Trypsin and chymotrypsin inhibitor activities in plant foods from Vietnam and Hungary

A method for the determination of chymotrypsin inhibitor activity and a screening test for evaluating higher activities of trypsin inhibitor were elaborated. The protease inhibitor activities of the most important plant foods from Vietnam and Hungary were determined. In cereals and legume seeds the activity of chymotrypsin inhibitors is generally lower than that of the trypsin inhibitors. In various soy products (isolates, texturates) the extent of lowering of chymotrypsin inhibitor activity was less than that of trypsin inhibitor related to raw soy bean. The cooking process according to the usual kitchen technique of Vietnam has more effect on the higher trypsin inhibitor level of soy bean than on other legumes of average activity.     

Tropical traditional fermented food,a field full of promise. Examples from the Tropical Bioresources and Biotechnology programme and other related French–Vietnamese programmes on fermented food

In tropical countries, traditional fermented foods are usually home‐made products obtained through spontaneous fermentation or backslopping. They are now facing an evolution aiming at responding to quality, safety and mass production issues. This requires acquisition of knowledge on raw materials, microbial ecosystems and fermentation processes. Vietnam is a laboratory for such studies as traditional fermented foods play an important role in the diet of Vietnamese and as these foods are very diverse. Among the most popular are nem chua (sausage reminding Thai Nham), dua muoi (cabbage reminding Kimchi), tom chua (shrimps) and the well‐known nuoc mam. The challenge for these products to enter the industrial era is to reach a level of quality and safety without losing their character. Beside the research for starters to elaborate these products, the world of fermented products is also a world of innovation and the microbial ecosystem of traditional products can also be used for the adaptation of fermented products from other regions, such as wines (from grape or other fruits), for cross‐cultural innovations such as soy‐yogurts, for technology transfer from one fermentation (soy sauce) to another one (fish sauce) and for evolution of traditional products towards higher nutritional qualities such as nem chua nam (replacing part of the sausage meat by mushrooms). Finally, these complex microbial ecosystems are a source of probiotic, antimicrobial compounds and biocatalysts, which can benefit health and improve food processes worldwide. After a presentation of Vietnamese traditional fermented foods, this article aims at illustrating the diverse applications of research on fermented products through examples obtained in past research and in the Tropical Bioresources and Biotechnology project.     

Changes in iron,zinc and chelating agents during traditional African processing of maize: Effect of iron contamination on bioaccessibility

The effect of the different unit operations of processing traditionally used to produce four maize foods commonly consumed in Africa on the nutritional composition of the products was investigated, using Benin as a study context. The impact of the processes on lipid, fibre, phytate, iron and zinc contents varied with the process. The lowest IP₆/Fe and IP₆/Zn molar ratios, the indices used to assess Fe and Zn bioavailability were obtained in mawè, a fermented dough. Analysis of maize products highlighted a significant increase in iron content after milling, as a result of contamination by the equipment used. Evaluation of iron bioaccessibility by in vitro enzymatic digestion followed by dialysis revealed that the iron contamination, followed by lactic acid fermentation, led to a considerable increase in bioaccessible iron content. Extrinsic iron supplied to food products by the milling equipment could play a role in iron intake in developing countries.     

Phytate × Calcium/Zinc Molar Ratios: Are They Predictive of Zinc Bioavailability?

The utility of the phytate/zinc and phytate × calcium/zinc molar ratios for predicting zinc bioavailability from processed soybean foods was investigated. Weight gain and bone zinc accumulation in rats fed various soy protein products were plotted against the calculated molar ratios. The phytate × calcium/zinc ratio was a better predictor of zinc bioavailability in similarly processed products than was the phytate/ zinc ratio. However, in some cases the phytate × calcium/zinc ratio was not effective since some processing procedures apparently altered binding of phytic acid to minerals and other food components.     

