三氯化铁比色法测定植酸含量的研究

大豆及其加工制品用１．２％ＨＣｌ１０％Ｎａ２ＳＯ４试剂提取，１５％ＴＣＡ试剂沉淀酸性蛋白质，０．７５ｍｏｌ／ＬＮａＯＨ调节上清液ｐＨ值到６．０～６．５，用０．３％磺基水杨酸０．０３％ＦｅＣｌ３６Ｈ２Ｏ试剂比色，于可见光５００ｎｍ处检测，并用标准加入法进行定量分析。结果，测定一种样品１０次变异系数为３．３３％，７种样品回收率范围为８９．８８％～１０３．３８％，１５种样品植酸含量为０．５１％～１．９２％。     

应用改良的离子交换树脂法测定食物中的植酸

本文介绍测定食物中植酸含量的改良的离子交换树脂法。该法的最低检出限为0．01mg／g，变异系数为1．20～3．24％，回收率为92．6～104．8％，具有灵敏度高、操作简便、快速、准确等优点。     

粮食、血中痕量硒蛋氨酸的溴化氰——荧光测定法

本法是利用溴化氰与硒蛋氨酸定量生成硒氰酸甲酯（ＣＨ３ＳｅＣＮ），ＣＨ３ＳｅＣＮ经氯仿萃取后用混合酸消化为Ｓｅ（ＩＶ），再用２，３－二氨基萘测定苤硒脑的荧光值推算硒蛋氨酸含量。本法硒蛋氨酸最低检出限为３ｎｇ／ｇ。用硒含量１０～５００ｎｇ的硒蛋氨酸标准进行测定，其回收率为９１．８％～９７．６％，相对偏差为１．９％～６．３％。样品回收率为９２．３％～９６．７％，相对偏差为２．７％～９．０％。硒胱氨酸、硒半胱氨酸、亚硒酸钠和蛋氨酸对测定无干扰。本法的精密度和准确度均较好。     

常见食物中植酸的含量

用离子交换树脂法测定了常见食物中植酸的含量，结果表明．植酸主要存在于豆类、谷类及油料作物的种子中，一般蔬菜及动物性食品中不含可检测到的植酸．同时提请注意，儿童膳食应注意豆类及谷类食物种类的选择．以避免植酸对锌等无机元素吸收利用的影响．     

石墨炉原子吸收法测定汽水中铜

建立了汽水中铜的石墨炉原子吸收光谱分析方法，最低检测浓度为２．１８μｇ／Ｌ，样品测定变异系数为２．２％～８．９％，回收率为９５．２％～１０３．７％，重复实验的变异系数为３．５％～１０．１％。     

固蓝盐B分光光度法测定食品及营养药剂中抗坏血酸含量

以ＥＤＴＡ为掩蔽剂可消除Ｐｂ２＋、Ｃｕ２＋、Ｆｅ３＋等离子的干扰，用空白减差法可消除合成及天然色素等物质的影响。成功地将本法应用于测定蔬菜、水果、饮料及营养药剂中抗坏血酸的含量，回收率为９０．Ｏ％～１０５％，变异系数小于３．０％。本法操作简便、快速、准确，每小时可连续测定２０～３０份试样。     

新银盐分光光度法测定尿中微量砷

尿样采用一次加入混合酸与钼酸钠的催化消化法，使样品前处理简便，速度加快。消化样品中的砷化物用锌加硫酸还原成砷化氢气体，经硝酸银－聚乙烯醇－乙醇溶液吸收和新银盐分光光度法测定。方法测定范围为０．０１５～０．４０ｍｇ／Ｌ，相对标准偏差３．８％～４．７％，最低检测限０．０１３ｍｇ／Ｌ。尿样加标回收率为９０．０％～１０３．２％。尿砷标样测定结果相对误差为７．０％。用本法测定４６名非接触者尿砷浓度范围为０．０１４～０．１０２ｍｇ／Ｌ。     

