EFFECTS OF INCLUSION OF OYSTER MUSHROOM (PLEUROTUS SAJOR-CAJU) ON THE PHYSICO-CHEMICAL, SENSORY AND MICROBIAL PROPERTIES OF HAMBURGER
This research was conducted to determine the contribution of mushroom on the physico-chemical, nutritive and sensory properties of hamburger. Four burger samples were prepared with different combinations (0%, 20%, 40% and 60%) of mushroom. The inclusion of mushroom caused a general decrease in the protein, fat, moisture, ash, mineral element, vitamin as well as soluble protein and an increase in the carbohydrate contents of hamburgers. The proximate and soluble protein contents of burgers without (0%) mushroom differed significantly (P < 0.05) from burgers with mushroom. Significant differences (P < 0.05) in the mineral element (Magnesium, iron, phosphorus, zinc, calcium and sodium) content were observed between burgers without (0%) mushroom and burgers with mushroom. The change in the potassium content of all the burger samples did not show any significant difference (P > 0.05). Burgers without mushroom differed significantly (P < 0.05) from those with mushroom in their vitamin C, A, thiamin and riboflavin content, while no significant difference (P > 0.05) was observed for niacin content among all the burger samples. The burgers with mushroom were found to still make appreciable contribution to the daily values (DV) of most of the nutrients in one serving size of 100g. The pH and water activity (aw) of the burgers ranged between 5.40 – 5.65 and 0.84-0.r96 respectively. The degree of “likeness” of the organoleptic qualities and general acceptability was rated highest for burgers without mushroom, and reduced gradually with progressive inclusion of mushroom. The least-rating (“slightly dislike”) was observed in the taste of ribeye and chuck muscle burgers with more than 20% mushroom. Chuck muscle burgers were most prefered to burgers from other muscle cuts. The microbial counts (TVC, mould and coliform counts) for burgers at the end of 8 days storage under ambient condition showed that significant differences (P < 0.05) existed among muscle at the various levels of mushroom. No specific trend could be established to account for the addition of mushroom on the microbial activities of hamburger during storage. Coliform and mould counts were generally lower than TVC throughout the storage period. No physical sign of spoilage was observed at the end of eight days of storage.