Inositol Phosphates in Processed Foods

Myo-inositol bis-, tris-, tetrakis-, pentakis- and hexakisphosphates (IP2–6) were quantified in nine thermally processed or fermented food products. Total inositol phosphate content (mmol/kg dry weight) ranged from 1.35 in white bread to 23.26 in tofu and 26.05 in soy isolate. In all foods analyzed, inositol hexakisphosphate (phytic acid) accounted for more than 40% of the total inositol phosphates on a molar basis. Step-gradient ion exchange and ferric chloride precipitation methods for phytate determination were evaluated with a soy isolate sample to which inositol phosphates or adenosine triphosphate (ATP) had been added individually. Both methods measured all of the inositol phosphates, while the former also measured ATP.     

Effect of fermentation on HCl-extractability of minerals from rice-defatted soy flour blend

Buttermilk fermentation at 25, 30 and 35°C for 12, 18 and 24 h brought about a significant increase in non-phytate and HCl-extractable phosphorus with a corresponding decline in phytate phosphorus of a rice-defatted soy flour blend mixed in a 50 : 50 proportion. The HCl-extractabilities of calcium, iron, zinc, copper and manganese from the rice-defatted soy flour blend also improved. Higher HCl-extractability of minerals may be partly ascribed to the decreased content of phytic acid, as a significant negative correlation between the phytic acid and HCl-extractability of dietary essential minerals was obtained.     

Lactic Fermentation of Non-Tannin and High-Tannin Cereals: Effects on In Vitro Estimation of Iron Availability and Phytate Hydrolysis

The effect on iron availability estimated in vitro and phytate hydrolysis was investigated in non-tannin and high-tannin cereals, lactic fermented as flour/water slurries or gruels. A natural starter culture initiated fermentation and addition of germinated flour and phytase in the fermentation process was tested. Lactic fermentation of nontannin cereals with added flour germinated sorghum seeds or wheat phytase increased iron solubility from about 4% up to 9 and 50%, respectively. Soaking flour in water before adding starter culture had a similar effect. The increase in soluble iron was strongly related to enzymatic deeradation of phytate (p<0.001). The reduction of inositol hexa- and pentaphosphates was about 50% with added germinated flour. Reduction was > 90% after soaking the flour prior to fermentation and almost complete with 50 mg phytase added. High-tannin cereals showed a minor increase in soluble iron after fermentation, ascribed to the inhibitory effect of tannins (both on iron solubility and on enzymatic hydrolysis of phytate). Lactic-fermented cereal foods have a potential in developing countries to improve iron nutrition.     

Fermentation and enzyme treatment of tannin sorghum gruels: effects on phenolic compounds,phytate and in vitro accessible iron

The presence of polyphenols and phytate in cereal products has been shown to interfere with the bioavailability of minerals such as iron. In the present study, we added enzymes (wheat phytase and mushroom polyphenol oxidase) during fermentation of tannin sorghum gruels prepared from flour with or without addition of 5% flour of germinated tannin-free sorghum grains (power flour), and investigated the effects on phenolic compounds, phytate and in vitro accessible iron. Assayable phenolic compounds were significantly reduced by fermentation, with high reductions observed in gruels with added enzymes. Fermentation of the gruels with addition of enzymes reduced (on average) total phenols by 57%, catechols by 59%, galloyls by 70% and resorcinols by 73%. The phytate content was significantly reduced by fermentation (39%), with an even greater effect after addition of power flour (72%). The largest reduction of phytate (88%) was, however, obtained after addition of phytase. The in vitro accessible iron was 1.0% in the sorghum flour and it increased after fermentation with power flour and/or with enzymes. The highest in vitro accessibility of iron (3.1%) was obtained when sorghum was fermented with addition of power flour and incubated with phytase and polyphenol oxidase after the fermentation process.     

