Effect of Temperature and Period of Fermentation on Protein and Starch Digestibility (In vitro) of Rabadi—A Pearl Millet Fermented Food

Rabadi was prepared by allowing pearl millet flour-country buttermilk mixture to ferment for three different periods (3, 6 and 9 hr) at four different temperatures (35°, 40°, 45°, and 50°C). As fermentation time increased, protein as well as starch digestibility (in vitro) of rabadi increased significantly at all the temperatures. Maximum increase in the digestibility of both protein (51%) and starch (58%) occurred after 9 hr fermentation at 45°C.     

Effect of fermentation on HCl extractability of minerals in Rabadi-an indigenous fermented food of India

Pearl millet flour/buttermilk mixture was fermented at 35, 40, 45 and 50°C for 3, 6 or 9 h to prepare rabadi. Fermentation at all temperatures decreased phytate P, increased non-phytate P and increased HCl extractability of P, Ca, Fe, Zn and Cu; the extractability increased with an increase in the period of fermentation. The largest improvement was seen in extractability of Fe, followed by that of P, Zn, Ca and Cu. Mn extractability did not change as a result of fermentation.     

Evaluation of the quality characteristics of flour and pasta from fermented cassava roots

The study investigated the effect of fermentation of cassava roots on the quality characteristics of flour and pasta. Cassava roots were fermented under natural condition for a period of 12, 36 and 60 h. Physicochemical properties, microbial analysis, pasting properties, in vitro digestibility, X-ray diffraction analysis of cassava flour, cooking properties, texture profile analysis (TPA) and sensory properties of the pasta were examined. The moisture content, carbohydrate, water absorption capacity, swelling and solubility index of fermented flour increased with an increase in fermentation period. Also, as fermentation progressed, increase in pasting viscosities of cassava flour was observed. The resistant starch (RS) content of cassava flour decreased with increasing period of fermentation. The duration of fermentation process significantly affected textural properties and cooking loss of cassava pasta. Sensory assessment showed that cassava roots fermented for 36 h gave pasta with the most acceptable qualities.     

In vitro digestibility of processed and fermented soya bean,cowpea and maize

Tropical legumes, ie soya bean and cowpea, were pre‐treated and subsequently fermented using pure cultures of Rhizopus spp. Impact of soaking, cooking and fermentation of the legumes on their digestibility was determined using an in vitro digestion method. Processing of white maize included, amongst others, natural lactic acid fermentation, cooking and saccharification using barley malt. An in vitro method was standardised to carry out comparative determinations of the dry matter digestibility of cereal and legume food samples as a function of processing conditions, without attempting to exactly mimic gastrointestinal digestion. Using this method based on upper digestive tract digestion, it was observed that digestibility of the legumes increased during cooking and fermentation. Cooking improved the total digestibility of both soya bean and cowpea from 36.5 to 44.8% and from 15.4 to 40.9% respectively. Subsequent fungal fermentation increased total digestibility only by about 3% for both soya bean and cowpea. Digestibility was also influenced by fungal strain and fermentation time. Cooking and subsequent saccharification using malt almost tripled total digestibility of white maize from 25.5 to 63.6%, whereas lactic fermentation of maize had no effect on in vitro dry matter digestibility. Although total digestibility of cooked legumes was only slightly improved by mould fermentation (3% for both soya bean and cowpea), the level of water‐soluble dry matter of food samples increased during fermentation with Rhizopus oryzae from 7.0 up to 27.3% for soya bean and from 4.3 up to 24.1% for cowpea. These fermented products could therefore play a role as sources of easily available nutrients for individuals suffering from digestive disorders. © 2000 Society of Chemical Industry     

Production of potentially probiotic beverages using single and mixed cereal substrates fermented with lactic acid bacteria cultures

