Zinc fortification of whole rice grain through parboiling process

The present study evaluated the effectiveness of zinc (Zn) fortification in a parboiling process for improving Zn density in parboiled-polished rice and its potential bioavailability in the human diet. Fortification of Zn in whole paddy rice grain with 50–400 mg Zn/kg paddy rice, during parboiling, increased Zn concentrations in polished-parboiled rice from 1.3 to 4.5 times those in unfortified parboiled rice. The added Zn rapidly penetrated into parboiled rice grains in the initial soaking process before saturation. There was an exponential correlation between Zn concentrations in unpolished (r = 0.63) (p < 0.01) and polished rice (r = 0.30) (p < 0.05) and soaking time. Zinc concentrations in unpolished rice were linearly correlated with Zn concentration in the polished rice (r = 0.60) (p < 0.01). Moreover, more than half of the added Zn is retained after a simulated washing process before cooking, ranging from 64–100%. In the Zn-fortified parboiled rice, 57–100% of Zn in polished rice grain was soluble in dilute acid, which was indicative of a high potential Zn bioavailability for human intake. The results suggest that parboiled rice has great potential for Zn fortification.     

Key factors affecting Fe density in Fe-fortified-parboiled rice: Parboiling conditions,storage duration,external Fe-loading rate and genotypic differences

The present study evaluated the key factors affecting the efficiency of iron (Fe) penetration into the endosperm in parboiled rice of different varieties. It also investigated effects of storage time on Fe bio-accessibility, rice colour and Fe retention after rinsing. Rice grains of three varieties were fortified with an increasing range of Fe-fortification rates during the parboiling process, under two typical parboiling conditions, which are ambient soaking temperature for 24 h and 60 °C soaking temperature for 6 h at neutral (6.0–6.5) and acidic pH (3.0–3.5). Soaking of paddy rice, at 60 °C in acidic water for 6 h before steaming, was found to be better for maximising the Fe concentration in white-parboiled rice than the former ambient soaking. Under this parboiling condition, adding 250 mg Fe kg⁻¹ of paddy rice, at soaking, produced the most desirable Fe concentration in white rice, ranging from 17.5 to 25.4 mg kg⁻¹ among the rice varieties tested. The concentrations of Fe in parboiled white rice exhibited an exponential increase with increasing concentrations of Fe in the soaking water in all varieties, which were linearly related to Fe concentration of brown rice (r = 0.96∗∗, p < 0.01). The colour of the parboiled rice fortified with Fe was initially light yellow, with variation among rice varieties, but it did become slightly darker after 16 weeks of storage, probably because of Fe oxidisation. This may be related to decreasing bio-accessibility after 20 weeks of storage. Storage, however, did not affect the total Fe retention after rinsing, though the retention rate was variety-dependent. Information about parboiling will provide the basis for formulating an optimal industry protocol for producing Fe-fortified-parboiled rice, which can be further refined in pilot studies on the industrial scale.     

Iron fortification and parboiled rice quality: appearance,cooking quality and sensory attributes

BACKGROUND: Iron (Fe) fortification of parboiled rice increases both Fe concentration and bioavailability in milled grains (i.e. white rice). The aim of the present study was to evaluate parboiled rice fortified with 250 and 450 mg Fe kg^?1 paddy rice for its pre‐cooking appearance, cooking quality, basic sensory attributes and overall acceptance in comparison with unfortified parboiled rice in Thailand and local parboiled rice in Bangladesh. RESULTS: Fe fortification at 250 mg Fe kg^?1 paddy rice significantly elevated Fe concentration in white rice to as high as 19.1 mg Fe kg^?1 white rice, compared with 6.2 mg Fe kg^?1 white rice for unfortified parboiled rice, without any adverse impact on consumer acceptance based on the current preliminary assessment. The added Fe was well retained in the cooked rice, with significant residual value for human intake. Panellists in Thailand and Bangladesh did not detect significant differences in the acceptability of parboiled rice fortified at 250 mg Fe kg^?1 paddy rice compared with unfortified and local parboiled rice respectively. However, Fe fortification of parboiled rice at the higher level of 450 mg Fe kg^?1 paddy rice significantly intensified the yellow colour of the grain and changed the off‐flavour, chewiness and flakiness of the cooked Fe‐fortified parboiled rice. This resulted in a low acceptability ranking of parboiled rice fortified at 450 mg Fe kg^?1 paddy rice by panellists in both Thailand and Bangladesh. CONCLUSION: Fe fortification of parboiled rice at an appropriate level (e.g. 250 mg Fe kg^?1 paddy rice) is dosage‐effective and acceptable to rice consumers. Consumer acceptability of Fe‐fortified parboiled rice is closely related to pre‐cooking appearance, cooking quality and sensory attributes. Copyright © 2009 Society of Chemical Industry     

