Fate of aflatoxin B1 during the cooking of Korean polished rice

The fate of aflatoxin B1 (AFB1), a mycotoxin known to occur in polished rice, during rice cooking was evaluated to determine reduction in AFB1 residues and mutagenic potentials. The amounts of AFB1 in three lots of naturally contaminated polished rice from Korea were analyzed by high-performance liquid chromatography after washing and after steaming. An in vitro mutagenicity assay with Salmonella Typhimurium TA100 was used to confirm the results of the chemical analyses. Cooking significantly reduced AFB1 (mean reduction, 34%) in naturally contaminated polished rice and reduced mutagenicity by ca. 27%. Processing factors (reflecting the removal of AFB1 residues during processing) for cooked rice were estimated at 0.66 to 0.73, as determined chemically and toxicologically, respectively. The revised Korean provisional daily intake of AFB1 from consumption of rice as a dietary staple (0.58 to 3.94 ng/kg of body weight per day) is still higher than that reported for foods in general in the United States (0.26 ng/kg of body weight per day). Thus, Koreans probably consume higher amounts of foodborne AFB1 than do Americans and thus are at higher risk for AFB1-induced health consequences.     

Effect of processing on ochratoxin A content in dried beans

Dried pink beans naturally contaminated with ochratoxin A (OTA) and dried carioca beans artificially contaminated with OTA by inoculation with Aspergillus ochraceus (ATCC 22947) were tested for ochratoxin A levels as follows: dried beans were washed with water for 2, 60 or 120 min, soaked in water for 60, 120 min or 10 h, and cooked for 60 or 120 min. At each step, test water and beans were separated. Test water, raw beans and cooked beans were analyzed for OTA. The amount of OTA partitioned into water and in residual beans was determined by methanol–sodium bicarbonate extraction, buffer dilution, immunoaffinity column cleanup, liquid chromatographic separation and fluorescence detection. The results demonstrated that the distribution of OTA in processing water and beans depends on the method of preparation. All treatments (washing, soaking and cooking) when applied individually reduced the amounts of OTA retained in bean flour and whole beans. Higher amounts of OTA remained in whole beans than in bean flour after removing the processing water. The combination of the three treatments eliminated about 50% of the toxin from whole beans. This study provides evidence that discarding the washing, soaking and cooking water leads to a significant reduction in OTA contamination in dried beans.     

不同烹煮方式对米饭食味品质的影响

以4种市售大米为研究对象,利用质构仪、气相色谱-质谱(gas chromatography-mass spectrometry,GC-MS)及感官评价等检测和评价手段,对不同烹煮方式的米饭进行基本蒸煮品质、质构特性以及风味物质等食味品质的评价,并探究其与感官评价的相关性。旨在探究不同大米品种(粳米和籼米),以及不同蒸煮工艺(高压烹煮、电饭锅烹煮、微波烹煮和电蒸锅烹煮)对米饭食味品质的影响,寻找一种能够综合评价米饭食味品质的方法,为米饭的制作及米饭食味品质的改善提供理论参考。结果表明:经高压烹煮后的米饭吸水率、膨胀率、碘蓝值均高于其他方式,且米饭硬度小,弹性和黏性较大,感官品质评价最优,而微波烹煮米饭食味品质最差。米饭膨胀率与感官评价中米饭的滋味和形态呈显著正相关(P0.05,P0.01),硬度与口感呈极显著负相关(P0.01),弹性与米饭形态呈极显著正相关(P0.01)。此外,米饭风味物质分析表明经高压烹煮和电饭锅烹煮的米饭,醛、醇、酮等主要的米饭风味物质含量和种类均高于其他烹煮方式,且因品种不同大米的香气有所差异。     