畜禽血食用产品及1其研究进展

畜禽血作为畜禽屠宰加工的主要副产物之一,营养价值丰富,应用前景广阔。在传统加工利用上,畜禽血可以制作为血豆腐、血肠等食品,通过微生物发酵、酶解、微胶囊化等新兴加工技术还可开发出各种保健品、功能性食品、调味品、食品添加剂及其他风味食品,如氨基酸口服液、血红素胶囊、血酱油、肉味香精、发色剂、乳化剂、补铁强化饮料等高附加值产品,文章对利用畜禽血开发食用性产品及其研究进展做了概要综述。     

Effect of Partial Phytate Removal and Heat upon Iron Bioavailability from Soy Protein-Based Diets

The effect of heat and partial phytate removal upon in vivo iron bioavailability from soy protein was studied by chick hemoglobin repletion. Iron repletion diets were formulated with unheated and heated soy protein isolates and phytate-reduced soy protein isolates, with and without iron supplementation. Heating at 120°C for 20 min, 75% phytate reduction and 20 mg/kg iron supplementation improved iron bioavailability by 65-77%, 6-11% and 10-17%, respectively. These beneficial effects were interpreted in terms of promoting protein and protein-Fe-phytate complex digestion and release of endogenous and added iron.     

Effect of fermentation on ionizable iron in cereal-pulse combinations

The average diet in most developing countries is predominantly cereal based. Wheat, rice and millets are major staple foods. Although these diets are sufficient in iron, their low bioavailability is one of the most significant factors for iron deficiency anaemia. Traditional techniques like fermentation show promise in improving iron bioavailability. In vitro ionizable iron was estimated in 31 different combinations of rice, wheat, sorghum, black gram, bengal gram, green gram and coriander in five replicates with or without, fermentation in steamed products. Results indicate that in general cereal pulse combination and fermentation significantly ( P <0.05) increase the per cent ape of ionizable iron. Combination effects dominated in rice whilst fermentation dominated in sorghum. There was a significant reduction ( P <0.05) in phytate phosphorus on fermentation but no loss of tannin.     

Soybean allergen detection methods--a comparison study

Soybean containing products are widely consumed, thus reliable methods for detection of soy in foods are needed in order to make appropriate risk assessment studies to adequately protect soy allergic patients. Six methods were compared using eight food products with a declared content of soy: a direct sandwich ELISA based on polyclonal rabbit antibody (ab) to raw soy flakes, a commercial and an in-house competitive ELISA both based on ab to denatured, 'renatured' soy protein, an enzyme-allergosorbent test (EAST) inhibition based on two sera from soy allergic patients, histamine release (HR) using basophils passively sensitized with patient serum and a PCR method detecting soy DNA. Eight food products were selected as model foods to test the performance of the methods. There was an overall good agreement between the methods in terms of ranks of soy content but not the quantity. The sandwich ELISA aimed at native soy proteins had the lowest detection limit of 0.05 ppm, but only identified soy in 5/8 products, and generally in lower amounts compared to other methods. The competitive ELISA had a higher detection limit of 21 ppm, but seemed more successful in detecting processed soy. Only HR, EAST inhibition and PCR detected soy in all eight products. In spite of a general good correlation in terms of ranks of soy content, more than a single method may be necessary to confirm the presence of soy in foods.     

Extent of phytate degradation in breads and various foods consumed in Saudi Arabia

The extent of phytate degradation in breads and various foods consumed in Saudi Arabia was followed after baking or cooking. Phytate phosphorus content in raw and baked or cooked food was determined by ion-exchange and colorimeteric methods. White bread containing soda, namely Tamees, had a lower degree of phytate degradation followed by pita brown bread, namely Burr, in comparison to pita, French and pan white breads not containing soda, namely Mafrood, Samouli and Toast, respectively. The phytate content in breads ranged from 0.11 to 0.2 8%. Wheat-based food made from whole wheat flour, namely Margoog, had a lower degree of phytate degradation in comparison to other wheat-based foods made from bulgur, grits and partially debranned grains, namely Kibbah, Gerish and Harees, respectively. The phytate content in these foods ranged from 0.08 to 0.25%. Rice-based foods made from parboiled rice, namely Kabsa, or not drained from steeping or cooking water, namely Saleeg, had a lower phytate degradation than rice drained from steeping or cooking water, namely Baryani or Rus Abiedh. The phytate content in these foods was lower and ranged from 0.04 to 0.1%. Similarly, faba beans-based food not drained from cooking water, namely Food Jerra, had a lower degree of phytate degradation than faba bean or chick pea-based foods drained from cooking water, namely Foul Mudames, Falafe and Balila. The phytate contents in these foods ranged from 0.11 to 0.4%. Food recipes and baking conditions or cooking procedures are the main factors that affect the extent of phytate degradation. To avoid adverse effects on mineral nutrients, reduction in the phytate content of the phytate-rich foods such as Burr bread, Margoog and Foul Jerra foods, is recommended.     

