MICRO-SCALE MALTING AND BREWING STUDIES OF SOME SORGHUM VARIETIES

The malting and brewing characteristics of three sorghum varieties were investigated in a micromalting and microbrewing plant. The optimum malting conditions for Sorghum vulgare c.v. Fara Fara (Australia), Sorghum bicolor (South Africa) and Sorghum vulgare c.v. SK5912 (Nigeria) were found to consist of steeping for 21 h, at 30°C, initial germination at 30°C for 24 h, followed by a further germination period of 4 days at 25°C. Kilning temperatures of 50°C and 82°C were investigated. Evidence of the presence of hydrocyanic acid was found. The extent of modification in all malts was markedly irregular with the kernels showing brown coloration on the outer layers. The brewing trials with 100% sorghum malt showed a slow and incomplete saccharification, slow lauter tun filtrations and very difficult beer filtrations. By supplementing commercial enzymes in the mash only the speed of lauter tun filtration improved significantly.     

Optimization of the sorghum malting process for pito production in Ghana

Pito is an alcoholic beverage obtained through a yeast (Saccharomyces cerevisiae) fermentation of wort extracted from sorghum (Sorghum bicolor L. Moench) malt. The malting conditions of sorghum are thought to influence the quality characteristics of the malt, and subsequently the quality of the pito obtained from it. Studies were carried out on a local sorghum cultivar grown in Ghana – chireh, to optimize the conditions for malting conditions for pito production in Ghana. A 3³ full factorial experimental design was replicated with steeping times of 12, 16 and 22 h, germination times of 3, 4 and 5 days, and malt drying temperatures of 30, 40 and 50 °C as factors. Diastatic power, extract yield, attenuation limit and free amino nitrogen were determined. Germination duration significantly affected diastatic power and free amino nitrogen (p < 0.001). Extract yield was also significantly influenced by germination duration (p = 0.001). The germination time, steeping time and drying temperature had no significant effect on the attenuation limit. The optimal conditions for malting this specific cultivar grown in Ghana to obtain critical malt quality indices are 12.0–12.5 h steeping, 5 days of germination at 30 °C and drying at 40 °C. Free amino nitrogen levels in all treatments were higher than the minimum requirement for good yeast nutrition and fermentation. Copyright © 2015 The Institute of Brewing & Distilling     

Peroxidase activity of germinating Sorghum bicolor grains: effect of some cations

We investigated some properties of the major ionic peroxidase (POD) from germinating Sorghum bicolor var Fara Fara. Peroxidase activity increased eightfold during the first 36 h of germination and declined thereafter to four times the value in the dry grain after 144 h. Gel filtration followed by ion exchange chromatography resolved the major peroxidase into two forms. The predominant POD had an optimum temperature of 55 °C, two pH optima at 5.0 and 7.0, with a sharp decline in activity below pH 4.5, an apparent activation energy of 463 kJ mol^?1, an apparent molecular weight of 63.1 kDa and was relatively heat‐stable up to 70 °C. The enzyme was strongly inhibited by dithiothreitol and sodium metabisulphite. Calcium chloride and magnesium chloride below 2 mM enhanced POD activity without any adverse effect on germination, while ammonium chloride and ferric chloride inhibited the enzymatic activity of both forms. At 5 mM , magnesium chloride inhibited POD activity by 50% with only a 14% reduction in germination, while calcium chloride achieved the same effect at 10 mM . These results are pertinent to controlling the undesirable activity of peroxidase in a typical malting or brewing process. © 2002 Society of Chemical Industry     

Breaking of structural dormancy in seeds of Tetrapleura tetraptera by Aspergillus niger

Aspergillus niger (strain UUF9202) significantly reduced the dormancy period and boosted aggregate germination percentage (AGP) in seeds of Tetrapleura tetraptera. A net reduction in mean germination time (MGT) to 12 days and an increase from 0 to 42% AGP were obtained in 32 days. The optimal spore inoculum of the fungus was 8.5 × 10≥10 ml^?1 per 100 seeds in 96 h pregermination incubation. The potential of some physical factors in combination with this fungal concentration in enhancing AGP was evaluated. The treatments were as follows: (i) hot water scarification at 30°C, 50°C, 80°C and 100°C plus A niger; and (ii) nicking by decoating at either the micropylar or chalazal ends plus A niger. Micropylar scarification plus A niger gave the highest AGP (94%) followed by chalazal scarification plus A niger (86%) and hot water dip at 80°C + A niger (82%). The control seeds which were soaked in presterilised (by autoclaving at 121°C for 15 min) A niger spore suspension at 30°C gave zero germination.     

