Improvement of Anthocyanin and Antioxidant Properties of Strawberry (cv. Amaros) by Calcium Lactate and Potassium Sorbate Application

Strawberry (Fragaria × ananassa Duch.) is one of the most popular soft fruits worldwide. It is a rich source of health promoting compounds such as essential macro/micro-nutrients, polyphenols, anthocyanin, vitamins and amino acids, while showing a high antioxidant capacity. Preharvest applications of calcium lactate and potassium sorbate have shown to be promising as a tool to improve the quality and extend the shelf life of various fruits. To our knowledge, however, little information is available regarding the effect of calcium lactate and potassium sorbate on strawberry fruits. Thus, the objective of the present study was to determine the effect of foliar application of calcium lactate and potassium sorbate on important quality characteristics and antioxidant properties of ‘Armas’ strawberries.

This research was performed at a commercial orchard on 2-year old strawberries in Marivan, Iran in 2015. The experiment was arranged as factorial based on randomized complete block design with two factors and four replications. The first factor included different levels of calcium lactate (0, 0.5 and 1%) and the second factor included different levels of potassium sorbate (0, 0.5 and 1%). Foliar spraying was performed in three stages: three weeks before commercial harvesting, at initial coloring, and one week before harvest. Fruit were harvested at commercial maturity and immediately transported to the laboratory at University of Zanjan and subjected to physicochemical analysis. Differences among means of data were analyzed by Duncan’s test at p ≤ 0.05 (n = 3). All statistical analyses were performed with SAS version 9.4.

The results showed that the combination of calcium lactate and potassium sorbate (0.5 Percent concentration) treatment significantly (P £ 0.01) increased the total anthocyanin content of the whole fruit, reuslting into further attractive fruit color and market than the control. It also increased antioxidant properties up to a level of 57.07%. On the other hand, the application of this treatment (calcium lactate and potassium sorbate 0.5 Percent) significantly increased the total flavonoid content, total soluble solids, flavor index (1.1 Percent) and calcium lactate (1 Percent). Potassium sorbate increased total phenol, total acidity, and fruit acidity significantly compared to other treatments and control (P £ 0.05).

In general, the results of the present study showed that a preharvest application of calcium lactate and potassium sorbate increased firmness, nutritional quality, and antioxidant potential of strawberry fruits. Thus, the use of these two materials is recommended to improve the qualitative and antioxidant properties of strawberry fruit.