Efficacy of Pork Loin as a Source of Zinc and Effect of Added Cysteine on Zinc Bioavailability

Based upon Zn uptake in chick tibia, Zn in raw and cooked pork loin was about 40% more bioavailable than that in ZnSO₄-H₂O. Neither roasting nor braising affected Zn bioavailability in the loin preparations. Adding 0.40% cysteine to diets containing ZnSO₄ improved Zn bioavailability by 73%. Pork loin is an excellent source of bioavailable Zn, and SH-containing compounds such as cysteine and glutathione that are present in meat may contribute to enhanced gut absorption of meat-source Zn.     

Bioavailability of new synthesised glucooligosaccharides in the intestinal tract of gnotobiotic rats

Using germ-free rats and previously germ-free rats inoculated with a complex human flora (heteroxenic rats), the digestibility of new glucooligosaccharides (GOS) and the effect of the digestive flora on their fermentation were studied. The GOS were synthesized using a glucosyltransferase reaction and were composed of a mixture of mono- to heptasaccharides (degree of polymerisation (DP) from 1 to 7), with α-1,6 and α-1,2 linkages. In germ-free rats, two diets containing GOS (20 g kg^?1 diet and 40 g kg^?1 diet) were compared to a control diet containing sucrose. The extent of GOS digestion was about 20% and the major component, DP 5, was almost fully resistant to the action of endogenous enzymes. In heteroxenic rats, only GOS (20 g kg^?1 diet) was compared to the control diet. Gaseous H₂ and CH₄ excretions measured in a respiratory chamber significantly increased by GOS fermentation (1.8 and 2.9 times, respectively, P < 0.001). As compared to the control group, there were no modifications of the pH, short-chain fatty acids (SCFA), and lactic acid concentrations in the caecum of rats fed with the GOS diet, but there were changes of the SCFA profile, ie butyric, isobutyric and isovaleric acid proportions significantly decreased (P < 0.01), whereas the caproic acid proportion increased (P < 0.05). GOS appeared to be completely fermented. Changes in the gaseous excretion and in the SCFA profile suggest that the intake of a low amount of this new synthetised GOS led to some decrease in the proteolytic activity and in an enhancement of the glycolytic fermentation.     

Bioavailability of a bilberry anthocyanin extract and its impact on plasma antioxidant capacity in rats

Anthocyanins are secondary metabolites from the flavonoid family, frequently found in fruits and vegetables. They have been shown to possess beneficial health effects and various in vitro assays have highlighted their powerful antioxidant capacity. However, little is known about their metabolism after digestion and their antioxidant potency in vivo. The aim of this work was to evaluate anthocyanin bioavailability and to determine the impact of an anthocyanin‐rich diet on plasma antioxidant status in rats. Animals were fed for 8 days with a vitamin E‐deficient diet supplemented with a bilberry (Vaccinium myrtillus L.) anthocyanin extract providing daily 1.43 mmol anthocyanins kg^?1 body weight. An anthocyanin‐enriched diet significantly enhanced the plasma antioxidant capacity compared with a control diet (P < 0.0001). Moreover, anthocyanins were recovered in urine in the intact glycosidic forms in addition to unknown metabolites. Urinary excretion of bilberry anthocyanins and their metabolites was 0.71 ± 0.08 µmol per 24 h (ie 0.22% of the ingested dose). Anthocyanins and their corresponding aglycones were detected in caecal contents. After a single oral administration of the bilberry extract, native anthocyanins quickly (30 min) appeared in plasma. Hence, in spite of a low bioavailability, bilberry anthocyanin extract consumption has a positive effect on plasma antioxidant capacity. Copyright © 2005 Society of Chemical Industry     

Potential for increasing the amounts of bioavailable zinc in dry beans (Phaseolus vulgaris L) through plant breeding

