碱酶分步法从米粉中提取大米蛋白工艺的研究

用碱法和酶法两步加工米粉,制备大米蛋白.通过研究pH,温度,时间及料液比对大米蛋白提取率的影响,确定稀碱提取大米蛋白的较佳工艺条件为:pH11.0,温度50℃,时间2h,及料液比1:8,然后用碱性蛋白酶对碱提残渣进行二次提取,通过正交试验确定酶提大米蛋白最适条件为:加酶量1%,pH8.0,时间1h,料液比1:8,温度50℃.两步提取使大米蛋白提取率达到90.49%.     

Contribution of water and cooked rice to an estimation of the dietary intake of inorganic arsenic in a rural village of West Bengal,India

Arsenic contamination of rice plants by arsenic-polluted irrigation groundwater could result in high arsenic concentrations in cooked rice. The main objective of the study was to estimate the total and inorganic arsenic intakes in a rural population of West Bengal, India, through both drinking water and cooked rice. Simulated cooking of rice with different levels of arsenic species in the cooking water was carried out. The presence of arsenic in the cooking water was provided by four arsenic species (arsenite, arsenate, methylarsonate or dimethylarsinate) and at three total arsenic concentrations (50,?250 or 500?µg?l^?1). The results show that the arsenic concentration in cooked rice is always higher than that in raw rice and range from 227 to 1642?µg?kg^?1. The cooking process did not change the arsenic speciation in rice. Cooked rice contributed a mean of 41% to the daily intake of inorganic arsenic. The daily inorganic arsenic intakes for water plus rice were 229, 1024 and 2000?µg?day^?1 for initial arsenic concentrations in the cooking water of 50, 250 and 500?µg?arsenic?l^?1, respectively, compared with the tolerable daily intake which is 150?µg?day^?1.     

Contribution of water and cooked rice to an estimation of the dietary intake of inorganic arsenic in a rural village of West Bengal, India

Arsenic contamination of rice plants by arsenic-polluted irrigation groundwater could result in high arsenic concentrations in cooked rice. The main objective of the study was to estimate the total and inorganic arsenic intakes in a rural population of West Bengal, India, through both drinking water and cooked rice. Simulated cooking of rice with different levels of arsenic species in the cooking water was carried out. The presence of arsenic in the cooking water was provided by four arsenic species (arsenite, arsenate, methylarsonate or dimethylarsinate) and at three total arsenic concentrations (50, 250 or 500 µg l^-1). The results show that the arsenic concentration in cooked rice is always higher than that in raw rice and range from 227 to 1642 µg kg^-1. The cooking process did not change the arsenic speciation in rice. Cooked rice contributed a mean of 41% to the daily intake of inorganic arsenic. The daily inorganic arsenic intakes for water plus rice were 229, 1024 and 2000 µg day^-1 for initial arsenic concentrations in the cooking water of 50, 250 and 500 µg arsenic l^-1, respectively, compared with the tolerable daily intake which is 150 µg day^-1.     

微波辅助水提法提取黑米花色苷的工艺研究

以黑米为原料,蒸馏水为提取剂,采用微波辅助水提法提取黑米中的花色苷,在单因素试验的基础上进行正交优化试验。结果表明:微波辅助水提法提取的最佳工艺参数为微波功率600 W、微波时间15 min、提取液pH 5、料液比1∶4(g/mL)。在该条件下,花色苷的得率最大为1.28%。     

响应面法优化水酶法提取米糠多酚

以脱脂米糠为原料,采用响应面法优化水酶法提取米糠多酚的工艺。在单因素试验的基础上,采用星点设计-效应面分析法,以米糠多酚提取量为响应值,对木聚糖酶添加量、料液比和酶解温度等工艺参数进行了优化。结果表明,米糠多酚的最佳提取工艺为木聚糖酶添加量2.3%、酶解温度55℃、料液比1∶29(g/mL)、酶解时间40min。在此条件下,米糠多酚的提取量为5.15mg/g,与预测值5.23mg/g的相对误差为1.62%。该法所得的优化提取工艺参数可靠,可为米糠资源的开发利用提供科学依据。     

Digestion study of proteins from cooked meat using an enzymatic microreactor

A semi automatic flow procedure with photometric detection was developed for the study of meat protein digestion. This system comprised two independent flow pathways, gathered by two compartments. The gastric compartment was simulated by an ultrafiltration cell fitted with a 10 KDa cut off membrane and the intestinal compartment was simulated by a 1 KDa cut off dialysis membrane. The pathways were filled with solutions simulating digestive conditions. The proposed system was employed in digestion studies of whole protein extracts from raw and cooked (100°C) meat. A mathematical modelling for the determination of the digestive kinetic constants was established. The results show that meat cooking leads to an important decrease of protein digestibility by proteases of the digestive tract.     

