Further studies on SS bonds in cereal glutelins

Flours of wheat, rye, barley, oats, maize and sorghum have been extracted to remove albumins, globulins and prolamins. The SS bonds of the starch-glutelin residues (4 to 8% protein) have been reduced with sulphite and titrated with phenyl mercury acetate (PMA) in the presence of 3 M -guanidine hydrochloride at 37 °C and, in its absence, at 2 and 37 °C. Attention has been paid to several possible sources of error including oxidation and the rate of diffusion of PMA into protein particles. Approximate values for the diffusion coefficients of PMA through cellulose and protein films were obtained. Titrations at 37 °C in the absence of guanidine hydrochloride are unsatisfactory due to reaction of intrachain SS links. Evidence in the literature suggests that the SS bonds titratable at 2 °C are inter-chain, possibly includingsomestrained intra-chain bonds. The results imply that most of the major polypeptide chains in the cereal glutelins examined, apart from barley and sorghum, contain two such bonds. In the case of barley glutelin probably less than half the chains have two labile SS bonds. Most of the chains in sorghum glutelin appear to have a single labile bond and the polymers may contain only a few chains. The molecular weights (in thousands) of the principal polypeptide chains of the glutelins, deduced from gel electrophoresis in sodium dodecyl sulphate (SDS), are: Cappelle-Desprez wheat 44, 41; Manitoba wheat, rye and barley, 44; oats, 33, 23; maize, 23, 19; sorghum, 22, 18.     

Determination of thiol groups and disulphide bonds in wheat flour and dough

A study was made of the conditions for determining all thiol (SH) groups and disulphide (S—S) bonds in wheat flour and dough. Thiol groups were determined by amperometric titration with Ag₂SO₄, the flour or dough which contains proteins and peptides being suspended in a solution of 6 m urea and 10^?4 M sodium dodecyl sulphate (SDS). The potential of the platinum electrode was ?0.24 V vs calomel reference electrode. Disulphide bonds were determined in two ways: (a) Using an excess of Ag₂SO₄ in the presence of 9 M urea; when the reaction was finished, the excess Ag₂SO₄ was removed by adding an exact quantity of glutathione. The glutathione which remained after binding the Ag₂SO₄ excess was determined by amperometric titration with a 5.10^?5 M Ag₂SO₄ solution, (b) Determination after reduction with NaBH₄; the disulphide bonds were reduced to thiol groups and the total amount of thiol groups was determined with Ag₂SO₄. The results indicated that wheat flour contains 5–7 μmol SH-groups, which is about six times the level found by previous workers, and 11-18 μmol disulphide bonds per gram flour. A correlation with baking quality was not observed.     

Introduction of sulphydryl groups into pea vicilin: Formation of intra-and inter-polypeptide disulphide bonds

Site directed mutagenesis was used to introduce two cysteine residues into the hydrophilic regions of the pea vichlin polypeptide previously expressed in Saccharomyces cerevisiae. The mutated polypeptide was expresed and the resultant protein was characterised by sodium dodecyl sulphatepolyacrylamide gel electrophoresis. The presence of both intra- and inter-polypeptide sulphydryl bonds was indicated by bands of different mobility from those of the native polypeptide. The association of mutated vicili polypeptides into disulphide-bonded aggregates within the yeast was not a random process, trimers being the major aggregate produced. When the mutated vicilin was extracted from yeast and purified, random aggregates of the vicilin polypeptide were formed.     

Effects of disulphide bonds between added whey protein aggregates and other milk components on the rheological properties of acidified milk model systems

Micro- and nanoparticulated whey protein (MWP, NWP) were added to non-fat milk model systems and processed into chemically (glucono-delta-lactone) acidified milk gels. Model systems contained 5% protein in total and were made at two levels of casein (2.5% and 3.5%, w/w) with and without the thiol-blocking agent N-ethylmaleimide. The systems were characterised in terms of thiol groups, gel electrophoresis, particle size, and rheology during processing (homogenisation, heat treatment and acidification). The results showed that the formation of disulphide-linked structures in milk model systems was closely related to the increased particle size and rheological behaviour of the gels. MWP enriched systems produced, upon acidification, weak protein networks and required the addition of whey protein isolate (WPI) to increase gel strength. However, systems containing NWP exhibited pronounced increase in particle size and higher firmness of acidified gels through both covalent and non-covalent interactions.     

