extraction, disinfectant, peracetic acid, pulp pressability, juice color

A solution of peracetic acid in hydrogen peroxide (PAA) has been used for two campaigns (2004, 2005) for microbial control of the extraction towers in the Minerbio sugar factory in Italy. The use of formalin has been greatly reduced and totally abandoned for some weeks. In some cases it was necessary to add another biocide in order to maintain the microbial activity within the target: D(l-lactate) # 300 mg/L. An alkaline solution of hop b-acids has also proved to be very effective in this particular use as a supplementary biocide in combination with PAA.

The addition of PAA into the extraction had a positive impact on the pressability of the exhausted pulp. In the 2004 campaign an improved pressed pulp dry substance was obtained (plus 1.4%), but in the 2005 campaign it was decided to reduce the dosage of pressing aids while keeping the dry substance constant. Another beneficial effect was the color reduction of thin juice (–300 IU) and thick juice (–600 IU). This color reduction can be explained by the decrease in the glucose content of the raw juice.

Because of the high price of PAA and taking into account also that the sugar losses are somewhat higher than with formalin, the simple economic calculation of the treatment with PAA is still not completely favorable relative to formalin. However an accurate benefit-cost analysis should also take into consideration the social and environmental advantage of replacing a dangerous chemical product such as formalin.