Optimization of Pigment Extraction from Red Beet

Abstract

Introduction The first quality attribute about food evaluated by consumer is visual characteristics. The apparent attributes of a product include its shape, color, packaging, size, and uniformity. The consumer considers the product's appearance in the first step before any other information about other characteristics, such as taste or smell, especially in the first purchase. Color is the most crucial indicator of the quality of food that affects consumer acceptance. To replace the color lost during the process, increasing the existing color and minimizing variation during processing; natural colors, synthetic and inorganic colorants are added to food. Red beet is one of the most important natural sources of color; the essential pigment in this plant is betalain, composed of two subunits, betacyanin, and betaxantine. Considering the growing demand to develop more effective methods for extracting active compounds present in vegetable materials, including naturally occurring betalain and other nutritious compounds, this research was conducted to optimize the extraction conditions of this pigment from red beet. Materials and Methods Preparation of red beet The red beets were washed, peeled, and grated to prepare the sample. Then, red beets were dried in an oven at 30 °C for 48 hours and milled. For extraction, 10 grams of red beet powder was mixed with 200 ml of solvent (water-ethanol in a ratio of 1:1) and subjected to ultrasonication at 37 kHz. Experiments in 27 runs were performed based on a historical data design, randomized subtype and quadratic model. After the implementation with the edition of Design Expert 7 software, the range of variables pH (3-5), temperature (15-25 °C), and time (10-20 min) were applied for extraction. The pulp was dried using a Wattman filter paper in an oven at 35 °C and used for subsequent tests. Yield measurements The efficiency of the extraction process was calculated by dividing the weight of the extract obtained by the weight of the beetroot. Measurement of pigments The betacyanin and betaxanthine pigments show maximum absorption in 522-559 nm and 474-480 nm, respectively. To measure betacyanin and betaxanthine in extracts, a certain amount of powder was dissolved in distilled water, and its absorbance was measured at 530 and 480 nm. The amount of pigments obtained from different extraction conditions was compared. Results and Discussion In this study, the overall results showed that an increase in the extraction pH and time increased the extraction of betacyanine and betaxanthine. It would be better to extract betacyanine at temperatures below 25 °C since this pigment is sensitive to high temperatures. The maximum yield was observed when pH value, temperature, and time were 5, 21 °C, and 20 min, respectively. Comparison of experimental and predicted values of the proposed responses at the proposed optimal points by t-test showed no significant difference (p<0.05). A quadratic model was suggested for the responses, and the lack of fit was not significant (p<0.05). The extraction of betaline from red beet using the ultrasonic assisted method causes a reduction in time, temperature, energy, and solvent consumption. ConclusionThe maximum yield was observed when pH value, temperature, and time were 5, 21 °C, and 20 min, respectively. Comparison of experimental and predicted values of the optimal points showed no significant difference by t-test (p<0.05). According to the results obtained from this research, ultrasonic assisted extraction can be considered an efficient and fast method. Extraction of betalain from red beetroot with ultrasonic assisted method is more efficient. It can replace the regular practice of extraction in the industry due to the reduction of time, temperature, energy, and solvent consumption, thus reducing cost and increasing profit.

Keywords

• betacyanine
• betaxanthin
• red beet
• response surface method