PROMOTING SORGHUM RESERVE PROTEIN MOBILISATION BY STEEPING IN ALKALINE LIQUOR

Mobilisation of sorghum storage reserve proteins by steeping in alkaline liquor for 48 h under four different regimes was evaluated. Germination was for 4 days at 30°C. Cold water soluble protein (CWS-protein), CWS-protein modification index, total non protein nitrogen (TNPN), peptide accumulation, FAN, endo- and exo-protease activities—all key indicators of protein mobilisation were highly significantly affected by steep regime, steep liquor and cultivar as well as their pairwise interactions. Mean FAN and TNPN were significantly higher (P < 0.0005) for malts derived from alkaline steep liquor except for KSV 8 which exhibited significant inhibition of TNPN development. Similarly, alkaline steeping promoted protein solubilisation and CWS-protein modification. While parallel improvements in amylolysis and proteolysis were recorded for ICSV 400, proteolysis in KSV 8 and SK 5912 seemed more enhanced except for SK 5912 exposed to air rest cycles. Steeping in alkaline liquor also caused significant repression of the proteases in KSV 8. Conversely, steeping SK 5912 under similar conditions promoted rather than inhibited development of these enzymes. Poor correlation between protein degradation products and enzyme development suggest major roles for factors other than proteolysis in sorghum reserve protein mobilisation.     

INFLUENCE OF CULTIVAR AND STEEP REGIME ON SOME PROTEIN RELATED PROPERTIES OF SORGHUM MALTS

Cold water extract (CWE), cold water soluble protein (CWS-protein), CWS-protein modification and free alpha amino nitrogen (FAN) were determined for three improved Nigerian sorghum cultivars malted under four different steep conditions. The levels of these variables in the sorghum malts differed significantly when malted under identical steep regimes. This indicates that soluble protein accumulation and modification in these grains are cultivar dependent. Grains exposed to a combination of air rest cycles and final warm steeping gave highest values of cold water solubles, CWS-protein modification and FAN. Amylolytic activity was enhanced over the rate of proteolysis when grains were steeped under regimes incorporating final warm steep. Cultivar SK 5912 with highest soluble protein solubilisation activity showed lowest FAN accumulation under all steep regimes suggesting roles for factors other than proteolysis in FAN accumulation.     

EFFECTS OF AIR REST PERIOD ON THE MOBILISATION OF SORGHUM RESERVE PROTEINS

The influence of air rest treatment period on the mobilisation of storage proteins of two improved Nigerian sorghum cultivars ICSV 400 and KSV 8 was evaluated. Grains were steeped in distilled water for a total period of 48 h at 30°C with a 6 h final warm steep at 40°C under four different cycles incorporating 1, 2, 3 or 4 h air rest period respectively. Cold water soluble protein, cold water soluble protein modification index, total cold water solubles, total free alpha amino acid nitrogen, carboxy-peptidase and proteinase activities were determined after 6 days malting. All these protein modification indices were highly significantly affected by length of air rest and cultivar, plus their pair-wise interactions. The levels of all these variables were also higher in sorghum cultivar ICSV 400 compared to KSV 8 except for proteinase activity. Significant differences in grain storage protein complexity and structure coupled with probable differences in key proteinase iso-forms are advanced as possible explanation for the higher proteinase activity recorded in KSV 8 malts.     

