Ever since man became civilized, there have been considerable changes in his palate. The advancements seen in different fields also encompass food science. Once of the important aspect of food science is the study regarding the changes that occur to proteins upon cooking and the different factors that affect the softness of the food (Varnam and Sutherland, 1995; Pearson and Gillett, 1996; Lawrie, 1998). The present study involves an analysis of the changes happening to meat proteins during cooking and the different processes that play a role in determining softness of meat. Studies have shown that juiciness of meat is affected and varies with cooking rate and final temperature (Aaslyng et al., 2003, Bejerholm and Aaslyng, 2003, Bowers et al., 1987, Heymann et al., 1990, Joseph et al., 1997, Laakkonen et al., 1970 and Wood et al., 1995). Cooking loss happens with increase in temperature. Initially it was accepted that variation in juiciness was attributed to water loss but recent studies have shown that this loss is accounted only by ten percent and the rest to multiple other factors. It is now accepted that cooking loss due to water content is not the only determinant of juiciness. Studies that focus on the property of the internal water content of meat and its contribution to juiciness and its relationship to temperature are few. Bertram et al (2005) have shown that juiciness reduces when temperature is elevated. They found that juiciness of pork reduced when temperature was elevated from 62°C to 75°C and attributed this loss to the change in the pores that hold the water in the muscle fibres and also due to elimination of water. Some studies show that meat tenderness is also contributed by proteolysis of important myofibrillar proteins during storage (Koohmaraie et al, 2002).
Several studies advocate the fact that lower temperatures preserve tenderness and reduce cooking losses. During cooking, several changes take place in the meat such as coagulation of proteins, gelatin formation, color change and change in juiciness (Lowe, 1937). The process of coagulation makes the meat proteins insoluble, the rate and extent of which is determined by a number of factors such as temperature, time, salt content, pH, type, freshness, and the stage of cooking. Prolonged cooking decreases the volume of the meat and makes it more firm and thicker in consistency. When meat is heated in a humid environment at a certain temperature there is connective tissue hydrolysis, especially collagen that is converted to gelatin. In addition to cooking, treatment with acid also aids in gelatin formation. Juiciness is inversely proportional to temperature, the higher the temperature, the less the juiciness. This of course does not hold true in the case of meat with high fat content because, fat melts and forms an emulsion with water at high temperatures, which retains most of the moisture. This is due to the fact that fat is heat resistant and can withstand higher temperatures. Also meat taken from young animals is juicier than that taken from old animals as the latter loses its ability to retain more water compared to the former. Pressure cooking is another factor that contributes to juiciness as lower cooking temperatures are needed for efficient cooking. During cooking the color of meat changes from red to light pink depending on the temperature and when high temperatures are used, it turns from brown color to gray color. This relationship between temperature and color is determined by the origin of meat i.e., the age of the animal from which it was taken. The reason behind the change in color has been attributed to the degradation of proteins and fats, the important protein being oxyhemaglobin (heamoglobin+oxygen) which is converted to a brown hematin by product. Meat tenderness is dependent on the breakdown of proteins usually by heat but can also be brought about by chemical hydrolysis.
The experiment had the following aims:
- Assess juiciness and tenderness in meat after cooking.
- Investigate the effects of different cooking methods on meat softness and juiciness.
A total of two chicken breasts were taken for the experiment. These breast pieces were used for three different studies. The pieces were subjected to boiling frying and grilling. Thus:
- Boiling was done at 70°C for 10 minutes. The size of the chicken uses was 0.5 centimeters.
- Frying was done by immersing chicken breasts (weighing 224 grams) into hot olive oil maintained at 110° for four minutes. The final temperature after cooking was 55°C.
- Grilling was done by marinating the chicken with herbs for five minutes and then putting it in an oven maintained at 230°C for seven to eighth minutes.
It was found that during boiling the color of chicken changed from pale pink to creamy white and the juice of the meat came into the water. The meat became soft and the final weight was 51 grams after boiling. On the contrary after frying, the color of the chicken changed from pale pink to golden brown. The comparison of the different cooking methods on meat juiciness and tenderness revealed that when meat is grilled, it retained more juices but when it is boiled, it was the softest.
Discussion and Conclusion
Experimental studies have shown that meat juiciness and tenderness vary from one cooking method to another (Przybylski et al, 2007; Ramadan, 2006; Dreeling et al, 2000). They show that meat tenderness is more when it is boiled. On the contrary when meat is grilled, it is juicier. The increased breakdown of the proteins, i.e. hydrolysis contributes to the greater softness in the boiled sample compared to the frying and grilling methods. During grilling, there is less meat hydrolysis which happens mainly around the surface. This results in the meat holding more juice because the proteins are more intact than that during boiling or frying. Moreover the surface denaturing seals shut the entry points for the internal water in the meat. So of all the three methods used in the present study boiling is the beast when meat tenderness is concerned but grilling is the best when juiciness is the requirement.