BLEACHING OF APPLE POMACE BY HYDROGEN-PEROXIDE IN ALKALINE CONDITIONS- OPTIMIZATION AND CHARACTERIZATION OF THE PRODUCTS

Dried apple pomace from a cider plant was bleached by sodium chlorite in acidic conditions, sodium hypochlorite or hydrogen peroxide inalkal ine conditions. The most satisfactory treatment for intensity and even ness of the bleaching was hydrogen peroxide. Response surface methodol ogy was used to study this treatment. Both pH and concentration of hyd rogen peroxide had very significant effects on bleaching, yield and sw elling capacity. At high pH values and peroxide concentration, white p roducts were obtained with high swelling capacities but low yields. As effects were not linear, empirical second degree models were built to fit results of yield and swelling capacity. Equations were obtained w ith high significance and good predictive value. The alkaline peroxide treatment extracted polyphenols but also pectic materials from the ap ple pomace, while hemicelluloses and cellulose remained in the bleache d material. Water absorption and retention were also increased, though less than swelling, and water uptake was faster.