Effect of wheat pearling on flour phytase activity, phytic acid, iron, and zinc content

This study examined the effect of wheat pearling on distribution of phytase, phytic acid, iron, and zinc in wheat fractions derived from pearling and roller milling. Grains of four wheat varieties were first pearled by a rice polisher at four levels, i.e. non-pearling (unpearled), 5% pearling (∼5% of the original sample weight was pearled), 10% pearling, and 15% pearling, to produce pearling fines (PF) and pearled grains. The unpearled and pearled grains were then milled through a Bühler MLU-202 laboratory mill, producing eight milling fractions. Results showed that pearling had a positive effect on flour yield, which may be attributed to the reduced yield of coarse bran and the improved yield of first and second reduction fractions. PF had high levels of all the four components, indicating that they could be a valuable source of iron and zinc. In addition, the differences between flours from the pearled and unpearled wheat were slight in terms of these four components.     

Effects of soaking, germination and fermentation on phytic acid, total and in vitro soluble zinc in brown rice

Rice is an important staple food in Asian countries. In rural areas it is also a major source of micronutrients. Unfortunately, the bioavailability of minerals, e.g. zinc from rice, is low because it is present as an insoluble complex with food components such as phytic acid. We investigated the effects of soaking, germination and fermentation with an aim to reduce the content of phytic acid, while maintaining sufficient levels of zinc, in the expectation of increasing its bioavailability. Fermentation treatments were most effective in decreasing phytic acid (56–96% removal), followed by soaking at 10 °C after preheating (42–59%). Steeping of intact kernels for 24 h at 25 °C had the least effect on phytic acid removal (<20%). With increased germination periods at 30 °C, phytic acid removal progressed from 4% to 60%. Most wet processing procedures, except soaking after wet preheating, caused a loss of dry mass and zinc (1–20%). In vitro solubility, as a percentage of total zinc in soaked rice, was significantly higher than in untreated brown rice while, in steeped brown rice, it was lower (p < 0.05). Fermentation and germination did not have significant effects on the solubility of zinc. The expected improvement due to lower phytic acid levels was not confirmed by increasing levels of in vitro soluble zinc. This may result from zinc complexation to other food components.     

植酸酶的研究与应用

对植酸酶的理化特性、功能、应用和亟待解决的问题进行了研究。     

Effect of phytic acid degradation by soaking and exogenous phytase on the bioavailability of magnesium and zinc from Pisum sativum, L.

The effect of dephytinization of Pisum sativum, L. flour on the bioavailability of Mg and Zn was evaluated in growing rats. Processing of legume flours under optimal conditions for phytase activity (pH 5.5, 37 °C, 60 min) and subsequent removal of the soaking solution led to a 42 and 61% reduction in the content of Mg and Zn, respectively. Treatment with phytase led to an additional reduction in the concentration of the above-mentioned seed flour components, compared to the raw pea flour (69% and 74% for Mg and Zn, respectively). The considerable reduction in the content of inositol phosphates with high degree of phosphorylation attained under both processing conditions did not affect the digestive utilization of Mg, whereas the metabolic utilization of this mineral increased significantly. The digestive and metabolic utilization of Zn increased significantly in response to both processes assayed, reaching the highest values in the experimental group that was fed the phytase-treated pea flour diet. The amount of Mg retained by the experimental animals was reflected in the content of this mineral in the different tissues studied (femur, sternum, kidney, and heart), whereas no correlation was found in the case of Zn.     

Effects of various phytase sources on phytic acid content,mineral extractability and protein digestibility of tarhana

Changes in phytic acid (PA), HCl-extractability (HCl-E) of some minerals and in vitro protein digestibility (IVPD) during the production of tarhana prepared with the addition of different phytase sources (bakers’ yeast, barley malt flour and microbial phytase) were investigated. PA content of tarhana decreased significantly (p < 0.01) after addition of the yeast, malt and phytase. With respect to wheat flour used as raw material, PA content of tarhana decreased by 95.3%. After tarhana production, average values of HCl-E of Ca, Mg, Zn and K, and also IVPD of tarhana increased up to 80.2%, 86.4%, 73.9% and 92.6%, and 91.9%, respectively. Significant negative correlation coefficients were found between the PA and HCl-E of the minerals, and also IVPD. Tarhana production processes, including fermentation, drying and grinding, were able to remove the antinutritional effects of PA. Each one of the phytase sources used alone decreased the PA content to a limited extend. The results show that tarhana has good potential in the total amounts and bioavailability of the minerals and proteins.     

植酸酶产生菌产酶条件研究

经采样、分离，筛选出多株植酸酶产生菌；并将其中产酶水平较高的黑曲霉（Ａｓｐ．ｎｉｇｅｒ７０）和无花果曲霉（Ａｓｐ．ｆｉｃｕｕｍＮＲＲＬ３１３５）用固态培养法进行了产植酸酶条件的对比研究。     

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.     