ANTIOXIDANT PROPERTIES OF ETHANOLIC AND METHANOLIC EXTRACTS FROM MONASCUS-FERMENTED SOYBEANS

Soybeans are very common foods in oriental countries used as a meat substitute. Monascus species possess functional components and have been used on traditional fermented food. Solid-state fermentation of the soybean substrate by Monascus species is a new area of investigation. In the present study, methanolic extracts from three samples exhibited better antioxidant activity in the conjugated diene method, reducing power, scavenging ability on 1,1-diphenyl-2-picrylhydrazyl radicals and chelating ability on ferrous ions. Monascus species inoculated onto the soybean substrate contributed higher reducing power, scavenging and chelating abilities and higher amounts of phenol components than uninoculated soybean product. Overall, Monascus- fermented soybeans showed better antioxidant properties and can be developed as a new dietary supplement and functional food.

PRACTICAL APPLICATION

Soybeans and soy products are rich in isoflavones and are very common foods used as a meat substitute in oriental countries. Fungus Monascus has been used as a traditional fermented food and its metabolic products are also utilized as food pigments or biological agents in oriental countries for centuries. Many reporters showed that soy isoflavone aglycones and Monascus spp. metabolite exhibited physiological activities. In addition, previous studies showed a fermentation process using microorganisms to inoculate onto a nonsoluble material that can produce chemicals and enzymes. Therefore, the ethanolic and methanolic extracts from Monascus -fermented soybeans were evaluated for antioxidant properties, and the information obtained would be more valuable than that from soybeans to develop new functional foods.     

Effects of reducing phytate content in sorghum through genetic modification and fermentation on in vitro iron availability in whole grain porridges

Improved iron availability from sorghum porridges will benefit many malnourished communities in rural Africa, where there is a high prevalence of iron deficiency. This research compared the efficacy of reducing sorghum phytate content by genetic modification (GM) and natural lactic acid fermentation on in vitro iron availability in porridges. GM low phytate, non-tannin (38% phytate reduction) and tannin (36% phytate reduction) sorghums and their null controls were processed into thick unfermented and fermented porridges. The inhibitory effect of the tannins seemed to prevent any increase in in vitro iron availability, regardless of the level of phytate reduction. Only the additive effect of GM in combination with fermentation in reducing the phytate content appeared to cause a substantial increase in in vitro iron availability in the GM fermented porridge (30%) made from the non-tannin line, compared to the GM unfermented porridge (8.9%) or the fermented porridge (17.6%) of the control sorghum. This could be of nutritional significance.     

植酸/植酸钠在食品工业上的应用研究进展

植酸/植酸钠广泛存在于谷类、豆类和油料作物等中,应用非常广泛,在食品工业上可用作食品抗氧化剂、抑菌剂、护色剂、螯合剂和保鲜剂等。本文简述了植酸/植酸钠的结构、组成和理化特性,并且综述其在食品工业中的应用与研究进展。重点介绍了植酸/植酸钠在果蔬制品、饮料、发酵食品、酿造酒、油脂和脂肪制品、水产品、肉制品、焙烤制品和面制品等加工中的应用及研究进展。同时探讨了目前植酸/植酸钠在食品工业应用中存在的问题及解决对策,并对其发展趋势进行展望。指出目前高纯度植酸和固体植酸的生产成本较高,将来可以在植酸的色谱层析分离材料上进行改进。同时,为了增加植酸在油溶性食品中的应用范围,可以通过植酸的改性或借助于乳化、微乳化技术制备植酸/植酸钠的乳液和微乳液产品,是将来的发展方向。     