ENHANCEMENT OF AMYLOLYTIC POTENTIAL OF SORGHUM MALTS BY ALKALINE STEEP TREATMENT

The effect of alkaline steep liquor on sorghum maltability was investigated using three improved Nigeria sorghum cultivara. Germination was for four days at 30°C after steeping under four different regimes. Grain germinability, root length and malting loss were significantly (P < 0.001) repressed by steeping in alkaline liquor for all the cultivars. However, the extent of this repression seemed in all cases significantly dependent on cultivar and steep regime plus their possible interactions. Similarly, the development of diastatic enzymes activities appeared to be highly significantly dependent on steep liquor, steep regime, cultivar, plus their possible pairwise and three way interactions. For ICSV400, highest diastatic power and α-amylase development were attained on steeping grains in alkaline liquor under a continuous steep regime incorporating final warm steep treatment. Conversely, exposure of KSV8 and SK5912 to a regime incorporating air-resting and final warm steep significantly enhanced diastatic power and α-amylase development. β-Amylase activity was in all cases enhanced by alkaline steeping. In fact, β-Amylolytic activity constituted over 70% of total diastatic activity in most alkaline steeped ICSV400 malts. However, SK5912 exhibited relatively low hot water extract in spite of the improved amylolytic activity.     

DURATION OF FINAL WARM WATER STEEP AS A FACTOR INFLUENCING SOME CARBOHYDRATE RELATED PROPERTIES OF SORGHUM MALT

The effects of duration of final warm steep at 40°C on main root length, malting loss, diastatic power, α- and β-amylolytic activities and extract of two improved Nigerian Sorghum cultivars (CSV 400 and KSV 8 were studied. The duration of final warm steep was varied between 1.5 h and 7.5 h. Germination was for four days at 30°C. All malt quality parameters evaluated were greatly influenced by duration of final warm steep and cultivar as well as their pair-wise interactions. Malting loss and average main root length decreased progressively as the duration of final warm steep increased. Conversely diastatic activity, α- and β-amylolvtic activity and extract yield of both ICSV 400 and KSV 8 generally increased as duration of final warm steep was increased up to 3 h before a progressive drop. Submission to varying lengths of final warm steeping appeared to progressively restrict formation of rootlets and malting loss without concomitant depression of diastatic enzymes development and extract yield. Maximum diastatic activity was attained on submission of grains to 3 h length of final warm steep. A second diastatic activity peak at 7.5 h for KSV 8 may result from increased β-amylolytic activity at 7.5 h final warm steep period. The occurrence of two β-amylase maxima at 3 h and 7.5 h duration of final warm steep for ICSV 400 indicates possible presence of at least two β-amylase components.     

EFFECTS OF FINAL WARM WATER STEEP AND AIR REST CYCLES ON MALT PROPERTIES OF THREE IMPROVED NIGERIAN SORGHUM CULTIVARS

The effects of final warm steeping at 40°C and air-rest cycles on malting loss and other malt quality parameters of three improved Nigerian sorghum cultivars were investigated. Grains were steeped for 48 h under four different steep regimes then germinated for 4 days at 30°C. The effect of final warm steeping on kernel growth, malting loss, diastatic power, α and β-amylase and extracts of the malts was significantly affected by air-resting, cultivar and the pair-wise interactions of cultivar and steep regime. Generally, malting loss and kernel growth reduced significantly (p< 0.001) when the steep cycle was a combination of air-resting and final warm water steep at 40°C. Diastatic power, α-amylase, β-amylase and extract also improved significantly in both ICSV 400 and KSV 8 when these grains were malted by a steep regime which combined both air-rest cycles and final warm water steep. However steeping these grains under a final warm water steep without air-resting led to a decrease in extract recovery and enzyme activity. Conversely steeping SK 5912 by a combination of air-resting and final warm water steep generally, inhibited rather than enhanced extract and enzyme development.     

EFFECTS OF AIR REST PERIODS ON MALTING SORGHUM RESPONSE TO FINAL WARM WATER STEEP

The effects off various lengths of air rests on response off malting sorghum main root length, malting loss, diastatic activity, α- and β-amyloytic activity and extract to final warm water steep at 40°C was investigated. Grains were steeped in distilled water for a total of 48 h at 30°C with a 6 h final warm water steep under four different cycles incorporating 1, 2, 3 or 4 h air rest periods. All malt quality properties evaluated were significantly affected by the length of air rest, the cultivar and their pair-wise interactions. Main rootlet length and malting loss reduced progressively as the length of air rest increased. Reducing power, α- and β-amylolytic activity and extract generally increased as the length of air rest was increased for both sorghum cultivars ICSV 400 and KSV 8 examined. The steep cycle incorporating 3 h length of air rest was found by experiment to give the optimum levels of malt quality indices analysed while at the same time causing considerable reduction in average main rootlet length and total malting loss for both grain cultivars.     