Influence of water activity and temperature on conidial germination and mycelial growth of ochratoxigenic isolates of Aspergillus ochraceus on grape juice synthetic medium. Predictive models

The first stages in the development of Aspergillus ochraceus, an ochratoxin A‐producing fungus that infects grapes and may grow on them, have been studied on a synthetic nutrient medium similar to grape in composition. Spore germination and mycelial growth have been tested over a water activity (a_w) and temperature range which could approximate to the real conditions of fungal development on grapes. Optimal germination and growth were observed at 30 °C for all three isolates tested. Maximal germination rates were detected at 0.96–0.99 a_w at 20 °C, while at 10 and 30 °C the germination rates were significantly higher at 0.99 a_w. Although this abiotic factor (a_w) had no significant influence on mycelial growth, growth rates obtained at 0.98 a_w were slight higher than those at other a_w levels. Predictive models for the lag phase before spore germination as a function of water activity and temperature have been obtained by polynomial multiple linear regression, and the resulting response surface models have been plotted. Copyright © 2005 Society of Chemical Industry     

Malt characteristics of sorghum vulgare varieties from ghana

Two local varieties, a white type and a red type, of Sorghum vulgare cultivated in Ghana were malted, using a micro-malting method, and their malt characteristics studied and compared to that of a commercial barley malt. The optimal germination time, at 30°C, to produce a good malt of high diastatic power and extract from local varieties of these varieties was 4-5 days. The local varieties were also found to have high diastatic activities of between 55 and 68% of the commercial barley malt. Hot-water extracts of the well malted sorghum varieties were also found to have higher and sustainable amounts of free amino nitrogen than the commercial malt. The hot-water extracts of sorghum malts were lower than the commercial barley malt, yielding about 66-77% of the barley malt, but contained a higher glucose to malt ratio. In terms of varietal superiority, the white sorghum yielded higher malt extracts than the red type.     

Germination and Heat Resistance of Bacillus cereus Spores from Strains Associated with Diarrheal and Emetic Food-Borne Illnesses

Bacillus cereus has been implicated as the cause of both diarrheal and emetic forms of food-borne illness. Spores of eight strains of B. cereus, representing diairheal, emetic and atoxigenic origins, were examined for heat resistance and germination responses. No correlation was observed between heat resistance at 85° or 90°C and origin of the strain. Germination of spores in Trypticase soy broth at 30°C, measured by loss of heat resistance, was more extensive for diarrheal strains than for emetic strains. These data should be useful in evaluating potential hazards from B. cereus in foods.     

Effect of Malting Conditions on Pearl Millet Malt Quality

The effect of malting conditions on pearl millet malt quality in two varieties, SDMV 89004 and SDMV 91018, was investigated. Grain was steeped and germinated at four temperatures, 20°, 25°, 30° and 35°C, over 5 days. Generally, malt quality parameters (percentage of roots and shoots, diastatic power (DP), α‐ and β‐amylase activity, free α‐amino nitrogen (FAN), and malting loss) were significantly affected (P < 0.001) by germination temperature and time, as well as by variety. Malt FAN and malting loss were not affected by variety. A germination temperature of 25–30°C and germination time of 3–5 days were optimal. These conditions resulted in high DP, α‐ and β‐amylase activity, good FAN and moderate malting loss. These malting conditions and the subsequent malt quality of pearl millet are similar to those reported for sorghum. Pearl millet malt can therefore be used for the production of sorghum type beers.     

Control of Bacillus cereus Spores and Spoilage Microflora in Sous Vide Chicken Breast

Safety of sous vide chicken breast with respect to Bacillus cereus and effect of processing parameters on natural microflora were evaluated. B. cereus, a facultatively anaerobic sporeformer, may cause foodborne illness and has been isolated from poultry. Product was inoculated and processed to 77°C or 94°C. Populations were reduced by 0.5- to 1.0-log and by 3-log in products heated to 77°C and 94°C, respectively. Spores germinated within 1 day at 10°C yet detectable changes in populations were not evident through 28 days storage. Lactate did not influence B. cereus populations or spore germination. Natural microflora was reduced by processing and remained low through 28 days storage at 4°C and 10°C.     

Effects of Germination and Osmopriming Treatment on Enhancement of Isoflavone Contents in Various Soybean Cultivars and Cheonggukjang (Fermented Unsalted Soybean Paste)

ABSTRACT: To develop soybean products containing high isoflavone contents, the effects of germination and osmopriming on the isoflavone contents of 3 soybean cultivars (Ilmi, Daehwang, and Taekwang) were investigated. Total isoflavone contents of Ilmi and Daehwang cultivars were not significantly different with soaking time at 20 and 25 °C. Ilmi and Taekwang cultivars had higher total isoflavone contents at 0.243 to 0.256 and 0.072 to 0.079 g/100 g, respectively, after 12 h of germination at 20 °C than those at 0.232 and 0.064 g/100 g at the initial stage. After 48 h of germination at 20 °C, contents of total isoflavone, daidzein, and genistein were 0.246, 0.094, and 0.147 g/100 g, respectively. In contrast, after 48 h of germination and 0.2 M NaCl treatment at 20 °C, those contents increased up to 0.346, 0.140, and 0.203 g/100 g, respectively. Total isoflavone and genistein contents of cheonggukjang prepared with germinated soybean or soybeans treated with osmopriming were 0.322 and 0.198 g/100 g, 0.332 and 0.201 g/100 g, respectively, at 48 h of fermentation, and were higher than those of the control group (0.277 and 0.169 g/100 g). We concluded that cheonggukjang would contain higher isoflavone contents after the treatment of germination and osmopriming.     

