Vegetables Processing

Written by Administrator | 02 February 2012

 Vegetables varieties

Vegetable processors must appreciate the substantial differences that varieties of a given vegetable will possess. When vegetables are maturing in the field they are changing from day to day. There is a time when the vegetable will be at peak quality from the stand-point of color, texture and flavor.

 Reception

This covers qualitative and quantitative control of delivered vegetables. The organoleptic control and the evaluation of the sanitary state, even if they are very important steps in vegetables' characteristics assessment, cannot establish their technological value.

 Temporary storage

This step should be as short as possible and better completely eliminated. Vegetables can be stored in: simple stores, without artificial cooling; in refrigerated stores; or, in some cases, in silos. Refrigerated storage is always preferable and in all cases a processing centre needs a cold room for this purpose, adapted in volume I capacity to the types and quantities of vegetables (and fruits) that are further processed.

 Washing

Washing is used not only to remove field soil and surface micro-organisms but also to remove fungicides, insecticides and other pesticides, since there are laws specifying maximum levels of these materials that may be retained on the vegetable; and in most cases the allowable residual level is virtually zero. Washing water contains detergents or other sanitizers that can essentially completely remove these residues.

 Sorting

This step covers two separate operations: removal of non-standard vegetables (and fruit) and possible foreign bodies remaining after washing, quality grading based on variety, dimensional, organoleptical and maturity stage criterion.

 Skin Removal/peeling

Some vegetables require skin removal. This can be done in various ways. Mechanical (This type of operation is performed with various types of equipment which depend upon the result expected and the characteristics of the fruit and vegetables). Chemical, Skins can be softened from the underlying tissues by submerging vegetables in hot alkali solution. Lye may be used at a concentration of about 0.5-3%, at about 93° C (2000 F) for a short time period (0.5-3 min). The vegetables with loosened skins are then conveyed under high velocity jets of water which wash away the skins and residual lye. Thermal,  Wet heat (steam). Other vegetables with thick skins such as beets, potatoes, carrots and sweet potatoes may be peeled with steam under pressure (about 10 at) as they pass through cylindrical vessels. This softens the skin and the underlying tissue.

 Size reduction

This step is applied according to specific vegetable and processing technology requirements

 Blanching

The special heat treatment to inactivate enzymes is known as blanching. Blanching is not indiscriminate heating. Too little is ineffective, and too much damages the vegetables by excessive cooking, especially where the fresh character of the vegetable is subsequently to be preserved by processing. This heat treatment is applied according to and depends upon the specificity of vegetables, the objectives that are followed and the subsequent processing / preservation methods.

 Canning

Large quantities of vegetable products are canned. A typical flow sheet for a vegetable canning operation (which also applies to fruit for the most part) covers some food process unit operations performed in sequence: harvesting; receiving; washing; grading; heat blanching; peeling and coring; can filling; removal of air under vacuum; sealing/closing, retorting/heat treatment; cooling; labeling and packing. The vegetable may be canned whole, diced, puréed, as juice and so on.