Relationship between some Sorghum Malt Quality Characteristics and Nature of Alkaline Steep Liquor

Two Nigerian sorghum cultivars, SK5912 and ICSV400 were used to evaluate the relationships between nature of alkaline steep liquor and some malt quality characteristics over a five day germination period. Patterns of development of the malt quality indices examined were significantly influenced by the nature of alkaline steep liquor, cultivar and duration of germination, plus all their possible interactions at p<0.001. Maximum diastatic activity development was attained in ICSV400 and SK5912 when grains were steeped in NaOH and Ca(OH)₂ respectively. Ca(OH)₂ treatment seemed to cause significant enhancement of diastatic enzyme development in SK5912 compared to other treatments presumably due to Ca²⁺ stabilisation of α-amylase. Mean malt cold water extract (CWE) and hot water extract (HWE) were generally similar within both cultivars for the treatments except for ICSV400 where CWE appeared to be remarkably enhanced by NaOH treatment. Data on cold water soluble carbohydrates (CWS-Carbohydrates), CWS — Carbohydrate/CWE and CWS — Carbohydrate/HWE ratios showed that solubilised carbohydrate matter produced during malting constituted significantly higher proportion of total HWE in ICSV400 in contrast to SK5912.     

STUDIES ON COLD WATER EXTRACT OF MALTS: SOLUBLE PROTEIN AND MALTING BEHAVIOUR

Modification of the IoB method for Cold Water Extract (CWE) allowed the determination of the CWE and Cold-Water-Soluble (CWS-) protein in 96 micromalts per day by a single operator. The method was used to follow the changes in CWS-protein of malts of four cultivars of barley with increasing modification. Malting and non-malting cultivars were shown to have different patterns of protein solubilisation during malting. The equivalent of a Kolbach determination carried out on Cold Water Extracts of malts of more than three days modification sharply differentiated between malting and non-malting cultivars. Cold-Water-measurable proteolysis was shown not to be the cause of an unexpectedly high malting potential shown by a variety with low Diastatic Power.     

Current Developments in Malting and Brewing Trials with Sorghum in Nigeria: A Review

Initially, large‐scale lager beer brewing with sorghum malts proved highly intractable due to a number of biochemical problems including: high malting losses estimated at 10–30% as against 8–10% for barley; high gelatinisation temperatures which limited starch solubilisation/ hydrolysis by the amylolytic enzymes during mashing; low extract yield/low diastatic power (DP) due to inadequate hydrolytic enzyme activities especially β‐amylase; low free α‐amino nitrogen (FAN) due to inadequate proteolysis limiting yeast growth during fermentation; high wort viscosities/beer filtration problems due to low endo‐β‐1,3; 1–4‐glucanase activities on the endosperm cell walls causing the release of some β‐glucans. Strident research efforts using improved Nigerian sorghum malt varieties (SK5912, KSV8 and ICSV400) have reported some encouraging results. The knowledge of the biochemical integrity of the endo‐β‐glucanases of the sorghum malt is helping to elucidate their mode of activity in the depolymerisation of the β‐glucans. This is bound to ensure process efficiency in sorghum beer brewing, reduce beer production costs and ultimately, produce a Pilsner‐type of lager beer with 100% sorghum malt.     

