eChapters

3.1 Introduction

The subject of heat transfer is firmly grounded in the sciences of thermodynamics and fluid mechanics. It has become exceedingly important for engineers to possess a clear understanding of the principles of heat transfer and its application to a large number of problems. In view of process engineering, the knowledge of heat transfer and its application is most important, because heat transfer is one of the basic unit operations in the agricultural processing activities. The design of process equipments, refrigerators, boilers or type of heat exchangers, thermal treatment of food grains, cooling of perishables, pasteurizations, sterilizations, freezing of milk and fruit juices and a large number of similar applications involve consideration of heat transfer rates. There may be other situations where heat is being generated during a certain operation, and may be detrimental to the equipment and the food product. In such cases we are often faced with the task of removing the undesirable amount of heat as far as possible.

2.1 Introduction

Many complicated engineering principles are to be analyzed and applied, before any food processing operations takes shape of a commercially viable enterprise. The size and type of the required equipments have to be specified and their sequences have to be arranged. Further, the process analysis consists of understanding of material and energy balances. This chapter provides the application of steady state conservation of mass and energy equations to analyze food-processing operations.

1.1 Importance of Food Process Engineering

Food occupies the first position among the hierarchal needs of human beings. It is more important than shelter and clothing. After production and be forec on sumpti on, food commodities are subjected to nume rous unfavourable physical, chemical, microbial or parasitic factors which may cause their spoilage or disease when consumed. To prevent such spoilage, a process engineer has to understand these and provide remedial measures. The two primary goals of processing operation are first to minimize post harvest losses and second value addition of raw food commodities through preservation and processing.

Present level of production of different types of food commodities and their estimated post-harvest losses along with monetary values are given in Table 1.1. It shows that various food items get lost, to the tune of 65 million tonnes, worth Rs. 76,000 crores per annum, during post-harvest phase. A substantial amount of these losses could be prevented if appropriate agro processing centers, having backward linkage with farmers to ensure constant supply of quality raw food materials, are established and operated. Profit generated through value addition must also be shared with farmers, who are only people in the world to create wealth every year, in the form of food, fiber and other commodities necessary for human survival. It can bring sea change in rural areas, where 65-70% population live, in respect of economy, health and happiness.

It sounds simple, but the above process is fairly complex and requires lot of coordination in order to succeed. The major challenge is to minimize the losses during the various post harvest operations and keep the food as fresh as possible. In order to do so, one must first try to understand the various causes of post harvest losses of food commodities and the various factors that influence theses causes. Secondly, we must use those food processing operations that will not only extend the shelf life of the produce but also convert the raw food commodities to more acceptable product to the consumer.