Effect of pomace drying on apple pectin

CONSTENLA, D.; PONCE, A.; LOZANO, J.E.

LEBENSMITTEL-WISSENSCHAFT UND-TECHNOLOGIE-FOOD SCIENCE AND TECHNOLOGY

ELSEVIER SCIENCE BV

Año: 2002 vol. 35 p. 216 - 221

0023-6438

ABSTRACT          The effect of temperature used for drying apple pomace on apple pectin characteristics, including chemical composition, color and gelpoint temperature (Tg) was determined. Pomace was obtained from commer­cial Granny Smith apples and dried in a rotary drier at different air temperatures (Tdr = 60, 70, 80 and 105°C). Pectin was extracted from dried pomace in nitric acid solution (pH = 2.5) at 80°C. Major minerals in apple pectin were Ca> Na> Mg. Galacturonic acid content (%AGA= 58.6 ± 2.0) was practically unaffected by drying temperature. Conversely, Tdr affected both the degree of methoxylation (DM) and the molecular weight (Mw) of extracted pectin. Mw was estimated by applying the Mark Houwink ? Sakurada equation, through determination of intrinsic viscosity of pectin solutions. Mw reduced with Tdr from approximately 122,000 (60°C) to 57,000 (105°C). Pectin color, as Hunter DE, was also affected by Tdr. A lighter color was obtained at 80°C. The higher gel point value (Tg= 80°C) was obtained with pectin from pomace dried at 80°C.Gel point was shown to be more sensitive to Tdr than other quality parameters: while DM had the same value both at 80° and 105°C, minimum Tg occurred at the higher temperature. Tg was also very sensitive to pH.