Changes in mineral absorption inhibitors consequent to fermentation of Ethiopian injera: implications for predicted iron bioavailability and bioaccessibility

Possible changes in mineral bioavailability during processing of different types of injera sampled in Ethiopian households were assessed using different methods: phytic acid/mineral molar ratio, absorption prediction algorithm and in vitro availability measurements. Most foods analysed were rich in iron, but most of the iron likely resulted from soil contamination. The highest iron, zinc and calcium contents were found in teff–white sorghum (TwS) injera and flour. The lowest phytic acid/Fe and phytic acid/Zn molar ratios were found in barley–wheat (BW) and wheat–red sorghum (WrS) injeras. Although ideal phytic acid/Fe molar ratios (<0.4) were found in BW and WrS injeras, no significant difference between in vitro iron bioaccessibility and algorithm predicted absorption was observed. In injera, phytic acid degradation alone is unlikely to improve iron bioavailability, suggesting interactions with other absorption inhibitors. The use of phytic acid/Fe molar ratios to predict bioavailability may thus be less appropriate for iron‐contaminated foods.     

Influence of malted barley and exogenous enzymes on the glucose/maltose balance of worts with sorghum or barley as an adjunct

The sugar profile of wort from laboratory malted barley, malted sorghum, unmalted barley and unmalted sorghum grains mashed with commercial enzyme preparations were studied. Similar levels of glucose to maltose (1:7) were observed in wort of malted barley and malted sorghum. Mashing barley or sorghum grains with commercial enzymes changed the glucose to maltose ratio in both worts, with a greater change in wort from sorghum grains. Although hydrolysis with commercial enzymes released more glucose from maltose in sorghum wort, the same treatment retained more maltose in barley wort. Adding malted barley to sorghum grains mashed with commercial enzymes restored the glucose to maltose ratio in sorghum mash. Fermentation of wort produced from all barley malt (ABM) mash and commercial enzyme/barley malt/sorghum adjunct (CEBMSA) mash of similar wort gravity was also studied. ABM and CEBMSA worts exhibited similar glucose to maltose ratios and similar amino acid spectra. However, ABM released more individual amino acids and five times more proline than wort from commercial enzyme/barley malt/sorghum adjunct. ABM produced 27% more glucose and 7% more maltose than CEBMSA. After fermentation, ABM mash produced 9.45% ABV whilst commercial enzyme/barley malt/sorghum adjunct mash produced 9.06% ABV. Restoration of the glucose/maltose ratio in the CEBMSA mash produced wort with a sugar balance required for high gravity brewing. © 2020 The Institute of Brewing & Distilling     

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.     

A Microbiological Study of Sudanese Date Wines

Procedures followed in the home fermentations of three date wines were investigated. Two wines, 'sherbote', and‘nabit’prepared from date sirup, are produced by a relatively quick fermentation taking about 36-48 hr. The fermentation of the third wine;‘dakkai', prepared from whole date fruits, is a slow process taking about 96 hr. The samll amounts of spices and sorghum malt used as additives in the preparation of 'sherbote’and‘nabit', respectively, contribute to the inoculum. In‘dakkai’fermentation of the inoculum comes from the natural flora of the data fruit itself. Changes in the production of ethanol, acetic and lactic acids and pH as well as in microbial populations were followed during fermentation of each wine. The most important genera of yeast, acetic and lactic acid bacteria were identified.     

Changes in some components of soymilk during fermentation with bifidobacteria

Bifidobacterium longum B6 and B. infantis CCRC 14633 were grown in soymilk for a period of 48 h. During various fermentation periods, changes in the contents of crude protein, sugars, B-vitamins, acetic and lactic acids in soymilk were examined. Crude protein and titratable acidity were increased during fermentation. Soymilk fermented with B. infantis had higher titratabale acidity than that fermented with B. longum. The degree of protein hydrolysis, thiamin and riboflavin contents were increased while niacin content was decreased in soymilk fermented with either B. infantis or B. longum. Acetic and lactic acid contents were increased while the molar ratio of acetic and lactic was decreased during fermentation. Stachyose, raffinose and sucrose contents were decreased, with stachyose showing the largest magnitude of reduction. On the other hand, contents of fructose and glucose plus galactose contents were increased during fermentation.     

