Abstract

BENITEZ, E. I.  and  LOZANO, J. E.. Influence of the soluble solids on the zeta potential of a cloudy apple juice. Lat. Am. appl. res. [online]. 2006, vol.36, n.3, pp.163-168. ISSN 0327-0793.

The effect of soluble solids on the Zeta-potential (ξ) of a cloudy apple juice was investigated. Apple juice was enzymatically treated with pectinolytic enzymes and diafiltred with a polysulphone UF membrane (100 kDa) to eliminate soluble solids. Most soluble solids were removed after 4 equivalent sample volumes (ESV) of washing water. During a second period, from 5 to 23 ESV, diafiltration rate was significantly reduced. ξ (mV) moderately increased its absolute value with diafiltration during the first diafiltration period, changing at a rate of -1.1 mV/^oBrix up to 0.3 ^oBrix). Results also indicated that after the only restitution of sugars ξ, remained practically constant. When malic acid was restituted to a diafiltred juice, remarkable changes in Zeta potential occurred. As particles in this type of colloids are strongly negative, pH modification had a significant influence.

Keywords : Cloudy Apple Juice; Diafiltration; Soluble Solids; Zeta-Potential.

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