EFFECTS OF THE COOKING PROCESS ON THE CHARACTERISTICS OF AROMATIC RED RICE WINE

Fermentation tests were performed with cooked and/or uncooked, polished aromatic red rice (Oryza sativa var. Indica, Tapol) and aromatic red rice bran using compressed baker's yeast and a preparation of glucoamylase produced by Rhizopus, sp. as saccharifying agent. The quality in terms of both aroma and taste of the red rice wine made with uncooked, unpolished aromatic red rice was much higher than that of rice wine made with cooked, unpolished aromatic red rice. However, the bran fraction of aromatic red rice was fairly resistant to the cooking process and this fraction was hardly affected or degraded by the cooking process. Furthermore, the bran fraction improved the quality of rice wine made from mash that contained cooked, polished rice which had a rather lower-quality aroma. In red rice wine brewing, the polished rice fraction of aromatic red rice may suffer from undesirable effects during the cooking process.     

Cooking rice in excess water reduces both arsenic and enriched vitamins in the cooked grain

This paper reports the effects of rinsing rice and cooking it in variable amounts of water on total arsenic, inorganic arsenic, iron, cadmium, manganese, folate, thiamin and niacin in the cooked grain. We prepared multiple rice varietals both rinsed and unrinsed and with varying amounts of cooking water. Rinsing rice before cooking has a minimal effect on the arsenic (As) content of the cooked grain, but washes enriched iron, folate, thiamin and niacin from polished and parboiled rice. Cooking rice in excess water efficiently reduces the amount of As in the cooked grain. Excess water cooking reduces average inorganic As by 40% from long grain polished, 60% from parboiled and 50% from brown rice. Iron, folate, niacin and thiamin are reduced by 50–70% for enriched polished and parboiled rice, but significantly less so for brown rice, which is not enriched.     

The impact of cooking method on the phenolic composition,total antioxidant activity and starch digestibility of rice (Oryza sativa L.)

This study investigated changes in the phenolic composition, total antioxidant activity (TAA) and starch digestibility in white and brown rice due to three different cooking procedures, and subsequent reheating of cooked rice after storage. Among the analyzed samples, brown rice showed the highest TAA and phenolic content (622.5 mg/kg DW). All cooking methods resulted in significant decrease of phenolic content and TAA of rice (p < 0.05). The greatest loss was observed after processing in rice cooker, which reduced phenolic content of both brown and polished rice by ～30% and ABTS radical‐scavenging activity by 20 and 28%, respectively. In general, the levels of polyphenols and TAA of cooked rice tended to further decline after storage and reheating, but to a much lesser extent when rice was prepared using microwaves. The application of in vitro digestion system disclosed that the microwave cooking resulted in the highest starch digestibility among cooking methods used.

Practical applications

Rice is one of the most commonly consumed staple foods worldwide. Scientific and epidemiological studies have showed that their phytochemicals exhibit antioxidant, anti‐inflammatory, antihypertensive and chemopreventive effects. Therefore, their high consumption, easy availability throughout the year and use as an additive to meat and high‐fat foods may make rice, especially in the form of whole grains, potentially important chemopreventive component of the diet. The appropriate cooking procedure of rice is crucial for preservation of bioactive compounds as well as digestion of starch and thus duration of the glycemic response. Preferably, this study is focused on the evaluation of the effect of cooking methods on the health‐related quality of rice. The results provide practical advice that the consumption of freshly cooked rice ensures its highest nutritional quality, while rice microwaving is recommended both when cooked rice will be reheated after storage (e.g., in restaurants) and accelerated starch digestion is in favor.     

Effects of processing and cooking on the levels of pesticide residues in rice samples

The effects of processing and cooking on the levels of pesticide residues in rice samples were investigated for 11 pesticides in pre-harvest (9 pesticides) and post-harvest (4 pesticides) samples. In the polishing process, the transfer ratio (%, total pesticide residue amount in product/that in brown rice) of rice bran ranged from 40% to 106%, and the transfer ratio of polished rice ranged from 9% to 65% in pre-harvest samples. These values varied from pesticide to pesticide. The processing factor (the concentration (mg/kg) of pesticide in product/that in the brown rice) of polished rice ranged from 0.11 to 0.73. The loss of pesticides during processing and/or cooking did not correlate to any single physical or chemical property. Investigation of changes of pesticide residues during processing and/or cooking is useful not only to establish MRLs, but also to recognize actual levels of pesticide residues 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.     