Effect of heat treatments on the phytic acid content of maize products

Processing of maize (Zea mays L fresh and dry) for the production of various traditional products results in the loss of phytic acid. Fresh mature corn contains less phytic acid (1·71 g kg^?1) than dry corn (7·15–7.60 g kg^?1). The loss of phytic acid varies from 18·1 to 46·7% for fresh maize and from 11·5 to 52·6% for dry maize respectively among the heat treatments given. From a nutritional viewpoint, consumption of maize as chapati and after roasting in a sand bath or on charcoal will improve the availability of minerals.     

Phytase activity and degradation of phytic acid during rye bread making

Changes in phytic acid content, activity of phytase and α-amylase in rye breads were determined during rye bread making. The activity of phytase is highest in grain and flour whereas the activity in the sourdoughs is almost the half of the activity in the flour. The activity was unchanged in the dough after mixing and proofing. Degradation of phytic acid (IP6) into lower inositol phosphates and free phosphate is almost completed during the production of rye bread with long fermentation time whereas the degradation is less completed when whole grains are included in the recipe. In rye bread made from milled rye (DB00), 99% of IP6 is degraded and IP3 becomes the dominating inositol phosphate in this bread type presumably resulting in a high level of bioavailable minerals. In rye bread made with 30% grains (SB30), 94% of the IP6 content was reduced with IP4 and IP3 being the dominating lower inositol phosphates. In rye bread made with 50% whole grains (KB50) the degradation of IP6 was 82%, and the three inositol phosphates IP5, IP4 and IP3 were found in equal amount in this bread type. Due to significant amounts of phytic acid and remaining IP5, some of the minerals might not be available for human absorption after consumption of this bread type.     

酶法水解大豆中植酸的研究

探讨了植酸酶在不同酶解条件(pH值、温度、时间、加酶量)下对大豆抗营养因子——植酸盐的水解作用。研究结果表明,适宜的酶解条件为:温度37℃,酶加量3750U/kg豆粉,酶解时间45min,pH值6.1。在此条件下,酶解后每克大豆粉游离无机磷的含量增加208μmol(约占总磷的66.4%);可溶性金属离子Zn2 、Ca2 、Mg2 和Fe2 的释放量分别达到73.0%、69.6%、62.9%和23.7%;植酸的降解率达到56.6%。结论:酶法水解大豆中植酸可以显著提高大豆的营养效价。     

植酸对白菜乳酸发酵过程中微生物生长代谢及亚硝酸盐积累影响初探

白菜乳酸发酵过程中添加不同浓度的植酸，研究其对发酵过程中细菌总数、pH值、亚硝酸盐含量变化的影响。结果表明，添加植酸对酸及上述三个指标影响明显。     

Iron,zinc and phytic acid content of selected rice varieties from China

Rice is the major Chinese staple food (per capita approx 250 g day^?1) and, as such, is an important source of essential minerals. However, due to a number of factors the bio‐availability of these minerals is limited. In this study, the variation of phytic acid (PA), iron (Fe) and zinc (Zn) levels in 56 varieties of Chinese rice was investigated. The samples included in this study were collected in proportion to the importance of the rice‐growing regions in China. Fe levels showed the biggest variation (9–45 mg kg^?1) and were not related with PA content or grain shape although growing locations were identified yielding higher (25.2 mg kg^?1) and lower (14.2 mg kg^?1) Fe levels. Zn showed a moderate variability (13–39 mg kg^?1), which was narrower than for Fe, while broader than for PA (7.2–11.9 g kg^?1). Zn content is correlated (R² = 0.5; P < 0.01) with PA content, and shows a relation with growing region and kernel shape. Variation of PA content is the least among the three components. Molar ratios of PA to Fe and Zn ranged from 15 to 105 and 27 to 67, respectively. The results of the mineral contents and PA content can be interpreted in terms of expected bio‐availability. This study shows that the mineral bio‐availability of Chinese rice varieties will be <4%. Despite the variation in mineral contents, in all cases the PA present is expected to render most mineral present unavailable. We conclude that there is scope for optimisation of mineral contents of rice by matching suitable varieties and growing regions, and that rice products require processing that retains minerals but results in thorough dephytinisation. Copyright © 2006 Society of Chemical Industry     

Quantitative analysis and free-radical-scavenging activity of chlorophyll,phytic acid,and condensed tannins in canola

Seeds, meals and cakes of 27 canola (Brassica napus L.) varieties and one Indian mustard (Brassica juncea L.) sample were investigated for chlorophyll, phytic acid and condensed tannin content. The DPPH free-radical-scavenging potential of minor components was also investigated. Chlorophyll contents ranged from 2.57 to 16.95, 5.38 to 8.52 and 1.15 to 6.19 mg/kg for canola seeds, cakes and meals, respectively. A positive correlation (R² = 0.99) was found between the oil and chlorophyll contents. Phytic acid contents were 2.16–3.75, 3.15–3.28 and 2.07–3.62 g/100 g for canola seeds, cakes and meals, respectively. The corresponding values for condensed tannins were 0.46–1.53, 1.12–1.32 and 0.59–1.19 g/100 g. These components showed good DPPH-scavenging activity with phytic acid having the highest effect followed by condensed tannins and chlorophyll. This information will be helpful in selecting varieties with appropriate content of these components for further application.     