7～9岁学龄儿童血钙调查

本文报道随机抽查成都市区四所小学１０３名７～９岁的健康儿童血清蛋白质与血钙含量，研究学龄期儿童蛋白质、钙营养状况及血钙水平与生长发育的关系。发现本组儿童血钙低于正常（２．２５ｍｍｏｌ／Ｌ）［１］者６３例（６３／１０３，６１．２％）。其中生长较快组４１例儿童中有３１例血钙值降低。结果表明：成都市区７～９岁的大多数健康儿童的血钙水平低下。生长速度较快者，低钙的发生率更高，提示对学龄儿童应适当补钙，对生长发育较快的儿童尤其应当重视钙的补充。该组儿童的蛋白质供给基本正常     

扩散－电极法测定食品中氟

样品中氟在扩散盒中与硫酸作用生成氟化氢，经扩散吸附在扩散盒的碱膜上。碱膜用缓冲液溶解后，氟化物含量由氟离子选择电极测定。用本法对菜花、菠菜、大米、鱼片干四种样品以及玉米氟样品的氟进行了精密度和准确度试验。相对标准偏差在５％以内，回收率为９０％～１０３％，最小检测量为０．２４μｇ。该法可直接测定含氟量在０．５～１００ｍｇ／ｋｇ（干重）的食品。     

扩散－电极法测定食品中氟

样品中氟在扩散盒中与硫酸作用生成氟化氢，经扩散吸附在扩散盒的碱膜上。碱膜用缓冲液溶解后，氟化物含量由氟离子选择电极测定。用本法对菜花、菠菜、大米、鱼片干四种样品以及玉米氟样品的氟进行了精密度和准确度试验。相对标准偏差在５％以内，回收率为９０％～１０３％，最小检测量为０．２４μｇ。该法可直接测定含氟量在０．５～１００ｍｇ／ｋｇ（干重）的食品。     

Effects of dietary phytate, calcium and magnesium levels on zinc bioavailability to rats

Young rats were fed diets containing 12 mg Zn/kg and varied levels of sodium phytate for 21-day ad libitum feeding periods. In experiment 1, Ca levels were 0.3, 0.5, 0.8 and 1.0%, and phytate:Zn molar ratio varied between 0 and 50. In experiment 2, Ca was maintained at 0.3%, Mg levels were 0.07, 0.22 and 0.37%, and phytate:Zn molar ratios were 0, 10, 20 and 30 at each Mg level. Major response criteria were body weight gain and tibia Zn accumulation. Weight gain was not influenced by Ca level in the absence of phytate or by phytate at 0.3% Ca; it was increasingly depressed as phytate was increased and by each increase in Ca in the presence of phytate. Total tibia Zn content was decreased at the highest Ca level in the absence of phytate; increasing the phytate progressively depressed tibia Zn at all Ca levels. Mg and phytate additions did not affect weight gain. Tibia Zn tended to be depressed by Mg and by phytate but these effects were significant only at the highest levels of the combined additions. These data corroborate and extend previously published findings on Ca and phytate effects on Zn utilization and show bone Zn accumulation to be a more sensitive criterion than weight gain in this connection. They also indicate that Mg exerts a less pronounced effect on Zn utilization in phytate-containing diets than does Ca.     

Chemical and Toxicological Evaluation of Extracts of Fermented Red Acalypha (A Calypha Wilkes/A Na) : A Suggested Tea Adjunct

This study aimed to develop and assess the feasibility of a home-based method to reduce the phytate content of maize and improve zinc bioavailability from maizebased complementary diets in rural Malawi. A method of extracting phytate through the soaking of pounded maize was developed, and found to reduce phytate content to 49% of unrefined maize. An educational program was used to teach the processing method to mothers of children receiving complementary foods in rural Malawian communities. Samples of maize flour prepared by this process by participants were collected and analysed for phytate and zinc content. Of these, 70% of samples were found to be adequately prepared; mean phytate content of these samples was 48% of unprocessed, unrefined maize flour controls. Most participants found the cooked product to have an acceptable taste (99%) and texture (68%), and felt the processing method took little or no extra time (86%) and was culturally acceptable (96%). The phytate and zinc content of the processed maize flour samples analysed from community prepared samples was substituted into the dietary analysis of complementary foods for 9- to 11-month-old children (n = 31). The bioavailability of zinc from the complementary diet would predict an increase from low (24%) to moderate (33%) levels.     

