A STUDY ON THE CHEMICAL CHARACTERISTICS AND GEL FORMING PROPERTIES OF PASSION FRUIT PEEL PECTIN

Abstract

Pectin, a high molecular weight, partially methylated potygalacturonic acid occurs in the middle lamella or Intercellular wall of plant material. Pectin is widely used in food industry, commonly as a gelling agent in Jams and jellies, as stabilisers in dairy products and frozen desserts and as a bulking agent or a fat reptacer in dietetic foods. Present commercial sources of pectin are citrus peel and apple pomace. Th e objectives of this study were (a) to extract and isolate pectin found in passion peel a waste product in food industry (b ) to compare the gel forming properties of the passion peel pectin with citrus pectin and (c) Investigate on methods for increasing the yield of pectin using surfactants Pectin was extracted and isolated from passion fruit peel after pre-processing, at pH 1.34 (using 1N H C I) and at 659C , for 2 hr and filtered. T h e pectin was isolated by precipitating with 9 6 % ethanol, filtering, washing with acidified ethanol and absolute ethanol and air- drying at 40 -4 5 °C. Four different pre-processing methods used are described as follows:Method 1 A: Fresh passion peel was blended with water ( 1:10 W/V).Method 1 B : Th e passion peel was dried at 5 0 -5 5 °C and powdered to pass through mesh size 40, using a Wiley Mill, Th e powder was blended with water (1,20 w/v)Method 2A : Passion peel was steamed and the endocarp was scooped out and blended with water (1:10 W/V),Method 2 8 : Passion peel was steamed and the endocarp was scooped out, dried at 50.55°C,powdered and blended with water (1 :20 W /V). The yield of pectin varied from 14,5 to 29.0 % with different pre-processing methods Results showed that Method 28 gave significantly higher yield of pectin, compared with other three methods. Passion peel pectin contains high methoxyl rapid set pectins (9 % of methoxyl content) with the acetyl value was 1.2 % or less, Th e purity of pectin was quantified as enhydrogalacturonic a d d and was (bund to be 6 3 % . The geMbrming properties of pectin at 140-get grade were of good quality, when compared with citrus pectin. Pectin extracted from Method (2A) and (2 8 ) formed better gets than from method (1 A )a n d (1 B ). This may be attributed to the decrease in % Acetyl content on steaming. The addition of 2.5% of a low molecular alcohol diethytene glycol to the acid extractant resulted in an increase in the pectin yield by 55-90%. ft was also shown that the addition of alcohols resulted In a measurable increase in the pectin gel strength.