Investigating and comparing the amount of water storage capacity and shelf life of chicken and ostrich meat

Dissertation for receiving a master's degree in the field of agricultural engineering, science and food industry

food chemistry orientation

Abstract:

In the meat industry, the durability and juiciness of meat is of particular importance, which is the goal of this research. In this research, thigh and breast muscles of chicken and ostrich meat were used, and 5 samples were taken from each of the chickens and ostriches immediately after slaughter. In this research, the temperature and pH at the moment of slaughter 1, 2 and 24 hours after slaughter and blood, which has a photo relationship with the water holding capacity (WHC), and at the moment of slaughter and 2 hours after that, cooking loss at C80 temperature for 35 minutes and storage loss for 7 days at C20 temperature and microbial load for 3 days and sensory evaluation for the first and third day were carried out.

Comparing the temperature in breast and thigh muscles and ostrich, there is a significant difference in the confidence level (99%) and for the storage capacity (WHC), loss of cooking and storage, and the amount of microbial load, a significant difference was obtained in the confidence level (95%).

Ostrich has the highest water retention capacity and longer shelf life and good sensory properties along with physical properties suitable for chicken and can be a substitute for chicken.

key words: water holding capacity, shelf life, ostrich, chicken

Chapter One:

General

1-1-Introduction

Meat and meat products are rich sources of high-quality protein, and the amino acids in them can compensate for the shortages related to limited foods in a region. They are a source of iron that can be easily absorbed and help absorb iron from other foods, and they are rich sources of some B vitamins. With the consumption of such nutrients, meat consumption can eliminate the usual nutritional deficiencies, but the harmful effects caused by the high consumption of animal fat have caused the consumption of red meat to decrease and the consumption of white meat such as chicken meat to increase. On the other hand, in the last few years, the ostrich meat market is rapidly expanding and developing and becoming a suitable alternative for other meats. Low-fat and low-cholesterol ostrich meat has a warm nature and contains iron, which is classified in the red meat group, this meat has a lot of nutritional value and is one of the lowest-fat and healthiest examples of red meat available, so that it can be said that the calories, cholesterol and fat of ostrich meat are lower than chicken and turkey meat, the amount of omega-3 fatty acids, its unsaturated fatty acids (which make up 30% of the total fatty acids) and low sodium. It has optimized ostrich meat for cardiovascular patients, people with high blood fat, obese people and for the elderly. Chicken meat is also an important source of high quality protein, minerals and vitamins, whose amount of unsaturated fatty acids is 2-3 times higher than red meat. Also, chicken meat has relatively low fat compared to other types of meat, and most of these fats are concentrated in the skin. 

1-2- The main question of the research (research problem):

Is there a difference in the water retention capacity of chicken and ostrich meat?

Is there a difference in the shelf life of chicken and ostrich meat under the same storage conditions?

1-2-1- Statement of the basic research problem In general (explanation of the problem and its introduction, etc.)

In recent years, increasing consumer awareness of the nutritional quality and health-giving effects of some foods, as well as the effect of fat in causing heart diseases, has led to changes in the pattern of food consumption, such that the consumption of high-fat meat has decreased, while the consumption of low-fat meat has increased (Jukna et al., [1] 2012).Therefore, in this regard, the consumption of chicken and ostrich is increasing day by day due to its nutritional value, cheap price, fast breeding cycle and low breeding cost compared to other animals. Animal meat contains about 75% water, and the force by which water binds to muscle proteins is very important for the preservation and processing of meat, and in this regard, water holding capacity is very important (Toldera et al., 2015 [2]). Factors such as transportation, storage, grinding, cooking, freezing and defrosting and drying can change the water holding capacity of meat. A relatively small part of water (4-5% of total water) is firmly absorbed on protein molecules and is called hydrated water, which has a structure similar to ice and its properties are different from free water. 15% of water is located in the extracellular space and the rest of the water is in the muscle fibers and saccoplasm of the reticulum. Hydrated water is hardly affected by changes in the structure and electric charge of muscle proteins. Therefore, significant changes in the water holding capacity that occur with changes in the electric charge of proteins due to changes in pH and in conditions such as freezing, heating, etc. cannot be due to changes in hydrated water. Therefore, the changes in meat water holding capacity should be related to 95% of the remaining muscle water that is in the space between myosin and actin (Toldera et al., 2015). Factors such as pH of meat, type and age of animal, legal position of muscles, condition of animal before slaughter are effective on water holding capacity. It is worth noting that water retention capacity is effective in increasing crispness, taste, pleasantness and improving the quality and color of meat.

The shelf life of fresh meat and meat products is a combination of internal and external factors. External factors include storage temperature, storage relative humidity, storage time, and internal factors include primary microbial load, nutrients, relative humidity, pH, etc. (Finer [3] 2006). Several factors have an effect on meat contamination, which include the following:

The degree of contamination of the digestive system and lymph glands of the animal,

The degree of contamination of the environment, tools and workers (Gill [4] 2005).

The speed of skinning and removal of stomach contents Livestock.

Hygienic situation in slaughterhouses and meat processing plants (Finer 2006).

In terms of microbial spoilage, a few Salmonella species can infect poultry meat, but all of them are capable of causing disease in the human digestive system, and therefore it is necessary to control dangerous species (Mead [5] 2004). Although the process conditions in the slaughterhouse change the predominant microflora of the poultry carcass from gram-positive spherical and rod-shaped microorganisms to gram-negative organisms, the microbial conditions of the final product are determined by the microbial load of the live poultry (Mead 2004).

pH: The best conditions for the growth of microorganisms is pH around 7 or 5.7-6.6, if some of them can grow at a pH lower than 4. In terms of maintaining meat quality, it has been observed that the meat of animals at rest spoils faster than animals slaughtered in exhaustion, which is due to the last pH created, leading to the complete mortuary stasis.