MSc

The present study entitled “Development of osmodehydrated bilimbi (Averroha bilimbi L.) and assessment of bioactive compounds” was carried out in the Department of Post Harvest Technology, College of Agriculture, Vellayani during 2015-17 with the objective to standardize the process variables for osmodehydrated bilimbi and to assess the retention of bioactive compounds.
Harvested mature bilimbi fruits of uniform size were washed, surface dried, pricked and blanched in hot water for one minute. Blanched fruits were subjected to osmotic treatment, with sucrose solution of 40, 60 and 80⁰B for 60, 120 and 180 minutes.
The osmodehydrated bilimbi fruits were analyzed for mass transfer, biochemical and sensory qualities. Mass transfer characters viz., solid gain, water loss, percentage weight reduction, yield and biochemical parameters such as reducing sugar and total sugar increased with increase in osmotic concentration and immersion time whereas free acids, ascorbic acid and antioxidant activity were decreased. The osmotic treatment of 80 0B for 180 minutes recorded the highest value for solid gain (5.10 %), water loss (16.72%), weight reduction (22.57%), ratio of water loss to solid gain (3.25%) and yield (21.13%) with a free acid content of 2.32 %, 21.66 mg/100g vitamin C, 47.81% antioxidant activity, 8.24% reducing sugar and 18.53% total sugar which exhibited superior sensory scores for taste (8.43), flavor (8.27), texture (8.46) and overall acceptability (8.43). The best three treatments selected based on sensory analysis (80 0B for 180 minutes, 80 0B for 120 minutes and 60 0B for 180 minutes) were subjected to storage stability studies under room temperature for four months.
The stored osmodehydrated bilimbi fruits were analyzed for biochemical, sensory and microbial qualities at monthly intervals. During storage, reducing sugar and total sugar increased while ascorbic acid, antioxidant activity and free acids decreased. Osmodehydrated bilimbi in 800B for an immersion time of 180 minutes recorded 2.06 % free acid content, 19.55% total sugar, 8.75% reducing sugar, 19.29% vitamin C and 44.59% antioxidant activity at the end of four month storage with highest sensory score. All the osmodehydrated bilimbi fruits were microbiologically safe till the end of storage.
Bioactive compounds viz. vitamin C, phenols, total flavonoids, antioxidant activity, carotenoids, free acids, and oxalate content of osmodehydrated, dried, hot water blanched, steam blanched and fresh bilimbi fruits were assessed. Osmodehydrated bilimbi fruits recorded the highest TSS (19.32 0B), total sugar (18.73 %), reducing sugar (8.22%), carotenoids (0.46 mg/100g) and lowest oxalate content (24.34 mg/g) whereas dried bilimbi showed highest ascorbic acid (43.18 mg/100g), total phenols (694.60 mg/100g), antioxidant activity (56.23%), total flavonoid content (338.03 µg g-1) and highest oxalate content of 31.78 mg/g. Blanching treatments was found to reduce TSS, free acids, vitamin C and oxalate content of fruits. Hot water blanched fruits exhibited lowest oxalate content (8.08 mg/g) and TSS (3.82 0B) whereas steam blanching recorded the highest antioxidant activity (74.83%) total phenol (1067.31 mg/100g) and total flavanoid (198.32 µg g-1) whereas fresh bilimbi recorded 975.67 mg/100g phenols, 134.38 µg g-1 total flavanoid with 68.35% antioxidant activity.
Osmotic treatment at 80 0B for 180 minutes was found as the best treatment for development of osmodehydrated bilimbi. Bioactive compounds in primary processed bilimbi are greatly influenced by the processing methods.