A home-based method to reduce phytate content and increase zinc bioavailability in maize-based complementary diets

This study aimed to develop and assess the feasibility of a home-based method to reduce the phytate content of maize and improve zinc bioavailability from maize-based complementary diets in rural Malawi. A method of extracting phytate through the soaking of pounded maize was developed, and found to reduce phytate content to 49% of unrefined maize. An educational program was used to teach the processing method to mothers of children receiving complementary foods in rural Malawian communities. Samples of maize flour prepared by this process by participants were collected and analysed for phytate and zinc content. Of these, 70% of samples were found to be adequately prepared; mean phytate content of these samples was 48% of unprocessed, unrefined maize flour controls. Most participants found the cooked product to have an acceptable taste (99%) and texture (68%), and felt the processing method took little or no extra time (86%) and was culturally acceptable (96%). The phytate and zinc content of the processed maize flour samples analysed from community prepared samples was substituted into the dietary analysis of complementary foods for 9- to 11-month-old children (n = 31). The bioavailability of zinc from the complementary diet would predict an increase from low (24%) to moderate (33%) levels.     

Zinc absorption from low-phytate hybrids of maize and their wild-type isohybrids

BACKGROUND: Identification of allelic variants in a single gene that determine the phytate content of maize kernels and the subsequent breeding of low-phytate maize have facilitated studies designed to determine quantitatively the effects of maize phytate on the bioavailability of minerals in maize. OBJECTIVE: The objective was to determine the relation between the fractional absorption of zinc (FAZ) and the phytate content and phytate:zinc molar ratios of maize tortillas prepared from hybrids with different phytate contents. DESIGN: Six healthy adults were fed, as the only food for 2 d, maize tortillas prepared from 1 of 2 low-phytate mutants: lpa1-1 (lpa1-1-LP) or Nutridense Low Phytate (ND-LP), which have phytate reductions of approximately 60% and approximately 80%, respectively, compared with their respective wild-type isohybrids. Four additional subjects were fed tortillas prepared from the corresponding wild-type isohybrids (lpa1-1-WT and ND-WT) according to the same study design. Meals were extrinsically labeled with zinc stable isotopes, and FAZ was determined with a dual-isotope-tracer ratio technique. Overall FAZ values were examined in relation to dietary phytate and phytate:zinc molar ratios by using a mixed nonlinear regression model. RESULTS: The mean (+/-SD) FAZ values from tortillas prepared from ND-LP, lpa1-1-LP, lpa1-1-WT, and ND-WT were 0.38 +/- 0.07, 0.28 +/- 0.04, 0.15 +/- 0.07, and 0.13 +/- 0.05, respectively. A negative relation (P < 0.001) was found between FAZ and both dietary phytate and the phytate:zinc molar ratio. The effect of dietary zinc (8-14 mg Zn/d) under these experimental conditions was not significant. CONCLUSIONS: FAZ from maize tortillas is positively related to the extent of phytate reduction achieved with low-phytate hybrids.     

Phytate intake and molar ratios of phytate to zinc, iron and calcium in the diets of people in China

