Dry Milling and Accelerated Fermentation of Maize for Industrial Production of Kenkey, a Ghanaian Cereal Food

The dry milling of maize and accelerated fermentation of dough for kenkey production were studied as part of a wider investigation into the possibility of industrial production of a dehydrated kenkey flour. Dough containing an enrichment of lactic acid bacteria was used successfully to achieve, within 24-h incubation at 30°C, the required level of acidification of dry-milled maeze flour to obtain kenkey dough. Cabinet and drum drying were used to prepare dehydrated kenkey flour and pre-gelatinised aflata, respectively. Drum-drying was an effective method for the preparation of pre-gelatinised aflata, but it resulted in a 34% reduction in the titratable acidity (TA) of the fermented dough. Cabinet drying, on the other hand, had a less drastic effect on the TA of fermented dough, suggesting the possible use of a mixture of drum-dried aflata and uncooked cabinet-dried flour for convenient preparation of kenkey at the household level. Dry-milled maize flours had pasting and set-back viscosities that were inferior to those of the traditionally prepared doughs, and consequently they were unsuitable for the production of pre-gelatinised aflatas. Pre-getalinised aflata from unfermented dry-milled flours resulted in a crumbly and friable kenkey product. It was concluded, therefore, that, although dry-milling of maize and accelerated fermentation of dough could drastically reduce kenkey production time, from about 6 days to within 24 h, omission of the soaking step practised traditionally results in a product with inferior textural quality.     

Effect of soy-fortification method on the fermentation characteristics and nutritional quality of fermented maize meal

Studies were conducted to develop an appropriate household/small-scale enterprise level technique for the production of soy-fortified fermented maize dough (or meal) by comparing different treatments, processing methods and fortification levels. The effects of fortification method of the Ghanaian traditional fermented maize dough with raw or heat-treated whole soybeans and full-fat soyflour at 0%, 10% and 20% replacement levels, on the rate of fermentation and product quality were investigated. Sensory characteristics, trypsin inhibitor activity, amino acid pattern, proximate composition and hot paste viscosity were used as the indices of quality. Addition of whole soybeans to maize before milling and fermentation reduced the fermentation time by 60% while increasing the protein content by 24% and 70% respectively for 10% and 20% levels of fortification. A significant improvement was also achieved in the amino acids pattern of the fortified dough. However, raw whole soybeans imparted an undesirable color and beany flavor and an appreciable concentration of trypsin inhibitor activity (TIA) to the dough. Boiling soybeans for 20 min before incorporation into the maize for milling and fermentation was found necessary for desirable flavor and low levels of TIA. Little or no changes in the pasting viscosity characteristics occurred in samples containing boiled soybeans, while the usual method of fortifying maize meal with soy flour was found to severely depress the pasting viscosity characteristics and drastically reduced the acidity of the fermented dough. Based on the findings of the study, the most appropriate technique for the production of soy-fortified high protein fermented maize dough has been suggested to involve incorporation of boiled whole soybeans in soaked maize before milling and fermentation for improved sensory characteristics, enhanced nutritive value and optimal functional properties.     

Expansion profiles of wheat doughs fermented by seven commercial baker's yeasts

Commercial baker's yeast consists of Saccharomyces cerevisae, however the strain can vary in each baker's yeast, which might influence the dough fermentation time. The scope of this research was to investigate the dough expansion of wheat doughs fermented by seven commercial baker's yeasts at different yeast concentrations (2.88·10¹¹, 5.76·10¹¹ and 8.64·10¹¹ colony forming units/kg flour) and fermentation temperatures (5 °C, 15 °C, 25 °C and 35 °C). Dough expansion was investigated by monitoring the dough height and it was found to be described well by a first order kinetic model. Doughs fermented with four of the seven yeasts generally had higher kinetic rate constants and hence shorter fermentation times compared to fermentation with the other three yeasts. The shortest fermentation times were found for doughs fermented at 25 °C and the highest yeast concentration, a trend found for all the yeasts tested. The differences in the kinetic rate constants indicate a differentiation in yeast strain among the commercial baker's yeasts emphasising the great importance of the choice of baker's yeast for the dough fermentation time.     

Preparation and fermentation of rice-defatted soy flour blends: Effect on protein,fat and ash content

Rice-defatted soy flour blends prepared in three proportions viz. 40:60, 50:50 and 60:40 were fermented with buttermilk at 25, 30 and 35°C for 12, 18 and 24h. Fermentation of these blends lowered the pH and raised the titratable acidity, maximum drop in pH and rise in titratable acidity being observed at 35°C for 24h. The fermentation either decreased or did not change the protein content of cereal-legume blends. Fat as well as ash content remained unaltered irrespective of temperature and time period of fermentation.     

