Investigation of Ultrasound and Coating with Wild Sage and Xanthan Gums Pretreatments on the Quality, Phenolic Compounds, Antioxidant Activity, and Sensory Properties of Dried Cornelian Cherry by Infrared Method

Abstract

Introduction Fruits have a limited harvest season, and the amount of their waste is significant. Drying extends the shelf life of food, and the infrared dryer reduces the time and cost of the drying process. In this study, the effect of sonication at different powers and temperatures along with edible coating with xanthan and wild sage seed gums on the drying process of cornelian cherry by an infrared dryer was investigated. Material and Methods Solutions of xanthan and wild sage seed gums were used for coating of fresh cornelian cherry. Xanthan gum powder (food grade) was purchased from FuFeng Co. (China). Wild sage seed gum was extracted and used in powder form after drying and grinding to prepare the gum solution. In this study, various concentration of gums solutions (xanthan and wild sage seed) were first prepared in a graduated glass beaker and placed in an ultrasonic bath (Backer vCLEAN1-L6, Iran). The fruits were immersed in the gum solutions (inside the beakers) and sonicated for 5 min (40 kH). Infrared dryer with an infrared radiation source (250 W, near-infrared (NIR), Noor Lamp Company, Iran) was used for drying samples. The distance of samples from the radiation lamp was 10 cm. After each pretreatment (sonication and coating), the samples were dried, until reaching a constant weight. The mass changes of samples were recorded using a Lutron GM-300p digital balance (Taiwan). The rehydration tests were conducted with a water bath (R.J42, Pars Azma Co., Iran). Dried samples were weighed and immersed for 30 minutes in distillated water in a 200 ml glass beaker at 50°C. Then, the extra moisture was drained for 30 s and the samples were re-weighed. The rehydration ratio values (%) of dried samples were determined as the ratio of the final weight of rehydrated samples over the dried samples weight × 100. The color of the cornelian cherry was calculated by determining the lightness (L*) and chromaticity (redness (a*) and yellowness (b*)), and was measured using a scanner (Hp Scanjet 300, China) and Image J software (V.1.42e, USA). The Folin-Ciocalteu (Folin-Ciocalteu's phenolics reagent, Sigma-Aldrich, USA) method was followed for measuring the total phenolics content of dried cornelian cherry. The absorbance of samples (765 nm, UV-VIS spectrophotometer, XD-7500, Lovibond, Germany) was compared with the Gallic acid standard curve. The results were expressed as mg GAE/g dry matter. Effect of applied power by the ultrasonic device at three levels of 0, 75, and 150 W and the effect of temperature at three levels of 20°C, 40°C, and 60°C on the rehydration and total color difference index of dried cornelian cherry were investigated. Also, the effect of coating with xanthan and wild sage seed gums on preserving phenolic compounds, antioxidant activity, and sensory properties of the product was evaluated. Results and Discussion The average drying time of uncoated cornelian cherry, coated with xanthan gum, and wild sage gum was 62 min, 48.7 min, and 48.4 min, respectively. The examined treatments in this research did not have a significant effect on rehydration change of the dried product. Ultrasonic pretreatment at both 75 and 150 W powers had a decreasing effect on the color changes, which indicates improvement of color and prevention of color change and decrease in desirability. The effect of coating on color changes was also investigated, and the amount of color changes in the uncoated, coated with xanthan gum and wild sage seed gum samples was equal to 26.71, 26.02, and 31.36, and there was no significant difference between them (p>0.05). Using wild sage seed gum preserved more of phenolic and antioxidant compounds. The total phenolics content of fresh cornelian cherry, and dried samples including market, without coating, coated with xanthan gum, and coated with wild sage seed gum was 23.0, 4.7, 0.8, 9.8, and 12.1 mg gallic acid/g, respectively. The market sample had a significant difference with other dried samples dried by infrared (p<0.05). The sample from the market had the least DPPH radical scavenging activity (p<0.05). The market sample scored as the lowest sensory evaluation and had a significant difference with all samples in all sensory attributes (p<0.05). Conclusion From the panelist’s point of view, the sample coated with wild sage seed gum was the best sample, and the highest score for sensory parameters and overall acceptance was associated with this sample.

Keywords

• antioxidant
• color change
• phenolic compounds
• sensory evaluation
• wild sage seed gum