High Temperature Storage Effect on Longevity of Rice Seeds

Storage of Indica (Oryza sativa L. cv. Katakutara) and Japonica (Oryza sativa L. cv. Kusabue) rice seeds at 30° and 40°C for 2 months in the dark did not result in the loss of viability in both cultivars. Storage at 60°C, however, resulted in a complete loss of germination after 45 days in the case of Kusabue while the Katakutara rice seeds retained the germination potential well above 95%. Corresponding increases in the linoleic acid content of the free fatty acid fraction and TBA values of the extracted lipid fraction were also observed in Kusabue rice seeds. The investigation indicated that the Indica rice seeds were better protected than the Japonica rice seeds by the enclosing rice hull during the storage period.     

Reduction of Postharvest Decay of Peach and Nectarine Caused by Monilinia laxa Using Hot Water Dipping

The effect of hot water dipping (HWD) at 40, 44 and 48 °C for 6 and 12 min on germination of conidia of brown rot fungus (Monilinia laxa) in vitro and the effect of HWD at 48 °C for 6 and 12 min on the fruit quality and development of M. laxa on peach cv. “Roig” and nectarine cv. “Venus” after artificial inoculation in cold storage were studied. Temperature and duration of treatment significantly affected germination of conidia. After HWD at 48 °C for 12 min, the lowest germination of conidia (9%) was recorded, which was more than 10 times lower than control (93%). After 3 days from inoculation, there were 80% of inoculated spots with visual symptoms of decay caused by M. laxa on control peaches and 40% of such spots on control nectarines. Successful infections were recorded on only 5% of inoculated spots of nectarine and 10% of inoculated spots of peach after HWD at 48 °C for 12 min. HWD at 48 °C for 12 min significantly decreased titratable acidity and increased soluble solids concentration/titratable acidity ratio in nectarines. No visual symptoms of heat damage were found on fruits as a consequence of any of the studied treatments. The results show that it is possible to control postharvest brown rot (M. laxa) on peach using HWD at 48 °C for 12 min and on nectarine using HWD at 48 °C for 6 min without a significant loss of fruit quality.     

Starch Related Changes in Stored Soft Sorghum Porridge

Soft sorghum (Sorghum bicolor (L.) Moench) unfermented porridge was prepared by cooking pearled sorghum flour (6% solids in water) in a microwave oven. Fermented porridge was prepared by mixing with Lactobacillus delbruekii for 12 hr at 48°C. followed by cookine. Porridge was aged (0–12 hr) at 25°C or 7.5%. Starch polymer solibility was determined by high performance size exclusion chromatography (HPSEC) and rheology followed with a rotational viscometer. During aging, solubilized and gelled amylose and amylopectin retrogradation rates were higher in porridge stored at 7.5 than at 25°C. Amylose polymer solubility decreased with storage, while solubilized amylopectin remained in solution. Fermented porridges were lighter in color and their initial consistency indexes increased faster. HPSEC of soluble polymers was more sensitive than enzymatic starch digestion.     

Effects of Germination on Proteins, Raffinose Oligosaccharides, and Antinutritional Factors in the Great Northern Beans (Phaseolus vulgaris L.)

During 5 day germination, the major reserve proteins of the Great Northern bean (Phaseolus vulgaris L.) were substantially hydrolyzed. In vitro trypsin digestion of the extracted proteins up to 4 hr at 37°C indicated that the major storage proteins in germinated and the ungerminated seeds, although substantially hydrolyzed, could not be completely degraded. In vitro susceptibility of the extracted proteins was improved on moist heat treatment (97°C, 30 min). A substantial increase in soluble essential amino acids occurred during germination. Highest decrease in stachyose + raffimose (76.40%) was observed at the end of the third day of germination. Trypsin, chymotrypsin, and α-amylase inhibitory activities and phytic acid were reduced respectively by 62.9, 73.4, 67.1, and 57.8% after 5 days of germination.     

Malted sorghum bicolor grains and physiology of associated microfungi

Certain aspects of the physiology of 2 microfungi associated with degradation of malted grains of Sorghum bicolor are studied. Isolated organisms are Fusarium pallidoroseum and Alternaria tenuissima. Fusarium utilized nitrogen free extract more than Alternaria in an acid medium, temperature of 20°C and 50°C enhanced protease production in Fusarium and Alternaria respectively, and both fungi preferred a substrate of malt extract agar. Both fungi have an enhanced growth in the presence of sulphur.     