Effects of Cultivar and Environment on β-(1,3)-(1,4)-D-glucan Content and Acid Extract Viscosity of Spanish Barleys

The acid extract viscosities and β-glucan contents of ten two- and six-rowed barley cultivars grown at seven locations in three consecutive years in Spain were studied in the present work. The viscosities varied from 2·4 to 24·8 centistokes (cSt) and the mean value was 6·4 cSt. The average β-glucan content of barleys determined by HPLC was 3·5% with a range of 1·9–5·5%. Significant differences were found in both β-glucan content and acid extract viscosity between different cultivars, locations and years. The β-glucan contents and viscosities of winter cultivars were higher than those of spring. Cvs. Barbarrosa and Hatif de Grignon were the genotypes with the highest values for both parameters, while cv. Beka had the lowest viscosity and β-glucan content. Environmental factors influenced both parameters. The acid extract viscosities of barleys were correlated negatively with the amount of precipitation (r=−0·754;P<0·05). Barleys grown in wet and rainy areas (Girona and La Coruña) had lower viscosity values.     

A preliminary study on the use of tempe-based formula as a weaning diet in Nigeria

Tempe, an Indonesian mold fermented food, was prepared from cowpeasand soybeans using the traditional oriental process with modifications whereappropriate. Four complementary foods were developed from whole maizemeal or dehydrated fermented maize (ogi) flour fortified with eithercowpea tempe or soybean tempe. Wholesomeness and potentials of thevanilla-flavored foods as weaning diets were determined. The nutrientcontent of all the developed products were within the range prescribed bythe FAO/WHO pattern for processed weaning foods. The products hadloose bulk densities between 0.40–0.55 g/ml and packed bulk densitiesbetween 0.68–0.75 g/ml; reconstitution indexes were between92.30–104.00 g/ml; viscosities were 34.2–65.0 CP at 70 ^°C and45.0–76.9 CP at 30 ^°C. Total plate counts ranged from 3.2 ×10³ – 4.3 × 10⁴cfu/g; coliforms staphylococcus, mold, andyeast were absent in some of the products. The results on sensoryattributes showed that tempe-based weaning diets were comparable withMameal, a commercial product. Maize and maize-fortified diets wereslightly higher in packed bulk density. Fortification reduced the viscosityof the diets and the values reduced with increasing temperature. Tempe-based weaning foods reconstituted easily in hot water, while cookingdestroyed most of the microorganisms present. Maize-based tempefortified foods were relatively inexpensive and have potential as weaningfoods.     

Dough/crumb transition during French bread baking

The modifications occurring during dough to crumb (D/C) transition of French bread (350 g) were studied in an instrumented pilot-scale oven for doughs with different contents of minor components, soluble, lipids and puroindolines. Internal temperature measurements showed that, for most compositions, complete D/C transition occurred between 55 and 70 °C, after 5 min of baking, and coincided with maximum loaf expansion. Differential scanning calorimetry (DSC) in excess of water performed on samples taken during baking (3 and 5 min) showed that starch gelatinization and melting developed continuously during D/C transition for various contents of the soluble fraction in dough. Dynamic thermomechanical analysis (DMA) on dough showed that dough stiffened between 60 and 70 °C, as seen by the increase of elastic modulus E′ by more than one decade, for all dough compositions. Relating these changes to the results of baking experiments, D/C transition was assigned first to gluten reticulation and, to a lesser extent, to continuous starch granule swelling.     

Modification of the rheological behavior of amaranth (Amaranthus hypochondriacus) dough

For people with celiac disease, a lifelong abdication of gluten including-products is necessary to live a life without celiac affected reactions. The production of high-quality bread from gluten free flour is not simple in comparison to gluten including flours such as those derived from wheat (Triticum spp.). The gas binding and crumb structure forming capacity are very low in gluten free batters. They can efficiently be analyzed through the rheological properties of the dough used. The use of acidification in amaranth (Amaranthus hypochondriacus) dough preparation is a possible means of changing the rheological behavior of amaranth in the desired direction. Methods include the use of lactic acid directly, or the fermentation via lactic acid bacteria. Adding up to 20 mL lactic acid/kg flour in amaranth dough preparation led, during oscillation tests, to an increase of the complex shear modulus up to 30% in the range of 0.1 up to 10 Hz. The use of sourdough fermentation decreased the complex shear modulus in the same test up to nearly 60%. In creep recovery tests, the elastic part of amaranth dough decreased from 65.4% without any treatment down to 63.9% by the addition of up to 20 mL lactic acid/kg flour. Sourdough fermentation by Lactobacillus plantarum was able to decrease it to 54%. The acidification showed a significant positive influence on the rheological parameters of amaranth dough only at the higher stress level. In contrast, sourdough fermentation was able to produce doughs with viscosity and elasticity similar to that found in pure wheat flours.     

