Antioxidant and antimicrobial properties of water soluble polysaccharide extracted from carrot peels by-products

The water soluble crude polysaccharides were obtained from the aqueous extracts of the carrot peels by-product (CWSP) through hot water extraction followed by isopropanol precipitation. Response surface methodology was applied to optimize the extraction of polysaccharides. A three-level, four-variable Box-Behnken design was employed to obtain the best possible combination of extraction time (X1: 60-100 min), ratio of water to raw material (X2: 15:1-25:1, v/w), extraction temperature (X3: 60-80 A degrees C), extraction cycle (X4: 1-3 times) for maximum yield of CWSP. The optimum extraction conditions were as follows: extraction time of 74.86 min, ratio of water to raw material of 24.86, extraction temperature of 60 A degrees C and extraction cycles of 3. Under these conditions, the experimental yield was 41.91 %, which is well in close agreement with the theoretical value (42 %) predicted by RSM model. Antioxidant activities and inhibitory activities against the bacteria of CWSP were investigated. CWSP at 1.2 mg/ml was found to scavenge the DPPH radical (80.21 %), to prevent bleaching of beta-carotene (65 %) and to chelate iron ion (40.25 %) in vitro systems. CWSP also exhibited the antibacterial activities. CWSP at 200 mg/ml could inhibit the growth of the Gram-negative and Gram-positive bacteria. CWSP have significant antioxidant and high antibacterial activity and may be potential functional food ingredients.