An evaluation of extraction techniques for arsenic in staple diets (fish and rice) utilising both classical and enzymatic extraction methods

Enzymatic extraction methods were evaluated with classical extraction approaches for the determination of arsenic in food. The extraction efficiency for total arsenic was determined by analysing CRM materials DORM-3 fish protein, NIES 106 rice flour and GBW10015 spinach. These were compared with total arsenic concentration determined using microwave-assisted acid digestion and ICP-MS. The total arsenic concentrations in the CRM materials were in good agreement with the certified values. Enzymatic hydrolysis using trypsin has been successfully employed to extract arsenic species in DORM-3 and fish samples. Whilst this method of hydrolysing the proteins worked well for the fish samples, an alternative approach was required to facilitate the digestion of cellulose in plant materials. However, enzymatic extraction using cellulase was found to give unsatisfactory results for both the NIES and GBW10015 CRM materials. Dilute nitric acid (1% HNO₃) was found to give a more efficient extraction for arsenic species in the same CRM materials and rice samples. The study was extended to evaluate a range of real samples. Total arsenic concentrations in 13 different types of fish tissue were determined following microwave-assisted acid digestion using nitric acid/hydrogen peroxide, followed by measurement using HPLC-ICP-MS for speciation analysis. The results obtained for fish were in the range of 3.53–98.80 µg g^?1 As (dry weight). Similarly, the results of 17 rice samples were in the range of 0.054–0.823 µg g^?1. This study demonstrates the importance of selecting an appropriate extraction technique for the quantitative measurement of arsenic species in food.     

Effect of cooking method and rice type on arsenic concentration in cooked rice and the estimation of arsenic dietary intake in a rural village in West Bengal,India

Arsenic (As) contamination of rice plants can result in high total As concentrations (t-As) in cooked rice, especially if As-contaminated water is used for cooking. This study examines two variables: (1) the cooking method (water volume and inclusion of a washing step); and (2) the rice type (atab and boiled). Cooking water and raw atab and boiled rice contained 40 μg As l^?1 and 185 and 315 μg As kg^?1, respectively. In general, all cooking methods increased t-As from the levels in raw rice; however, raw boiled rice decreased its t-As by 12.7% when cooked by the traditional method, but increased by 15.9% or 23.5% when cooked by the intermediate or contemporary methods, respectively. Based on the best possible scenario (the traditional cooking method leading to the lowest level of contamination, and the atab rice type with the lowest As content), t-As daily intake was estimated to be 328 μg, which was twice the tolerable daily intake of 150 μg.     

响应面法优化米糠多酚水酶法提取工艺

以辽宁产大米糠为原料,采用响应面法优化米糠多酚的水酶法提取工艺。在单因素试验的基础上,采用响应面分析法,以米糠多酚得率为响应值,对酶加入量、料液比和酶解温度等工艺参数进行了优化。结果表明,以pH 4.8的柠檬酸缓冲溶液为提取溶剂,纤维素酶酶解提取米糠多酚的最佳工艺为:酶加入量4.80%,酶解温度63℃,料液比1∶28 g/mL,酶解时间1 h。此条件下,米糠多酚的得率为4.45 mg/g,与预测值4.52 mg/g的相对误差为1.57%。该法所得的优化工艺参数准确可靠,具有一定的实际应用价值;该研究结果为米糠的基础研究提供了理论依据。     

Antiproliferative and immunoactivatory ability of an enzymatic extract from rice bran