In the present work, single and mixed cereal substrates were fermented with lactic acid bacteria to study and compare the effect of the media formulation on fermentation parameters. Three cereal flours namely malt, barley and barley mixed with malt (barley–malt) were selected and fermented with two probiotic strains: Lactobacillus plantarum (NCIMB 8826) and Lactobacillus acidophilus (NCIMB 8821). The effect of the single and mixed cereal flour suspensions on the fermentation of these two strains of lactic acid bacteria (LAB) was studied at an incubation temperature of 30 °C for 28 h. It was found that the LAB growth was enhanced in media containing malt and significant amounts of lactic acid were produced (0.5–3.5 g/L). A cell concentration between 7.9 and 8.5 Log₁₀ CFU/mL and a pH below 4.0 was achieved within 6 h of fermentation. Though the cell populations in the mixed culture fermentations of mixed substrates were similar to the ones obtained with single cereal flours, significant differences in the production of lactic acid were observed. These results suggest that the functional and organoleptic properties of these cereal-based probiotic drinks could be considerably modified through changes in the substrate or inocula composition.     

Effect of natural fermentation on phytate and polyphenolic content and in-vitro digestibility of starch and protein of pearl millet (Pennisetum typhoideum)

Natural fermentation at 20, 25 and 30°C for 72 h brought about a significant reduction in phytic acid content of pearl millet (Pennisetum typhoideum Rich) flour. The phytate content was almost eliminted in the flour fermented at 30°C. An increase in polyphenol content of fermented flour was noticed, the higher the temperature of fermentation the greater was the increase in polyphenol content of pearl millet. An improvement in starch as well as protein digestibility (in vitro) was noticed at all the temperatures of natural fermentation, the highest being at 30°C.     

Effect of germination and probiotic fermentation on nutrient composition of barley based food mixtures

Food mixtures formulated from non-germinated and germinated barley flour, whey powder and tomato pulp (2:1:1w/w) were autoclaved, cooled and fermented with 5% Lactobacillus acidophilus curd (10⁶ cells/ml) at 37 °C for 12 h. The cell count was found significantly higher (8.88 cfu/g) in the fermented food mixture formulated from germinated flour as compared to the non-germinated barley based food mixture. A significant drop in pH with corresponding increase in titratable acidity was found in the germinated barley flour based food mixture. Processing treatments like germination, autoclaving and probiotic fermentation did not bring about any significant change in ash and fat contents, but significant decrease was noticed in crude protein, crude fibre, starch, total and insoluble dietary fibre contents. The combined processing caused significant improvement in reducing sugar, thiamine, niacin, lysine and soluble dietary fibre contents of barley based food mixtures. In conclusion, a combination of germination and fermentation is a potential process for enhancing the nutritional quality of food mixtures based on coarse cereals.     

Effect of processing on starch digestibility in some legumes — An in vitro study

The effect of processing treatments on the rate of starch digestibility in three legumes, viz., bengal gram (Cicer arietinum L.), cowpea (Vigna unguiculata) and green gram (Vigna radiata) was studied using an in vitro dialysis system. The processes studied were fermentation, germination, pressure cooking and roasting. The released sugars measured as glucose equivalents after 3 h digestion were expressed as digestibility index (DI). All the processing treatments except roasting, increased the rate of starch digestibility in all the three legumes. Subsequent cooking of the germinated/fermented legumes lead to a further increase in starch digestibility. The results of the study indicate that ‘slow release’ property of legumes is heat labile and that loss of this property is independent of macro-nutrient and starch content.     

Effect of various types of fermentation on in vitro protein and starch digestibility of differently processed pearl millet

Pearl millet (Pennisetum typhoideum) grains were fermented with Lactobacilli and yeast alone, in combination and with natural flora at 30 °C for 48 h after giving various processing treatments viz, fine and coarse grinding, soaking, debranning, dry heat treatment, germination and autoclaving after adding of water. Fermentation was carried out with Lactobacillus acidophilus and Rhodotorula isolated from naturally fermented pearl millet and Lactobacillus acidophilus, Candida utilis and natural fermentation using freshly ground pearl millet flour as inoculum. All the processing treatments except coarse grinding improved the protein and starch digestibility. Autoclaving enhanced the digestibilities of processed samples which was further improved by different types of fermentation, the maximum being in case of germinated and naturally fermented pearl millet. A combination of Lactobacilli and yeast was more effective in increasing the protein as well as starch digestibility as compared to pure culture fermentation.     