Study through surveys and fermentation kinetics of the traditional processing of pearl millet (Pennisetum glaucum) into ben-saalga, a fermented gruel from Burkina Faso

Traditional cereal-based fermented foods are frequently used as complementary foods for infants and young children in Africa. This is the case for ben-saalga, a popular fermented gruel produced from pearl millet (Pennisetum glaucum) in Burkina Faso. Detailed knowledge of traditional processing is a prerequisite for investigating ways to improve both the nutritional and sanitary qualities of the corresponding foodstuff. In this work, the traditional processing of pearl millet into ben-saalga was investigated in 24 production units, and fermentation kinetics were studied in pilot scale experiments. Processing steps include: washing (optional), soaking of the grains (first fermentation step), grinding and sieving of the wet flour, settling (second fermentation step), and cooking. The soaking step was mainly characterized by alcoholic fermentation whereas lactic acid fermentation occurred during the settling step. Fermentation kinetics during settling indicates a temporal variation of metabolic activity. Initially, both homofermentative and heterofermentative pathways were simultaneously active, and later only a homofermentative pathway was active. The paste produced at the end of settling had a low pH (4.0+/-0.4) and its microflora was dominated by lactic acid bacteria (LAB) with an amylolytic LAB/LAB ratio of 12%. Sucrose disappeared in the grains during soaking but was not detected in the soaking water, whereas glucose, fructose and maltose appeared transiently. Glucose and fructose were the main substrates observed for lactic acid fermentation during the settling step; however unbalanced fermentation led to the hypothesis that starch hydrolysis products may also serve as substrates for lactic acid formation. At the end of the processing, a 75% and 83% decrease was observed in phytate (IP6) and raffinose, respectively. The sour gruel ben-saalga resulting from cooking the sour paste had inadequate nutritional characteristics with respect to infants' and young children's requirements; it was characterized by fluid consistency (Bostwick flow: 137 mm/30 s) and low energy density (about 30 kcal/100 g of gruel).     

Effect of Amyloglucosidase on Wort Composition and Fermentable Carbohydrate Depletion in Sorghum Lager Beers

A three‐factorial experiment with a level of confidence of P < 0.05 was performed to study fermentable carbohydrate depletion and ethanol production during 144 h fermentations of lager beers produced with barley malt (BM), sorghum malt (SM), refined maize (MZ) or waxy sorghum (WXSOR) grits treated during mashing with or without amyloglucosidase (AMG). The percentage glucose, maltose and maltotriose, based on total fermentable carbohydrates for the BM wort was 20, 68 and 13% and for the SM wort 35, 48 and 17% respectively. Treatment with AMG increased wort glucose from 9.3 to 24.5 g/L wort and total fermentable sugar equivalents, expressed as g glucose/L, from 59.2 to 72.6 g/L wort. The SM worts had approximately 50% more glucose and 40% less initial maltose content respectively compared to the BM worts. The WXSOR grits produced worts and beers with similar properties to those produced from the MZ adjuncts. AMG addition led to a >2.5 fold increment in wort glucose and 23% in total fermentable carbohydrate content. Linear regression analysis determined that the consumption rate of fermentable carbohydrates during fermentation followed first order reaction kinetics. Depletion times to reach 50% of the initial concentrations of glucose, maltose and maltotriose were 49, 128 and 125 h, respectively, clearly indicating that the fermenting yeast preferred glucose. Maltose and maltotriose depletion times of the AMG treated worts were significantly faster and lower, respectively, when compared with the untreated worts. At the end of the fermentation, the BM beers contained higher ethanol levels (5.1% v/v) than the SM beers (3.9% v/v). For AMG treated beers, no significant differences in ethanol content were observed among samples mashed with BM and beers produced from SM and MZ grits. The results demonstrated that AMG could be used to increase the initial concentration of glucose and total fermentable carbohydrates thus decreasing dextrin levels, especially from sorghum mashes.     

Exploration of high‐gravity fermentation to improve lactic acid bacteria performance and consumer's acceptance of malt wort‐fermented beverages

Lactic acid bacteria (LAB) fermentation performance is essential for aroma metabolites formation and product flavour quality. Hence, this study appraises high‐gravity malt wort fermentation (HGF) by three LAB strains to improve the fermentation performance and consumer's acceptance of lactic acid‐fermented malt‐based beverages (LAFMB). HGF at 20% (w/w) provided higher amino acid content and buffering capacity that allowed greater cell development, viable cell count and sugar utilisation. Moreover, the pH change was lesser although marked lactic acid accumulation. It is noteworthy that HGF significantly incremented the content of higher alcohols (+0 – 161%), 2‐phenylethanol (+11–147%), acetaldehyde (+27–44%) and β‐damascenone (+25 – 66%) comparing to low‐gravity malt wort at 12%. Thus, HG‐fermented beverages were significantly preferred with greater hedonic scores (4.6 ± 2.1). Our results indicate that HGF is a valuable strategy for improving LAB fermentation performance in malt wort, which in turn increases key aroma compound content resulting in enhanced acceptance of LAFMB.     