Effect of Different Steeping Conditions on Endosperm Modification and Quality of Distilling Malt

This study showed that when barley was steeped in water for either 8 h or 16 h, hydration of endosperm materials was suboptimal and modification of endosperm materials of barley malt was inadequate. The malt produced under these steeping regimes gave poor friability scores and produced a large number of whole grains. When barley was steeped for 24 h on a continuous basis, or when a regimented standard steeping method was used, the malt produced gave higher friability scores and a much lower number of whole grains. An important relationship was found between friability scores and whole grain results for the malt samples produced under these conditions. Optic barley, whose endosperm was more difficult to hydrate, gave a strong negative correlation between friability scores and number of whole grains at R² = 0.8689. Oxbridge, whose endosperm was more easily hydrated, gave a much stronger negative correlation between friability scores and number of whole grains at R² = 0.9769. Rapid visco‐analysis (RVA) results also confirmed that steeping the barley samples for only 8 h or 16 h produced malt that modified poorly as the RVA peak viscosities were very high. RVA pasting results further confirmed that when barley was steeped for 24 h on a continuous basis, or when a standard regimented steeping method was used, good quality malt was produced and no differences were found in the RVA peak viscosities of the barley malt samples produced under the two different steeping conditions. The results of protein breakdown (proteolysis) during these experiments, measured in terms of total soluble nitrogen (TSN) production, or soluble nitrogen ratio (SNR) further confirmed that optimal proteolysis was achieved when barley was steeped for either 24 h on a continuous basis, or with a standard steep. Optimal results were also found for hot water ex‐tractable materials such as hot water extract (HWE) and free amino nitrogen (FAN) when barley was steeped for 24 h or the standard steep. The 24 h continuous steep for barley produced quality malt comparable to that obtained when the standard regimented steep was used for steeping barley. For both Optic and Oxbridge barley, with a 24 h continuous steep, produced malt that gave significantly higher fermentabilities and PSY values, regardless of germination time, than those obtained using a standard regimented steep. Therefore steeping barley for 24 h on a continuous basis prior to malting will produce good quality malt for some barley samples/varieties. This will help to reduce water usage during steeping, will save steeping time thereby reducing malting time and will reduce the amount of water for effluent treatment. All of these factors result in an overall cost saving for the malting industry.     

Some Relationships Between Malted Barleys of Different Nitrogen Levels and the Wort Properties

Barleys containing different levels of total nitrogen seem to have similar initial patterns for endosperm modification during malting. The higher nitrogen barley had a slower rate of endosperm modification, whilst the lower nitrogen barley had a faster rate of endosperm modification as germination progressed. Although the higher nitrogen barley had slower rate of endosperm modification, it transferred more nitrogen materials to the roots and shoots, whilst the lower nitrogen barley transferred less nitrogen materials to the roots and shoots. The higher nitrogen barley produced a lower yield of extract, but released higher levels of soluble nitrogen, free amino nitrogen (FAN) and peptides in the extract. The lower nitrogen barley produced a higher yield of extract and higher levels of carbohydrates (reducing sugars) in the extract. These results suggest that other important relationships exist between barleys of different nitrogen content. A drop in peptide nitrogen occurred on the same day of germination in both barley samples.     

ASSESSMENT OF MODIFICATION PATTERNS IN MALTING BARLEYS

Three cultivars of diverse melting quality were melted end samples taken daily between 2 end 7 days germination. Over this period a linear relationship wee observed in all 3 cultivars, between cell well modification, measured by loss of calcofluor fluorescence, and both wort nitrogen content end loss of milling energy. Differences in the slopes of regression lines suggested variation in patterns of modification, with very rapid proteolysis in Triumph, but a time leg between cell wall modification and degradation of the protein matrix in Koru. These predicted patterns were confirmed by Scanning Electron Micrographs of endosperms from germinated grains.     

