Extracted Lipids and Carbohydrates During Washing and Boiling of Milled Rice

Washing and cooking of waxy and nonwaxy milled rice and rice flour resulted in extraction of lipids, and carbohydrates, principally starch and nonstarch polysaccharides. Lipids, nonstarch polysaccharides and amylose contributed to hardening of waxy rice (IR 29) starch gel consistency in H₂O. Lipids extracted were mainly nonstarch lipids, principally free fatty acids. Nonstarch polysaccharides extracted in cold water were rich in glucose, galactose and arabinose, but those extracted in hot water were mainly glucans. Hot water extractable starch was more in waxy than in nonwaxy rice but complexed less with IR 29 amylopectin.     

Effect of Various Processing Methods on the Physical Properties of Cooked Rice and on in vitro Starch Hydrolysis and Blood Glucose Response in Rats

The effects of various cooking methods on the physical and structural properties cooked rice, on the in vitro hydrolysis of the contained starch and on blood glucose response in rats were investigated. At optimum cooking state, a larger filamentous network was formed and most of the starch granules were fragmented, furthermore the samples heated by microwave and electric cooker showed a more compact structure compared to those treated in an autoclave or stone pot. The highest degree of gelatinization (DG) was observed in the sample treated in an autoclave (75.2%), followed by stone pot (71.1%), electric cooker (66.9%) and microwave oven (64.6%). The highest firmness (3.49 N) was observed in cooked rice heated by microwaves and no significant differences (p > 0.05) were found between the other samples. All cooked rice samples showed increased pasting temperatures and decreased peak viscosity compared to those of raw rice flour. The starch hydrolysis rates and their kinetic constants of cooked rice samples increased with increase in DG, and relatively higher values were observed in samples treated in the autoclave and stone pot. There was a significant difference in the blood glucose content depending on cooking methods, and the highest glucose level was observed in the sample heated by autoclaving.     

Nonstarch Polysaccharide Fractions of Raw, Processed and Cooked Carrots

The total and soluble nonstarch polysaccharide (NSP) components of raw, processed (canned and frozen) and home-cooked (boiled) Royal Chantenay carrots have been analyzed. NSP fractions were characterized by separation and summation of the monosaccharides resulting from acid hydrolysis of the parent polysaccharides. Total NSP was primarily composed of glucose, ?37%, and uronic acid, ?35%, containing polysaccharides. Soluble NSP was composed of >50% uronic acids. Processing and simulated home-cooking of raw carrots resulted in an increase in the amount of NSP/unit dry weight. Relative to raw carrots, cooking of canned product resulted in the largest (～twofold) increase in total and soluble NSP/unit dry weight. Relative differences in NSP were not as great when compared on a wet weight basis.     

Effects of Cooking Methods and Starch Structures on Starch Hydrolysis Rates of Rice

This study aimed to understand effects of different cooking methods, including steamed, pilaf, and traditional stir‐fried, on starch hydrolysis rates of rice. Rice grains of 3 varieties, japonica, indica, and waxy, were used for the study. Rice starch was isolated from the grain and characterized. Amylose contents of starches from japonica, indica, and waxy rice were 13.5%, 18.0%, and 0.9%, respectively. The onset gelatinization temperature of indica starch (71.6 °C) was higher than that of the japonica and waxy starch (56.0 and 56.8 °C, respectively). The difference was attributed to longer amylopectin branch chains of the indica starch. Starch hydrolysis rates and resistant starch (RS) contents of the rice varieties differed after they were cooked using different methods. Stir‐fried rice displayed the least starch hydrolysis rate followed by pilaf rice and steamed rice for each rice variety. RS contents of freshly steamed japonica, indica, and waxy rice were 0.7%, 6.6%, and 1.3%, respectively; those of rice pilaf were 12.1%, 13.2%, and 3.4%, respectively; and the stir‐fried rice displayed the largest RS contents of 15.8%, 16.6%, and 12.1%, respectively. Mechanisms of the large RS contents of the stir‐fried rice were studied. With the least starch hydrolysis rate and the largest RS content, stir‐fried rice would be a desirable way of preparing rice for food to reduce postprandial blood glucose and insulin responses and to improve colon health of humans.     