OBJECTIVE: To assess the phytate intake and molar ratios of phytate to calcium, iron and zinc in the diets of people in China. DESIGN: 2002 China Nationwide Nutrition and Health Survey is a cross-sectional nationwide representative survey on nutrition and health. The information on dietary intakes was collected using consecutive 3 days 24 h recall by trained interviewers. SUBJECTS: The data of 68 962 residents aged 2-101 years old from 132 counties were analyzed. RESULTS: The median daily dietary intake of phytate, calcium, iron and zinc were 1186, 338.1, 21.2 and 10.6 mg, respectively. Urban residents consumed less phytate (781 vs 1342 mg/day), more calcium (374.5 vs 324.1 mg/day) and comparable amounts of iron (21.1 vs 21.2 mg/day) and zinc (10.6 vs 10.6 mg/day) than their rural counterparts. A wide variation in phytate intake among residents from six areas was found, ranging from 648 to 1433 mg/day. The median molar ratios of phytate to calcium, iron, zinc and phytate x calcium/zinc were 0.22, 4.88, 11.1 and 89.0, respectively, with a large variation between urban and rural areas. The phytate:zinc molar ratios ranged from 6.2 to 14.2, whereas the phytate x calcium/zinc molar ratios were from 63.7 to 107.2. The proportion of subjects with ratios above the critical values of phytate to iron, phytate to calcium, phytate to zinc and phytate x calcium/zinc were 95.4, 43.7, 23.1 and 8.7%, respectively. All the phytate/mineral ratios of rural residents were higher than that of their urban counterparts. CONCLUSIONS: The dietary phytate intake of people in China was higher than those in Western developed countries and lower than those in developing countries. Phytate may impair the bioavailability of iron, calcium and zinc in the diets of people in China.     

Accessibility of trace metals,co-precipitated with calcium phytate,to soluble chelating agents

This study was designed to show the extent to which some trace metals, i.e. cadmium, copper, lead, and zinc, when co-precipitated in vitro with calcium phytate, are accessible to soluble chelating agents. Accessibility was found to range from 58% to 92%, depending on the metal, temperature, ratio of trace metal to phytate, and concentration of calcium phytate. Zinc was most sensitive to the conditions under which precipitation occurred. Less cadmium, copper, and zinc were accessible when co-precipitated at 37°C compared with co-precipitation at 20°C, and more cadmium and zinc were accessible at lower ratios of trace metal to phytate, than at higher ratios. At the lower concentration of calcium phytate, co-precipitated zinc was less accessible.     

Studies on the phytate: zinc molar contents in diets as a determinant of Zn availability to young rats

1. Studies were carried out in vitro to examine the effects of phytate on the solubility of the trace elements zinc, copper and manganese. Appropriate volumes of a solution of sodium phytate were added to a mineral solution to achieve phytate: Zn values of from 0 : 1 to 45 : 1. In a second series the same values for phytate: Zn were achieved by varying the amount of added Zn at a fixed phytate concentration. 2. In both experiments greater than 85% of the Zn was rendered insoluble at pH 6.5 even at the lowest value for phytate: Zn (5 : 1). The effect of phytate on Zn solubility was greater than effects on Cu or Mn. 3. In a dietary study, rats were offered a semi-synthetic egg-albumin-based diet with added phytate. Two series of diets were prepared, the first had a constant Zn content (18.5 mg Zn/kg) and the amount of sodium phytate varied so as to achieve values for phytate: Zn of from 0 : 1 to 40 : 1 (series 1). In the second series, the same values for phytate: Zn were achieved by adding a fixed amount of phytate (7.4 g phytic acid/kg) while the amount of Zn was varied (series 2). 4. Dietary phytate caused significant reductions in growth rates, plasma Zn concentrations and hair Zn concentrations and greying of the coat at values for phytate: Zn of 15 : 1, 10 : 1, 15 : 1 and 15 : 1, respectively. 5. While phytate was apparently slightly more effective in reducing Zn status when phytate: Zn values were achieved at the lower absolute levels of phytate and zn (series 1 diets), the differences at equivalent phytate: Zn values were small. It was concluded that phytate: Zn values can be used as an indicator of Zn availability from phytate-rich diets. 6. Rats offered three diets containing soya-bean-based textured-vegetable-protein (TVP) exhibited low rates of weight gain compared with rats offered an egg-albumen-based diet of similar Zn content (14.5 mg Zn/kg). Additional Zn supplied in drinking-water (25 mg Zn//l) was without effect on rats consuming the egg-albumin diet but significantly improved the weight gain of rats on the TVP diets. 7. It was concluded that phytate naturally present in TVP behaves similarly to phytate added to an otherwise phytate-free diet and that the reduced availability of Zn in TVP diets can be accounted for entirely by their phytate contents.     

