Effect of Drying Methods on Proximate Composition, Physicochemical, Antioxidant and Sensorial Properties of Red Spinach (Amaranthus Tricolor) Flakes

Teh, Mei Kuen (2020) Effect of Drying Methods on Proximate Composition, Physicochemical, Antioxidant and Sensorial Properties of Red Spinach (Amaranthus Tricolor) Flakes. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Red amaranth (Amaranthus tricolor), is also known as red spinach or Chinese spinach or Bayam merah in Bahasa Malaysia, belongs to Amaranthaceae family. The effect of different drying methods on proximate composition, physicochemical, antioxidant, microbiological and sensorial properties of red spinach (A. tricolor) flakes were evaluated. The moisture content of dried red spinach flakes were ranged from 5.97 % to 9.00 % with the least moisture content was observed in hot air oven dried samples. Freeze dried samples had the highest crude protein content (32.94 ± 0.25 %), crude fat content (3.37 ± 0.09 %) and crude fiber content (10.20 ± 0.08 %) among all dried samples. However, the percentage of ash content and carbohydrate content in sun dried samples were the highest among the three dried samples. The color, pH and water activity of dried red spinach flakes were evaluated. A significant difference of lightness (L*) and redness (a*) were observed among the dried red spinach flakes (P < 0.05). Besides, the pH values of dried red spinach flakes were ranged from 6.96 to 7.22. Hot air oven dried samples had the lowest water activity (0.130 ± 0.02) among all dried samples. There was significant difference in the free radical scavenging activity of fresh leaves and dried samples (p<0.05) with the highest DPPH radical scavenging activity (75.13 ± 0.49 %) was exhibited in freeze dried samples. Among the dried samples, the highest concentration of phenolics and flavonoid compounds were found in freeze dried samples as 17.33 ± 0.76 mg GAE/g DW and 19.67 ± 0.58 mg QE /g DW, respectively. In microbiological analysis, no bacteria were detected in all three dried samples, indicating product safety. In sensory evaluation, the mean scores of hot air oven dried red spinach flakes‟ appearance, color, taste, aroma, texture and overall acceptability were the highest compared to that of freeze dried and sun dried red spinach flakes. The results of paired comparison test indicated that hot air dried red spinach flakes was the most preferred samples compared to other dried samples.