白酒酿造过程中Lactobacillus panis乳酸合成关键环境因子的鉴定

Lactobacillus panis是酱香型白酒酿造过程中主要产乳酸微生物。然而,不同环境因子对L.panis乳酸合成及乳酸合成途径关键基因的表达尚未有相关研究。作者分析了温度、乳酸、乙醇及葡萄糖4种不同的发酵过程相关的典型环境因子对L.panis乳酸产量的影响。结果表明,不同环境条件能够显著调节L.panis的生长和乳酸产量,且乳酸和乙醇是酿造过程中其乳酸合成的关键影响因素。当添加10.0 g/L乳酸后,L.panis的乳酸产量最高,达到12.3 g/L;当添加体积分数4.0%乙醇后,L.panis的乳酸产量最低,仅为7.2 g/L。使用实时荧光定量PCR方法对不同条件下L.panis乳酸合成相关基因的表达进行分析,结果表明添加乳酸能够显著上调包括编码L-乳酸脱氢酶和D-乳酸脱氢酶的ldhL和ldhD在内的乳酸合成基因的表达。然而,添加乙醇会导致L.panis乳酸合成相关基因的整体显著下调。分析调控乳酸合成的关键环境因素,对于白酒酿造过程中乳酸和酿造微生物群落调控及白酒质量控制具有重要意义。     

Chemical studies with silage microorganisms in artificial media and sterile herbages

The fermentation changes in artificial media and in sterile herbages inoculated with strains of yeast, hetero-and homo-fermentative lactic acid bacteria isolated from silage were studied in two experiments. In the first, using malt extract broth, four treatments were employed: aerobic, high level of glucose; aerobic, low level of glucose; anaerobic, high level of glucose; anaerobic, low level of glucose. The pH decreased in all cultures. There were no appreciable differences in pH among the cultures of the heterofermentative lactic acid bacterium, but in the cultures of the homofermentative organism there was a greater decrease in pH aerobically than anaerobically. The lowest pH values in the yeast cultures, occurred in the high glucose treatments both aerobically and anaerobically. In all the yeast cultures, acetic, propionic, butyric, isobutyric and isovaleric acids were present. The heterofermentative lactic acid bacterium produced only acetic acid, the greatest amount occurring under aerobic conditions. Ethanol was detected in the culture of the heterofermentative lactic acid bacterium but not in that of the homofermentative organism. Relatively large amounts of i-pentanol were found in the aerobic yeast cultures. In the second experiment, inoculated grass was ensiled with similar treatments to those used in the first experiment. Two incubation periods, 3d and 10d were used. The pH values in all treatments were high (> pH 5.0). In aerobic conditions, the lactic acid contents after the 10d incubation were higher than after 3d. The losses of water soluble carbohydrates during fermentation were greater in the aerobic than anaerobic treatments. Acetic acid was present in all cultures but the higher volatile fatty acids (C₃-iC₅) were only detected in appreciable amounts in the aerobically treated herbages after 10d. In addition to ethanol, n-propanol and i-butanol were also present in all the 10d anaerobic treatments. i-Pentanol occurred in both the aerobic and anaerobic treated herbages.     

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.     

Prospects for the utilization of the endogenous enzymes in sorghum malt in the hydrolysis of starch: Case study with utilization of breadfruit starch for ethanol production

Hydrolysis of breadfruit flour by acid and enzymes of sorghum malt were investigated. Mash (malt to breadfruit flour) ratios of 2: 3 and 1: 1 were used. The optimum mashing profile of 20 minutes at 64°C followed by 30 minutes at 72°C was established. The addition of an exogenous enzyme improved the wort properties. Kinetic study of the enzymatic hydrolysis revealed non‐adherence with either the simple Michaelis‐Menten Kinetics or one with product inhibition. Anaerobic fermentation of the hydrolysate by Sacchammyces cerevisiae at pH 4.7 and temperature of 30°C, was carried out with and without mineral and nitrogen sources supplementation of the wort. The results showed that the enzymes in sorghum malt could be used, with some external enzyme supplementation, to hydrolyse breadfruit starch to yield appreciable amounts of sugar which may be used as food sweetener, substrate for single cell protein production, and in the production of beverages. This is particularly relevant to operations in developing countries.     