The validation of natural products as source of functional foods or nutraceuticals has become an important issue in current health research. Thus, the present work has tested on MOLT-4 cells (human T cell acute lymphoblastic leukemic) the antiproliferative effect of a water-soluble enzymatic extract from rice bran (EERB). Present work shows that EERB induces cellular death in MOLT-4 cells in a dose-dependent way (0–10 mg/mL) but not in non-tumoral lymphocytes. Flow cytometric analysis of MOLT-4 cells treated with EERB showed the presence of death cells by apoptosis rather than necrosis. Additionally, EERB also exerts an immunoactivatory effect on N13 microglia cells, by inducing TNF-alpha (tumour necrosis factor-α) expression, which plays a key role in the innate immune response to infection. Accordingly, we can propose EERB as a useful natural standardized extract with antiproliferative and immunoactivatory ability that would be beneficial to apply in the functional food field.     

酶法提取枸杞多糖的研究

研究了纤维素酶提取枸杞多糖的最佳工艺条件。以提取率为指标,分别考虑了加水量、酶解pH、酶解温度、酶解时间、加酶量对纤维素酶酶解反应的影响。试验确定了纤维素酶酶解工艺的最佳条件为加水量50mL、pH5.0、酶解温度50℃、酶解时间60min、加酶量0.5%。在这种条件下,枸杞多糖的得率为11.2%。     

糙米和发芽糙米吸水动力学研究

采用Peleg方程,探讨了糙米和发芽糙米在不同温度(25～65℃)和不同时间间隔下(20～140min)的吸水动力学性质。实验结果表明:Peleg方程能较好地描述糙米和发芽糙米在实验条件下的吸水性质,且相对误差(E)小于10%。在糙米和发芽糙米的吸水模型中,Peleg方程参数K1均随温度升高而减小,K2无明显变化趋势。     

酶水解米渣蛋白制备大米肽研究

该研究利用米渣蛋白制备大米肽的适宜酶水解条件,结果表明:在pH 8．5、温度55℃、酶用量2．0％条件下水解3h,水解液中5％TCA可溶性肽含量可达37％以上。     

Removal of arsenic from contaminated soils by microbial reduction of arsenate and quinone

We investigated bioremediation of As-contaminated soils by reductive dissolution of As using a dissimilatory As(V)-reducing bacterium (DARB), Bacillus selenatarsenatis SF-1. We also examined the effect of anthraquinone-2,6-disulfonate (AQDS), an extracellular electron-shuttling quinone, on the As extraction. When B. selenatarsenatis was incubated with As(V)-laden Al precipitates, no acceleration of As dissolution was observed in the presence of AQDS, even though the microbial reduction of AQDS occurred actively. In contrast, AQDS addition significantly enhanced the reductive dissolution of As and Fe in analogous experiments with As(V)-laden Fe(III) precipitates, whereas As dissolution did not occur in the absence of the As(V) reducer. These results indicate the dissolution of As was accelerated by indirect reduction of solid-phase Fe(III) following microbial AQDS reduction, although As(V) reduction is vital for As extraction. B. selenatarsenatis was able to extract As from two types of industrially contaminated soils through reduction of solid-phase As(V) and Fe(III). The copresence of AQDS with B. selenatarsenatis improved the removal efficiency of As from the contaminated soils, concomitantly releasing Fe(II), suggesting that simultaneous use of DARB and electron-shuttling compounds can be an effective strategy for remediation of As-contaminated soils.     

酶解-亚临界水提取沙姜有效成分的研究

考察了酶解-亚临界水提取沙姜精油中主要成分对甲氧基肉桂酸乙酯的效果。分别研究了提取过程中的提取温度、提取压力、加酶量、投料量和提取时间等因素对提取得率的影响,并与亚临界水提取(SWE)进行对比。结果表明,酶解-亚临界水提取过程,最适宜的温度为120℃,与SWE一致;最佳提取压力为8MPa,比SWE的最适宜压力低了2MPa;加酶量为0.3%(m酶/m沙姜);投料量100g,与SWE相同;提取时间为20min,比SWE法缩短了10min;沙姜精油中有效成分得率提高约10%。     

