EFFECTS OF INCLUSION OF OYSTER MUSHROOM (Pleurotus sajor-caju) ON THE PHYSICO-CHEMICAL, SENSORY AND MICROBIAL PROPERTIES OF HAMBURGER

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ABSTRACT

 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 0.84-0.96 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.

CHAPTER ONE

1.0                                         INTRODUCTION

Meat is the flesh or muscular tissue of animals (Fox and Cameron, 1977). Similarly, Forrest et al, (1975) defined meat as the flesh of animals which is suitable for use as food. Although meat eating remains at a high level, there have been distinct changes in the type of meat eaten (Varnam and Sutherland, 1995). The most striking is the rise in consumption of poultry and sea food and less red meat (Kinsman, 1994). It was further emphasized that the success of fast-food outlets means that increasing quantities of beef and, to a lesser extent, other meats are eaten as burgers and similar products. Still according to Kinsman (1994), meat is the preferred food eaten at home.

Mushroom is the fleshy, spore bearing fruiting body of a fungus, typically produced above ground on soil or on its food source (Moore, 2003). Mushroom is more of common application to macroscopic fungi fruiting bodies than one having precise taxonomic meaning (Chang and Miles, 2004). However, according to Bahl (2000), mushroom is a general term applied to the fruiting bodies of the fleshy fungi and as such belongs to different groups of fungi. The majority of mushrooms belong to Hymenomycetes (Basidiomycotina) while others belong to Discomycetes (Ascomycotina).

How long man has been eating mushrooms is, of course, impossible to determine, but one can speculate with reasonable assurance that such fungi have periodically been a part of his diet for many centuries (Gray, 1970). It was further stressed that until recent times in the United States, mushrooms were used primarily as a condiment to garnish steaks. With the development and expansion of the mushroom canning industry however, they appear to be gaining favour as a base for soup and as ingredient in many dishes in which they were formerly seldom used. Bano et al (1963) reported that mushrooms represent one of the world’s greatest untapped resources of nutritious and palatable foods.

Some mushrooms are edible while others are poisonous (Bahl, 2000). Edible mushrooms are distinctive in some ways. Once their distinguishing features are learned, they cannot be confused with any dangerously poisonous species.

Mushroom is being cultivated in many parts of the world presently. Commercial mushroom growing was first initiated in India (Bahl, 2000). Mushrooms have the capacity to convert nutritionally valueless substances into high protein food. It was stressed further (Bahl, 2000) that on an area basis they are a more valuable source of protein (Table 1). Besides being a food article, mushrooms are variously exploited by man (Bahl, 2000).

Table 1: Approximate annual yield of mushroom (Agaricus bisporus), beef and fish (dry protein, kg/ha).

Protein source                                                               yield

Beef, cattle by conventional Agriculture                        78

Fish, intensive pond rearing                                          675

Agaricus bisporus                                                                    65, 000

          Source: Bahl (2000)

Hamburger: A Ground Meat Product

According to Wikipedia (2008), ground beef, beef mince or hamburger meat (in North America) or minced meat (in the rest of the English world) is a ground meat product made of beef finely chopped by a meat grinder. Burgers are usually made from ground meat or meat substitute, then reshaped to form patties and cooked and eaten (Uncyclopedia, 2008). Burgers made with beef are traditionally known as hamburgers, though due to the profusion of burger types over the last few decades are also called beef burgers. Uncyclopedia (2008) further emphasized that other meats such as venison, bison, pork, chicken, turkey, and fish can be used. The name generally changes accordingly with the name of the burger prefixed by that of the meat source. For example turkey burger, buffalo burger, jersey burger, vegiburger, etc. Burgers not made from beef are often marketed as more exotic than hamburger or as being healthier than beef patties. In the UK, the word burger often refers to the filling of a burger sandwich (that is what in USA would be termed a patty).

1.1     Statement of Problem

          Though, meat is a versatile item of the diet, several reports have indicted meat in respect of a host of human health problems, which are not commonly found with plant foods. There is too much dependence on the use/consumption of meat, especially red meat in the diet, with a consequent high cost. Meat is an ideal nutritious food. In many communities it is eaten to confer prestige and class distinction. Many plant materials cannot form satisfactory total replacement for meat, nor achieve compatible and acceptable combination with meat as a product to enable reduction of meat intake, yet meeting the nutritional requirements of humans. The role of meat in the diet is so unique that it cannot be completely removed from the diet.

          Mushrooms are valuable sources of high quality cheap food, which have been denied attention, especially in Nigeria and hence not utilized in the diet. The nutritional attributes of mushrooms as well as the physical and sensory qualities are such that mushrooms could combine well with meat to produce a novel nutritious and acceptable product.

EFFECTS OF INCLUSION OF OYSTER MUSHROOM (Pleurotus sajor-caju) ON THE PHYSICO-CHEMICAL, SENSORY AND MICROBIAL PROPERTIES OF HAMBURGER