A whole‐body radioassay procedure was used to assess the bioavailability to rats of zinc (Zn) in seeds of 18 genotypes of beans (Phaseolus vulgaris L) that were grown hydroponically. Dry beans that were labelled intrinsically with ⁶⁵Zn were added to test meals fed to rats that were marginally Zn‐deficient. The amount of Zn in the seeds varied between genotypes and ranged from 26.7 to 62.4 µg g^?1 (from 0.41 to 0.95 µmol g^?1) dry weight (DW). Similarly, the amount of iron (Fe) in the beans varied nearly twofold (from 52.3 to 96.3 µg g^?1 DW), and Zn and Fe concentrations were positively correlated. Concentrations of myo‐inositolhexaphosphate (IP6) plus myo‐inositolpentaphosphate (IP5) varied from 18.1 to 27.3 µmol g^?1 DW. Cultivars with white‐coloured seeds contained relatively small amounts of tannins varying from 0.12 to 0.16 mg g^?1 DW (determined as catechin equivalents) compared to those with coloured seed coats (up to 2.58 mg g^?1 DW). All rats readily ate the test meals so that Zn intake varied directly with seed‐Zn concentration. As indicated by ⁶⁵Zn absorption, the bioavailability to rats of Zn in the seeds varied between genotypes and ranged from about 78 to 95% of the total Zn in the seeds. The bioavailability of Zn to marginally Zn‐deficient rats was not affected markedly by either IP5 + IP6 or tannin in the dry beans. These results demonstrate that the concentration of Zn in dry beans can be increased through traditional plant‐breeding techniques and that this may result in significant increases in the amount of bioavailable Zn in the beans. Increasing the amount of Zn in beans may contribute significantly to improving the Zn status of individuals dependent on beans as a staple food. © 2002 Society of Chemical Industry     

Cooking Temperature of Turkey Ham Affects Lactate Dehydrogenase, Serum Albumin and Immunoglobulin G as Determined by ELISA

Protein indicators were identified and enzyme-linked immunosorbent assays (ELISA) were developed for verifying endpoint processing temperatures (EPT) of turkey ham. Lactate dehydrogenase (LDH), immunoglobulin G (IgG), and turkey serum albumin (TSA) were identified by electrophoresis, Western blotting or enzyme assays as potential markers in turkey ham processed between 66.9 and 73.9°C. TSA and IgG were quantified using indirect competitive ELISAs, and LDH was quantified by a sandwich ELISA. The concentration of all indicators decreased as processing temperatures were increased. At 73.8°C, 9.3 μg TSA and, 0.5 μg LDH or TSA were detected/g meat. At the USDA required EPT of 68.3°C, residual concentrations of 1221 ng IgG/g meat, 330 ng LDH/g meat and 51,852 ng TSA/g meat were detected.     

喷射蒸煮处理对米糠蛋白功能特性及体外消化性的影响

研究了喷射蒸煮(HTC)处理对天然米糠蛋白(RBP)与热稳定米糠蛋白(HRBP)提取的影响,并对蛋白的粒度、亚基组成、接枝度、功能性及体外消化性能进行表征。研究表明:HTC处理能显著提高RBP与HRBP的得率(分别从44.9%与14.8%增加到52.2%与44.5%),但对蛋白的纯度没有显著影响。HTC处理后RBP与HRBP的粒度分别从73.6 nm与149.1 nm降低到46.8 nm与96.6 nm,同时生成接枝度28.0%与9.4%的糖基化产物。SDS-PAGE电泳图谱表明,处理后的米糠蛋白生成高分子质量的蛋白聚集体与糖基化产物。HTC处理更有利于HRBP功能性与消化性的提高,且HRBP具有RBP类似的溶解度曲线、起泡能力、泡沫稳定性与良好的乳化能力与消化能力,尽管该处理降低了天然米糠蛋白的消化性。     

蛋鸡对叶黄素和叶黄素酯生物利用率的比较

将40只产蛋后期海兰灰商品蛋鸡,随机分为2个组,用低叶黄素饲粮耗空2周后,分别饲喂在基础日粮中添加叶黄素酯和游离叶黄素的叶黄素强化日粮,两组均含有效叶黄素15 mg/kg.结果显示,蛋鸡采食叶黄素后,血浆中叶黄素含量提高显著(P＜0.05),但两组在第3、7和12 d时血浆叶黄素含量差异不显著(P＞0.05).     