稻谷、糙米吸水动力学研究

以Peleg方程为依据,通过线性回归分析,计算式中的斜率K2和常数K1,利用实验测定水分含量与预测数据间的相对误差E进行拟合度的判定。建立了普通稻谷、高水分稻谷及糙米的吸水动力学方程,经检验,实验测定水分含量值与预测数据间的相对误差E均小于10%。可利用建立的浸泡吸水动力学方程对稻谷和糙米浸泡过程中的近似水分含量进行预测。     

Arsenic in soil and irrigation water affects arsenic uptake by rice: complementary insights from field and pot studies

Groundwater rich in arsenic (As) is extensively used for dry season boro rice cultivation in Bangladesh, leading to long-term As accumulation in soils. This may result in increasing levels of As in rice straw and grain, and eventually, in decreasing rice yields due to As phytotoxicity. In this study, we investigated the As contents of rice straw and grain over three consecutive harvest seasons (2005-2007) in a paddy field in Munshiganj, Bangladesh, which exhibits a documented gradient in soil As caused by annual irrigation with As-rich groundwater since the early 1990s. The field data revealed that straw and grain As concentrations were elevated in the field and highest near the irrigation water inlet, where As concentrations in both soil and irrigation water were highest. Additionally, a pot experiment with soils and rice seeds from the field site was carried out in which soil and irrigation water As were varied in a full factorial design. The results suggested that both soil As accumulated in previous years and As freshly introduced with irrigation water influence As uptake during rice growth. At similar soil As contents, plants grown in pots exhibited similar grain and straw As contents as plants grown in the field. This suggested that the results from pot experiments performed at higher soil As levels can be used to assess the effect of continuing soil As accumulation on As content and yield of rice. On the basis of a recently published scenario of long-term As accumulation at the study site, we estimate that, under unchanged irrigation practice, average grain As concentrations will increase from currently ～0.15 mg As kg(-1) to 0.25-0.58 mg As kg(-1) by the year 2050. This translates to a 1.5-3.8 times higher As intake by the local population via rice, possibly exceeding the provisional tolerable As intake value defined by FAO/WHO.     

籼米、粳米及泰国香米吸水性质及其动力学研究

以籼米、粳米及泰国香米为研究对象,探讨了籼米、粳米及泰国香米的吸水性质及其影响因素.并用Peleg方程计算了浸泡吸水常数K1和K2,确定了籼米、粳米及泰国香米的吸水动力学方程,运用方程计算的预测数据与实验数据有较好的一致性.因此,可运用吸水动力学方程对大米浸泡过程中的近似水分含量进行预测.     

米糠蛋白碱法提取联合微波与酶法改性工艺的优化

以新鲜脱脂米糠为原料,以乳化性为指标,将米糠蛋白碱法提取和微波与酶法共同改性相联合,应用Plackett-Burman试验设计筛选出提取时间、提取温度和酶用量3个主要影响因素;采用最陡爬坡法得出响应面试验中心点为提取时间95 min、提取温度39℃、酶用量4 900 U/g;通过Box-Behnken试验得到米糠蛋白最佳改性工艺参数为提取时间100 min、提取温度38℃、酶用量4 960 U/g,预测米糠蛋白的乳化性达到26.69 m~2/g,实际乳化性达到26.53 m~2/g。同时,在优化条件下,吸水性、吸油性和乳化稳定性分别提高了7.81%、67.52%和84.12%。米糠蛋白的提取和改性连续进行,提高了米糠蛋白功能特性。     

酶法辅助提取杏仁种皮黄酮的研究

杏仁种皮是杏仁加工的副产物,约占杏仁质量的5%,其中含有一定量的黄酮类物质。黄酮类物质是一种重要的活性物质,除具有一般的生化性质外,还具有抗氧化、抑菌、消炎、抗肿瘤等多种功效。本试验以杏仁种皮为试验材料,研究果胶酶解辅助乙醇提取杏仁种皮黄酮的工艺条件。考察了果胶酶浓度、酶解时间、乙醇浓度、液固比、提取温度、提取时间6个单因素对杏仁种皮黄酮提取率的影响,在单因素试验的基础上,选择四因素三水平进行正交试验,确定了最佳工艺条件为:果胶酶浓度0.6%,酶解时间90min,乙醇浓度80%,料液比1∶40,提取温度50℃,提取时间30min,此工艺条件下杏仁种皮黄酮的提取率可达24.5mg/g。