Vitamin fortified rice grain using spraying and soaking methods

The objective of this work was to fortify three types of rice grains (brown, white milled and parboiled) with B complex vitamins (B₁, B₂, B₃, B₅, B₆, B₁₂), using two different physical treatment methods, (1) soaking of whole dehusked or milled rice kernels in vitamin solutions at 90 °C for 15 min and (2) full spraying of whole kernels with vitamin solution at 35 °C, both followed by oven drying. Various nutrient concentrations were added and the vitamin retention of dried fortified as well as of cooked rice were determined. Fortified rice was evaluated based on vitamin retention, estimated as the percentage of vitamin in rice after fortification treatment versus the total amount of added plus its initially vitamin quantity. It was found that the average retention of all vitamins in dried rice was high and varied from 54.3% to 85.3% for the spraying and from 53.5% to 76.2% for the soaking method respectively. After rice cooking, the retention was maintained in sufficient level (>70%) for all vitamins except for B₁₂. When excess of water was used for cooking, the water-soluble vitamins were leached; however a significant amount of vitamins still remained, varying from 13.5% (B₁₂) to 51.2% (B₁). The good retention of vitamins, even after cooking, achieved applying these relatively simple techniques, may be attributed to the absorption and diffusion of vitamins in the interior of rice kernels in high concentrations. Dried fortified rice samples properties were evaluated.     

蒸谷米快速浸泡工艺研究

研究不同浸泡工艺包括温度-时间、微波、酸碱溶液、低浓度乙醇、酶对稻谷吸水率的影响,结合蒸谷米外观品质及米饭质构分析,筛选有效的快速浸泡工艺。结果表明,在稻谷∶水为1∶1(g/mL)、温度60~70℃、浸泡4~5 h时,便达到浸泡工艺要求,吸水率达到30%;能显著提高稻谷吸水率的方法是质量比5%的纤维素酶浸泡4 h,吸水率达30.07%;能显著缩短浸泡时间方法是5 min、700 W微波浸泡,吸水率为31.69%。且2种浸泡工艺对蒸谷米的外观品质和米饭质构无不良影响,有望作为蒸谷米快速浸泡工艺进行应用。     

The bioavailability of iron fortified in whole grain parboiled rice

The present study was to evaluate the bioavailability of iron (Fe) fortified in parboiled rice grain, expressed as Fe uptake by Caco-2 cells after in vitro digestion. The bioavailability of Fe-fortified in the rice grain was closely and positively correlated with increasing concentrations of Fe in the grains of the three cultivars (r = 0.96∗∗). The uptakes of the Fe-fortified in parboiled rice milled for 120 s (34.2, 47.7 and 107 ng ferritin mg protein⁻¹ in three cultivars, respectively) were well above those of the unfortified raw (6.1, 4.9 and 5.7 ng ferritin mg protein⁻¹) or parboiled rice (4.7, 3.6 and 4.4 ng ferritin mg protein⁻¹), the high Fe rice line IR68144-2B-3-2-2 (4.0 ng ferritin mg protein⁻¹) and popular Jasmine rice cultivar KDML 105 (3.9 ng ferritin mg protein⁻¹). Increasing milling time and rinsing the Fe-fortified parboiled rice decreased Fe bioavailability, due to their negative effects on total Fe concentrations in the parboiled rice grains, but uptakes were still well above that of their unfortified raw or parboiled rice grains. Rinsing or washing the Fe-fortified and milled rice grains decreased the bioavailability to 85 ng ferritin mg protein⁻¹ in the YRF cultivar, compared to about 100 ng ferritin mg protein⁻¹ in its non-rinsed grains. Dilute acid-extractable (DAE) Fe was linearly, positively correlated with the uptake of Fe assessed by the in vitro digestion/Caco-2 cell technique (r = 0.90∗∗), which can be used as a rapid method for optimizing levels of bioavailable Fe to be fortified in the parboiled rice by parboiled-rice mills if this Fe-fortification technique should be adopted in south and southeast Asia.     