Protein Efficiency Ratio and Amounts of Selected Nutrients in Mechanically Deboned Spent Layer Meat

Three types of mechanically deboned spent layer meat (MDSL) were found to have adjusted protein efficiency ratios (PER) equivalent or superior to a standard (casein) diet. These same materials proved to be good sources of calcium, iron and zinc. Percentage protein ranged from 15.39 for MDSL from whole spent layers to 16.55 for MDSL from spent layer frames with wings. Fat levels were highest for whole birds (20.41%) and lowest for frames without skin (16.84%). High levels of unsaturated fatty acids were found to be associated with these products.     

Bioaccessible Iron and Zinc in Native and Fortified Enzyme Hydrolyzed Casein and Soya Protein Matrices

Casein and soybean are superior quality proteins; however, these are known to inhibit mineral absorption. These investigations were aimed at enzymatic modification of these proteins and to study their effect on mineral bioaccessibility. Casein and soybean proteins were hydrolyzed with alcalase and trypsin individually under optimum conditions. The protein hydrolysates, prepared with different degrees of hydrolysis, were freeze dried, fortified with either iron or zinc and analyzed for bioaccessible minerals in vitro. Proteolytic hydrolysis enhanced the bioaccessibility of iron and zinc in proportion to the degree of hydrolysis. Tryptic hydrolysis enhanced the bioaccessible iron from 1–4% in casein and from 1.3–3.3% in soybean. Alcalase hydrolysis showed a comparatively higher enhancement with both the proteins. Tryptic hydrolysis enhanced zinc bioaccessibity by 3-fold in casein and alcalase hydrolysis enhanced by 2- to 2.5-fold. In soybean, dephytinization showed a synergistic effect. In conclusion, enzymatic hydrolysis of proteins looks promising for enhancing bioaccessibility of minerals in protein matrices.     

Effect of zinc source and dietary level on zinc metabolism in Holstein calves

Forty-eight Holstein male calves were stratified by origin and body weight and randomly assigned to one of 4 treatment groups. Dietary treatments were administered in 2 phases. In phase 1, treatment groups received the basal diet with no supplemental Zn (control), basal diet plus 20 mg of Zn/kg of DM as ZnSO4 or Zn proteinate (ZnProt), or basal diet plus 20 mg of Zn/kg of DM with 50% of the Zn supplied from each source (ZnM) for 98 d. In phase 2, calves continued to receive the same Zn source fed in phase 1; however, half of the calves in each treatment group were randomly selected to receive 500 mg of Zn/kg of DM (HiZnSO4, HiZnProt, HiZnM) for 14 d. Gain, feed intake, and feed efficiency of calves were not affected by treatment in either phase of the experiment. Treatment had no affect on plasma Zn concentration or alkaline phosphatase activity in phase 1, but liver Zn concentration was greater in calves fed ZnSO4 than those fed ZnProt. In phase 2, plasma Zn was greater in calves fed HiZnProt and HiZnM than in those fed HiZnSO4. Liver Zn was greater in calves fed HiZnProt than in those fed HiZnSO4. Duodenal Zn concentrations were greater in calves supplemented with HiZnProt and HiZnM than those supplemented with HiZnSO4. Liver metallothionein was greater in calves that received 500 mg of Zn/kg than in calves that received 20 mg of Zn/ kg, but was not affected by Zn source. Calves fed HiZnProt and HiZnM had greater kidney Zn concentrations than those fed HiZnSO4. Heart, spleen, testicular, and bone Zn concentrations were not affected by Zn source. Hoof wall samples contained nearly 3-fold greater Zn concentrations than hoof sole. Calves fed ZnSO4 had greater Zn concentration in hoof wall samples than those fed ZnM. Hoof sole Zn concentration was not affected by Zn source or concentration. Plasma and tissue Zn concentrations at harvest were generally similar in calves supplemented with 20 mg of Zn/kg from ZnSO4 or ZnProt. However, when supplemented at 500 mg of Zn/kg, ZnProt was absorbed to a greater extent than ZnSO4, based on higher plasma, liver, duodenal, and kidney Zn concentrations.     

