Influence of the Soluble Solids on the Zeta Potential of a Cloudy Apple Juice.

BENITEZ, ELISA INES; JORGE E. LOZANO

LATIN AMERICAN APPLIED RESEARCH

UNS

Lugar: Bahía Blanca; Año: 2006 vol. 36 p. 163 - 168

0327-0793

The effect of soluble solids (mainly sugars, malic acid and metal ions) 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. After that point ξ changed at a rate of -25 mV/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.