Iron-fortified parboiled rice – A novel solution to high iron density in rice-based diets

The present study pioneered an investigation of a novel and cost-effective approach to fortify Fe in rice and to greatly improve Fe nutrition in rice-based diets through parboiling, though it remains at its preliminary phase. Rice grains of seven cultivars were parboiled in deionised water containing different levels of Fe chelate made by mixing different proportions of Fe sulfate (FeSO₄) with ethylenediaminetetra-acetic acid disodium salt (Na₂EDTA). Adding Fe to the parboiling water resulted in an increased Fe concentration in the most grain, effectively where FeSO₄ and Na₂EDTA were mixed at 2:1 molar ratio (11.16 g Fe per 100 g raw paddy grain). This treatment resulted in Fe concentrations in white rice milled for 60 s and 120 s, which were 20–50 times higher than those in the unfortified milled raw rice grains. The Fe concentrations in milled rice grains were 50–150 mg Fe kg⁻¹ in 60 s milled grains with a slight reduction in 120 s milled grains. Perls Prussian blue staining of the cross section of Fe-fortified parboiled rice grains suggested inward movement of added Fe into the endosperm through the apoplastic pathway in the dorsal region of the rice grain. The retention rates of fortified Fe varied among the different cultivars, possibly due to different physical–chemical properties of the grains. The percentages of soluble fraction of the total Fe were higher than 50% in all cultivars tested, indicating its high bioavailability potential, though it remains to be evaluated. The present findings provided a preliminary basis for further investigation of this innovative technique, before its adoption by parboiled rice industry, such as optimising the levels of Fe addition and industrial process and Fe bioavailability in Fe-fortified-parboiled rice.     

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.     

Milling breakage susceptibility and mechanical properties of parboiled brown rice kernels

Parboiling, a hydrothermal treatment of paddy or brown rice, impacts both head rice yield and texture and nutritional characteristics of cooked rice. Here, milling breakage susceptibility of parboiled brown rice was investigated on both bulk and kernel level. Brown rice was parboiled by soaking at 40, 55 or 65 °C and steaming at 106, 120 or 130 °C. The breakage susceptibility and changes in starch and proteins of bulk samples were related to the properties of individual rice kernels. An increase in milling breakage susceptibility from 1% to 11% corresponded to a decrease in average bending force of individual kernels from 34.9 to 14.6 N. Furthermore, both white bellies and fissured parboiled rice grains were more breakage susceptible. Their average bending force was respectively 14.1 N and 17.6 N compared to an average of 39.6 N for intact parboiled rice grains. Whereas the level of proteins extractable with sodium dodecyl sulfate containing medium had no impact, the degree of starch gelatinization was critical in determining the presence of both white bellies and fissured parboiled rice grains. More in particular, complete starch gelatinization ensured the absence of white bellies and minimized fissuring in the parboiled end-product, thereby decreasing milling breakage susceptibility.     

Folate content in frozen vegetarian ready meals and folate retention after different reheating methods

Folate content and retention were evaluated in 10 different precooked vegetarian ready meals before and after reheating. Folate was quantified using a validated high-performance liquid chromatography method. The only form of folate found was 5-methyltetrahydrofolate. Folate content in thawed ready meals varied from 23 to 81 μg/portion (400 g) on fresh weight basis. Products served with couscous and potatoes contained more folate than products served with rice. Folate retention during reheating was investigated in the microwave oven (900 W/5.5 min), in a saucepan on stove until the food reached 85 °C, and in oven (225 °C/40 min). The true vitamin retention varied for the three investigated portions as follows: on stove (63-93%), microwaving (55-89%) and in oven (50-92%). Our results indicate that folate content in the ready meals prior to reheating, contributed to 6-27% of the recommended intake (300 or 400 μg folate per day). After reheating folate content was significantly (P<0.05) reduced in some meals but were kept constant in others and folate content was reduced to 3-25% of the recommended value. No clear pattern in folate retention between different heating methods was seen. However, the meals with ingredients suggesting high concentrations of antioxidants were less prone to loose folate when heated since the antioxidants probably protected the folates.     