富铁锌苜蓿芽对小鼠血液和脏器铁锌积累的研究

研究富铁锌苜蓿芽对小鼠生长发育,毒性及血液和脏器铁锌含量及吸收率。通过用试验培育出的苜蓿芽和用无机盐硫酸亚铁和硫酸锌作为对照饲喂昆明种小白鼠,考察各个剂量组对小鼠生长发育,死亡率及铁锌富集规律的影响。结果表明:苜蓿芽组比无机盐组更能促进小鼠的生长发育,随剂量的增加,小白鼠生长逐渐减慢。苜蓿芽组比无机盐组对小鼠毒害作用小,铁和锌元素吸收率高,但随着剂量的增加,吸收率降低。     

锌离子在啤酒酿造中的作用与控制

啤酒中锌离子来源于麦芽、大米、酿造用水、酒花。Zn^2 在啤酒酿造过程中可起到催化荆作用,与氨基酸结合形成Zn-氨基酸螯合物。在啤酒酿造过程中,可激活酶提高酶的作用;促进糖化、发酵;促进蛋白质合成及其稳定性;缓解某金属离子的毒性作用,促进挥发物质的产生和双乙酰的还原,缩短发酵时间,提高啤酒质量;但含量过量会使啤酒非生物稳定性降低,影响啤酒质量。通过对糖化过程和发酵过程的控制,可降低醪液pH值。加入少量小麦芽,加入适量ZnCl2,ZnSO4及酵母营养盐等,可实现对Zn^2 的有效控制,达到最佳酿造浓度。     

Effect of thermal processing on available lysine,thiamine and riboflavin content in soymilk

Soymilk was heated over a range of temperatures (90–140°C) and times (0–6 h). The available lysine, thiamine and riboflavin content of the soymilk samples were determined. There was no significant change in available lysine during a 3 h heating period at 95°C. At elevated temperatures of 120 and 140°C, optimum heat processed soymilk gave higher measured values of available lysine than did soymilk processed at 95°C. Prolonged heating at 120 and 140°C caused a decline in available lysine. Kinetic data on the thermal degradation of thiamine and riboflavin in soymilk were fitted with first-order kinetics and the kinetic parameters were determined. © 1998 SCI.     

Bioavailability of vitamin D from fortified process cheese and effects on vitamin D status in the elderly

We conducted 2 studies to determine the effect of vitamin D-fortified cheese on vitamin D status and the bioavailability of vitamin D in cheese. The first study was designed to determine the effect of 2 mo of daily consumption of vitamin D₃-fortified (600 IU/d) process cheese on serum 25-hydroxyvitamin D (25-OHD), parathyroid hormone (PTH), and osteocalcin (OC) concentrations among 100 older (≥60 yr) men and women. Participants were randomized to receive vitamin D-fortified cheese, nonfortified cheese, or no cheese. Serum levels of 25-OHD, PTH, and OC were measured at the beginning and end of the study. There were no differences in 25-OHD, PTH, or OC after 2 mo of fortified cheese intake. The vitamin D-fortified cheese group had a greater decrease in 25-OHD than other groups, due to higher baseline 25-OHD. A second study was conducted to determine whether the bioavailability of vitamin D₂ in cheese (delivering 5880 IU of vitamin D₂/56.7-g serving) and water (delivering 32,750 IU/250 mL) is similar and whether absorption differs between younger and older adults. The second study was a crossover trial involving 2 groups of 4 participants each (younger and older group) that received single acute feedings of either vitamin D₂-fortified cheese or water. Serial blood measurements were taken over 24 h following the acute feeding. Peak serum vitamin D and area under the curve were similar between younger (23 to 50 yr) and older (72 to 84 yr) adults, and vitamin D₂ was absorbed more efficiently from cheese than from water. These studies demonstrated that vitamin D in fortified process cheese is bioavailable, and that young and older adults have similar absorption. Among older individuals, consuming 600 IU of vitamin D₃ daily from cheese for 2 mo was insufficient to increase serum 25-OHD during limited sunlight exposure.     

