Optimising the Wagashie (A Traditional Cottage Cheese) Process and Sensory Quality

Abstract

Wagashie is a traditional West African cottage cheese produced by the Fulani who are semi- nomadic. It is a good protein source and can replace fish or meat in the diet of low income families in Africa. However, it is a product with high moisture content (60%) which is favourable for the growth of microorganisms and thus has a short shelf life of 3 days; it also has a bland taste with limited patronage. This research was therefore carried out to reengineer wagashie for a larger market with a focus on improving its sensory quality, safety and shelf life. A brief survey was carried out to confirm the wagashie production procedure and identify retailers and producers for collection of samples. The safety of market samples of fresh and fried wagashie samples were determined by assaying for various indicator and pathogenic microorganisms including aerobic mesophiles ,Yeast and moulds , coliform bacteria, E. coli, Staphylococcus aureus Bacillus cereus, Salmonella spp ,Enterococcus, Enterobacteriaceae. Studies were also carried out to replace the traditional coagulant of milk which involves the use of plant extract of Sodom apple (Calotropis procera) with commercial rennet used in industrial cheese production and ferment fresh milk used in the preparation. The traditional method of preparation was also standardised to improve its sensory quality. The process variables of wagashie, which are salt concentration, coagulant and fermentation time, were thus optimised using the Box Behnken design which is a response surface methodology and an affective testing was carried out to evaluate the consumer preference of the product with a nine-point hedonic scale. The sensory profile of the ‘wagashie’ samples were described by a Quantitative Descriptive Analysis by a trained 13 member panel. They evaluated the wagashie samples for desirable and undesirable attributes of wagashie. The rheology of ‘wagashie’ which involves Texture Profile Analysis (TPA) with a texture analyser and colour determination using a chroma photometer were carried out on the improved product which were the rennet coagulated fresh and smoked wagashie samples. Chemical analyses were carried out on the samples whereby the protein, ash, fat, free fatty acids (FFA), moisture, pH and Titratable acididty (TTA) of wagashie were determined. The safety of the laboratory prepared wagashie was assessed and shelf life studies were carried out for 5 weeks. The results of the microbiological tests carried out on the market wagashie showed that, Salmonella and Staphylococcus aureus were not detected in the samples whiles Bacillus cereus was detected in low counts in half of the samples. The rest of the microorganisms were found in fairly high counts. The optimum levels of the process variables which was used in standardizing the product were 23 g of salt, 150 g of plant extract and 0 h fermentation for the traditional preparation and 11 g of salt, 5.35ml of commercial rennet and 4 h fermentation for the improved wagashie The results of the consumer preference testing showed that the panelists preferred the non-fermented product to the fermented wagashie for the traditional preparation (Sodom apple extract as coagulant). The same panelist however preferred the fermented product to the non-fermented product for the preparation with commercial rennet as coagulant. After a confirmatory affective test where the wagashie samples were processed by frying and smoking, the panelists rated the acceptability of the traditional non- fermented smoked and the fermented rennet coagulated fried sample significantly higher at p<0.05, followed by the fermented rennet coagulated smoked sample. However, all three samples were rated ‘like- moderately’ on the 9-point hedonic scale. Thus the fresh and smoked samples were considered for the rest of the study due to health concerns raised by consumers which involved the reduction of fat in wagashie. In the Quantitative Descriptive Analysis, the panellists scored higher intensities of the desirable attributes in the improved wagashie which were mainly milky aroma, milky taste, cheesy aroma, cheesy taste, yoghurt aroma. The undesirable descriptors which were bitter taste, bland taste, spoilt milk aroma, fermented cassava dough aroma were rated high in the market samples. Generally, there were no significant differences between the plant extract coagulated samples and the rennet coagulated samples prepared in the laboratory. The Texture profile analysis showed that the wagashie samples were ‘hard’, ‘gummy’ and ‘chewable’. The instrumental colour determination showed that the fresh wagashie sample had higher L* values which indicated a lighter colour while the smoked samples had lower L* values which indicated a darker colour which corresponded to the results of the Quantitative Descriptive analysis of the fresh and smoked wagashie samples. The chemical analysis showed that the rennet coagulated smoked sample had the highest protein content of 30.18 g/100g and the highest FFA value of 0.53. The fried samples had the highest fat content of 25.32 g and the highest ash content of 2.0 g and the fermented fresh samples had the highest moisture content of 56.10 g. Generally the FFA values for the samples were low. The safety of the improved wagashie samples was improved with fermentation and smoking, this is because the count for microorganisms reduced when compared with the safety of the market wagashie.The result of the shelf life study showed that preserving the wagashie samples with vacuum packaging and irradiation extended the shelf life of wagashie from 3 days to 3 weeks of storage under ambient conditions.