蒸谷晚籼米的制备及其无机元素和农药残留分析

对蒸谷晚籼米加工工艺中的浸泡、汽蒸、干燥三个重要环节进行了实验,并对蒸谷晚籼米中重要无机元素含量和有机磷农药残留进行了分析。实验结果表明,蒸谷晚籼米制备过程中浸泡、汽蒸和干燥的工艺条件为:在70℃水中浸泡2.5h,于100℃下汽蒸30min,先在110℃下干燥3h后,再在60℃下干燥4h。在此条件下生产的蒸谷晚籼米爆腰率为7.6%,远低于普通白米加工的爆腰率;蒸谷后晚籼米总灰分含量比未蒸谷前增加了34.5%,其中Ca、Fe、Zn等重要无机元素的含量明显增加;此外蒸谷晚籼米中未检出有机磷农药,说明蒸谷晚籼米食用安全性高。     

Effect of soaking medium on the physicochemical properties of parboiled glutinous rice of selected Laotian cultivars

The effect of various soaking mediums, viz. water (control), 3% NaCl and 0.2% acetic acid, and without soaking on the physicochemical properties of parboiled selected glutinous (TDK8 and TDK11) and non-glutinous (Doongara) was investigated in the present study. Results showed that the chemistry of soaking had a significant effect on the head rice yield (HRY), grain hardness, crystallinity, color, pasting and thermal properties, textural attributes, and glycemic index of these rice varieties. Soaking with NaCl and acetic acid significantly increased the grain hardness and HRY than control and without soaking treatments. Acetic acid and NaCl soaking significantly affected crystalline regions of starch resulting in reduced crystallinity in X-ray diffraction analysis and thermal endotherms in DSC analysis. NaCl soaking induced swelling of starch granules resulting in high peak and final viscosities. However, acetic acid restricted swelling resulting in reduced peak and final viscosities. NaCl and acetic acid soakings also resulted in increased hardness and adhesiveness of cooked grains than normal water soaked and un-soaked parboiled rice samples. Interestingly, change in textural attributes was prominent in parboiled glutinous rice. The color difference value for fresh parboiled samples was significantly lower for acetic acid soaked samples compared to NaCl soaked and un-soaked samples probably due to bleaching effect of acetic acid. Moreover, parboiling also resulted in significant reduction in glycemic index of glutinous rice. These findings revealed the potential application of parboiling with modified soaking techniques to improve the grain quality.     

Low folate content in gluten-free cereal products and their main ingredients

Folate content in some gluten-free cereal products and their main ingredients was determined using a validated method based on reversed-phase high performance liquid chromatography (HPLC) with fluorescence and diode array detection. The main folate forms found in gluten-free products were 5-methyl-tetrahydrofolate and tetrahydrofolate. Starches and low protein flours commonly used as main components in gluten-free products appeared to be poor folate sources with folate content ?6 μg/100 g fresh weight. Folate content in gluten-free breads was higher (15.1–35.9 μg folate/100 g fresh weight) due to use of bakery yeast which is a rich folate source. Overall, folate content in gluten-free products was lower than in their gluten-containing counterparts. Therefore, fortification of gluten-free products with folic acid or enrichment of these products with nutrient-dense fractions of cereals naturally free from gluten (such as buckwheat, quinoa, amaranth or millet) can be of interest.     

Migration of mycotoxins into rice starchy endosperm during the parboiling process

Considering the occurrence of rice contamination by mycotoxins and the increase in rice consumption, the present work had the objective of assessing the migration of mycotoxins into the starchy endosperm during the parboiling process, as to propose conditions that provide lower contamination levels. The newly harvested rice grain sample was examined for the natural occurrence of mycotoxins (aflatoxin B₁, aflatoxin B₂, deoxynivalenol, ochratoxin A, and zearalenone); only the presence of aflatoxin B₁ was found (17 ng/g). The samples were then artificially contaminated with deoxynivalenol and zearalenone, and the parboiling process was conducted according to a 2³ factorial planning with central point, having as variables the contamination level deoxynivalenol 720, 1440, and 2160 ng/g, and zearalenone 476, 952, and 1428 ng/g the soaking time (4, 5, and 6 h) and autoclave time (15, 22.5, and 30 min). Mycotoxins aflatoxin B₁ (AFA B₁), deoxynivalenol (DON), and zearalenone (ZEA) were confirmed and determined through gas chromatography. Findings showed a lower migration trend for AFA B₁ under 6 h of soaking and 30 min of autoclaving, for DON under 6 h of soaking regardless of the autoclaving time, and for ZEA under 4 h of soaking and 15 min of autoclaving. This information can contribute to the choice of process parameters that limit the migration of these mycotoxins if they happen in the raw material.     

