Comparison of Solid-Liquid Separation (SLS) and Vacuum Concentration of Tomato Juice

Abstract
Hot break, cold break and commercially canned tomato juice was concentrated by vacuum concentration and solid-liquid separation (SLS). Tomato products from vacuum concentration had higher soluble solids than those from SLS because of loss of soluble solids into the filtrate. Most volatile levels in vacuum concentration greatly decreased initially then remained constant during further concentration. In SLS, volatile levels linearly decreased with increasing concentration so SLS had greater retention of volatile compounds than vacuum concentration. Viscosity of the rediluted samples decreased with concentration, except in the hot break and commercial samples from SLS, which maintained the same viscosity. Samples from SLS were close to the original color while vacuum concentration was redder due to heat-induced Maillard browning. Vitamin C decreased during concentration with greater loss during SLS than vacuum concentration. SLS consumed 45 times less electric power energy than vacuum concentration, which also needed water for creating vacuum conditions.

Practical Applications
Solid-liquid separation (SLS) is a new technology for dewatering products, such as concentration of tomato juice. SLS does not need heat to concentrate the product; therefore, the processor may be able to reduce energy consumption while better preserving flavor and viscosity of the product.