eChapter Name: Concentration of Fruit and Vegetable Juices : Concepts and Trends
9789390591411
eBook Name: POSTHARVEST MANAGEMENT OF FRUITS AND VEGETABLES
by S.K. Sharma, Deepa Saini
1. INTRODUCTION
Juices and pulps are produced from a wide variety of fruits and vegetables around the world, while some medicinal plants and herbs are also used for preparation of extract of beneficial bioactive compounds. These juices and extracts contain very high proportions (upto 75-90%) of water. Due to their seasonal nature, these products can not be produced round the year in various parts of the world. Preservation, storage, transportation and marketing of single strength juices, pulps and extracts is not at all economical due to the presence of large quantities of water. Under these circumstances, the technology of concentration offers many advantages.
In chemistry, concentration, as a state, may be defined as “the abundance of a constituent divided by the total volume of a mixture” and can be mathematically explained in four types i.e. mass concentration, volume concentration, molar concentration and number concentration. Generally, the term concentration can be applied to any mixture (solid or liquid) but most frequently it refers to the presence of solutes in solvents. Mass concentration is defined as mass/volume (m/V) of mixture and represented in kg/m3, volume concentration as volume of a constituent divided by the volume of all constituents of the mixture (v/V) and represented in m3/m3, molar concentration as moles of a constituent divided by the volume of all constituents of the mixture (n/V) and represented in mol/m3, while, number concentration is defined as the number of entities of a constituent in a mixture divided by the volume of the mixture (N/V) represented in 1/m3.
In food technology or fruit juice industry in particular, concentration refers to a process of separation of water (or any other solvent) from the solids of the pulp, juice, extract by making use of any of the three basic methods i.e. evaporation, freezing and membrane technology. Pulps, juices and extracts are the basic material used for preparation of various types of processed products. But due to their bulk and presence of large quantities of water they are difficult to store and transport. Concentration of juices, not only provides microbial stability, but also reduces the costs of packaging, transportation and storage by reducing the bulk of the material. Concentrated juice, contains far less water than normal, or “not-from-concentrate” forms of juice.