6 According to May 1990, pectin is a negatively charged polygalacturonic acid. Pectin reacts to
positively charged macromolecule. Gel formation can occur rapidly at low pH, but this reaction can be inhibited by the addition of salt. According to Rouse 1977, pectin degradation and decomposition can be
caused by the oxidation reaction. Rate of degradation depends on temperature, pH, and concentration of oxidizing agent.
4. Production of pectin
Stages in the pectin manufacture are material preparation, extraction, concentration, washing, and drying. The method used to extract pectin from plant tissues is various. But generally pectin extraction is
done using acid extraction. Several types of acid can be used in the pectin extraction. According Kertesz 1951, the acids that usually used in the extraction pectin are tartaric acid, malic acid, citric acid, lactic
acid, acetic acid, phosphoric acid. But there is a tendency to use a cheap mineral acid such as sulfuric acid, hydrochloric acid, and nitric acid. Some current article suggested that using hydrochloric acid Kalapathy
and Proctor 2001; Hwang et al. 1998; Dinu 2001 and nitric acid Pagan et al. 2001. Extraction using mineral acids produce higher yield than organic acids. The used of mineral acid at
low pH is better than at high pH Rouse and Crandal 1978. The role of acid in the extraction of pectin is to separate polyvalent ions, break the bonds between the amino pectinic cellulose, hydrolyzing protopectin
into smaller molecules and hydrolyzing methyl ester pectin Kertesz 1951. High temperatures during the extraction can increase pectin yield. Higher temperature will help the diffusion of solvent into the plant
tissue and can increase the activity of the solvent in hydrolyzing pectin Towle and Christensen 1973. The used of extraction temperature that is too high will result in pectin that is not clear, so the gel obtained
will be cloudy and reduced gel strength Kertesz 1951. Pectin in many plant tissues usually forms a protopectin that insoluble in water. The acidic solution
with a low pH conditions makes hydrolyzing protopectin become pectin easier. Extraction of pectin from vegetables and fruits is done on pH range between 1.5 to 3.0 with the heating temperature of 60-100
o
C during half an hour to an hour and a half Towle and Christensen 1973. If the extraction time is too long
will result in hydrolysis of pectin becomes galacturonic acid. In acidic conditions, methyl ester bond of pectin tend to be hydrolyze become unesterified galacturonic acid Smith and Bryant 1968.
Pectin precipitation process is a process of pectin separation from the solution. Pectin is a negatively charged hydrophilic colloids from free carboxyl groups that are ionized and do not has an isoelectric
point like most of colloidal hydrophilic. Pectin is more likely stabilized by its hydration of the particles rather than by its charge. Increasing ethanol can dehydrate the pectin that disrupts the stability of its
colloidal solution, and consequently pectin will be coagulated Rouse 1977. Ranganna 1977 uses 95 concentration ethanol with twice amount of filtrate volume to precipitate the orange peel pectin. West
Sumatra Science, Technology and Industry Council 2004 precipitates pectin using 95 ethanol containing 2 mL of concentrated hydrochloric acid every one liter of ethanol as much as 1.5 times of the
filtrate volume. At pectin purification stage, the West Sumatra Science, Technology Industry Council 2004
washing pectin from passion fruit by using 95 alcohol until it becomes chloride-free pectin. Suradi 1984 washing pectin from orange peels with 80 alcohol until becomes chloride free. One of the goals
is to wash pectin and eliminates chloride in pectin. The final stage of the pectin extraction is drying the pectin. Ranganna 1977 recommends drying is done at low pressure so the pectin is not degraded.
According to the West Sumatra Science, Technology Industry Council 2004, drying passion fruit pectin can be done using the oven at a temperature of 40-60
o
C for 6-10 hours.
5. Pectin application
