No abstract

Aim: In view of high cost of agar in Nigeria, the study evaluated the suitability of cocoyam starch and cocoyam starch-agar blends as alternative gelling agents in mycological culture media. Methodology: Media characteristics and ability of the media to support growth and sporulation of the test fungi A. niger and A. flavus were determined using standard procedures. Potato dextrose agar (PDA) served as the control medium. Results: Addition of cocoyam starch to the media did not significantly affect media clarity, viscosity, and ease of pouring. Media in which cocoyam starch made up 57% or less of the gelling agent solidified while those with higher contents of starch were either semi solid or watery. Mean radial growth ranges were 75.00 ± 0.70 – 84.00 ± 1.00 mm and 77.50 ± 0.50 – 86.50 ± 0.50 mm for A. niger and A. flavus respectively. Cocoyam starch-agar blend (4:3) medium produced significantly higher mean radial growth (84.00 ± 1.00 mm and 86.00 ± 0.50 mm for A. niger and A. flavus respectively) than all the other treatments (P = .05). Mean spore counts per mycelial disc of the various media ranged from 8.6×103 to 9.3×103 for A. niger and 7.9×103 to 9.5×103 for A. flavus. Though both fungi sporulated well on all the media, the PDA medium and the 2 g of cocoyam starch + 4 g of agar medium had significantly higher mean spore counts compared to the other media. Conclusion: The findings show that cocoyam starch can partially substitute agar as gelling agent in mycological culture media.

The cost of animal milk used in yoghurt production in Nigeria has continued to rise, making the price of yoghurt to become prohibitive. This study investigated the suitability of tiger nut milk for yoghurt production. Five milk formulations prepared from tiger nut milk and cow milk were used to produce yoghurts. pH and titratable acidity (TA) of the milks and yoghurts were determined. The yoghurts were assessed for total plate count (TPC), total fungal count (TFC), fat content and sensory properties. Sensory properties were evaluated by a 10-man taste-panel using a 5-point hedonic scale. pH values of the yoghurts ranged from 3.94 – 4.68. TA values ranged from 0.56 – 0.64. TPC of the yoghurts ranged from 1.0 x 102 – 1.3 x 103 cfu/ml while TFC ranged from 0.1 x 101 – 0.3 x 101. The microbial counts of the yoghurt samples were within acceptable safety limits. The yoghurts were generally acceptable to the panelists. There were significant (P < .05) differences in the sensory scores for appearance, taste, texture, and overall acceptability. Tiger nut-cow milk (75:25) yoghurt had the highest appearance and taste scores while tiger nut milk (100) yoghurt had the highest texture and overall acceptability scores. Tiger nut milk (100) yoghurt was the most preferred yoghurt with an overall acceptability score of 4.8±0.42 followed by tiger nut-cow milk (75:25) yoghurt. Yoghurts analysed had fairly high fat contents. The study showed that tiger nut milk and tiger nut-cow milk composites could be used as alternatives to cow milk for yoghurt production.