农村寄宿制学校用铁强化酱油状况及铁含量分析

贫血在我国属于中度公共卫生问题,铁强化酱油是安全有效的人体铁营养改善方法。本研究采集了24个省寄宿制学校使用的43个铁强化酱油产品,采用原子吸收分光光度法测定铁强化酱油总铁含量。结果显示,抽样地区农村寄宿制学校用铁强化酱油产品铁含量均值为（216.1±17.9） mg/kg,铁含量分布范围为191.5～263.8 mg/kg。农村寄宿制学校铁强化酱油中一级酱油占51.2%,桶装酱油占60.5%,高盐稀态发酵工艺的酱油占88.4%,生抽占55.8%。铁含量与酱油保存时间没有相关性,不同等级、不同包装形式铁强化酱油中铁含量无显著性差异,不同品种酱油中铁含量有显著差异,生抽中铁含量显著高于老抽。所有农村寄宿制学校铁强化酱油中铁含量均符合我国相应的食品安全国家标准。     

Effect of food processing of pearl millet (Pennisetum glaucum) IKMP‐5 on the level of phenolics,phytate, iron and zinc

Pearl millet is consumed as a staple food in semi‐arid tropical regions. With a view to upgrading the micronutrient status of pearl millet‐based foods, the effects of single operations and of porridge preparation scenarios on levels and in vitro solubility (IVS) of iron and zinc and mineral complexing factors (phytates: inositol phosphates and phenolic compounds) were tested. Disc milling of grain may add significant iron but this is not necessarily IVS iron. Soaking of grains results in a 25% loss of iron, but also facilitates endogenous phytate degradation, particularly when combined with milling and cooking. Germination and lactic acid fermentation both result in partial phytate degradation. Cooking does not decompose phytates, but results in complex formation of phenolic compounds as measured by a significant reduction in reactive hydroxyl groups. Because of its different distribution in the grain, zinc is generally less affected than iron. Phytate reduction by endogenous phytases is inhibited at low pH as caused by fermentation. Kanwa (alkaline rock salt) could be a functional cooking ingredient as a source of minerals and to react with phenolic substances. The relative IVS of iron was doubled by germination of grain and increased 3‐fold by fermentation of wholemeal slurry. Zinc IVS tended to increase on cooking with kanwa, but decreased in cooked fermented flour. Copyright © 2006 Society of Chemical Industry     

Impact of brewing process operations on phytate, phenolic compounds and in vitro solubility of iron and zinc in opaque sorghum beer

Opaque sorghum beer is a significant component of the diet of millions of poor people in rural Africa. This study reports the effect of traditional brewing operations on its level of micronutrients, especially iron and zinc. The example of a West African sorghum beer, tchoukoutou, in Northern Benin was studied. The beer was characterized and the impact of process unit operations on phytate, phenolic compounds, and Zn and Fe in vitro solubility was evaluated. The major microorganisms involved in the beer fermentation were Saccharomyces cerevisiae and heterofermentative lactobacilli. The manufacturing process reduces the phytate content by nearly 95%, particularly during germination, mashing-boiling and fermentation. The level of reactive phenolic groups increased as a result of germination and fermentation as well as from a shift in dry matter composition. Simultaneously with these modifications, an increase of Fe solubility was observed, and a correlation between phytate and Fe solubility (R²=0.85) was established. No clear correlation could be established between the Zn solubility and the phytate content of the products. During beer manufacturing, significant losses of minerals occur particularly during soaking and mashing/filtration; thus the quantity of minerals available to consumers is restricted. Improvements aiming to minimize such losses are highly desirable.     

中国传统豆制品生产工业化过程中存在的问题

我国豆制品历史悠久,品种繁多,风味独特,营养丰富,因而成为东方传统食品中的一支奇葩。然而许多传统豆制品的生产工业化程度低,保质期短、卫生质量差,产品标准化程度低,品质不稳定。豆制品生产工业化、规模化是发展的必然趋势。从我国传统豆制品的现状看还存在着许多问题,制约着工业化生产。