The Journal of Commerce, Vol. 4, No. 1, ISSN: 2218-8118, 2220-6043 Hailey College of Commerce, University of the Punjab, PAKISTAN 13 CONSIDERING DIFFERENT TYPES OF CONSTRAINTS FOR PRODUCTION PLANNING FOR A DAIRY PRODUCT: A CASE STUDY Milad. Gorji Ashtiani  Faezeh. Mohammadipour Department of Industrial Engineering , Iran University of Science and Technology , Tehran, Iran Abstract Dairy industry plays a critical role in the economics of many countries. Recently, dairy companies have faced challenges in Iran due to their present position and new governmental policies. In this paper, a dairy company which has the significant market share in Iran is chosen. Despite having a variety of products which are manufactured in this company, yoghurt is selected due to its attractiveness in Iranian food habits. Therefore, this company is looking for a production planning which helps it gain a considerable profit and boost its current market share. For this reason, a linear programming model is formulated and the obtained results show that profit achieved by this model is higher than those obtained in the last years. Key Words: Dairy industry; Production planning; Yoghurt; Iran INTRODUCTION Household spending investigation in Iran depicts that people spend a significant amount of money for dairy products. Research has shown that one of the dairy products that Iranian people often eat along their main course is yoghurt. Many diary companies were established in Iran and are selling their products all over the country. Therefore, dairy product market is intensively competitive. These companies quest new methods to differentiate themselves from others and expand their market share. New bills which are passed in Iranian parliament have also engendered new concerns for these companies and caused the price of yoghurt material to be raised significantly in a condition that these companies are still forced  Corresponding author. Contact M_Gorji_Ashtiani@ind.iust.ac.ir not to increase the selling prices of their products. Therefore, diary companies are looking for new polices to soothe this situation and encounter efficiently with this wealth of challenge. In this paper, one of Iranian diary companies called here X Company is studied .The owners of X Company are reluctant that the name of their company is stated directly. X Company is an Iranian leading diary company which produces different types of products such as milk, ice cream, cheese, butter and yoghurt. Since yoghurt is considered as a strategic product for this company, it is investigated in this paper. 25 types of yoghurt are produced in X Company and each has its own demand. Since milk is the core raw material of yoghurt and it plays a critical role in its production, milk management is considered a critical factor but a complex task which is noticed in this paper. All types of yoghurts are categorized into 9 groups on the basis of their weights. Since the diversity of yoghurt types and market competitive condition is being noticed by this company and this company also struggles with production planning and processing due to the quantity and quality of its main raw material i.e. milk, a production planning optimization is considered for this company to help it not to hinder from its competitors and gain a considerable profit. In other words, X Company is going to acquire a production planning which helps it gain profit in this tender condition, become more efficient and easily control the behaviors of other manufactures. This paper is organized as follows: in the next section, the related studies found in literature are presented. Section III describes the problem and provides the mathematical model. The results of this study are discussed in section IV. Section V includes the main finding and future research avenues. THEORETICAL BACKGROUND Developing mathematical models for maximizing the profit is the method which has been utilized in many different industries. Ioannou (2005) developed appropriate