Effect of fermentation and cooking on protein quality of maize (Zea mays L.) cultivars

Maize like other cereals shows qualitative and quantitative deficiency in protein content. Efforts were made to correct this by fortification, supplementation and fermentation. Two maize cultivars, Hudeiba 1 and Mugtama 45, were used to study the effect of fermentation followed by cooking on their protein quality. Maize flour was fermented for 32 h; samples were withdrawn at 8 h intervals. Results indicated that the proteins fractions albumins plus globulins were significantly (P < 0.05) increased in the fermented doughs. This is an indication of improvement in the protein quality of maize. Cooking resulted in significant (P < 0.05) changes in protein solubility. The essential amino acids particularly lysine increased from 1.82 to 2.06 and from 1.88 to 2.60 g/100 g (i.e. an increase of 11.6% and 27.7%) for Hudeiba 1 and Mugtama 45, respectively. The in vitro protein digestibility of cooked samples decreased significantly (P < 0.05); however, the negative effects of cooking were lower than those of unfermented cooked samples.     

Tepary Bean Starch Part III: In vitro Digestibility

In vitro digestibility of starch from tepary bean, Phaseolus acutifolius var. latifolius, was determined in comparison with tepary bean flour and maize starch. The extent of sample hydrolysis by α-amylase was measured as mg reducing sugar (maltose) released per 100 mg substrate. After 2 h incubation at 37°C, values obtained for tepary starch, tepary flour and maize starch treated in various ways were as follows: raw 8.0, 8.6 and 25.6; freeze dried 2.6, 3.2 and 17.8; autoclaved 7.4, 5.7 and 27.7; cooked (15 min) 81.7, 23.1 and 87.8; resp. Raw tepary starch was more resistant to hydrolysis than maize starch due, perhaps, to differences in granule structure and amylose content. Freeze-drying and autoclaving slightly decreased digestibility of both tepary starch and flour. Cooking greatly increased susceptibility to hydrolysis for each substrate. The rate of increase was reduced after 15 min exposure to enzymes, and no appreciable difference was found between cooked tepary and maize starches.     

Fermentation of rice-bengal gram dhal blends with whey: Changes in phytic acid content and in vitro digestibility of starch and protein

Whey fermentation of various rice and bengal gram dhal blends prepared by mixing them in different proportions at 35 °C for 18 h brought about a significant decline in phytic acid content. Phytic acid content in various blends decreased to the extent of 23 to 36 per cent over the control values. Whey incorporation as well as fermentation improved the starch and protein digestibility (in vitro) of all the rice-bengal gram dhal mixtures. Improvement in starch and protein digestibility is related to the reduction in phytic acid content, as this antinutrient is known to inhibit amylolysis and proteolysis. A significant negative correlation found between phytic acid and digestibility of starch and protein strengthens our findings.     

Comparative study of phytic acid content,in-vitro protein digestibility and amino acid composition of different types of flat breads

Phytic acid content of eight different types of leavened and unleavened flat breads was determined. It was highest in unleavened and non-fermented whole wheat chapati and lowest in the leavened and fermented white wheat flat bread roghni nan. The effect of baking conditions, bread composition and phytic acid content on in-vitro digestibility of protein was measured using a pepsin multienzyme pH stat technique. The amino acids released were separated by ultrafiltration. The rate of protein digestibility of flat bread and amino acid released depended upon the type of flour used, baking conditions, phytic acid content and other antiproteolytic constituents of breads. Leavening and fermentation of breads resulted in an increase of protein digestibility and availability of amino acids. Addition of soya flour increases the protein digestibility of breads whereas millet flour decreases it.     