Phytic acid content and “in vitro” iron, calcium and zinc bioavailability in bakery products: The effect of processing

Whole-grain bakery products and cereals are valuable sources of dietary fiber, vitamins, and trace elements. However, the presence of phytate, could decreases mineral bioavailability due to its chelating properties. In this study, the effect of fermentation and baking on the phytate content of different bakery products was measured by HPLC; the mineral availability in bakery products during processing was investigated by measuring solubility and dialysis, as well as the mineral uptake and transport by Caco-2 cells after in vitro digestion. Raw materials showed the highest amount of phytate, causing an important effect on the stage of processing. The solubility and dialyzability of iron increased with fermentation, meanwhile calcium and zinc showed a high variability depending on the product analyzed. After baking, the dialyzability of minerals increased with respect to the fermented dough in most cases. The highest uptake and transport efficiency of iron and calcium in cells corresponded to dough after fermentation of wheat flour with respect to the baked samples. For zinc, no differences were observed between fermented dough and after baking on uptake and transport efficiencies. This study showed that in vitro mineral availability of bakery products is influenced by the stage of processing and ingredients used.     

Effect of roasting and fermentation on viscosity of cereal-legume based food formulas

With the view of preparing semi-liquid weaning foods of high energy content, the influence of roasting (stationary hot air treatment) and fermentation (with natural and pure culture inocula) on the viscosity of maize-sorghum-soya porridges was investigated. Roasting resulted in porridges of significantly higher viscosity (cooked porridge cooled to 40 °C). Porridges made from the individual ingredients (maize, sorghum, soya) did not show this behaviour. Natural fermentation of mixed ingredients resulted in lower porridge viscosities (cooked porridge cooled to 40 °C, as well as hot-paste peak viscosity) when pH was 5.0–5.5. At lower pH the viscosity of the final porridges increased. Fermentation experiments of individual ingredients inoculated with pure cultures ofLactobacillus plantarum andCandida famata lead to the conclusion that various factors contribute to the effect of fermentation on porridge viscosity. Porridges of minimum viscosity are obtained at pH 5.0–5.5 corresponding with a moderate extent of fermentation. From a consumer safety point of view, it would be preferable to acidify to lower pH values (pH<4.5). If necessary, viscosity adjustments could be made using malted cereals.     

Glucose and pyranose oxidase improve bread dough stability

When used in bread dough systems, glucose oxidase (GO) and pyranose oxidase (P₂O) generate H₂O₂ from O₂. We here studied their potential to improve dough and bread characteristics. Neither GO nor P₂O significantly affected the volume of straight dough bread produced with fermentation and proofing times of respectively 90 and 36 min at dosages up to 0.50 nkat/g flour. Supplementation with 1.00 nkat/g flour of GO or P₂O significantly decreased bread loaf volume. The resistance of dough (fermented for 20 min and proofed for 56 min) to an applied shock was substantially improved by inclusion of 0.08, 0.25, 0.50 or 1.00 nkat/g flour of GO or P₂O in the dough recipe. Thus, the proofed doughs showed significantly less collapse and the resultant breads had higher loaf volumes than did the reference breads. Yeast probably exerts an oxidizing effect on dough, which, depending on the exact breadmaking protocol used, might veil the positive oxidizing effect of the enzymes on dough properties during prolonged fermentation.     

