Pectin

Pectin is th best thickening additive for jellies and marmalades production. Albedo and cores are fruit parts more rich in pectin. Pectin may be produced both from fresh and dried peels, but in this last case its jelly power is lower. Peels are crushed by shredders and countercurrent washed to eliminate soluble solids. For obtaining a good quality pectin is very important to correctly size washing plant respect to fresh peels availability fro extraction lines because it is very important to avoid prolonged holding times with consequent pectins degradation by natural enzymes.  

Countercurrent washing system is usually made by three or four stages, each one followed by a mechanical dewatering system; after last washing step, peels are pressed and dried in a rotary dryer; if pectin production take place at the same time peels are remoisturized with clean water and sent to pectin extraction section. Dry peels are added with water (ratio from 40:1 to 70:1) and extracted in a tank equipped with mechanical stirrer and direct steam heating system. Critical factors are pH, time and temperature; pH varies from 1,5 to 2,5 , time from 30 a 60 minutes and temperature from 80 to 100°C. Immediately after extraction, mixture is cooled down to about 60°C e is centrifuged to separate solids from pectic liquor. Centrifuged liquid contains from 0,4 to 0,7 % pectin, it is decolorized and deodorized and clarified, then it is concentrated with an under vacuum evaporator to increase pectin content up to 3 - 5 % ; concentrated product is neutralized with Sodium carbonate or ammonia up to pH about 4,2. Pectin is precipitated with aluminium salts or isopropyl alcohol. For precipitation two volumes of alcohol are mixed with one volume of pectic liquor and the mixture is held, under stirring, to complete precipitation. Precipitate is drained, washed with 70 % alcohol and pressed. Final washing is made with 99 % alcohol to help complete dehydration of pectin in the next pressure stage; finally pectin is crushed and dried at temperature below 60°C.  Alcohol is recovered by distillation; if aluminium salts are used, aluminium pectinate floats to surface and an energetic stirring is necessary to precipitate it. Precipitate is washed with cold water to remove non-pectic substances; after pressing pectin cake is crushed and washed with acid (pH 1,0) isopropyl alcohol to eliminate aluminium. Some further washing steps follows to eliminate acid and final washing is made with alcohol (pH 4,0). Pressed pectin is then dried under vacuum.