Degradation products of bran phytate formed during digestion in the human small intestine: effect of extrusion cooking on digestibility

To investigate the digestion of phytate in the stomach and small intestine in humans, studies were performed in subjects with established ileostomy. A recently developed high performance liquid chromatography method made it possible to analyze phytate and its degradation products in food and digesta. The digestibility of phytate in raw bran and extruded bran was investigated in seven ileostomy patients. Each subject was studied for two 4-d periods while consuming a constant low fiber diet with the addition of either 54 g/d of a bran-gluten-starch mixture or the corresponding extruded product. During passage through the subject's stomach and small intestine 58%, on average, of the phytate in unprocessed bran was hydrolyzed to inositol penta-, tetra- and triphosphates. When bran was subjected to extrusion cooking, 25% of the inositol hexaphosphate was hydrolyzed to penta- and tetraphosphate and the phytase activity ceased. Essentially no phytate digestion occurred when the ileostomy subjects consumed the extruded product. The reduced digestibility might be due to the lost phytase activity or to formation of indigestible phytate complexes during extrusion cooking.     

Blood lipid and oxidative stress responses to soy protein with isoflavones and phytic acid in postmenopausal women

BACKGROUND: Postmenopausal women are at risk of cardiovascular disease (CVD) as a result of unfavorable blood lipid profiles and increased oxidative stress. Soy protein consumption may help protect against these risk factors. OBJECTIVE: Our objective was to ascertain the effect of the soy protein components isoflavones and phytate on CVD risk in postmenopausal women. DESIGN: In a double-blind 6-wk study, 55 postmenopausal women were randomly assigned to 1 of 4 treatments with soy protein (40 g/d) isolate (SPI): low phytate/low isoflavone (LP/LI); normal phytate/low isoflavone (NP/LI); low phytate/normal isoflavone (LP/NI); or normal phytate/normal isoflavone (NP/NI). Blood lipids (total, LDL, and HDL cholesterol and triacylglycerol) and oxidative stress indexes (protein carbonyls, oxidized LDLs, and 8-iso-prostaglandin-F(2alpha)) were measured at baseline and 6 wk. RESULTS: The oxidative stress indexes were not significantly affected by either phytate or isoflavones. Phytate treatment had a minimal but nonsignificant effect in reducing protein carbonyls and 8-iso-prostaglandin-F(2alpha); the reductions were 6-8% and 4-6% in the NP/LI and NP/NI groups and 1-4% and 3-4% in the LP/LI and LP/NI groups, respectively. Similarly, circulating lipids were not significantly affected by either phytate or isoflavones. The decline in total (6%-7% compared with 2%-4%) and LDL (10%-11% compared with 3%-7%) cholesterol did not differ significantly between the normal- and low-isoflavone groups, respectively. CONCLUSION: In postmenopausal women, neither phytate nor isoflavones in SPI have a significant effect of reducing oxidative damage or favorably altering blood lipids.     

A stable isotope study of copper absorption in young men: effect of phytate and alpha-cellulose

A sixty-three day study was conducted with young men confined to a metabolic unit to study the effects of alpha-cellulose and phytate on copper absorption. Copper absorption was determined with 65Cu, a stable isotope of copper, during each of 3 dietary treatments (basal diet, basal diet + alpha-cellulose, or basal diet + phytate). The addition of alpha-cellulose or phytate to the basal diet did not affect copper absorption. Average copper absorption was 35.0% from the basal diet, 34.1% from the diet with 0.5 g alpha-cellulose per kg body weight added, and 31.4% from the diet with 2.34 g of phytate as sodium phytate added to the diet. Copper absorption was significantly different between subjects and averaged 44.1%, 26.8%, 33.4%, and 29.5% in individual subjects. The results suggest that high levels of either alpha-cellulose or phytate do not have marked effects on copper absorption, but copper absorption differs between individuals.