Food processing
Food processing is the transformation of agricultural products into food, or of one form of food into other forms. Food processing takes many forms, from grinding grain into raw flour to home cooking and complex industrial methods used in the making of convenience foods. Some food processing methods play important roles in reducing food waste and improving food preservation, thus reducing the total environmental impact of agriculture and improving food security.
Food Processing Levels are defined according to physical and chemical changes occurring during food treatments. FPL are required in processed food classifications, such as the Nova classification, to categorise processed foods according to their FPL for different purposes.
Primary food processing is necessary to make most foods edible while secondary food processing turns ingredients into familiar foods, such as bread. Tertiary food processing results in ultra-processed foods and has been widely criticized for promoting overnutrition and obesity, containing too much sugar and salt, too little fiber, and otherwise being unhealthful in respect to dietary needs of humans and farmed animals.
Processing from farm to fork
Primary food processing
Primary food processing turns agricultural products, such as raw wheat kernels or livestock, into something that can eventually be eaten. This category includes ingredients that are produced by ancient processes such as drying, threshing, winnowing and milling grain, shelling nuts, and butchering animals for meat. It also includes deboning and cutting meat, freezing and smoking fish and meat, extracting and filtering oils, canning food, preserving food through food irradiation, and candling eggs, as well as homogenizing and pasteurizing milk.Contamination and spoilage problems in primary food processing can lead to significant public health threats, as the resulting foods are used so widely. However, many forms of processing contribute to improved food safety and longer shelf life before the food spoils. Commercial food processing uses control systems such as hazard analysis and critical control points and failure mode and effects analysis to reduce the risk of harm.
Secondary food processing
Secondary food processing is the everyday process of creating food from ingredients that are ready to use. Baking bread, regardless of whether it is made at home, in a small bakery, or in a large factory, is an example of secondary food processing. Fermenting fish and making wine, beer, and other alcoholic products are traditional forms of secondary food processing. Sausages are a common form of secondary processed meat, formed by comminution of meat that has already undergone primary processing. Most of the secondary food processing methods known to humankind are commonly described as cooking methods.Tertiary food processing
Tertiary food processing is the commercial production of what is commonly called processed food. It covers further processing of multiple ingredients in the manufacturing of fabricated foods, such as the ultra-processed foods category of the Nova classification. Many of these are ready-to-eat or heat-and-serve foods, such as frozen meals and re-heated airline meals.Food processing level
Food processing level is a parameter used for grouping of food processing according to physical and chemical changes taking place in food materials during processing. Definition of the extent of processing benefits from the use of an ordinal level of measurement. Arbitrary grouping of processed food using nominal scales, such as extent of change, nature of change, raw material sources, ingredients used, place of processing, purpose of processing, traditional, novel and other type of treatments is often criticised. Ranking of food processing at an ordinal scale at any stage from food production in agriculture to eating by consumer describes the extent of food processing using the order of the different levels of processing.Processed food classifications often identify processing as a criterion for the grouping of processed foods. Some processed food classifications, such as the Nova classification, emphasise the role of processing in the development of obesity and noncommunicable diseases. The public health interest is particularly in the Nova category of ultra-processed foods, a highly processed foods category, which often causes controversy on whether ingredients of processed foods or food processing relate to adverse health outcomes.
Unit operations and unit processes
Food processing results in physical and chemical changes in food materials independently whether processing involves home cooking, food services or industrial food manufacturing. Food processing is typically covered by food engineering, biochemical engineering and chemical engineering disciplines. Description of processes relies on understanding physical phenomena occurring in unit operations and kinetics of chemical reactions in unit processes which form the building blocks of food processing.Unit operations in food processing are building blocks of operations resulting in physical changes in food materials. Unit operations are governed by general physical laws and include heat transfer and mass transfer required in different operations, such as separation processes, mixing and crystallization.
Unit processes in food processing consist of unit operations and biochemical processes and chemical reactions resulting in chemical changes in food materials. In chemical reaction engineering multiple unit operations are combined with unit processes to achieve the desired chemical changes.
Unit operations and unit processes are the premise of food processing systems. Multiple unit operations are often needed to carry out food processing designed to result in physical changes. Biochemical and chemical changes during food processing, such as loss of vitamin C, can accompany intended physical modifications, e.g., during heat treatments.
