In this study, three saskatoon berry varieties (Martin, Northline and Pembina) grown in Saskatchewan, Canada were analyzed for their physicochemical properties (berry size, colour, pH and % seeds), proximate composition, amino acids, major carbohydrates/polyols/galacturonic acid, major minerals, oligosaccharides, organic acids and phenolics. In addition, the phenolic subclass composition and antioxidant activities of whole fruit and pomace from commercial and laboratory scale juice production, and aqueous alcohol fractions were determined.
Fruit varieties were found to differ in colour and size but showed similar pH and °Brix values. Proximate analysis results ranged from 80.18-82.79% for moisture, 7.39-10.82% for carbohydrate, 1.13-1.79% for protein, 0.28-0.48% for lipid, 4.23-9.42% for total dietary fibre, and 0.53-0.74% for ash. Major carbohydrates and polyol identified were fructose, glucose, and sorbitol. This work represents only the second report of the detection and quantitation of sorbitol in this fruit. Oligosaccharide profiles were determined by high performance anion exchange chromatography with pulsed amperometric detection (HPAE-PAD) and capillary gas chromatography with flame ionization detection (CGC-FID) and showed the presence of a number of dextrose (DP2-5) and pectin polymers. Oligosaccharide profiles have not been reported previously. Amino acid contents ranged from 0.83-1.22 g/100 g fresh weight (FW), with arginine, aspartic acid/asparagine, glutamic acid/glutamine and leucine predominating. Major minerals quantified were calcium, magnesium, potassium and sodium, with potassium having the highest concentration that ranged from 219-248 mg/100 g FW. The major organic acids identified were malic (304.7-393.9 mg/100 g FW) and succinic (120.4-316.3 mg/100 g FW).
Phenolics from the three fruit varieties were extracted employing water, ethanol:formic acid:water, and methanol:formic acid:water (70:2:28 v:v) mixtures. The ethanol:formic acid:water (EFW) extracts from all samples were found to have the highest phenolic concentrations as determined by total phenolic content analysis. Based on total phenolic chromatographic index (TPCI) results as determined by high performance liquid chromatography with photodiode array detection (HPLC-PDA), the Northline variety had the highest TPCI at 504.2 mg/100 g FW. This variety was also shown to have the highest antioxidant activities by both the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2´-azinobis-3-ethylbenzthiazoline-sulphonic acid (ABTS) radical scavenging assays, of 23.1 1/IC50/100 mg FW and 327.5 mM TEAC/100 mg FW, respectively.
Solid phase extraction (SPE) using Amberlite® XAD16N resin and aqueous ethanol (40, 70 and 100%) was employed to produce phenolic fractions from the three fruit varieties. It was found that hydroxybenzoic acids eluted in the 40% ethanol fraction; hydroxycinnamic acids and anthocyanins eluted in the 70% ethanol fraction; and anthocyanins, flavanols and flavonols eluted in the 100% ethanol fraction. The 70% ethanol fraction had the highest TPCI and DPPH/ABTS radical scavenging abilities for all saskatoon berry varieties.
Wet and dry pomace from commercial saskatoon berry juice production had TPCI values of 404.2 mg/100 g and 250.0 mg/100 g, respectively. The ABTS values of wet and dry pomace were found to be 304.8 and 327.8 mM TEAC/100 mg, while the DPPH results were 19.4 and 16.8 1/IC50/100 mg FW, respectively. These results show that pomace from commercial juice production was a good source of phenolics with high antioxidant capacities. Results from laboratory scale juice production of the Northline variety employing commercial conditions (i.e. time, temperature, and enzymes and dosages) showed that 29% of the phenolics remained in the pomace after juice production as determined by TPCI analysis
