Preliminary Investigation of Bio-preservative Effect of Cola millenii Extracts on the Shell-Life of “Kunu-Zaki”

Aim: The aim of this study was to investigate the potentials of Cola millenii seed and pulp extracts as a possible bio-preservative agent for kunu-zaki, a Nigerian fermented beverage.

Methodology: The plant materials were grinded mechanically and macerated in solvent (acetone and ethanol) for 72 hrs. Kunu-zaki was produced using traditional procedures and the reconstituted extracts were aseptically introduced into it. Thereafter, the samples were stored at room temperature and in the refrigerator for 15 days.

Results: The pH and total titrable acidity of the freshly produced kunu-zaki were 4.49±0.01 and 0.38±0.00 respectively. The total heterophilic bacterial count of the freshly produced kunu-zaki was 5.6 X 102 cfu/ml, total fungal count was 2.7 X 102 cfu/ml while the lactic acid bacterial count was 11.1 X 102 cfu/ml. Moreover, seven bacteria and six fungi were isolated from the freshly prepared kunu-zaki, they were Pseudomonas aeruginosa, Bacillus subtilis, Bacillus licheniformis, Micrococcus luteus, Lactobacillus acidophilus, Lactobacillus plantarum, Streptococcus species, Geotrichum candidum, Saccharomyces cerevisiae, Aspergillus niger, Rhizopus stolonifer, Fusarium species and Penicillum species. The seed and pulp extracts of C. millenii reduced the bacterial load in the kunu-zaki compared with the controls, and C. millenii pulp extracted with ethanol (PEE) totally suppressed microbial growth in kunu-zaki from day 10 onward. C. millenii pulp extracted with acetone (PAE) and PEE had the best scores for aroma from day 7 to day 15 of storage while PAE, PEE and kunu-zaki without preservative stored in the refrigerator (FRG) had a significantly higher rating for taste throughout the storage period. The overall acceptability of the bio-preserved products as well as the controls was not significantly different (p≤0.05) during the first three days and tenth day of storage.

Conclusion: From the foregoing, there is great amount of evidence suggesting that the ethanol extract of Cola millenii pulp possess bio-preservative potentials against kunu-zaki spoilage. Therefore, it may be expediently exploited in the food and beverage industries to extend the shelf-life of their products.