Control of Deacetylation in Gum Karaya on Storage for Quality Retention

Gum karaya is natural exudate from Sterculia urens and it is a partially acetylated polysaccharide which is composed of 10-14 % acetyl groups. On ageing, deacetylation process takes place and with the result that there is continuous loss of acetic acid is formed and the quality of gum karaya deteriorates subsequently. As there is no data available on the effect the quality aspects of gum karaya, therefore a detailed study was undertaken for the control of loss of acetyl groups from gum karaya samples with time and storage conditions using different packaging films. Gum karaya samples packed in Low Density Polyethylene (LDPE), High Density Polyethylene (HDPE), Polypropylene (PP) and Aluminium Coated Polyethylene (ACP) with normal sealing and vacuum packaging with nitrogen filling. Samples were stored under ambient conditions as well as under refrigerated condition. On the basis of quarterly estimation of quality parameters of gum karaya packed in above film it was established that gum karaya samples can be stored for longer period in HDPE under cold condition for controlling the deacetylation process of karaya gum for retention of all quality parameters.

Gum Karayais the dried exudate obtained from trees of Sterculia urens Roxburgh. It is also known as Katira or Kullu gum in trade. In the natural state, the gum is in irregularly shaped pieces, sometimes of worm like appearance. They are white or pinkish-brown in colour and generally striated. The gum, especially when fresh, may have an acetous odour. After acid hydrolysis, Gum Karaya commonly produces D-galaturonic acid, D-galactose, L-rhamnose and small proportions of D-glucuronic acid. The total uronic acid residue content in the gum can be up to 35-40%. (Anderson et al. 1985). Structurally, it is acetylated acidic polysaccharide containing α-D-galacturonic acid α-L-rhamnose residues as the main chains with O-4 of the acid and O-2 of rhamnose linkages (Meer W, 1980;Stepien et al. 1995 andFranco YL andCiapara IH, 2009). Natural Gum Karaya is a complex, branched, partially acetylated polysaccharide with a reported molecular weight of 9,500,000 dalton. An average, new Gum Karaya contains about 10-14% acetyl groups (IS: 12498 and JECFA 1988), from which acetic acid is formed and is split off an ageing. Increased temperature, humidity and fine particle size increases the rate of acetic acid formation. Gum karaya loses viscosity-forming ability when stored in dry state. The loss is greater for a powdered material than for the crude gum (Money, 1951). It has been reported that the decrease in viscosity related to the loss of acetic acid (Goldstein, 1954). In the present investigation, an effort will be made to check the loss of the acetyl group in gum karaya by keeping the samples in different packaging material under ambient and cold conditions.

MATERIALS AND METHODS
Fresh samples of gum karaya was collected from the Hyderabad. The gum karaya samples (100g each) were packed in different types of packaging material such as Low Density Polyethylene (LDPE), High Density Polyethylene (HDPE), Polypropylene (PP) and Aluminium Coated Polyethylene (ACP) with normal sealing (NS), and vacuum packaging with nitrogen filling (NVS). Samples were stored under ambient conditions as well as under refrigerated condition with 3 replicates for each film (Fig. 1). The analysis of 192 samples were carried out in four quarters each quarters comprises of 48 samples. The sample were analyzed quarterly for physicochemical parameters viz. Loss of drying (percent by mass), volatile acid (percent by mass), swelling property (ml) and water absorption (ml) as standard specification of BIS for gum karaya (IS: 12408 -1988) to asses the deacetylation process with the time and storage condition. The statistical analysis was carried out in SPSS package version 16 using factorial RBD design.

RESULTS AND DISCUSSION
The fresh sample was analyzed for physicochemical parameters and results are given in table 1 with the requirements as per BIS specification.
The quality parameters of gum karaya (1 st quarter) were analyzed (Table 2) and on comparing the data of 1 st quarter for acid value (%) of the gum karaya samples packed in LDPE, HDPE, ACP and PP showed that there is not much change in the acid value among all the above treatments. But swelling index showed higher value for the samples of gum karaya kept in cold condition with normal seal and vacuum packaged nitrogen seal as compared to the samples kept in ambient condition with normal seal and vacuum packaged nitrogen seal.
The same quality parameters of gum karaya (2 nd quarter) were analyzed (Table 3) and on comparing the data of 2 nd quarter for acid value (%) and swelling index (ml) of the gum karaya samples packed in LDPE, HDPE, ACP and PP kept in cold conditions showed higher value than the samples kept in ambient temperature for all the above treatments. The samples packed in HDPE and LDPE showed highest values for both and swelling index (ml) among all treatments.
The analysis of quality parameters of gum karaya (3 rd quarter) samples were continued and the data of 3 rd quarter revealed the same trend observed as in the 2 nd quarter (Table 4). On comparing the data of 3 rd quarter for acid value (%) and swelling index (ml) of the gum karaya samples packed in LDPE, HDPE, and PP kept in cold conditions showed higher value than the samples kept in ambient temperature for all the above treatments except in the ACP. The samples packed in HDPE, LDPE and ACP under cold condition showed higher values for both swelling index (ml) and water retention (ml) among all treatments.
The analysis of quality parameters of 4th quarter (Table 5 & Fig. 2) revealed that the acid value (%) of the samples packed in LDPE, HDPE and ACP kept in cold conditions showed higher value than the samples packed in PP in cold condition and samples packed in LDPE, HDPE and ACP and kept in ambient temperature. After keeping the sample for almost one year of storage, it has been observed that the samples kept in ambient temperature showed drastic reduction in the value of swelling index than the samples kept in cold condition. The combined statistical analysis by pooling all the data of four quarters were carried out ( Table  6) and observed that storage temperature under cold condition has significant effect in controlling the deacetylation and in addition to the above, the packaging films also has a role in retaining the