Ergot on cereal grains

Ergot is caused by a fungus (Claviceps species) which has been found on hundreds of plants in almost every country of the world. The fungus can adapt itself to form many different varieties. New species of the fungus and new hosts are still discovered today. The alkaloids in ergot have caused hundreds of thousands of deaths in the Middle Ages after consumption of contaminated cereal grains, but during the last two decades there has not been a recorded outbreak of ergotism. Grain standards in most countries are very strict and do not permit grain which contains ergot to reach commercial food channels. All involved in cereal grain production and utilization should be cognizant of the potential danger, however, since ergot contamination at levels above those permitted by grain standards cannot necessarily be detected by the normal evaluation of a flour sample in the cereal chemistry laboratory. There always have been and always will be ergot infections and a possible danger to human health, but man has learned to minimize the potential problem by using proper agricultural practices. Furthermore, techniques for the removal of ergot from contaminated grains have been developed. While human ergotism is a disease of the past, ergotism in animals still occurs frequently. The problem is not a simple one because of many unanswered questions. What is the tolerance of different breeds or species of livestock to ergot? What are the effects of low‐level long‐term ingestion of ergot on livestock? What is the difference in toxidty to animals of ergot from different cereal grain varieties? What is the effect of storage and processing of cereal grain products on the potential ergot toxicity? The last and most important chapter in the history of ergot concerns ergot as a source of pharmacologically useful alkaloids which have found applications in internal medicine and obstetrics. The future promises to bring some new ergot alkaloids and some new uses. Recent research data indicate the possibility of using ergot alkaloids in contraceptives, which would be truly remarkable.     

谷物色素研究进展

谷物中的色素大部分属于类胡萝卜素、花色素,例如小米、玉米黄色素中叶黄素、玉米黄素属类胡萝卜素,黑米中黑米色素、花色小麦中的色素和高粱中的高梁红色素属花青素类。介绍了玉米、小麦、黑米、高粱和小米等谷物中色素的性质、提取和应用进展。     

Ergot on cereal grains.

Ergot is caused by a fungus (Claviceps species) which has been found on hundreds of plants in almost every country of the world. The fungus can adapt itself to form many different varieties. New species of the fungus and new hosts are still discovered today. The alkaloids in ergot have caused hundreds of thousands of deaths in the Middle Ages after consumption of contaminated cereal grains, but during the last two decades there has not been a recorded outbreak of ergotism. Grain standards in most countries are very strict and do not permit grain which contains ergot to reach commercial food channels. All involved in cereal grain production and ulilization should be cognizant of the potential danger, however, since ergot contamination at levels above those permitted by grain standards cannot necessarily be detected by the normal evaluation of a flour sample in the cereal chemistry laboratory. There always have been and always will be ergot infections and a possible danger to human health, but man has learned to minimize the potential problem by using proper agricultural practices. Futhermore, techniques for the removal of ergot from contaminated grains have been developed. While human ergotism is a disease of the past, ergotism in animals still occurs frequently. The problem is not a simple one because of many unanswered questions. What is the tolerance of different breeds or species of livestock to ergot? What are the effects of low-level long-term ingestion of ergot on livestock? What is the difference in toxicity to animals of ergot from different cereal ingestion of ergot on livestock? What is the difference in toxicity to animals of ergot from different cereal grain varieties? What is the effect of storage and processing of cereal grain products on the potential ergot toxicity? The last and most important chapter in the history of ergot concerns ergot as a source of pharmacologically useful alkaloids which have found applications in internal medicine and obstetrics. The future promises to bring some new ergot alkaloids and some new uses. Recent research data indicate the possibility of using ergot alkaloids in contraceptives, which would be truly remarkable.     

谷物脱皮加工技术的研究现状

脱皮处理是谷物加工过程中的一个重要环节,它直接影响谷物籽粒的后续加工及产品的品质.从谷物机械脱皮、化学脱皮以及脱皮程度对谷物品质影响三个方面综述了谷物脱皮加工技术的研究现状.重点阐述了影响机械脱皮效果的因素:谷物皮层所占的比例、机械脱皮的温度、加水量、调质时间以及设备技术参数等,为深入研究不同的谷物脱皮加工方法提供参考.     

Reaction of wheat proteins with sulphite. 3. Measurement of labile and reactive disulphide bonds in gliadin and in the protein of aleurone cells

Qualitative evidence for the intra-chain character of the disulphide bonds in gliadin, has been confirmed by quantitative measurement of the total number of bonds, and of the number reacting with sulphite under differing conditions of urea concentration. The results indicated that gliadin was composed of single polypeptide chains, which contained an average of four disulphide bonds each, in labile H-bonded configurations. Similar measurements on the protein of wheat aleurone cells, showed the presence of a high proportion of thiol groups, and a relatively low content of disulphide groups. All of the groups were accessible to reaction with sulphite, which implied that short polypeptide chains were involved in this soluble protein system. The results are discussed in relation to the development of protein in the endosperm, and in the aleurone layer, and to the rǒle of both types of protein in germination.     