Effect of rabadi fermentation of barley on HCl-extractability of minerals

Rabadi fermentation of raw (freshly ground) as well as autoclaved barley flour at 30, 35, and 40°C for 6, 12, 18, 24, and 48 h brought about a significant increase in HCl-extractability of iron, copper, zinc, manganese, calcium, and phosphorus; longer periods and higher fermentation temperatures increased HCl-extractability. Increased non-phytate phosphorus and inorganic phosphorus in the fermented product, with a corresponding decrease in phytate phosphorus, was maximum at 40°C for 48 h and minimum at 30°C for 6 h. The level of phytic acid was significantly negatively correlated with HCl-extractability of minerals in the fermented products.     

In vitro digestibility,pasting, and structural properties of starches from different cereals

Starches isolated from seven different cereals were evaluated for their composition, physicochemical, in vitro digestibility, structural, morphological, and pasting properties. The in vitro starch digestion rate and estimated glycemic index (GI) of cereal starches were evaluated along with the impact of cooking on starch digestion. The cooking of starch slurries increased the rapidly digestible starch content from a range of 34.7–54.4% to a range of 60.5–78.5%. On the basis of hydrolysis index, the GI ranged from 83.6 to 91.8 and after cooking it increased from 95.1 to 98.6 for different cereal starches. Both the swelling power and solubility showed an increasing trend with rising temperature. Paste clarity of starches negatively correlated with fat content. The amylose content of various starches ranged from 17.7 to 24.7% and was negatively correlated to crystalline index (r = -0.975, p ≤ 0.05). XRD pattern revealed A-type pattern of crystalline starch, where crystallinity index ranging between 28.2 to 44.9%. FTIR revealed slight differences among chemical bonding of starches from different cereals. From scanning electron micrograph observations, wheat and barley starch granules proved smoother as compared to other cereal granules. Barley contained the highest (27.5 µm) and rice had the lowest (10.2 µm) size starch granules. The pasting properties were significantly (p ≤ 0.05) different for different cereal starches. Peak, breakdown, and final viscosities were the highest for maize starch (1725, 384, and 2112 mPa.s, respectively), whereas rice and oats exhibited the highest trough and setback viscosities (1420 and 954 mPa.s, respectively).     

Effect of Sorghum Flour Addition on In Vitro Starch Digestibility,Cooking Quality,and Consumer Acceptability of Durum Wheat Pasta

Whole grain sorghum is a valuable source of resistant starch and polyphenolic antioxidants and its addition into staple food like pasta may reduce the starch digestibility. However, incorporating nondurum wheat materials into pasta provides a challenge in terms of maintaining cooking quality and consumer acceptability. Pasta was prepared from 100% durum wheat semolina (DWS) as control or by replacing DWS with either wholegrain red sorghum flour (RSF) or white sorghum flour (WSF) each at 20%, 30%, and 40% incorporation levels, following a laboratory‐scale procedure. Pasta samples were evaluated for proximate composition, in vitro starch digestibility, cooking quality, and consumer acceptability. The addition of both RSF and WSF lowered the extent of in vitro starch digestion at all substitution levels compared to the control pasta. The rapidly digestible starch was lowered in all the sorghum‐containing pastas compared to the control pasta. Neither RSF or WSF addition affected the pasta quality attributes (water absorption, swelling index, dry matter, adhesiveness, cohesiveness, and springiness), except color and hardness which were negatively affected. Consumer sensory results indicated that pasta samples containing 20% and 30% RSF or WSF had acceptable palatability based on meeting one or both of the preset acceptability criteria. It is concluded that the addition of wholegrain sorghum flour to pasta at 30% incorporation level is possible to reduce starch digestibility, while maintaining adequate cooking quality and consumer acceptability.     