The Effect of Heat–Moisture Treatment on the Structure and Physicochemical Properties of Normal Maize,Waxy Maize,Dull Waxy Maize and Amylomaize V Starches

Normal maize, waxy maize, dull waxy maize and amylomaize V starches were heat treated at 100 °C for 16 h at a moisture content of 30%. The results showed that the X-ray intensities of the major d-spacings of all starches increased on heat–moisture treatment (waxy maize > normal maize > dull waxy maize > amylomaize V). This treatment decreased the apparent amylose content (amylomaize V > normal maize), swelling factor (amylomaize V > waxy maize > dull waxy maize > normal maize), amylose leaching (amylomaize V > normal maize), pasting viscosities (amylomaize V > normal maize), acid hydrolysis (amylomaize V > normal maize > waxy maize > dull waxy maize), enzyme hydrolysis (amylomaize V > normal maize > dull waxy maize > waxy maize) and syneresis (amylomaize V > normal maize > waxy maize ≈ dull waxy maize). The gelatinization transition temperatures of all starches increased on heat–moisture treatment (amylomaize V > normal maize > waxy maize > dull waxy maize). However, the gelatinization temperature range increased only in normal maize and amylomaize V starches (amylomaize V > normal maize), while it remained unchanged in both the waxy starches. The enthalpy of gelatinization remained unchanged on heat–moisture treatment in all starches and the pasting viscosities of the two waxy starches were also unaffected. The foregoing data showed that starch chains within the amorphous and crystalline regions of the granule associate during heat–moisture treatment. However, the extent of this association was of a greater order of magnitude within the amorphous regions. DSC studies have indicated associations involving amylose chains (amylose–amylose and amylose–native starch lipids) resulted in the formation of new crystallites of different stabilities. In contrast, associations involving amylopectin chains (amylopectin–amylopectin) did not lead to crystallite formation.     

Levels of antinutritional factors in pearl millet as affected by processing treatments and various types of fermentation

Pearl millet (Pennisetum typhoideum) was fermented with Lactobacilli or yeasts alone and in combination, and with natural microflora after various processing treatments, as grinding, soaking, debranning, dry heat treatment, autoclaving and germination. Fermentation was carried out at 30°C for 48 hours withLactobacillus plantarum (LP) andRhodotorula (R) isolated from naturally fermented pearl millet andLactobacillus acidophilus (LA),Candida utilis (CU) and natural microflora (NF). Germination and autoclaving, and debranning and autoclaving were the most effective processing treatments to reduce the phytic acid, amylase inhibitors and polyphenols. There was a further reduction in these antinutrients due to fermentation. Phytic acid and amylase inhibitors were completely eliminated after fermentation in some of the samples especially in soaked, debranned and germinated ones. Polyphenols were altered non-significantly in general but fermentation with Lp+R and NF caused a significant increased in polyphenols.     

Reduction in the Levels of Phytate During Wholemeal Bread Making; Effect of Yeast and Wheat Phytases

No difference in wheat phytase activity was observed when different types of acid were used to adjust the pH of wholemeal wheat flour suspensions to pH 5·0, the optimum for wheat phytase. When whole wheat bread was made without additives or after adjustment of the dough pH with acetic acid or lingonberry (traditional ingredients in bread making in Sweden), 64%, 96% and 83%, respectively, of the initial phytate was hydrolysed. A small but significant difference between breads with and without yeast or with deactivated yeast was found, indicating that yeast contributed some phytase activity under the conditions of bread making (pH 5·3–5·8 and 30–37°C). The optimum pH of yeast phytase was found to be 3·5. The isomers of IP₅formed with purified wheat phytase or yeast phytase were studied using sodium phytate as substrate. Wheat phytase formed 1,2,3,4,5-IP₅whereas yeast phytase formed 1,2,4,5,6-IP₅. Determination of the isomers of inositol pentaphosphate demonstrated that the reduction in phytate levels in bread compared with wholemeal flour resulted from both wheat and yeast phytase activities.     

Influence of temperature on the fermentation of bambara groundnut (Vigna subterranea) to produce a dawadawa-type product

Bambara groundnut (Vigna subterranea) was fermented to produce a dawadawa-type product using a starter culture of Bacillus licheniformis isolated from naturally fermenting bambara groundnut beans. Fermentation was carried out at 30 and 37 °C for four days and at 45 °C for two days. The pH of the substrate decreased after 24 hours and then rose at 30 and 37 °C but remained constant at 45 °C after the initial drop. Total titratable acidity of the fermenting beans mimicked the pH values. Proximate analyses for moisture, protein and fat of the cotyledons showed an increase in all three constituent at each of the three fermentation temperatures. At the end of fermentation, total available carbohydrate was 55%, 59% and 62% of the original value at 30, 37 and 45 °C, respectively. Fermentation of bambara groundnut at 45 °C for two days is recommended as the ideal fermentation temperature and time.     

