Development of a Ready-to-eat Sorghum Snack Supplemented With Sesame and Baobab Fruit for Nutritional and Sensory Quality

Abstract

Orphan crops of sorghum, sesame and baobab fruit remain underutilized despite their nutritional and commercial advantages to modern high value food products that can address food and nutrition security in majority of sub-Saharan Africa. This study aimed at evaluating the nutritional, antinutrients and shelf-life stability of a ready to eat snack bar as influenced by the processing method and storage conditions. The study employed an experimental study design of a 3 × 4 factorial arrangement with three factors of malting, fermenting and roasting with four supplementation blends of 60:25:15; 70:20:10; 80:15:5; and 100:0:0 of sorghum, sesame and baobab fruit pulp respectively. Raw unprocessed samples of sorghum, sesame and baobab fruit pulp were acted as controls. The results showed that the nutritional composition of the snack bars made by supplementing with sesame and baobab fruit improved significantly (p<0.05). The protein and fat content improved significantly at 25% sesame and 15% baobab fruit pulp supplementation with roasted formulation RSF1 recording the highest at 16.74% for protein, and fermented sorghum formulation FSF1 at 19.73% for fat content respectively. Fiber content ranged between 5.59g/100g and 9.46 g/100g with formulations FSF4, RSF1, and MSF1 exhibiting high contents at 10.46%, 8.18% and 7.9% respectively. The mineral contents were significantly different (p<0.05) to the control samples with Iron levels ranging between 5.46 mg/100g and 14.611 mg/100g, with roasted formulation RSF1 having high content at 14.61 mg/100g as compared to MSF1 at 11.44 mg/100g, and FSF1 at 11.45 mg/100g respectively at 25% sesame and 15% baobab fruit pulp supplementation. Calcium levels in the snack formulations ranged between 82 mg/100g and 246 mg/100g, with malted formulation MSF1 at 25% sesame and 15% baobab fruit pulp supplementation having high content at 246.7 mg/100g, followed by RSF1 and FSF1 at 227.2 mg/100g and 171.5 mg/100g respectively. Zinc concentrations were significant for roasted and malted formulations at 25% sesame and 15% baobab fruit pulp supplementation at 4.82 mg/100g and 4.98 mg/100g respectively. The carbohydrate content in roasted sorghum snacks ranging between 48.20-59.85%, malted sorghum snacks between 48.54-59.71%, and fermented sorghum snacks between 46.37-60.31%. The calculated energy content ranged between 397-426.9kcal/100g in roasted sorghum formulations, 387.1-428.8 kcal/100g for malted sorghum formulations and between 377.3-425.1 xviii kcal/100g for fermented sorghum formulations respectively. The sensory evaluation of the snacks was done by use of a 5-point hedonic scale and revealed significance differences (p<0.05) in color, taste and overall acceptability with mean scores above 3.5. The aroma and crunchiness of the snacks were found to not be significant (p>0.05) with mean scores of 3 indicating neither like or dislike. Snack bars with no added baobab were found to be generally acceptable with RSF4 (3.853±0.99), MSF4 (3.529±0.99) and FSF4 (3.676±1.34) being the most preferred. The effect of processing method on antinutrients in the snack bars differed significantly (p<0.05). Roasting averagely reduced tannic content by 82.71%, phytates by 53.26%. Malting process decreased on average the tannic content by 78.66%, phytates by 48.89%, while fermentation was 78.71% on tannins and 51.54% phytates respectively. The phenolic content retention in the snack bars was significantly different (p<0.05) with average retentions at 59.58% for roasted formulations, 59.6% for malted formulations and 58.31% for fermented sorghum formulations respectively. The microbial and physicochemical properties of the snack bars were within acceptable limit up to day 3 of accelerated shelf-life storage at 55±2ºC. Snack bars stored in Flexible package exhibited better keeping quality than Kraft and Poly/PE-coated packages. The mean count of TVC and yeast and molds for samples stored in kraft and poly/PE-coated packages were highest at the second day of storage as compared to the flexible package which recorded high mean counts at day 3 of storage (p<0.05). The S. aureus mean counts were found to be of acceptable limits of 102 log cfu g-1. The pathogenic microorganisms were not detected in the formulations during the duration of storage. The oxidative stability of the snack bar formulations was significant (p<0.05) among the packaging materials with Kraft package exhibiting faster detection after day 2 of accelerated storage period at 5.084 meq O2/kg. Autooxidation was detected in poly/PE-coated and Flexible packages at day 3 of accelerated storage at 4.942 meq O2/kg and 2.031 meq O2/kg respectively. The FFA content among the snack formulations was not significantly different (p>0.05) during the accelerated shelf-life period in the three packaging materials. Oxidative stability of the snack formulations was best after three months of storage in Flexible packaging material as compared to Kraft and poly/PE-coated materials. The study concludes that sorghum, sesame and baobab are viable crop alternatives for food and nutrition security and innovative opportunities in food product development. This can support the xix economic wellbeing to sorghum farmers, micro-processors along the sorghum value chain. However, to achieve full utilization of orphan crops, more research should be extended on accessible processing technologies to achieve these objectives.