干热处理对藜麦淀粉结构和理化性质的影响

以高筋小麦粉为原料添加酵母制作面团,在温度28℃、湿度80%条件下发酵1～6 h,提取小麦淀粉。研究发酵时间对小麦直链淀粉含量、损伤淀粉含量、粒径、颗粒表面结构、糊化及消化特性的影响。结果表明：面团发酵1 h后直链淀粉含量和损伤淀粉含量均显著低于原淀粉(P<0.05)。快速黏度分析结果表明,发酵1 h的小麦淀粉峰值黏度、热浆黏度和冷浆黏度最低。发酵处理后淀粉的粒径均小于原淀粉,其中发酵5 h的平均粒径最小。扫描电镜结果表明,发酵6 h的小麦淀粉颗粒表面出现破裂现象。体外消化实验表明,发酵5 h和6 h小麦淀粉的消化速率最高,发酵后抗性淀粉含量低于原淀粉,而慢消化淀粉含量高于原淀粉(P<0.05)。     

Saccharification and Fermentation of Whole Barley Ground in the Szego Mill

Barley, after steeping in water, was ground with ease and efficiency in the Szego mill, and its starch was liquefied, saccharified and fermented to very high yields of ethanol. The Szego mill consists of vertical rollers with helical grooves which rotate within a fixed cylinder, resulting in very fine grinding and a somewhat flaky product. The steeped barley was ground to a fine paste. This was readily liquefied and saccharified by amylolytic enzymes (dual enzyme process), and the resulting sugars were fermented in 24 h by ordinary bakers' yeast Saccharomyces cerevisiae, resulting in over 450 1 ethanol/t of barley. Still shorter time, 12 h, and the same high yield were achieved when liquefied barley starch was simultaneously saccharified by glucoamylase and fermented. Fermentation to ethanol by a glucoamylase-producing yeast S. diastaticus strain 164 A (from Labatt Brewing Company) enabled the amount of this enzyme required for saccharification to be reduced to about one-half the normal quantity, but at some cost in slower fermentation and slightly lower ethanol yield.     

Application of Hydrothermically Treated Barley in Beer Production

Production of beer using native and hydrothermically treated barley (extruded barley flakes) as malt substitute was examined in this work. Nine samples of beer were produced on a laboratory scale, and malt was substituted (10–40%) by native barley flour or hydrothermically treated barley. Infusion mashing was employed, and native barley flour was pretreated by cooking. Worts were boiled with 150 g/hl native hops for one hour. Saccharomyces uvarum strain 112 was used for the fermentation, at 8°C, for 10 days. The results showed that the fermentation was normal in all samples. The use of hydrothermically treated barley in beer production produced beers, similar to those made with native barley as malt substitute, minimising the time needed for beer production and maximising the capacity of the brewhouse.     

Effect of hydrothermal treatment of runner bean (Phaseolus coccineus) seeds and starch isolation on starch digestibility

The study investigated the effect of traditional soaking and cooking, storage after cooking and freezing (? 18 °C, 21 days) and autoclaving of two varieties of runner bean on starch digestibility. Results achieved were compared with digestibility of isolated starch subjected to similar treatments. The digestibility of native starch from Nata var. seeds was lower after isolation than in raw flour. This starch was characterized by a higher content of fat and lower values of swelling power (SP) and amylose leaching (AML). After the thermal treatment, a significantly higher content of rapidly digestible starch (RDS) was observed both in seeds and starch. It was accompanied by reduced contents of resistant starch (RS) and slowly digestible starch (SDS). In flours from cooked seeds, the content of RDS was observed to be higher than in flours from autoclaved seeds, despite similar changes in contents of other constituents (ash and protein). It was probably due to better starch gelatinization owing to the long-lasting soaking of seeds. This resulted in a greater decrease of amylose content of starch compared to the other flours. Differences in SP, AML and thermal properties between starches isolated from two bean varieties had no influence on their digestibility after cooking. The storage of starch pastes at a temperature of ? 18 °C, unlike that of seeds, resulted in a significant increase in RS content, which shows the importance of other flour components in the process of starch retrogradation.