蒸烤模式对南美白对虾食用品质的影响

以南美白对虾为研究对象,以色差值、质构品质、游离氨基酸含量及感官评分为指标,通过色彩色差计、物性测试仪、氨基酸专用高效液相色谱仪以及感官评价法考察不同蒸烤模式（纯蒸、纯烤、先蒸后烤、先烤后蒸、蒸烤交替）对虾肉食用品质的影响。结果表明：先烤后蒸模式下虾皮和虾肉的L*值显著低于其他4 种模式（P＜0.05）;纯烤模式下虾的硬度和咀嚼性均显著高于其他4 种加热模式（P＜0.05）;游离氨基酸含量分析结果显示,纯蒸模式下虾的游离氨基酸总量最多,蒸烤交替模式下甜味氨基酸比例最高、苦味氨基酸比例最低。最后综合感官评定结果得出,在南美白对虾的不同蒸烤模式中,纯蒸和蒸烤交替模式优于其他3 种加热模式。     

EFFECT OF ARTISANAL PARBOILING METHODS ON MILLING YIELD AND COOKED RICE TEXTURAL CHARACTERISTICS

ABSTRACT

One of the main objectives of artisanal rice parboiling is to reduce the levels of broken grains (brokens) on milling. Rice samples that had been parboiled using different regimes of soaking temperatures and steaming times were analyzed for their physical properties and cooked rice textures. It was established that inappropriate soaking and steaming regimes resulted in greater levels of brokens than raw‐milled paddy. Consequently, in artisanal parboiling, the initial soaking temperature should be about 90C and the steaming time should be more than 8 min, ideally, about 12 min. On cooking, more severely parboiled rice samples had firmer textures than mildly parboiled samples. The commercially parboiled sample and the more severely laboratory‐parboiled samples required a rice‐to‐water ratio of 1:3, while the raw‐milled sample and the mildly parboiled ones required a 1:2½ rice‐to‐water ratio for optimum cooking.

PRACTICAL APPLICATIONS

Artisanal rice parboiling is carried out mainly to reduce the levels of broken grains and increase the yield of milled rice in many countries. If this is carried out very well, there are economic benefits as more rice of better quality is available to be sold. This study provides information on optimum processing conditions, i.e., initial soaking temperature of about 90C and a steaming time of about 12 min. The study also provides recommendations on optimum cooking conditions, i.e., rice‐to‐water ratio, for the variably parboiled rice samples.     

Effects of rice cleaning and cooking process on the residues of flutolanil,fenobucarb, silafluofen and buprofezin in rice

We studied the effect of cleaning and cooking on the residues of flutolanil, fenobucarb, silafluofen and buprofezin in rice. The rice had been sprayed in a paddy field in Wakayama city, with 3 kinds of pesticide application protocols: spraying once at the usual concentration of pesticides, repeated spraying (3 times) with the usual concentration of pesticides and spraying once with 3 times the usual concentration of pesticides. The residue levels of pesticide decreased during the rice cleaning process. Silafluofen, which has a higher log Pow value, remained in the hull of the rice. Fenobucarb, which has a lower log Pow value, penetrated inside the rice. The residue concentration of pesticide in polished rice was higher than that in pre-washed rice processed ready for cooking. During the cooking procedure, the reduction of pesticides in polished rice was higher than that in brown rice.     

Reduction of pesticides residues on okra fruits by different processing treatments

For the first time, the effect of washing, water boiling, chemical boiling, steaming and cooking treatments on the reduction of residues of indoxacarb, fenarimol, acetamiprid and chlorfenapyr in okra fruits was investigated. Residues were analyzed using quick, easy, cheap, effective, rugged, and safe (QuEChERS) method combined with liquid chromatography tandem-mass spectrometry (LC–MS/MS). Our results show that some treatments could significantly decrease pesticide residues. The reduction of residues by washing treatment was not correlated to water solubility: Chlorfenapyr (non-systemic pesticide) was decreased by 90 % and acetamiprid (systemic pesticide) was removed by 48 %. Therefore, we suggest that pesticide residues were washed off by removing the loosely attached pesticides on the okra fruit surface. The time of exposure in both boiling and steaming treatments has no significant effect on reduction of pesticides residues. Additionally, cooking after the washing and boiling treatments reduced the pesticides residues. In particular, acetamiprid was reduced after the cooking treatment to 90 %.     