植物乳杆菌对高产酯酿酒酵母酒精发酵及酯醇代谢的影响

在高粱汁培养基内同时接种植物乳杆菌（Lactobacillus plantarum）和高产酯酿酒酵母（Saccharomyces cerevisiae）,探究植物乳杆菌及其代谢产物对高产酯酿酒酵母酒精发酵及酯醇代谢的影响。结果表明：植物乳杆菌对高产酯酿酒酵母生长及酒精发酵的影响不大,发酵结束后残糖量均＜5 g/L,乙醇含量为74～78 g/L;植物乳杆菌使高产酯酿酒酵母乙酸乙酯和高级醇产量下降,分别最多下降了15.31%、36.14%;培养基内不同乳酸质量浓度使酿酒酵母乙酸乙酯产量提高,乳酸质量浓度为7.1 g/L时,乙酸乙酯最多提高了39.84%;培养基内乳酸质量浓度在1.8～7.1 g/L时,高产酯酿酒酵母高级醇的产量明显降低,特别是苯乙醇的产量显著下降,下降了25.05%～75.64%。     

Identification of microorganisms producing lactic acid during solid‐state fermentation of Maotai flavour liquor

Lactic acid is the main acid produced during the Maotai liquor brewing process, influencing the quality of the base liquor and fermentation process. However, the microorganisms responsible for lactic acid production have not been identified. In this work, the dynamic changes in bacterial community structure in the Zaosha round (second sorghum feeding and fermentation) of the brewing process were analysed by 16S rRNA high‐throughput sequencing. Results show that lactic acid bacteria (LAB) and Bacillus spp. are the dominant bacteria in the brewing process, where Bacillus spp. are found in the early stage, whilst LAB are found throughout the brewing process. Furthermore, 10 types of LAB and five Bacillus spp. were isolated from Zaopei (a mixture of fermented grains including sorghum and wheat) by a culture‐dependent method. Lactobacillus panis accounts for 68% of the LAB, and Bacillus amyloliquefaciens for 54% of Bacillus spp. Solid‐state fermentation experiments were performed with L. panis and B. amyloliquefaciens and lactic acid production was consistent with the accumulation of lactic acid in Zaosha. The results showed that L. panis was the main producer of lactic acid in pits, while B. amyloliquefaciens plays an important role in the production of lactic acid in the early stages of fermentation. The approach used in this study may facilitate the identification of key microorganisms with specific functionality involved in other food and beverage fermentation processes. © 2018 The Institute of Brewing & Distilling     

Production of Kefir from Soymilk With or Without Added Glucose, Lactose, or Sucrose

ABSTRACT: The effects of added glucose, lactose, and sucrose on microbial growth, acid, and ethanol production, and galactosidase activity in soymilk fermented with kefir grains were studied. Immediately after the addition of kefir grains to soymilk, the lactic-acid bacterial counts were higher, but the yeast counts were lower than in milk kefir. After fermentation for 32 h, the concentrations of yeast, lactic acid, and ethanol in soymilk were significantly lower than those in milk kefir. Addition of 1% glucose to soymilk stimulated growth of lactic-acid bacteria and yeast, the production of lactic acid and ethanol, and the β-galactosidase activity. Nevertheless α- galactosidase activity was suppressed by 1% glucose.     

ROLE OF ALPHA-GLUCOSIDASE IN THE FERMENTABLE SUGAR COMPOSITION OF SORGHUM MALT MASHES*

The cause of the high glucose to maltose ratio in sorghum malt worts was studied. Mashing temperature and pH strongly affected both the amount of glucose and the proportion of glucose relative to total fermentable sugars. The relative proportion of glucose was higher when mashing was performed. at pH 4.0, close to the pH optimum for sorghum alpha-glucosidase, than at the natural pH of the mash (pH 6.0–5.5). Mashing according to the EBC procedure using an enzymic malt extract with pre-cooked malt insoluble solids producing a wort containing maltose and glucose in an approximately 4:1 ratio, whereas mashing with a malt extract without pre-cooking the malt insoluble solids resulted in a wort with approximately equal amounts of maltose and glucose. Both treatments gave the same quantity of total fermentable sugars and amount of wort extract. Sorghum alpha-glucosidase was confirmed to be highly insoluble in water. All or virtually all activity was associated with the insoluble solids. Hence, it appears that the high amount of glucose formed when sorghum malt is mashed conventionally is due to alpha-glucosidase activity. Pre-cooking the malt insoluble solids inactivates the alpha-glucosidase, preventing the hydrolysis of maltose to glucose.     

