Accumulation of Total Phenolics and Antioxidant Activity in Different Tissues of Peach Fruit

Nutritional composition and content in peach fruit is often measured using flesh tissue, based on the assumption that consumers usually remove skin (peel) prior to consuming the flesh, and that the flesh tissue accounts for most of the peach fruit. To determine if there are differences in the total phenolic content between different tissues of peach fruit, we evaluated ten peach cultivars and two advanced selections with different flesh color (white, yellow, and red) and blush level (low, medium, and high) for the total phenolic content and antioxidant activity in different fruit tissues (peel and flesh, separately and together) across two years. Total phenolics showed no significant differences between fruit tissues regardless of the flesh color. In contrast, antioxidant activity exhibited significant differences among different tissues regardless of the flesh color. The lowest antioxidant activity was observed in the flesh (836.5 µg Trolox/ g FW), and the highest in the peel (1,610.5). Total phenolics also showed no significant differences among different flesh colors regardless of fruit tissues.  However, individual phenolic compounds, such as flavonoids and anthocyanins exhibited significant differences in different flesh colors and tissues. Interestingly, individuals with yellow flesh color, the most popular peach flesh color in the U.S fresh market, showed no significant differences in accumulation of total phenolics among peel and flesh, suggesting that similar levels of total phenolics are consumed regardless of peel presence. Our present study also revealed the highest antioxidant and total phenolics accumulation in low blush yellow and white-fleshed peaches compared to other blush levels. As expected, anthocyanin accumulation was the highest in the high blushed fruit and red flesh. The relative antioxidant capacity (RAC) was positively correlated with total phenolics in the flesh plus skin tissue among the different flesh colors, with the highest correlation observed in red flesh (r = 0.965, P < 0.01).  The pros and cons of analysis of total nutritional content in peach fruit and the differences in individual compound accumulation between different tissues will be discussed.