Food processing includes the methods and techniques used to transform raw ingredients into food for human consumption. The process transforms agricultural products into food, or changes one form of food into another. Food preservation covers any of the numerous physical, chemical or biological methods to eliminate, stop or slow down natural deteriorative processes in foods and extend their shelf-life as edible and safe products for longer term and practical preservation, as required for most of our food supply. These are largely directed at inactivating or controlling microorganisms, enzymes, and reducing or eliminating chemical reactions which can cause food spoilage. Food processing enhance food security and creates wealth while also adds value to and stimulates agricultural production, contributing to market expansion and generating collateral activities and industrial services. Other benefits include toxin removal, preservation, easing marketing and distribution tasks, and increasing food consistency. In addition, it increases yearly availability of many foods, enables transportation of delicate perishable foods across long distances and makes many kinds of foods safe to eat. There are several factors which affect food quality and lead to spoilage. They are categorized as physical, microbial and chemical factors. The process of deterioration in quality of food leads to food spoilage and is related to food safety. Food quality is an important food manufacturing requirement, because food consumers are susceptible to any form of contamination that may occur during the manufacturing process. Food processors rely on modern quality management systems to ensure the quality and safety of the products they produce. Unit operations in food processing ensure that each step in the process is carried out correctly and consistently, resulting in a safe and high-quality end product. Unit operations may include numerous different activities e.g. mixing includes agitating, beating, blending, diffusing, dispersing, emulsifying, homogenizing, kneading, stirring, whipping and working, cleaning, coating, concentrating, controlling, disintegrating, drying, evaporating, fermentation, forming, separating, heating, cooling, materials handling, mixing, packaging and pumping. Conventional methods used in food preservation include refrigeration, canning, irradiation, drying, salting, smoking, and fermentation, which help improve the shelf stability of foods products. However, the food industry is trying to design novel, less invasive technologies such as use of high pressure, hurdle technology, radiations like UV light, Oscillating Magnetic Field beyond the traditional conventional methods like drying, freezing, chilling, curing, heating, boiling, sugaring, salting, canning, pickling, and fermentation. Food preservation techniques including drying, pasteurization, freezing, chilling, jellying and jugging, smoking, fermentation, packaging, bio preservation, use of herbs and spices, irradiation, radiation, modified atmosphere, Controlled Atmospheric Storage, nanotechnology, Pulsed electric field electroporation, High pressure preservation of food, Chemical methods, Preservation with Sugar, Preservation with Salt, Pickling, Ozone treatment, Nonthermal plasma and Hurdle technology have been described in this chapter.