Dimethyl disulphide in the blood of cattle fed on brassicas

Dimethyl disulphide (DMDS), the main cause of brassica anaemia in ruminant animals, was determined in the blood of steers ingesting S-methylcysteine sulphoxide (SMCO) present in leafy brassicas. Blood samples were treated with Zn and dilute phosphoric acid and the DMDS reduced to methanethiol which was determined by gas chromatography headspace analysis. DMDS levels increased as the intake of SMCO with the brassicas progressed. They were maximal at the haemolytic crisis; thereafter, with the appearance of young red cells or reticulocytes, they declined sharply, but again increased as the new cells matured. The distribution of DMDS was; red cell 85%, plasma 15%. The distribution reached equilibrium in vitro in about 2 h.     

酶制剂在婴儿营养米粉生产中的应用研究

采用酶解技术将组成婴儿米粉的主要成分一淀粉部分水解成糊精和低聚糖、麦芽糖等，从而成功地解决了传统米粉生产工艺中存在的缺陷，对婴儿营养米粉的生产具有参考价值。     

国内外谷物蛋白发展概况

本文综述谷物蛋白组成特性、应用和改性方面最新研究概况。开发利用谷物蛋白，已成为谷物科学领域研究热点。     

酶制剂在谷物食品加工中的应用

0前言面粉的质量是谷物食品(包括面包、饼干、馒头、面条及冷冻食品等)加工过程中一个至关重要的因素,它作为谷物食品的主要原料,其质量与小麦质量密切相关。小麦品种、来源、小麦收割时的气候及制粉技术等常常造成面粉质量的差异。尽管近年来我国不断优化小麦品种、提高小麦制粉技术,但要保证小麦面粉的质量,尤其是小麦面粉品质的稳定性,仍存在一定的困难,这必然会在很大程度上影响谷物食品的质量控制。利用食品添加剂(如化学氧化物、乳化剂)或酶制剂等可以改良小麦面粉质量,提高和稳定谷物食品的品质,而酶制剂又以其健康安全性、特异性以…     

谷物戊聚糖国内外研究进展

就戊聚糖在谷物中的分布 ,戊聚糖的分离、分级、纯化方法 ,物理化学特性 ,以及戊聚糖与谷物品质之间的关系进行了综述     

Mycotoxins in cereal grain Part VII. A simple method to assay mycotoxin potential of cereal grain and cereal products

A simple test to assay mycotoxin potential of cereal grain and products was elaborated. In cereal grain samples during 1977 and 1981 formation of ochratoxin A, citrinin and zearalenone was observed respectively in 40%, 7 % and 31 % of cereals samples. Aflatoxin and sterigmatocystin were not formed in any sample of cereal grain. Citrinin and penicillic acid were found as mycotoxins accompanying ochratoxin A.     

Disulphide interchange in cereal proteins

A method of measuring the extent of disulphide interchange between a model compound, cystamine, and cereal flour proteins has been applied to wheat, steamed wheat, rye, barley and maize. The results indicate that, if the extent of protein-protein S.S interchange is of the same order as that found in the model reaction, it is several times greater in wheat than the calculated minimum necessary to create a continuous protein network. In the case of rye the extent seems to be sufficient to just comply with this minimum condition. Steamed wheat, barley and maize (none of which can form doughs) fall below the limiting extent of interchange required. It has been assumed that insoluble proteins are precluded from taking part in protein-protein S.S interchange reactions, and evidence from the literature has been cited to support this.     

Mycotoxins in cereal grain. Part VII. A simple method to assay mycotoxin potential of cereal grain and cereal products

A simple test to assay mycotoxin potential of cereal grain and products was elaborated. In cereal grain samples during 1977 and 1981 formation of ochratoxin A, citrinin and zearalenone was observed respectively in 40%, 7% and 31% of cereals samples. Aflatoxin and sterigmatocystin were not formed in any sample of cereal grain. Citrinin and penicillic acid were found as mycotoxins accompanying ochratoxin A.     

液态谷物饮料原淀粉抗老化问题探讨

对液态谷物饮料原淀粉老化机理及影响因素进行分析,在实验测试的基础上提出了液态谷物饮料原淀粉抗老化及延长饮料货架期的有效方案：即采用乳化剂、亲水胶体、磷酸盐组成复配体系。     

Studies on trace elements content in some cereal products

The aim of the investigations was the determination of the lead, cadmium, copper, zinc, iron and manganese content in some cereal products. It was found that all the analysed cereal products contained lead and cadmium contaminations. The content of the tested metals found in cereal products remained within the range of the minimum and the maximum values given for the Polish commercial products by other authors.