Dependence of physiochemical,functional and textural properties of high‐resistant starch rice on endogenous nonstarch polysaccharides

To investigate the possibility of improving the quality of rice rich in resistant starch through operation of nonstarch polysaccharides, the high dietary fibre (7.24%) mutant cw and its wild‐type R7954 were selected to study the physiochemical characteristics of starch before and after removal of nonstarch polysaccharides. Results showed that hydrolysed or partially hydrolysed nonstarch polysaccharides in cw decreased the resistant starch content significantly, from 15.23% to 10.8%. Nonstarch polysaccharides had significant influences on the gelatinisation temperature, RVA parameters of R7954, but no significant influences on that of cw. For cw, removal of cellulose increased swelling power and adhesiveness, decreased the hardness significantly, from 0.3 to 0.23 N, while the resistant starch content was still as high as 13.72% and showed no significant difference from the wild type. This suggests that the influences of nonstarch polysaccharides on starch properties depend both on the type of rice and the nonstarch polysaccharides. Operation on nonstarch polysaccharides for obtaining rice with lower glycemic index is feasible, but operation on nonstarch polysaccharides may also be an alternative way of improving the palatability for rice high in resistant starch.     

Non-Starch Polysaccharides and in Vitro Starch Digestibility of Raw and Cooked Chick Peas

The effects of domestic and industrial cooking methods on the non-starch polysaccharides (NSP) content and in vitro starch digestibility of chick pea (variety “blanco lechoso”) have been studied. Total and soluble NSP increased, as did the slowly digestible starch (SDS), whereas the resistant starch (RS) fraction decreased after cooking, showing higher content in domestic than industrially cooked chick peas. The in vitro starch digestible rate index (SDRI) was similar in the cooked chick peas, as was the rapidly available glucose (RAG). Due to the low values of RAG, chick peas would give a slow post-prandial glycaemic response. Domestic cooked chick peas consumption would increase the intakes of RS in human diet, whereas the industrially cooked chick peas with lower content of RS would result in less flatulence problems.     

压力烹调对五种食材中淀粉消化性的影响

目的:探讨不同烹调方法对红小豆、莲子、山药片、芡实、薏米5种富含淀粉的保健食材的碳水化合物消化特性的影响,为科学食用传统食材提供依据。方法:体外模拟消化方法测定各时间点的水解率、快消化淀粉、慢消化淀粉和抗性淀粉等指标。结果:压力烹调显著影响样品的水解速率和淀粉类型,水解指数增大,快消化淀粉含量增加,抗性淀粉含量减少。但所有样品的预期血糖负荷均显著低于粳米样品。红小豆和莲子经过压力烹调仍保持低消化速度和低EGL特性。结论:压力烹调对提高难烹煮碳水化合物消化率有利,需要控制血糖的人可以通过选择慢消化食材和烹调参数来控制淀粉类型和EGL的变化。     

Fresh pasta quality as affected by enrichment of nonstarch polysaccharides

ABSTRACT:  Nonstarch polysaccharides (NSPs), both soluble and insoluble, were added to pasta doughs at levels of 2.5%, 5%, 7.5%, and 10% levels. The cooking and textural characteristics of the pastas were evaluated using a range of analytical techniques. Generally, NSP addition was found to increase the cooking losses, and reduce the protein and starch contents of the pasta. This effect was dependent on the level of NSP added and also the type (soluble or insoluble). Pasta firmness was generally reduced in relation to the level of NSP addition, although some gel-forming NSPs resulted in higher firmness values. Pasta stickiness, adhesiveness, and elasticity were also affected. The results indicate that careful selection of NSP addition is needed to ensure optimum textural and cooking characteristics in NSP enriched pasta products.     