Changes in Textural,Pasting and Thermal Properties of Wheat Buns and Tortillas During Storage

The texture, pasting and thermal properties of two common baked products made from wheat flour, buns and tortillas, were characterised periodically over 8 days of storage. Firmness of buns and tortillas increased throughout storage as measured using a texture analyser. Pasting viscosities of crumb-water slurries were measured with a Rapid Visco Analyser. Pasting viscosities at 74 °C, 95 °C of fresh products (one min after baking) were significantly lower than their respective dough pasting viscosities. No particular trend was observed in the pasting properties of bun and tortilla samples upon further storage up to 8 days. Amylose solubility decreased significantly immediately after baking in both buns and tortillas and continued to decrease throughout the storage period. Thermal analysis with a differential scanning calorimeter detected amylopectin recrystallisation almost immediately after baking (1 min) in tortillas, whereas amylopectin recrystallisation in buns was evident only after storage for 1 day. Amylopectin recrystallisation in tortillas continued to increase during storage. Overall, the harsher processing of buns, i.e. higher temperature, longer time and higher moisture environment, resulted in greater dispersion of amylose and amylopectin, and retrogradation of amylose in buns than in tortillas. Further, amylopectin crystallisation by itself did not contribute to staling, because more amylopectin crystallisation was observed in tortillas than in buns, even though the shelf life of tortillas is longer than buns.     

A new method to determine viscoelastic properties of corn grits during cooking and drying

The working principles and the theoretical background of a new method to measure the viscoelastic properties of grains during cooking and drying processes are presented. Specifically, corn grits at different processing stages of cooking and drying were chosen as the model grain and their viscoelastic characteristics, namely elastic stiffness and viscous damping, were determined. During the measurements grits were squeezed between a rigid bottom plate and a top round element oscillating at random frequencies in a range 10–10,000 rad/s. A frequency response of the mechanical impedance of the samples, which is defined as the ratio between the force applied to the samples and the oscillation velocity, was obtained. Corn grits were measured in their raw state, after cooking in a pressure cooker for different times (2, 7, 15, 30, and 60 min), and at different times of drying (30, 60, and 120 min) at 65 °C. The measured mechanical impedances of the samples showed that rheological changes upon processing can be monitored by the newly developed method. Non-destructive and quick measurements, data covering a wide range of frequencies, and the adaptability of the method to be used with available instruments used in texture measurement such as texture analyzers are some of the important advantages that the new method provides to the area of cereal processing.     

Preparation nutritional value and acceptability of barleyrabadi — an indigenous fermented food of India

Rabadi fermentation of barley flour-buttermilk mixture (fresh and autoclaved) at 30, 35 and 40°C for 6, 12, 18, 24 and 48 h lowered pH, enhanced titratable acidity and did not change fat and total mineral (Ca, Fe, Cu, Zn, Mn and P) content. Protein content of fermented fresh as well as autoclaved barley flour-buttermilk mixture either decreased or remained unchanged.Rabadi prepared from both types of barley flour at different temperatures and time periods was acceptable; but that which was fermented at 40°C for 48 h was less acceptable in terms of taste.     

Effect of fat level,mixing pressure and temperature on dough expansion capacity during proving

In this work the effect of fat content on dough aeration during proving was investigated using dynamic dough density measurements. Doughs of three different fat levels (0%, 0.04% and 0.2% flour basis) were mixed under various pressures using a Tweedy mixer and proved at five different temperatures (30, 35, 40, 45 and 50 °C) in the dynamic dough density system. The dough expansion capacity and the time of the gas loss of each dough sample were measured and related to fat level, mixing pressure and proving temperature.     

Volume change of bread and bread crumb during cooling,chilling and freezing,and the impact of baking

During baking, bread dough undergoes an expansion followed by a slight contraction at the end of baking. The contraction during baking has been evidenced by some authors. However, there is a limited amount of literature about the contraction of the crumb during the chilling phase and also during the freezing phase in the case of freezing. A study has been carried out to better understand the impact of the baking degree on the contraction of the crumb during chilling after baking and during freezing. The volume of the samples has been evaluated with a laser volumeter. Breads (70 g dough) were baked until reaching 75 °C, 85 °C, 95 °C, 98 °C and then 98 °C for 10 min. Results showed that a longer baking resulted in a lower contraction of the bread. The volume change was between 25% and 2.5% for baking at 75 °C—0 min dwell and 98 °C—10 min dwell, respectively. The contraction was compared to the contraction of degassed bread crumb samples, which was more important. SEM pictures showed that the degree of baking also corresponded to a very different structure of the crumb. For the longer baking, the starch granules were fully gelatinized and no ghosts of starch granules were visible. The magnitude of the contraction was thus associated with the degree of baking and with the degree of starch granule destructuration.