Effect of Malting and Fermentation on α-amylase inhibitors and subsequent digestibility in Pearl Millet OBILANA, A.O., MAREMA, T.R., MASHEGO, A., FAKUDE, S.Q. Department of Food Technology, Cape Peninsula University of Technology, P O Box 1906, Cape Town 7535 In this study, a combination of malting and fermentation was used to reduce the alpha amylase inhibitor levels in pearl millet and to increase starch digestibility. The samples were subjected to three different processing treatments (malting, fermentation, malting / fermentation), and compared to the raw unprocessed grain. Malted samples were prepared by steeping 500g of millet for 3h at 25 0 C and germinating at 30 0 C for 5d and dried at 50 0 C in a hot air vacuum drier. Fermented samples were prepared by subjecting 500g of millet to natural fermentation for 24h in distilled water at 30 o C, drained and dried at 50 0 C in a hot air vacuum drier. The malted/fermented samples were prepared by first malting the grain, then subjecting the malted grain to natural fermentation as described above. Triplicate samples of raw, malted, fermented, malted/ fermented millet were assayed for alpha-amylase inhibitor and starch digestibility. A significant (P<0.05) difference was observed in the alpha amylase inhibitor content values for the malted/fermented samples (44.9%), malted samples (47.7%), raw samples (54.3%) and fermented samples (55.6%). This reduction would seem to have contributed to the observed increase in the digestibility of the samples, with the fermented (38.0%), malted (40.2%) and Malted/fermented (48.5%) samples been significantly (P<0.05) higher than the raw (22.1%) samples. Pearl millet (Pennisetum glaucum) is a lesser known grain that can be utilized as food especially in the arid and semi arid regions of the world. It grows under hot and dry conditions, on infertile soils with low water binding capacity. It is high in carbohydrates and a source of proteins and essential amino acids. Anti-nutritional constituents naturally present in pearl millet such as alpha-amylase inhibitors, limit the digestibility of and starch. In recent times, however, some of these “antinutrients” (fibre, polyphenols) have been found to have functional / health benefits when consumed and as such have become the focus of numerous researches to determine their role in human health. REFERENCES CONCLUSIONS RESULTS AND DISCUSSION RESULTS AND DISCUSSION – Cont’d ABSTRACT INTRODUCTION OBJECTIVE DATA ANALYSES. The aim of this study is to investigate the effect of a combination of malting and fermentation processing in reducing or destroying enzyme (α- amylase) inhibitors in pearl millet, with a view to increase its digestibility hence nutritional value. Figure 3.Alpha amylase inhibitor activity, and starch digestibility of raw and processed pearl millet. A significant (p ≤ 0.05) increase in starch digestibility between the different groups was noted (fig. 3). This increase was based on the amount of maltose produced after digestion as compared between the groups. Fermented millet and malted millet had an insignificant increase in starch digestibility suggesting that fermentation and malting has almost the same effect on the digestibility of starch. Onyango et. al. (2004) reported an increase in starch digestibility during fermentation in there study, which is in agreement with results obtained in this study. However a slightly lower increase in digestibility was noted in this study. During malting, a 17% - 40% increase in digestibility was observed and from 17% - 38% for fermented. A significantly (p ≤ 0.05) higher increase in the malted & fermented millet was obtained (17%-48%). These results are also in agreement with those reported by Archana et al., (2001). He reported an increase in digestibility of pearl millet from 17% - 36%. Due to the degradation of starch as indicated by the decrease in starch content as the pearl millet samples are processed, a higher concentration of simple carbohydrate is obtained which suggest that more starch is digested. Thus processing of pearl millet by fermentation and malting, with fermentation < malting< malted & fermented increases it’s starch digestibility. A reduction in alpha-amylase inhibitor content in between the groups was obtained as illustrated in fig 3. Though the reduction was insignificant, a slight decrease was obtained. A trend between the treatments was observed. A decrease in sequence from raw, malted and fermented & malted was 54% - 47%- 44%. However no decrease was observed for fermented millet. These results show that malting of pearl millet has a reductive effect on alpha amylase inhibitor content. Similar reduction in alpha-amylase inhibitor content after germination of great northern beans was reported by Abdelrahaman et. al. (2005) in their studies on pearl millet. A much lower reduction in this study was obtained as compared to other research work. Since natural fermentation is this instance was used, the high microbial load during the first hours might have used up most of the carbohydrates and further converted the product into other matter thus resulting in excess of enzymes without substrate to break down. Therefore the inhibitor content might appear to be higher since the assay basis the inhibitor amount on the product produced. The slight reduction during malting might be due to removal of shoot after germination which may have contained some simple carbohydrates in it which could have resulted in a higher reduction when considered. The overall reduction of alpha-amylase inhibitor in pearl millet resulted in the increase in starch digestibility as indicated. Although there was a corresponding increase in starch digestibility with decreasing α-amylase inhibitor activity, these increases can not be solely attributed to the decreasing inhibitor activity, as other factors (eg. Fibre, phenolic compounds etc.) present in pearl millet that could be affecting starch digestibility. The experiment was repeated 3 times. All analyses were performed in triplicate (n=3). Data obtained was then analysed by one way analysis of variance followed by the least significant difference test (LSD test). Mean differences was evaluated at the 5% significance level and correlations at the 1% and 5% significance level. All statistical analyses were carried out using the SPSS Statistics program 2008 version Figure 1.Process flow diagram for the preparation of millet samples. Figure 2.Malted pearl millet METHOD AND MATERIALS There were four (4) samples prepared for analyses in total. The process flow for the preparation of samples are given in figure 1. The starch digestibility and α- amylase inhibitor assays were carried out according to the methods of Oyongo et al., (2004) and Alonso et al., (1998) respectively. Combination of malting and fermentation has shown potential in reduction of α- amylase enzyme inhibitors in pearl millet. With this in mind, it is possible to use these relatively inexpensive processing methods in rural areas where pearl millet is used as a food source, to help increase digestibility ALONSO, R., ORUE, E. & MARZO, F. (1998) Effects of extrusion and conventional processing methods on protein and antinutritional factor contents in pea seeds. Food Chemistry, 63, ARCHANA, S. S. & KAWATRA, A. (2001) In vitro protein and starch digestibility of pearl millet (Pennisetum gluacum L.) as affected by processing techniques. Nahrung/Food, 45, ONYANGO, C., NOETZOLD, H., BLEY, T. & HENLE, T. (2004) Proximate composition and digestibility of fermented and extruded uji from maize–finger millet blend. LWT, 37, ABDELRAHAMAN, M. S., ELMAKI, B. H., BABIKAR, E. E. & TINAY, H. A. (2005) Effect of Malt Pretreatment Followed by Fermentation on Antinutritional Factors and HCl Extractability of Minerals of Pearl Millet Cultivars. Journal of Food Technology, 3,