Effect of drying techniques on the retention of antioxidant activities of Saskatoon berries

Pranabendu Mitra,Venkatesh Meda,Rick Green

doi:10.7455/ijfs.v2i2.183

Abstract

The main objective of this research was to compare the retention of antioxidant activity and total anthocyanin content of Saskatoon berries dried by freeze drying, microwave-vacuum drying, thin layer hot air drying and vacuum drying. Antioxidant activity of berry samples was determined by DPPH radical scavenging and ABTS radical scavenging, and the pH differential method was used to determine total anthocyanin content of the berry samples. The results showed that the freeze dried Saskatoon berries exhibited the highest retention of anthocyanin and antioxidant activity among the dried samples, followed by microwave-vacuum dried berries, thin layer hot air dried berries and vacuum dried berries. There were significant differences between the berry samples at P<0.05. DPPH radical scavenging and ABTS radical scavenging were correlated linearly with an R2 value of 0.99 at P<0.05 showing their effectiveness for the determination of the antioxidant activity of the Saskatoon berries. However, the DPPH radical scavenging assay was more effective than the ABTS radical scavenging assay. The results also showed that antioxidant activity of the berries was highly correlated with the total anthocyanin content of the fruit. The reduction of anthocyanin in dried berry samples was linearly correlated with the reduction of DPPH radical scavenging with an R2 value of 0.97 at P<0.05 and, also, linearly correlated with the reduction of ABTS radical scavenging with an R2 value of 0.88 at P<0.05.

Highlights

The consumption potentiality of Saskatoon berries (Amelanchier alnifolia) was started by the native Canadian and Northern people and the early settlers in these areas
The Duncan’s Multiple Range Test (DMRT) analysis showed that the DPPH radical scavenging of each sample was significantly different for all samples (Table 1)
The results showed that antioxidant activity of the berries was significantly attributable to the presence of total anthocyanin content of the berry samples

Summary

Introduction

The consumption potentiality of Saskatoon berries (Amelanchier alnifolia) was started by the native Canadian and Northern people and the early settlers in these areas. The vacuum drying can result in greater retention of nutrients as well as volatile compounds in the dried products, but this drying method is limited in use because of higher costs and prolonged drying time (Dev & Raghavan, 2012; Mitra & Meda, 2009; Ratti, 2001; Sagar & Kumar, 2010). Antioxidants scavenge free radicals produced in the body during metabolic reactions and prevent the damage of lipids, proteins and DNA caused by free radicals (Mitra, Chang, & Yoo, 2011) They are purported to help prevent some diseases such as cancer, inflammation, atherosclerosis, and aging (Jeong et al, 2010; Subhasree, Baskar, Keerthana, Susan, & Rajasekaran, 2009). The DPPH (2, 2-Diphenyl-1-picrylhydrazyl) and ABTS (2, 2 Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt) radical scavenging assays are popular because these methods are simple, inexpensive and widely used to determine total antiox-

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Conclusion