Pasting Properties of Ohmically Heated Rice Starch and Rice Flours

ABSTRACT:  Pasting characteristics were examined for conventionally or ohmically heated rice starch and rice flours. Brown rice flour showed the greatest cooking stability and least retrogradation potential. Brown rice flour also showed the greatest pasting temperature and lowest peak viscosity, whereas commercial starch had the lowest pasting temperature. Nonstarch components of the brown rice flour, such as fat and protein, may have acted as stabilizers delaying water access into the granules and reducing swelling of the starch. Ohmic heating reduced pasting temperature for commercial rice starch, resulting in a starch that swelled faster. Furthermore, ohmic heating produced better cooking stability in white rice flour 1 and 2 than in the native sample, and caused white rice flour 2 to have less potential for retrogradation than the conventionally heated sample. At lower electric field strength (20 V/cm), ohmic heating resulted in the greatest cooking stable starches compared to higher voltages (40 and 70 V/cm) because more starch granules were disrupted from a longer cooking time, so there were fewer intact granules for pasting. Ohmic heating has been shown to alter rice starch and flour pasting characteristics with an added influence of lipids, proteins, and amylose contents.     

Structure of pectin in relation to abnormal hardness after cooking in pre-peeled, cool-stored potatoes

Unacceptable hard tissue can be detected in pre-peeled potatoes after cooking. Pectin methyl esterase (PME) has been suspected to facilitate formation of Ca-bridges between pectin molecules by deesterification of the uronic acids. But this has also been questioned, due to the low storage temperature of the peeled tubers, optimum of PME being 50-70 °C. Hardness in tubers was induced by several packaging methods. Annual and seasonal variations were observed. In the work, analysis of nonstarch polysaccharides (NSP) are considered representative of the pectin content. Analyses revealed an increase in insoluble NSP during storage after peeling and cooking, and a decrease in branching (arabinose, galactose) and degree of methyl esterification of total NSP, in both fresh and cooked tissue, dependant on storage period. Reduction of steric hindrance by debranching of the pectin molecules as well as a PME-induced increase of possible Ca-cross-linking sites may favor hardening of the tissue. The microscopy does not show any pectin changes until after cooking, but the chemical data do. This suggests that hardening, at least partly, is due to the removal of methyl ester groups, as well as galactose and arabinose in the side chains. The Ca-bridges can probably not be formed until sufficient calcium is released from the starch during gelatination.     

Digestibility of common native starches with reference to starch granule size,shape and surface features towards guidelines for starch-containing food products

Influence of diverse botanical sources (wheat, maize, waxy maize, cassava, potato, rice or waxy rice) on in vitro native starch digestibility has been investigated. Physicochemical properties (chemical composition, particles size and shape, surface features) of starch granules were determined with a view to explaining digestibility differences between samples. Rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS) contents were measured according to Englyst method. Potato starch was shown to be composed of large rounded granules having smooth surfaces, which explains its slow enzymatic breakdown. Potato starch displayed the highest RS (86%) content and the lowest RDS content (9.9%). Since RS positively influences health and SDS may result in cell, tissue and/or organ damages, potato starch is an ideal starch nutrient. Conversely, waxy rice starch was rich in amylopectin and displayed small diameters and angular shapes, which are both known to facilitate enzymatic starch hydrolysis. It exhibited a near-zero RS content (0.9%) and a high RDS fraction (60%). According to this study, potato starch exhibited the best nutrient profile, followed up in this order by cassava, waxy maize, wheat, maize and waxy rice starches.     

β-环糊精结合脱支处理对重结晶大米淀粉消化性和结构的影响

为了提高抗性淀粉(RS)的含量,探究重结晶大米淀粉(RRS)、β-环糊精重结晶大米淀粉(β-CD-RRS)、重结晶脱支大米淀粉(DB-RRS)、β-环糊精重结晶脱支大米淀粉(DB-β-CD-RRS)的消化性和结构的差异。采用体外模拟消化法测定其消化性,通过X-射线衍射(XRD)、傅立叶变换红外光谱(FT-IR)、扫描电子显微镜(SEM)和差示扫描量热法(DSC)对其晶体结构、形貌和热稳定性进行表征。体外消化实验显示:RRS、β-CD-RRS、DB-RRS和DB-β-CD-RRS的抗性淀粉含量分别为16.45%、19.03%、43.83%和52.34%;蒸煮后,RRS、β-CD-RRS、DB-RRS和DB-β-CD-RRS的抗性淀粉含量分别为1.54%、5.73%、15.49%和20.18%。XRD分析表明,β-CD-RRS与RRS没有明显的衍射峰,DB-RRS和DB-β-CD-RRS均呈B+V型结晶,结晶度分别为23.6%和30.13%。但DB-β-CD-RRS的XRD图谱中在5.2 °处出现衍射峰,这表明形成了淀粉-β-环糊精复合物。SEM结果显示:RRS和β-CD-RRS呈片状结构,而DB-RRS和DB-β-CD-RRS呈紧密的球形颗粒结构。结果表明,β-环糊精结合脱支处理可促进淀粉重结晶及淀粉-β-环糊精复合物的形成,从而协同增加抗性淀粉的含量。     