烹食过程对蔬菜中五种农药残留的动态影响

利用色谱分析法研究白菜和菜豆中克百威、甲胺磷、氧乐果、PP-DDT和氰戊菊酯等5种农药在洗涤和烹饪处理后残留量的动态变化情况,为农药残留风险分析与限量标准制订提供参考。结果表明,洗涤处理后农药残留去除率在8.0%—77.7%之间,清水洗涤效果最差;不同烹饪方式的去除效果差距明显,炸制处理最高达94.1%,而蒸制处理仅为48.3%;白菜样品的洗涤处理效果好于菜豆,烹饪处理效果则相反;克百威、甲胺磷和氰戊菊酯的洗涤处理效果较好,而氧乐果的煮制处理去除率最高,PP-DDT在其它烹饪方式处理后去除率较高。     

馒头的微波烹制工艺与特性研究

采用正交试验研究加水量、醒发时间、微波剂量和烹制时间对微波烹制馒头感官品质的影响,确定最佳工艺参数,并对比分析微波和蒸汽2种不同烹制方式下馒头的微观形貌、质构特性和消化特性。试验表明,微波烹制馒头的适宜工艺参数为:加水量为50 g/100 g小麦粉,醒发时间为35 min,采用2.76 W/g的微波剂量,烹制时间为2.5 min。在此工艺条件下所制作的馒头感官品质与蒸汽烹制馒头较为接近。与蒸汽烹制馒头相比,微波烹制馒头的口感稍劣;内部微观结构较为粗糙,孔洞均匀性稍差,孔壁较厚,局部区域略呈聚集状,部分网络结构有轻微程度的断裂;硬度、黏聚性和咀嚼度较大,弹性较小;淀粉消化率较高,蛋白质消化特性与之相近。     

Textural and morphological changes of Jasmine rice under various elevated cooking conditions

The effects of cooking at elevated temperatures (80, 100, 120 and 140 °C) and pressure levels (0, 0.1, 0.3 and 0.5 MPa) on the textural and morphological properties of cooked Jasmine rice were investigated. The developed high pressure cooker was utilized to process Jasmine rice in excess water under isothermal conditions. Rice cooking at higher temperature produced softer and stickier grain texture as well as more off-white colour. Using scanning electron microscopy technique, the microstructure revealed that the soft texture at high cooking temperature corresponded well to the increase of pore size and thickness of the sponge-like texture of inner layer endosperm. As the temperature increased, the outer layer of cooked rice became less porous. Boiling significantly altered the external appearance (namely colour and exterior integrity) and texture of cooked rice while cooking pressure had a little or no effect.     

基于响应面法大米蒸煮方式与参数对米饭物性的影响分析

利用响应面分析法研究大米蒸煮方式及参数对米饭物性的影响,为米饭的制作及食味的调节与改善提供参考。在常压蒸煮方法下研究大米加水、浸泡、蒸煮条件对米饭物性的影响确定各因素的水平范围,然后进行响应面设计与模型分析。通过响应面分析法建立了常压蒸煮法下大米加水量(水米比),浸泡时间和蒸煮方式三因素与米饭黏硬比的二次回归模型,方差分析证明了模型的可靠性。实验结果表明:水米比、浸泡时间和蒸煮方式及它们的交互作用对米饭黏硬比影响显著,三个因素对黏硬比的影响强弱依次为:蒸煮方式、水米比、浸泡时间。水米比与蒸煮方式的交互作用对米饭黏硬比的影响最显著,浸泡时间与蒸煮方式次之,而水米比与浸泡时间影响最小。     