Assessment of Sorghum Malt Sprout Acid Hydrolysates as Organic Nitrogenous Base for the Cultivation of Saccharomyces Cerevisiae

The effects of method of hydrolysis and source of sorghum sprout (sorghum cultivar) on the nitrogen and mineral contents of acid digests from three commercial malting varieties of sorghum were assessed. The mineral and nitrogen contents and constituents of the digests varied significantly (p < 0.05) with respect to the method of digestion, sprout source and the pair-wise interaction of the two factors. Higher digest nitrogen, in both ICSV 400 and SK 5912, was supported by acid digestion in the autoclave while reflux digestion produced higher nitrogen in KSV 8. Of all the digests, those from ICSV 400 (both reflux and autoclave) displayed the best balance of yeast-essential acids as well as superior growth-promoting activity. In their growth-producing activity, the digests also compared very favourably with seven commercial nitrogenous bases used industrially for yeast cultivation. Results suggest that sorghum sprout acid digests are good alternative sources for nitrogen and mineral nutrients in media for microbial cultivation.     

Grain and malt quality properties of some improved Nigerian sorghum varieties

To determine their grain and malt quality properties, ten improved Nigerian sorghum varieties were subjected to several tests. The parameters that were tested included thousand corn weight, germinative energy, germinative capacity, water sensitivity, malting losses, hot and cold water extracts and free amino nitrogen (FAN). Results obtained showed variations among the sorghum varieties in most of the parameters assessed. While variety SK5912 was heaviest (40.25 g), variety Nafelen 6 had the lowest weight (22.45 g). For germinative capacity, variety KSV8 gave the highest value (97.0%), while variety ICSV400 gave the lowest value (90.5%). Variety KAT487 was the most water sensitive (5%), while four varieties simultaneously gave the lowest value. Boboje gave the lowest malting loss (13.77%), while the highest loss (37.74%) was given by White Kaura. For the extracts, variety SK5912 gave the highest value, as was the case also with FAN. Generally, there were significant differences across the different varieties of sorghum for malting loss, FAN, cold water extract and hot water extract at both p < 0.05 and p < 0.01. The results showed significant agreement with previous reports, with the key findings being that grain size mostly correlated positively with high expression of the critical malting parameters. Copyright © 2014 The Institute of Brewing & Distilling     

A Comparison of Maize,Sorghum and Barley as Brewing Adjuncts

Sorghum and maize adjunct, at a 5 to 20% level, resulted in a decrease of extract recovery, solubilisation of nitrogen, and production of free amino nitrogen and peptide nitrogen progressively. Both sorghum and maize adjuncts released higher levels of FAN and peptide nitrogen in their extracts than barley adjuncts, but the peptide levels were higher in sorghum than maize and barley adjuncts. The solubilisation of nitrogen and hydrolysis of the soluble nitrogen were higher for high nitrogen barley adjunct than for low nitrogen barley. Although maize adjunct is used extensively in brewing, the results of this study showed that sorghum has the potential to release higher levels of peptides than maize. This difference may influence fermentation potential.     

EFFECT OF SUGAR LEVEL ON PHYSICOCHEMICAL,BIOCHEMICAL CHARACTERISTICS AND PROTEOLYSIS PROPERTIES OF CANTONESE SAUSAGE DURING PROCESSING

ABSTRACT

The effects of sugar levels (3, 6, 9, 12%, w/w) on gross composition, the main physicochemical parameters, microbiology, protein composition and proteolytic change of water soluble protein (water soluble nitrogen [WSN]) of Cantonese sausage were evaluated. The sample with 12% sugar addition had low a_w as well as pH values. During processing, sarcoplasmic and myofibrillar protein content decreased, while alkaline‐soluble fraction and nonprotein constituent (nonprotein nitrogen) content increased. Sugar exhibited stabilizing effect against denaturation of both sarcoplasmic and myofibrillar protein fractions. The water soluble protein with molecular weight of >10 and 3–5 kDa was the main fraction, and progressive decrease of peptide fractions of >10 kDa was observed during ripening process. Higher sugar levels showed protective effects against proteolysis of WSN and advantages on improving the textural characteristics. Samples with higher sugar levels had lower microbial counts in Cantonese sausage.