Effect of malting conditions and quality characteristics of malt and roasted malt extract from ‘acha’ grains (Digitaria exilis Stapf)

BACKGROUND: Considering the importance of malting and roasting on the quality of ‘acha’ beverages, a study was conducted to find optimum conditions for malting and the production of a high‐quality roasted extract that could be used for an ‘acha’ beverage. RESULTS: The data obtained were analysed using response surface methodology. The results revealed that the most significant (P < 0.05) malting factors that affect the response variables were the linear terms of germination time and drying temperature. However, for the extract production, the linear term of roasting temperature was the most significant (P < 0.05) factor. The quadratic and interaction terms exhibited significant (P < 0.05) effect in all cases apart from the flavour. CONCLUSION: The overall optimum regions were established at 28 h of germination time, 55 °C drying temperature and 5.0% moisture content for the malting conditions while for the extract production, a roasting temperature of 210 °C, extraction temperature of 70 °C and extraction duration of 20 min were established. Copyright © 2010 Society of Chemical Industry     

Physiochemical and Rheological Characterization of Sorghum Starch

Starch was isolated from the seeds of 3 sorghum cultivars and compared with commercial wheat starch. The amylose content of sorghum starches was in the range of 22.0–27.8%. Sorghum starches had less total lipids than wheat starch (1.66%) but there was no difference between sorghum Milo and Sorghum “100”. The water binding capacity of sorghum Dabar did not differ from that of wheat (100%) whereas differences in swelling power were observed, over a range of temperatures, between wheat and sorghum starches except for Sorghum “100” at 70°C. Sorghum starches showed single-step viscoamylographic curves with pronounced pasting peaks, good pasting stability and good set-back on cooling.     

Combined use of UV‐C irradiation and heat treatment to improve postharvest life of strawberry fruit

The effects of UV‐C (4.1 kJ m^?2) and heat treatment (45 °C, 3 h in air) either separately or combined on the quality of strawberries (Fragaria × ananassa cv Seascape) at the 75 or 50% surface red ripening stage were assessed, the latter stage being used only in the firmness test. In addition, the development of surface fungal infections was followed and in vitro germination assays on conidia of Botrytis cinerea and Rhizopus stolonifer performed. Both heat and combined treatments, decreased hue and delayed changes of the L* parameter. All treatments reduced the accumulation of anthocyanins. Control fruit softened most while fruit treated by the combined method were the firmest. The combined treatment reduced fungal infections and delayed in vitro germination of Botrytis cinerea conidia. After 2 days at 20 °C, treated fruit had lower amount of phenolics than the control. Neither the heat nor UV‐C irradiation modified the total sugar content, although the combined treatment decreased it slightly relative to the control. Titratable acidity increased through storage at 20 °C in all fruit, but no differences between control and treated fruit were detected. The combination of UV‐C and heat treatments enhanced the benefits of applying each treatment separately, and could be useful to improve and extend strawberry fruit postharvest life. Copyright © 2004 Society of Chemical Industry     

Radiation-Injured CIostridium Botulinurn Type E Spores: OutGrowth and Repair

Spores of Clostridium botulinum type E surviving irradiation doses of 0.1–0.4 Mrad were injured as evidenced by their inability to form typical macrocolonies at 10°C in the presence of polymyxin and neomycin, antibiotics which did not similarly affect growth of unirradiated spores. Several degrees of severity of injury were demonstrated. Radiation injury was not associated with the germination lytic system but with the post germination growth system. Radiation-injured spores formed aseptate filaments during outgrowth in microcultures. Some of these filaments lysed; others divided and formed microcolonies less dense than those formed by unirradiated cells. Radiation-injured spores repaired when incubated at 30°C for ca. 15 hr on TP-EY agar medium with polymyxin and neomycin, and formed typical macrocolonies when shifted to 10°C.     

Elucidation of the Mechanism of the Acid-blanch and EDTA Process Inhibition of Clostridium sporogenes PA 3679 Spores

Acid-blanching followed by addition of ethylenediamine tetraacetic acid to the can brine had been shown to control germination of mesophilic spores following sub-lethal thermal processes. The mechanism of this control was investigated using C. sporogenes PA 3679 spores in buffered solutions. Spore suspensions in buffered 0.05M citric acid solutions, pH 3.5 and 5.8, and Sorensons phosphate buffer, pH 7.0, were heat-activated at 80 °C and then heated for 5 min at 121 °C. The mechanism of inhibition appeared to involve destruction of the spore germination system by heat at reduced pH as a result of collapse of the cortex peptidoglycan layers, possible hydration of the core and concommitant increase in the core volume.