Effect of phytase treatment on iron bioavailability in faba bean (Vicia faba L.) flour

The effect of dephytinisation, using an exogenous phytase under optimal conditions (pH 5.5, 37 °C), and subsequent removal of the soaking solution after processing, on the bioavailability of iron from faba bean (Vicia faba L.) flour was studied. Soaking of the faba bean flour led to a considerable reduction in the content of iron (39%), whereas a lower reduction in iron content (10%), was obtained after additional treatment with phytase, than in the soaked faba bean flour. The digestive utilisation of iron from the raw and soaked faba bean flours by growing rats was negligible, but increased significantly as a result of phytase treatment. The low iron absorption obtained for the former two treatments, during an experimental period of 10 days, was not reflected in any of the haematological indices (red blood count, haemoglobin, haematocrit) or tissues (femur, heart, kidney) studied, with the exception of the sternum. The latter appears to be a useful indicator of iron bioavailability.     

In vitro analysis of binding capacities of calcium to phytic acid in different food samples

The present work was performed to study the role which plays phytic acid in calcium binding, and to determine the calcium binding capacities in different foods, using in vitro extractions. Different food samples (soybeans, oats, chickpea, rice flour, and corn semolina) were extracted for 4 h at 37 °C using artificial simulated gastrointestinal juice (pepsin) at pH=2. The total calcium and phytic acid concentrations were determined by AAS and capillary electrophoresis, respectively, at pH=2 and pH=8 after neutralisation with a sodium hydroxide solution (3 M). Having determined the binding capacities of calcium in each food, we then use these results to estimate the fraction of calcium available for resorption during the process of digestion, when food moves from the acid pH of the stomach to the alkaline milieu of the intestines. The results obtained for the foods analysed show that the capacity of calcium to bind to phytic acid exhibits a clear pH dependence. The calculated calcium binding capacities, or the molar ratio of calcium to phytic acid in the in vitro extracted foods, varies from 3 mol calcium per mol phytic acid for soybean, chickpea and oats, to 2 mol calcium per mol phytic acid for rice, to1 mol calcium per mol phytic acid in corn semolina. Calcium may bind to one or more of the phosphate groups of phytic acid. Previous studies have demonstrated that phytic acid has the ability to bind minerals, proteins, and starch, and have then considered it as an inhibitor to the bioavailability of minerals and trace elements.     

The effects of phytic acid on the Maillard reaction and the formation of acrylamide

Phytic acid, myo-inositol hexaphosphoric acid, exists in substantial (1–5%) amounts in edible plant seeds. In this study the effects of phytic acid on the Maillard reaction and the formation of acrylamide were investigated. Both phytic acid and phosphate enhanced browning in glucose/β-alanine system, but phytic acid was less effective than phosphate. Higher pH favoured the catalytic activities for both of them. The influence of the types of sugar and amino acid on the reaction was also examined. Browning was suppressed by the addition of calcium and magnesium ions, but an additive effect was observed for ferrous ions and phytic acid in glucose/β-alanine solution at pH 8.0. Both phytic acid and phosphate promoted the polymerisation of the reaction intermediates. The kinetics of Maillard reaction was first-ordered reaction in the presence of phytic acid. Phytic acid was less effective than phosphate in the formation of acrylamide. When potato slices were treated with sodium phytate and calcium chloride successively, the formation of acrylamide was greatly suppressed.     

浸泡处理对方便米饭品质的影响

对浸泡处理对方便米饭品质的影响作了初步研究。结果表明，用０．０４％氢氧化钠、０．８％柠檬酸、０．５％乙酸、１．０％乙醇、０．４％柠檬酸和０．５％乙醇混合液浸泡大米，均能改善成品方便米饭的色泽、香味、口感，提高成品的复水速度，其中用０．４％柠檬酸和０．５％乙醇混合液浸泡大米后所制得的成品复水后，感官评分最高（３４．８）且有较高的复水速度（２４０ｍｇ／ｇ·ｍｉｎ）和复水率（２．６２）。     

植酸在啤酒酿造中的应用

植酸具有广泛的用途和较高的经济价值，可以应用于食品，医药，日用化工，金属加工，纺织工业，高分子工业，塑料加工等方面，在我国植酸的应用范围还比较小，在很多领域有待开发。介绍了植酸在啤酒酿造中的应用。