茶叶中的硒、锌元素营养价值的研究现状

随着经济的发展和生活水平的提高,人们对茶品质的要求越来越高。本文对硒、锌元素的营养价值以及如何提高茶叶中硒、锌元素含量进行了综述,讨论了茶叶中硒、锌的研究现状,对今后的天然茶叶培植和人工添加硒、锌营养元素以及提高茶叶经济附加值有一定借鉴意义。     

Estimation of the Bioavailability of Iron and Phosphorus in Cereals using a Dynamic In Vitro Gastrointestinal Model

A recently developed in vitro gastrointestinal model was evaluated for the estimation of the bioavailability of Fe and phosphorus and its correlation with biovailability in vivo. In vitro experiments were carried out without and with phytase supplementation (750 FTU kg^-1 feed) using rapeseed, sunflowerseed, wholewheat and white wheat flour. Phytase addition during in vitro digestion of rapeseed and sunflowerseed resulted in markedly increased dialysability of iron (67% and 20%) and phosphorus (31% and 66%). The release of free phosphorus during digestion of wholewheat and white wheat flour in the in vitro gastrointestinal model was observed to be correlated with the endogenous phytase activity in wheat. Comparison with different in vivo studies revealed that the in vitro gastrointestinal model could be used for a relative estimation of the bioavailability of Fe and phosphorus. © 1997 SCI.     

Kinetics of sensory quality changes in soymilk during thermal processing,by parametric and non‐parametric data analyses

Soymilk was subjected to various heat treatments at 90, 120 and 140 °C for various lengths of time. The colour and flavour of the soymilk samples were evaluated by a sensory panel consisting of eight semi‐trained assessors on (1) a 9‐unit hedonic scale, with analysis based on the assumption that the units are equidistant, and (2) a 15‐point hedonic ‘Smiley’ pictorial scale, the results being analysed non‐parametrically. The proportion (%) of ratings higher than or equal to/higher than the overall median of the samples was used as a rigorous estimate of product quality. These values were used to determine the colour and flavour changes in heated soymilk and their temperature dependence. The Z‐values derived from the parametric and non‐parametric analyses were in close agreement, ranging from 31 to 33 °C and from 30 to 32 °C for colour and flavour respectively. © 2000 Society of Chemical Industry     

Effects of Phosphorus and Zinc Fertiliser Management on Cadmium Accumulation in Flaxseed

Field studies were conducted over 3 years on three soil types to evaluate the interactive effects of phosphate and zinc fertilisers on the concentration and accumulation of Cd in flaxseed. Flaxseed tends to accumulate high concentrations of Cd relative to cereal crops, which may be of concern when the flaxseed is entering the health-food market. Application of P, as monoammonium phosphate, increased Cd concentration and accumulation and decreased Zn concentration in flaxseed; the effect being greater with banded as compared to broadcast placement. Application of Zn, as zinc sulphate, generally decreased Cd concentration, but had little effect on Cd accumulation in flaxseed. Concentration of Cd in flaxseed decreased as seed concentration of Zn increased, across soil types and fertiliser treatments. Therefore, lower Zn concentration in the seed, whether due to low soil Zn levels, reduced Zn phytoavailability caused by P application or dilution of seed Zn due to increased dry matter production may be associated with increased Cd concentrations in flaxseed. © 1997 SCI.     

对产蛋鸡实用日粮中铜、铁、锌、锰平衡供应方案的探讨

探讨蛋鸡铜、铁、锌、锰的补充方案.试验1选用420只19周龄罗曼褐壳蛋鸡,随机分为4处理,每处理7重复,每重复15只.试验2选用360只39周龄罗曼褐壳蛋鸡,随机分为4处理,每处理6重复,每重复15只.以基础饲粮铜、铁、锌、锰的实测值为基础,结合1994年NRC逐步平衡饲粮4种元素.结果显示,两试验基础日粮配方相似,但铜、铁、锌、锰含量差异较大.试验1依次添加锌、铜、锰提高产蛋率,不影响铜、铁、锌的表观利用率,显著影响锰的表观利用率.试验2依次补充锰、铜、锌降低产蛋率和4种元素的表观利用率.从生产性能考虑,1994年NRC中铜、铁、锌、锰的比例不适宜作为微量元素的最佳平衡比,典型蛋鸡饲粮中锌是产蛋性能的限制性因素.