There is much criticism indicating that the Nova classification refers to formulation and additives while processing levels must relate to unit operations and food processing. Food processing categories with typical processes are given in Table 1.
| Processing category | FPL | Object | Result | Typical processes |
| Unit operations | 0 | Minor physical change. | Retention of natural food characteristics. | Washing, hulling, peeling, mixing, blending, forming, shaping, molding, shredding, cutting, sieving, screening, filtration, centrifugation, refrigeration, freezing. |
| 1 | Major physical change. | Intense physical operation and disintegration of natural cellular structures. | Grinding, milling, mincing, pressing, brining, salting, churning, coagulation, gelling, emulsifying, homogenization, whipping, high pressure processing, blanching, pasteurization, aqueous extraction, concentration, membrane separations, crystallization, evaporation, distillation, steaming, drying. | |
| Unit processes | 2 | General food processing but minor chemical changes. | Physical, chemical and enzymatic changes as part of food preparation, processing and traditional fermentation. | Baking, boiling, brewing, canning, cooking, grilling, frying, puffing, toasting, cocoa and coffee roasting, fermentations, yeast autolysis, simple extrusion and extrusion cooking, smoking, UHT processing, electrodialysis, ion exchange. |
| 3 | Chemical processing. | Major chemical and compositional transformations. | Organic solvent extraction, intended chemical/ enzymatic/thermochemical transformations, irradiation, biochemical/technological processes aiming at chemical modifications. | |
| 4 | Modified constituents processing. | Formulated foods with chemically transformed ingredients. | Post-processing of food formulations with FPL 3 and 4 and other ingredients. |
Food processing levels
The level of measurement in food processing classification uses nominal or ordinal variables for qualitative grouping of food processing. Processed food classifications, such as the Nova classification, categorise processed foods and often use subjective criteria in processed foods grouping. Nominal food processing classifications group food processing according to qualitative variables, such as raw material sources, purpose of processing, traditional or novel, and type of treatment. Food processing levels are derived from ordinal scaling of food processing impact on processed foods.Food processing levels indicate the object and result of food processing and provide means for the use of the extent of food processing at an ordinal scale for various purposes, e.g., processed food classification. The relative impact of FPL on the expected extent of food processing results from the combined effects of physical and chemical changes during food processing as is described in Figure 1.
Studies of food processing impact on public health and other outcomes, such as affordability, energy efficiency, food safety and sustainability benefit from the use of FPL. Several food ingredients, which have different FPL, are often used in food products. The highest FPL used to obtain ingredients for intermittent processing of formulated foods and the FPL of final processing, whichever is the highest, indicates the FPL of the final food. Final food products may be formulated using ingredients from several FPL which, when including ingredients or processing at FPL 3 and 4, are assigned to the highest FPL 4.
History
Food processing dates back to the prehistoric ages when crude processing incorporated fermenting, sun drying, preserving with salt, and various types of cooking, Such basic food processing involved chemical enzymatic changes to the basic structure of food in its natural form, as well served to build a barrier against surface microbial activity that caused rapid decay. Salt-preservation was especially common for foods that constituted warrior and sailors' diets until the introduction of canning methods. Evidence for the existence of these methods can be found in the writings of the ancient Greek, Chaldean, Egyptian and Roman civilizations as well as archaeological evidence from Europe, North and South America and Asia. These tried and tested processing techniques remained essentially the same until the advent of the Industrial Revolution. Examples of ready-meals also date back to before the preindustrial revolution, and include dishes such as Cornish pasty and Haggis. Both during ancient times and today in modern society these are considered processed foods.Modern food processing technology developed in the 19th and 20th centuries was developed in a large part to serve military needs. In 1809, Nicolas Appert invented a hermetic bottling technique that would preserve food for French troops which ultimately contributed to the development of tinning, and subsequently canning by Peter Durand in 1810. Although initially expensive and somewhat hazardous due to the lead used in cans, canned goods would later become a staple around the world. Pasteurization, discovered by Louis Pasteur in 1864, improved the quality and safety of preserved foods and introduced the wine, beer, and milk preservation.
In the 20th century, World War II, the space race and the rising consumer society in developed countries contributed to the growth of food processing with such advances as spray drying, evaporation, juice concentrates, freeze drying and the introduction of artificial sweeteners, colouring agents, and such preservatives as sodium benzoate. In the late 20th century, products such as dried instant soups, reconstituted fruits and juices, and self cooking meals such as MRE food ration were developed. By the 20th century, automatic appliances like microwave oven, blender, and rotimatic paved way for convenience cooking.
In western Europe and North America, the second half of the 20th century witnessed a rise in the pursuit of convenience. Food processing companies marketed their products especially towards middle-class working wives and mothers. Frozen foods found their success in sales of juice concentrates and "TV dinners". Processors utilised the perceived value of time to appeal to the postwar population, and this same appeal contributes to the success of convenience foods today.
Also in the late 20th century, food manufacturers began changing their product model from a single "platonic dish", such as one version of jarred spaghetti sauce, to offering multiple variations, such as a plain version, a spicy version, and a chunky version.