PRACTICAL APPLICATIONS

Cantonese sausage is a traditional Chinese meat product that is well accepted by consumers over the world. The aim of this article was to evaluate the effect of sugar level on changes in physicochemical and biochemical characteristics, including chemical composition, proteolysis, textural profile and microorganism of Cantonese sausage during processing. The results will be favor of process control of reduced sugar Cantonese sausage production that consumers can enjoy as part of an ongoing healthier diet and lifestyle.     

Effects of Mashing Parameters on Mash β‐Glucan,FAN and Soluble Extract Levels

To gain further technological knowledge of mashing, pilot scale mashing trials were carried out varying mashing programme (upward/isothermal mashing), milling procedure, grist:liquor ratio, time of mash stands, and grist modification level (well and poorly modified malt). During mashing β‐glucan, free amino nitrogen (FAN) and extract contents were analysed as key indicators for cytolysis, proteolysis, and amylolysis, respectively. The malt modification was of major impact for the β‐glucan release in contrast to a variation of milling procedure and of grist:liquor ratio. Extended stands lead to increased final values only for poorly modified malt. Similarly, FAN release was predetermined by malt modification while variation of milling and of grist:liquor ratio was not relevant in contrast to stand extension. None of the variations applied influenced extract yield as long as gelatinization temperature was reached. Greatest gains occurred around 57°C. In conclusion, wort quality is critically determined by malt modification. Mashing with well modified malt in combination with short stands should result in a mash of low β‐glucan and sufficient FAN level without losing extract yield. However, for poorly modified malt the variation of mashing parameters has an impact on the key indicators in which cytolysis plays the dominating role.     

Barley and Malt Proteins and Proteinases: III. A Simple Method for Estimating the Combined Actions of Malt Proteinases and the Extent of Protein Degradation during Malting

The activities of barley and malt proteinases have been measured using haemoglobin and the highly degradable barley protein fraction (HDBPF) in malting and feed barley varieties. In conjunction, the barley and malt total protein and its components: hordein, glutelin, soluble proteins and free amino nitrogen (FAN) as well as Kolbach index were investigated. The comparative analysis of results revealed that the general grain modification index of Kolbach (KI), which was higher in malting varieties, was much more strongly associated with the levels of hordein degraded during malting than any other parameter investigated. The KI levels were also correlated with the increase in the levels of FAN, but not with the increase in the levels of soluble protein or changes in the glutelin component. The changes in total proteinase activity were low and cannot account for the increase in KI or the degraded hordein. The levels of total proteinase activity in both feed and malting barley varieties were similar. The results suggest that estimation of the levels of degraded hordein, during malting, is a sensitive indicator of the total proteolytic action of proteinases as well as the degradability of the reserve proteins. Therefore, we recommend measuring the amounts of hordein degraded during malting for the assessment of the impacts of grain protein and proteinases on malting barley quality of different varieties, in addition to KI and FAN.     

Ripening Profile of Semi-Hard Standard Goat Cheese Made From Pasteurized Milk

The microbial groups, physico-chemical characteristics, proteolysis, lipolysis, and rheological properties over a 30-day ripening period of a semi-hard cheese from pasteurized goat's milk were investigated. The count of aerobic mesophilic flora was high in cheese throughout ripening with lactic acid bacteria being the main microbial group. Halophilic bacteria, yeast and molds showed initial low counts but maintained their levels relatively constant during the ripening period. The main biochemical modification of cheese during ripening was related to the extent of proteolysis. The water soluble nitrogen in the semi-hard cheese increased during ripening. Lipolysis also occurred throughout the ripening period, with the major constituents being the palmitic, oleic, myristic, capric, and lauric acids. The rheological study suggested that the most important factors influencing the texture of the goat cheese is the level of total solids, and the extent of protein degradation recorded as soluble nitrogen during the ripening period. Rheological properties of goat cheese showed a transformation from a soft and elastic consistency to a hard and brittle body as a function of aging.