Production and physicochemical properties of resistant starch from hydrolysed wrinkled pea starch

The content and physicochemical properties of resistant starches (RS) from wrinkled pea starch obtained by different molecular mass reduction processes were evaluated. Native and gelatinised starches were submitted to acid hydrolysis (2 m HCl for 2.5 h) or enzymic hydrolysis (pullulanase, 40 U g^?1 for 10 h), followed by hydrothermal treatment (autoclaving at 121 °C for 30 min), refrigeration (4 °C for 24 h) and lyophilisation. Native starch showed RS and total dietary fibre contents of 39.8% and 14.3%, respectively, while processed ones showed values from 38.5% to 54.6% and from 22.9% to 37.1%, respectively. From these, the highest contents were among acid‐modified starches. Processed starches showed endotherms between 144 and 166 °C, owing to the amylose retrogradation. Native and processed starches showed low viscosity, which is inversely proportional to the RS concentration in samples. The heat treatment promoted an increase in the water absorption index. The pea starch is a good source for obtaining resistant starch by acid hydrolysis.     

Functional properties of water-soluble non-starch polysaccharides from rice and ragi: Effect on dough characteristics and baking quality

Water-soluble non-starch polysaccharides (NSP) were isolated from native and malted rice and ragi. The effects of addition of water-soluble NSP on dough rheological characteristics and baking quality were investigated. Water-soluble NSP had low relative viscosity and showed no gelling activity despite considerable amount of ferulic acid (∼492.5-528.0 μg/g). However, they were found to stabilize protein foams against thermal disruption. Addition of water-soluble NSP (0.25 and 0.50%) to wheat flour resulted in increased water absorption and decreased dough development time. However, prolonged mixing resulted in slightly lower dough stability. Increase in dough extensibility and improvement in starch pasting characteristics were observed upon the addition of water-soluble NSP. Significant increase in loaf volume and softness of the bread was also observed. Water-soluble NSP both from malted rice and ragi had higher effect compared to the native one. Results showed that water-soluble NSP can be added to various low-fiber food preparations with positive dough functionality.     

Production of Resistant Starch by Extrusion Cooking of Acid-Modified Normal-Maize Starch

ABSTRACT:  The objective of this study was to utilize extrusion cooking and hydrothermal treatment to produce resistant starch (RS) as an economical alternative to a batch-cooking process. A hydrothermal treatment (110 °C, 3 d) of batch-cooked and extruded starch samples facilitated propagation of heat-stable starch crystallites and increased the RS contents from 2.1% to 7.7% up to 17.4% determined using AOAC Method 991.43 for total dietary fiber. When starch samples were batch cooked and hydrothermally treated at a moisture content below 70%, acid-modified normal-maize starch (AMMS) produced a greater RS content than did native normal-maize starch (NMS). This was attributed to the partially hydrolyzed, smaller molecules in the AMMS, which had greater mobility and freedom than the larger molecules in the NMS. The RS contents of the batch-cooked and extruded AMMS products after the hydrothermal treatment were similar. A freezing treatment of the AMMS samples at −20 °C prior to the hydrothermal treatment did not increase the RS content. The DSC thermograms and the X-ray diffractograms showed that retrograded amylose and crystalline starch–lipid complex, which had melting temperatures above 100 °C, accounted for the RS contents.     