浸泡对早籼稻水分含量及蒸谷米品质的影响

以早籼稻为对象,通过改变浸泡时间和温度,测定分析浸泡条件对早籼稻的水分含量、蒸谷米VB1的含量以及蒸谷米品质的影响。结果显示,浸泡条件对蒸谷米品质影响明显,当浸泡温度为75℃、时间为3.5 h时,蒸谷米的品质最好,VB1含量最高。     

Development of fortified dried broken rice as a complementary food

BACKGROUND: Commercially produced dried broken rice is widely used to prepare complementary foods for Thai infants, and it is both convenient and acceptable to persons from all socioeconomic classes. However, inadequate levels of calcium, iron, thiamine, and folate are common in complementary foods for breastfed infants. OBJECTIVE: We developed dried broken rice fortified with these nutrients at levels recommended by the 2001 guidelines of the World Health Organization. METHODS: The fortification process involved predrying broken rice at 90 degrees C for 1 hour, soaking in a nutrient solution (2:1 ratio of rice to solution), and drying at 70 degrees C for 1 hour and 50 minutes. Calcium lactate or calcium lactate gluconate was the calcium source, and ferrous sulfate, ferrous lactate, or ferric sodium ethylenediaminetetraacetic acid (NaFeEDTA) was the iron source. The vitamin sources were thiamine hydrochloride and folic acid. The product contained 40 mg of calcium, 5.3 mg of iron, 0.08 mg of thiamine, and 11 microg of folate per 20-g serving. RESULTS: Approximately 5% and 10% of calcium and iron, respectively, were lost during processing, with a thiamine loss of approximately 13%, and a folate loss ranging from 17% to 23%. The thiamine loss during accelerated storage (42 degrees C for three months) was not significant (p > .05). CONCLUSIONS: NaFeEDTA was the most appropriate iron fortificant because it provided prolonged product stability and high in vitro dialyzability.     

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.     

蒸谷米浸泡工艺参数初探

通过研究浸泡温度、浸泡时间、浸泡压力对蒸谷米含水量的影响,采用正交试验优化蒸谷米浸泡工艺参数,经过中试试验修正的工艺参数为:浸泡温度55℃、浸泡压力400kPa、浸泡4 h.     

Chemical composition and mineral content of rice bran of two egyptian rice varieties heated by microwave

Two rice varieties, a short grain (Giza 175) and a long grain (Giza 181), were parboiled by soaking in water at 80—85 °C for 1.5 h, then dried in the microwave oven for 3, 5, 6 and 8 min. The effect of such parboiling treatment on the chemical composition and mineral content (Zn, Mn, Cu, Fe, Na, K, Ca, Mg and P) of rice bran were studied. The ash and protein contents of parboiled rice bran varieties decreased with microwave time. The oil extraction increased until 5 min, then decreased after 6 and 8 min microwave time, while acid value of the oils decreased gradually. Each of the mineral components of the brans exhibited different magnitudes of loss, but Mg loss was smaller.     

Parboiling improved oxidative stability of milled white rice during one-year storage

Parboiling was investigated to improve the long-term oxidative stability of milled white rice beyond its current application to paddy brown rice. White rice was steamed at 105°C for 20 min, 120°C for 5 min, or 120°C for 20 min without soaking in water, followed by drying at 70°C for 3 h. During oneyear storage at 25 and 4°C, acid value as an index of oxidative deterioration of rice remained relatively constant in parboiled rice samples, while significant increases were observed in raw rice with higher acid values at 25°C compared with 4°C. This indicates that the parboiling improved the oxidative stability of white rice over the long period of time even at room temperature, therefore it can be an efficient alternative to retard the oxidative deterioration of white rice.