Evaluation of the Effect of L-arginine and Aloe vera Gel Edible Coating on Storage of Cultivar of Piyarom Date Palm

Introduction Date fruit (Phoenix dactylifera L.) is one of the oldest known fruit crops and is considered as an important component of the diet in many Middle Eastern and North African countries. The fruit of date is nutritious, which is incredibly rich in carbohydrates, minerals, dietary fibers and amino acids. Dates are one of the most important tropical fruits that play an important role in the country's economy. Among the date palm cultivars in Hormozgan province, Piyarom is one of the most commercial cultivars. Recent studies by scientists have shown that the use of chemical compounds, in addition to environmental hazards, will cause various diseases in consumers due to the residual transfer of toxins to their bodies. Therefore, the management orientation of food preservation methods has moved towards reducing and eliminating chemicals and determining suitable alternatives, so that a certain time frame was set for the removal of some of the most important tobacco toxins. In recent years, attention has been paid to aloe vera gel as a coating layer for fruits and vegetables to maintain their storage quality, and because it has no smell or taste, eating it does not pose a problem for humans and it is even good for health. L-arginine is one of the 20 major amino acids of living cells, which is a semi-essential amino acid in the human body. L-arginine and D-arginine are natural forms of common isomers of this type of amino acid. The aim of the present investigation was the assess the effect of L-Arginine and Aloe vera gel edible coating on maintaining the external properties and the quality of semi-dried date fruit cultivars including Piyarom during storage.   Material and Method  The experiment was conducted as a factorial arrangement in a completely randomized design. The first factor was including seven treatments consisting of control, L-Arginine (1, 2, and 8 mM) and Aloe vera gel (25, 50, and 75%) and the second factor included storing (sampling) time for 9 months. In every measurement, the different attributes were evaluated such as weight loss percent; TSS; total acid; total phenol; flavonoid; color indexes including L*, a*, and b*; and antioxidant capacity. The level of antioxidant activity was evaluated by antioxidant agents by the method described by based on the trapping of free radicals of 2, 2-diphenyl 1-picryl hydrazyl (DPPH). DPPH solution was well combined with the methanol extract by means of a vortex and was incubated in the dark for 30 min. Then the absorption rate was read at 517 nm using a spectrophotometer. The color was determined using a colorimeter (Minolta, CR-400, Japan) after different months of storage. All measurements were done in triplicates. L* (100=white, 0=black), a* (–green, +red) and b* (–blue, +yellow) values were obtained at 400-700 nm range. The assay of the total phenol content was performed by applying the Folin–Ciocalteu colorimetric procedure. The total soluble solid (TSS) content of the fruit juice obtained for each replicate was determined using a hand-held refractometer Atago (Atago Co. Japan) at 25 °C; the results are expressed as % (°Brix). Titratable acidity (TA) was measured by titrating diluted juice with 0.1 N NaOH to a phenolphthalein end-point (pH 8.1-8.3). The results are expressed as citric acid %.   Results and Discussion  Based on the results, the treatments of Aloe vera gel and L-Arginine had significant effect on the quantitative and qualitative traits of Piyarom date fruits during storage. Storing time had significant influence (p<0.01) on the all parameters so that by passing storage time, the parameters including L*, a*, b*, a weight loss percent significantly increased and the parameters such as phenol, flavonoid and antioxidant significantly decreased. In the Piyarom cultivar, the treatments had significant effects on a*, b*, weight loss percent, phenol, flavonoid, and antioxidant, but it had no significant influence on TSS and total acid, so that the highest a* and b* color indexes was observed in the use of L-Arginine 1 mM, the greatest phenol and flavonoid in the application of L-Arginine 2 mM, the lowest weight loss percent in the use of Aloe vera gel 25 and 75%, respectively.   Conclusion  According to the results, 1 mM L-arginine treatment and 75% Aloe vera gel had a more effective role in maintaining the storage quality of Piyarom dates. The use of these treatments requires more extensive research on soft and dry dates.