Investigation of Correlation of Enzymatic Browning fruit tissue and Amount of Phenolic Compounds, Flavonoid, and Anthocyanin Red-flash and Some Iranian Spring Apple Cultivars

Introduction :

Apple is one of the most important horticultural crops in Iran. The aim of this study was to investigate the effect of genotype on physical and chemical properties of fruit; to evaluate the amount of fruit secondary metabolites and correlation between them with the enzymatic browning in some Iranian apple cultivars. Recently red-fleshed apples have been attracted the attention of many researchers and fruit marketers because the flesh of those cultivars contains a high amount of red pigment anthocyanins, which show strong antioxidant activity. These cultivars have a better place in the market for the consumers because of the attractiveness, quality and high levels of anthocyanins and other phenolic compounds in fruits. Development of such new varieties with unique properties is important for improving the apple breeding and processing industry in the world. Phenolic compounds and flavonoids are products of the phenylpropanoid pathway. They are secondary metabolites and are responsible for different functions in the plant life cycle. Secondary metabolites play an important role in the quality of food (color, flavor, and odor). Also production of secondary metabolites may be a part of the plant defense system.

Materials and Methods:

 The fruits of ‘Morabaee-Mashhad’, ‘Top Red Delicious’, ‘Golab Kohanz’, ‘Winter Banana’, ‘Golab-e Kermanshah’, ‘Early Devan’ and ‘Pepin’ apple cultivars were harvested manually from trees at commercial maturity stage in Mashhad city, and ‘Red-flash’ apple cultivar was harvested in Shahrood city (Bekran Village), Iran. Fruits were transported to the laboratory soon after harvest. The measured chemical properties were consisted of total soluble solids (TSS), titrable acidity (TA), TSS: TA, total phenol content (TPC) and Antioxidant. Titratable acidity (TA) was determined by Korean models GMK855 and reported g 100 g-1 of malic acid. Total soluble solids (TSS) was determined at 20 ◦C with a refractometer and reported as ◦Brix. The pH value of fruit was measured with a pH meter at 20◦C. The pH differential method was used to determine the total anthocyanin content. The absorbance of the solution was measured at 510 nm. The total phenolic content was determined by a modified Folin-Ciocalteu reagent method. This experiment was conducted according to the completely randomized design; with thirty replicates. Data were analyzed statistically by SPSS statistical software and differences among means were determined for significance at p< 0.05 using Duncan’s multiple range test.

Results and Discussion:

 The highest and lowest of enzymatic browning was found in ‘Pepin’ and Red-flash apple cultivars, respectively. Red Delicious, Macintosh, and Liberty showed high levels of enzymatic browning. According to some researchers, there is a strong correlation between the amount of browning and total phenol content of apple varieties "Empire", "Rome", "Golden Delicious" and "Delicious"(oseteng and Lee 1987; Milani and Hamedi 2005).  San et al. (2002) revealed that there was a direct correlation between fruit phenolic content and antioxidant activity in 11 fruit species, indicating a significant contribution of phenolic compounds in the antioxidant activity of fruits. The results showed that the effect of cultivar on physic-chemical properties of fruit was significant at 5% probability level. The concentration of total soluble solids was significantly affected by cultivar, the highest concentration of total soluble solids was observed for Red-flesh apple cultivar while the lowest was recorded in Golab-e Kermanshah. Red-flesh and Golab-e Kermanshah cultivars had the highest and the lowest anthocyanin contents andthe highest and lowest of pH values were observed in Red-flesh and Golab Kohanz cultivars, respectively. The highest concentration of total phenolics was observed for Morabaee-Mashhad while the lowest was seen in Early Devan cultivars. The correlation between the enzymatic browning and antioxidant capacity of fruits was -0.507*.

Conclusions:

 The present research confirms that Red-flesh apple cultivar as a native fruit has been of interest to researchers and consumers because of its high amount of soluble solids, anthocyanins and flavonoids content, high level of antioxidant capacity and having a specific flavor and taste. Therefore, it can be a worthy cultivar for apple breeding programs and development in future.