Effects of cooking, drying and pretreatment methods on texture and starch digestibility of instant rice

Instant rice produced from a conventional process consisting of the cooking, washing and drying steps possesses poorer eating quality compared with that of freshly cooked rice. The objective of this work was therefore to study the effects of cooking, pretreatment and drying methods on microstructure, textural properties and starch digestability of instant rice after rehydration; jasmine white rice was chosen as a test material. Conventional boiling method and electric rice cooking were selected as the methods to prepare cooked rice. In the case of boiling, cooked rice was frozen at −20 °C or cooled at 4 °C for 24 h prior to drying, while the cooked rice from an electric rice cooker was washed with ambient or cool water for 30 s prior to drying. After pretreatment the cooked rice was dried either by freeze drying or hot air drying at 80 °C. Based on the scanning electron microscopic results it was found that the cooking, pretreatment and drying methods all affected the rice morphology. The hardness and stickiness of instant rice after rehydration were lower for samples prepared from the rice cooker than those of freshly cooked rice, while both textural properties appeared to be improved significantly for the samples from boiling. The texture of the freeze-dried products was not different from that of the air-dried one. The freezing pretreatment provided the texture and glycemic index of instant rice after rehydration similar to those of the freshly cooked rice. On the other hand, the cooling pretreatment resulted in the harder texture and higher glycemic index of the samples.     

不同烹饪方式对盐渍鱼干风味和微观结构的影响

本文对比研究了微波烹饪、空气炸锅烹饪、烘烤烹饪和蒸煮烹饪4种常用烹饪方式对盐渍鱼干咀嚼性(质构)、滋味(游离氨基酸),风味(挥发性物质)和微观结构的影响。结果表明:4种烹饪方式均可通过显著降低盐渍鱼干的硬度和咀嚼性、增加弹性来改变其质构特性;微波烹饪、空气炸锅烹饪和烤箱烹饪都能不同程度的降低盐渍鱼干的游离氨基酸总量,而蒸煮烹饪提高了氨基酸总量,从原始量586.66 mg/100 g增加至631.45 mg/100 g;4种烹饪方式均可使鱼干样品中醛酮类物质和酯类物质含量显著上升,烷烃类物质含量显著下降,其中空气炸锅烹饪处理鱼干样品中醛酮类物质含量最高,达到37.07%;烹饪处理使盐渍鱼干肌肉纤维严重皱缩,纤维束间充满了烹饪用油,空气炸锅和烘烤烹饪处理后盐渍鱼干纤维束间的空隙较明显。     

冷藏与家庭处理对黄瓜中7 种农药残留的影响

通过对黄瓜中7 种农药及2 种代谢物的残留量来评价冷藏与清洗、烹饪处理对农药及其代谢产物的影响。结果表明,在5 ℃贮藏条件下,黄瓜中的农药残留量随着冷藏时间的延长越来越低,10 d后黄瓜中的7 种农药降解率达38.9%～58.3%;清水清洗后7 种农药降解率在27.17%～80.00%之间,而清洁剂清洗的降解率可达33.33%～90.00%,2 种清洗方式所产生的农药降解率的差异与农药的水中溶解度相关;蒸、煮、炒3 种处理均能有效降低黄瓜中的农药残留量,煮处理对黄瓜中的农药消除效果最好,降解率在22.76%～85.00%之间,炒处理次之,降解率在21.52%～75.00%之间,蒸处理最差,在10.13%～53.25%之间。在烹饪处理过程中,烹饪所产生的温度为农药降解的关键因素。     

Effect of cooking on the chemical composition of lentils,rice and their blend (Koshary)

Lentils, rice and their blend (Koshary) were cooked by traditional Egyptian methods. Cooking resulted in slight changes in the total nitrogen, as well as in the non-protein nitrogen (NPN), ether extract and crude fibre of the three products, compared with raw grains. In contrast, significant decreases were found in the mineral elements, indicating losses through leaching, on washing and cooking. The mineral composition of lentils' cooking liquor confirmed this.