湿热及酶解处理对糯米粉体外消化特性和血糖生成指数的影响

目的 研究酶解处理、湿热处理和湿热复合酶解处理对糯米粉体外消化特性和血糖生成指数(glycemic index, GI)的影响。方法 采用体外消化法测定了不同处理糯米粉的水解度和血糖生成指数值, 并通过X-射线衍射和激光共焦拉曼光谱实验测定了不同处理糯米的淀粉晶体结构。结果 3种处理的水解度和抗性淀粉(resistant starch, RS)相对含量增加, 慢消化淀粉(slowly digestible starch, SDS)相对含量降低; 其中湿热复合酶解处理条件下, RS相对含量最高, 为71.31%; 酶解处理条件下, RS相对含量最低, 为67.66%。酶解处理、湿热处理和湿热复合酶解处理的GI值分别为79.1、76.0和70.6。3种处理后糯米淀粉的晶体结构发生改变, 3种处理均使分子短程有序度与结晶度增加, 其中湿热复合酶解处理条件下, 结晶度最高, 为34.41%。 结论 湿热复合酶解处理后的糯米粉抗消化特性增强且GI值降低, 湿热复合酶解工艺可能通过影响糯米粉的体外消化率来降低GI值。     

核磁共振技术研究普通玉米淀粉与玉米抗性淀粉对肉糜持水性的影响

将玉米抗性淀粉、普通玉米淀粉按不同比例添加于猪肉肉糜中,利用磁共振技术研究肉糜中水分状态及含量的变化。结果表明:玉米抗性淀粉与普通玉米淀粉均能提高猪肉肉糜的保水性能。当抗性淀粉的添加量为4%时,肉糜保水性最强,而玉米淀粉的最佳添加量为6%,且添加4%玉米抗性淀粉的肉糜其保水性较添加6%普通玉米淀粉的要好。     

酸解时间对大米淀粉结构性质的影响

以4种不同直链淀粉含量的大米淀粉(0%的优糯3号、10.90%的稻花灿、21.03%的聚两优、28.46%的华优香占)为原料,酸解处理不同时间,以酸解大米淀粉的酸解率、颗粒形貌、结晶性质、溶解度的变化为指标衡量不同酸解时间对大米淀粉结构及性质的影响。结果表明,不同直链淀粉含量的大米淀粉具有不同的耐酸性,酸解时间对不同直链淀粉含量大米淀粉的结构和性质有着不同的影响。大米淀粉酸解率与直链淀粉含量成反比,优糯3号为50%而华优香占仅为30%;所有淀粉颗粒在酸解后均产生一定程度的破碎,偏光十字变形直至消失,酸解相同时间,直链淀粉含量高的大米淀粉破碎率低;酸解未改变淀粉的晶型,仍为A晶型;随着酸解时间的延长相对结晶度增加;淀粉的溶解度随着酸解时间的增加而增大。     

Effects of gamma irradiation on starch digestibility of rice with different resistant starch content

Three rice cultivars (RS3M, RS4H and RS5L) differing in resistant starch contents but similar in genetic background were chosen to study the effects of gamma irradiation on starch physicochemical properties and digestibility. Irradiation increases the resistant starch content in all the three cultivars and in a dose‐dependent manner in rice with low‐resistant starch content (RS5L). Irradiation decreases apparent amylose content and gelatinisation temperature and changed the starch granule structure, while increasing V‐type crystallinity. Starch enzymatic hydrolysis rate was reduced following irradiation, and the effect of irradiation on reducing starch digestibility was negatively correlated with resistant starch content. Treatment with gamma irradiation has therefore a potential for increasing resistant starch content and producing low digestibility of starch in common rice.     

Resistant starch from differently processed rice and ragi (finger millet)

 Resistant starch (RS) formed during parboiling, expanding, popping, flaking, roller drying, extrusion cooking, malting and autoclaving of rice and ragi was determined. The processing conditions were chosen to represent the limits that are being used commercially. RS formation was more pronounced in autoclaving and a drastic increase (∼fivefold) in its content was observed during repeated autoclaving (heating and cooling) was observed. Though processed ragi samples contained more nitrogen, protein and dietary fibre, the RS content was very low compared to rice. Hot paste viscosity studies showed the extruded and malted samples to have low peak and set-back viscosities. Determination of the percentage of starch gelatinization revealed that powdered samples showed 100% gelatinization at higher temperatures whereas malted and extruded samples showed the same at low temperatures.