EXTRACTION AND MICROENCAPSULATION OF BIOACTIVE COMPOUNDS FROM AVOCADO SEED (Persea americana Mill) AND ITS STABILITY EVALUATION

Abstract

Avocado seed is a by-product that contains a large amount of extractable polyphenols, which have attracted the attention of food and cosmetic industries due to their high antioxidant capacity. Exploiting these antioxidant properties can add value to sustainable development goals to eradicate extreme poverty, hunger and diseases. This study was aimed to determine proximate composition and mechanical properties of avocado seed, extract its polyphenols using ethanol (99%), aqueous (100%) and ethanol/ water (50:50), determine the chemical properties, antinutritional factors and antioxidant activities of the avocado seed extract. The ethanolic avocado seed extract was encapsulated with corn starch (A) and cassava starch (B) as cell wall material at three different concentrations and freeze dried. Microencapsulate was evaluated for its antioxidant activity, stability (storage) and in vitro starch digestibility. The avocado seed contained 6.45% crude fibre, 10.57% crude protein and 17.93% crude fat. The ethanolic and aqueous ethanolic extract differed in their quality indices (Saponification value, Peroxide value, Free fatty acid, Iodine value, TBA, and Acid value) which were 39.72 and 56.27 mgKOH/g, 1.20 and 1.85 meq/kg, 9.33 and 5.66%, 9.23 and 4.81 g/100g, 0.95 and 1.89 mg/kg, 18.44 and 11.32 mgKOH/g respectively. The extracts possessed significant anti-nutrients including alkaloids, glycosides, tannin, terpenoids, saponins, phytate, oxalate which ranged from 0.00 to 23.81%, 9.41 to 24.87 mg/g, 4.49 to 7.11 mg/g, 8.42 to 18.39 mg/g, 12.27 to 31.36 mg/g, 3.30 to 7.00 and 0.41 to 0.90 mg/g respectively. Avocado by-products seed extract (100% ethanolic) presented a distinct profile in total phenol content and flavonoid contents (25.51 mg/g and 3.21 mg/g), radical scavenging ability DPPH, ABTS and OH* were (76.05%, 20.21 mol/g and 32.55%) and the reducing properties Fe2+ and FRAP (65.32 % and 34.93 mg/g) respectively. Antioxidant activities of the microencapsulate after day 1 and 30 days of storage showed that A2 (corn starch) and B2 (cassava starch) possessed highest scavenging ability but A2 possessed superior hydroxyl free radical scavenging ability to the least hydroxyl radical induced by decomposition of deoxyribose. The In vitro starch digestibility of the encapsulate A2 and B2 were different (23.96 and 1.04 mg/g respectively). The study showed that ethanolic extract of avocado seed were higher in antioxidant activities than that of aqueous extract. The antinutrients were within safe limits. Encapsulate was able to retain the bioactive component for a month. The phenolic content increased during storage. In addition, corn starch was a better cell wall material compared to cassava starch wall material.