The simultaneous saccharification and fermentation of malt dust and use in the acidification of mash

In brewing, the mash or wort is frequently acidified by the addition of lactic acid or the bioacidification of the mash. The present study provides an alternative approach for mash or wort acidification by the simultaneous saccharification and fermentation (SSF) of malt dust. In this method, fermentable carbohydrates released by the enzymatic breakdown of the cellulosic portion of the malt dust are converted to lactic acid by lactic acid bacteria. The effect of temperature, ranging between 45 and 51°C, solid loading of malt dust at 2, 5 and 10% (w/v) on a dry basis, and enzyme loading at 0.65, 2.6 and 6.5 filter paper units (FPU) per gram malt dust on SSF and change in pH in mash acidification were examined. The final pH and lactic acid concentration and final glucose concentration of the SSF media were significantly affected by the temperature of the process (p < 0.05). The highest lactic acid titre (9.7 g/L) and the lowest pH (3.12) were obtained by SSF of 10% (w/v) malt dust at 45°C with 6.5 FPU/g. The pH of the mashing solution [containing 20% (w/v) ground malt] decreased to around 5.4 and 5.2 after adding 1.9 and 2.9% of SSF media with pH 3.39. © 2019 The Institute of Brewing & Distilling     

Effect of substrate composition and inoculum on the fermentation kinetics and flavour compound profiles of potentially non-dairy probiotic formulations

Most of the commercialized probiotic formulations are dairy-based, and the development of non-dairy probiotic products could be a key area for new functional products. It has been proved that probiotic microorganisms can grow on cereal-based substrates, but flavour development in these has not been studied. In this work nine prospective cereal-based probiotic beverages were produced by inoculating oats, barley and malt substrates with single cultures of Lactobacillus acidophilus (NCIMB 8821), Lactobacillus plantarum (NCIMB 8826), and Lactobacillus reuteri (NCIMB 11951). Volatile, and non-volatile flavour compounds, as well as cell growth, pH, free amino nitrogen (FAN), and total reducing sugars (TRS) profiles were monitored during fermentation. The malt beverage inoculated with L. plantarum had the highest amounts of acetaldehyde and diacetyl with concentrations of 6.21 mg/L and 0.38 mg/L respectively. The greatest amount of lactic acid (4.2 g/L) was measured in the malt beverage inoculated with L. acidophilus. In most of the beverages the maximum cell growth was reached after 8 h of fermentation (6.4–8.2 Log₁₀ CFU/mL). It is clear from this work that each microorganism develops different flavours in the three media tested, and the right combination of microorganisms and substrates could lead to palatable probiotic products.     

麦芽表面乳杆菌的筛选及其产酸特性的初步研究

从多种大麦、商品麦芽和绿麦芽表面筛选出96株乳杆菌,最终筛选得到1株菌被鉴定为发酵乳杆菌。对其在麦汁中的产酸性能进行了初步研究,发酵温度为48℃,12 h产酸能达到0.48%。该菌培养液在50%分割剩余量下,14 h能恢复到分割前的酸度;在90%分割剩余量下,6 h能达到起始酸度。     

Phenolic inhibitors involved in the natural fermentation of Gemlik cultivar black olives

Olive fruits of the Gemlik variety harvested from different regions of Turkey were placed in aseptic or non-aseptic brines containing 6 % NaCl. Olives of non-aseptic treatment were left to spontaneously ferment under anaerobic conditions. Samples for microbiological and chemical analysis were taken periodically during the course of the fermentation. No lactic acid bacteria growth was observed in three of the six samples, and yeasts were the prevailing microbial group in the other samples. Brines were analyzed for fermentable substrates (glucose, fructose, sucrose and mannitol), fermentation products (organic acids and ethanol) and phenolic–oleosidic compounds. Most of the unprocessed fruits had a low concentration of oleuropein. Hydroxytyrosol and oleoside 11-methyl ester were the main phenolic and oleosidic compounds in all brines. Likewise, the content of antimicrobials such as the dialdehyde form of decarboxymethyl elenolic acid, either free or linked to hydroxytyrosol, in brines was very low, which may permit the growth of lactic acid bacteria in these media. A growth test with two strains of Lactobacillus plantarum was applied to aseptic brines of all samples to determine whether these compounds inhibited lactic acid bacteria growth. The results of this study indicated that Gemlik olive is a “sweet” variety with a low antimicrobial compound content that can be fermented by lactic acid bacteria under favorable conditions.