原理

本文介绍用高温加工与高压加工相结合的方式,直接用谷物或面粉生产粉状淀粉粘合剂的工艺流程和原理。工艺简单,不耗费大量的化工原料,无“三废”问题。所得产品具有容易储存,便于运输和包装,使用方便,贮存期长等优点。     

埃洛石纳米管/聚乙烯醇-淀粉复合膜的结构与性能

采用溶液流延法制备了埃洛石纳米管(HNTs)/聚乙烯醇(PVA)-淀粉复合膜,并利用SEM、XRD、DMA、TGA等分析测试手段研究了该复合膜的结构与性能。结果表明:随着HNTs含量增加,HNTs/PVA-淀粉复合膜的力学性能、热稳定性、耐水性能和紫外屏蔽性能均有提高。当HNTs与PVA-淀粉质量比为10%时,力学性能达到最佳,拉伸强度提高了22%。扫描电镜分析表明:HNTs能够以纳米尺度均匀分散于HNTs/PVA-淀粉复合膜中,且以单管状分布,与PVA-淀粉基体界面结合较好。动态力学性能分析表明:HNTs的加入对HNTs/PVA-淀粉复合膜的玻璃化转变温度影响不大,复合膜的储能模量升高,力学损耗下降。透光率测试结果表明:HNTs对HNTs/PVA-淀粉复合膜的透明性影响不大,而在紫外光区域(200~400nm),透光率随HNTs量的增加而下降。     

Biocompatible Blends of an Intrinsically Conducting Polymer as Stretchable Strain Sensors for Real-Time Monitoring of Starch-Based Food Processing

Because stretchable strain sensors that have a resistance or capacitance sensitive to strain can sense skin deformation during physical movement, they have been extensively studied as wearable devices for healthcare monitoring. In principle, they can be used to monitor starch-based food processing in real time, since starch-based food can have remarkable volume change during processing. Monitoring starch-based food processing in real time can help achieve high quality and high productivity while reducing energy consumption. Nevertheless, there is no such report in the literature. Here, a blend of starch and a biocompatible intrinsically conducting polymer, poly(3,4-ethylenedioxythiophene): polystyrenesulfonate (PEDOT:PSS), is reported as a stretchable strain sensor to monitor starch-based food processing including fermentation, steaming, storage, and refreshing in a real-time manner. The resistance of the blends increases during the food volume expansion mainly caused by the fermentation, steaming, and refreshing, and it decreases as a result of the food volume shrinkage during cooling or storage. The signals can be thus used to optimize the processing conditions and control the food quality. This technology can be easily combined with the Internet of Things.     

干法制备阳离子淀粉的研究

以3-氯-2-羟丙基三甲基氯化铵(CHPTMA)为阳离子化剂,碱性条件下,采用干法工艺制备了季铵型阳离子木薯淀粉.通过单因素实验研究了淀粉与CHPTMA用量之比、CHPTMA和NaOH用量之比、混合时间、反应时间、反应温度、水用量以及NaOH在淀粉和醚化剂之间的分配比等诸因素对取代度和反应效率的影响.采用NaOH在淀粉和醚化剂之间分开加入的工艺方法,其分配比为3.0时,可降低反应温度和提高反应效率.