The performance of beeswax coating containing vegetable oil-based lecithin as an emulsifier on weight loss and shelf life estimation of mango

Fruits are one of the agricultural commodities grown in Indonesia and mango constitutes the third largest. One of the disadvantages in transporting mangoes to long distant markets is the short shelf life when fruits are stored at the room temperature. Some efforts to maintain quality and freshness have been coating the fruits with natural wax/beeswax. This study aimed to determine the effects of beeswax coating containing vegetable oil-based lecithin on physical and weight loss in mango, as well as estimate the shelf life using the Accelerated Shelf-Life Testing (ASLT) method. The coating formulation consisted of beeswax, triethanolamine, stearic acid, vegetable lecithin (soybean: rice bran), and water. Mango coated with beeswax coating with a concentration of vegetable lecithin emulsifier were varied at 0.25, 0.5, 0.75, 1%, and control (without beeswax coating) stored at room temperature 301K and cooler temperature 286K. Samples were monitored for five weeks and evaluated periodically for physical change and weight loss. Beeswax coated mango exhibited slower rate of ripening than the control stored in both room and cooler temperatures. The lowest total weight loss of mangoes at both temperatures for 5 weeks with beeswax coating at 0.25% vegetable lecithin emulsifier was 7.25%. The estimation of shelf life using ASLT method and Arrheinus model to mango fruit coated with beeswax coating at 0.25% vegetable lecithin concentration as emulsifier was 36.91 days.


INTRODUCTION
Fruits contribute significantly to horticulture in Indonesia. According to the Government reports released by the Central Bureau of Statistics (BPS), mango production ranked third at 2.2 million tons in 2017 [10]. Mango has a good market potential as well as a promising export commodity [5].
The biggest disadvantage of long-distance markets of mango is the short shelf life when stored at room temperature. Mango experiences full ripening within two to three days postharvest [13]. The most common method to increase shelf life in fruits has been lowering the storage temperature. However, this method does not apply optimally on mango because of it requires very low temperatures of 10-13 o C [7,9]. In addition to lowering the storage temperature, another common method to increase shelf life in fruits is by employing food-grade wax/beeswax as coating. By coating the surface of fruits with wax, water evaporation can be reduced and freshness can be maintained longer [13].
One of the main ingredients in the wax coating is an emulsifier that functions to form the product. Lecithin is widely used as the emulsifier in food-grade wax and is obtained by extracting oil from animal and vegetable oil sources. Rice bran oil can used ina lecithin mixture because it contains 1.0-2.0% of phosphatide gum [11].
In previous research, pineapple, papaya and cempedak are horticultural commodities that are perishable. Based on that, technologies are required for processing them, and one alternative is juice technology. To ensure that the juice is still suitable for consumption and unspoiled, information on shelf life is necessary. Method of estimating shelf life used *Corresponding Author: ratri.ariatmi@ftumj.ac.id is ASLT (Accelarated Shelf Life Test). The estimated shelf life of pineapple-cempedak juice at a temperature of -5 °C was 197.85 days [1]. Further research use fruit leather technology on manalagi apples, Fruit leather is a thin sheet-shaped slurry product with 2-3 mm in thickness. To ensure that the fruit leather is still suitable for consumption, information on shelf life is necessary. Method of estimating shelf life used is ASLT. Shelf life calculation result of manalagi apples fruit leather based on sensory colour parameter values through the Arrhenius approach on the storage temperature of 30°C is 33.11 days [8].
The objectives of this study were to determine the effects of beeswax containing vegetable oilbased lecithin, at several concentrations, on the quality and weight loss in mango. The vegetable oil-based lecithin was a mixture of lecithin extracted from rice bran oil and soy oils. The determination on shelf-life estimation was also conducted using the Accelerated Shelf-Life Testing (ASLT) method.

METHODOLOGY Preparation and application of beeswax coating
In the preparations of beeswax coating, the concentrations of vegetable oil-based lecithin, (rice branand soybean) wih ratio 1:6, were varied at 0.25, 0.5, 0.75, and 1%. Beeswax (12 g) and water (82 g) were heated at the same time in different containers to temperature of 90-95°C. Stearic acid (1.75. 1.5, 1.25, 1) g and lecithin (0.25. 0.5, 0.75, 1) g were added into the beeswax, while triethanolamine (4 g) was added into water. The two solutions were thoroughly mixed, and the temperature was lowered to 80°C under constant stirring. The water-TEA mixture was added into the beeswax solution and mixed thoroughly. The final mixture was cool down to the room temperature for 30 minutes and filtered for a cleaner result [4].
Two layers of the beeswax coating was applied to mangoes with a brushand air dried for two hours. The coated mangoes were stored either at room temperature 301 o K and cooler temperature at 286 o K. The control mangoes were uncoated and placed on a tray without any cover to simulate a market display. One mango for each sample was sampled for analyses every week for five weeks.

Weight loss [13]
Weight loss is calculated based on the difference in initial weight and weight at the time of measurement during the fruit storage period expressed in percent as shown in the following formula.

Analyses for the prediction of shelf-life using Accelerated
Shelf-LifeTesting (ASLT) method, Arrhenius Equation

Quality Change (A) Vs. Time (t) Curves [2]
The change of product quality during storage was measured with physical analyses. At this stage, data were plotted into the A (y axis) versus t (x axis) curve, and ln (A) versus (t)curve to obtain two linear formulas representing two storage temperatures from each curve with the equation of y = a + bx, in which b was the slope and k was a constant.

Determining the Reaction Order [2]
Reaction orders were determined from the curve formula with the highest correlation coefficient (R 2 ). Zero order was chosen when the R 2 for A vs t curve was greater than the R 2 ln A vs t curve. Whereas first order was chosen when the R 2 for ln A vs t was greater than the R 2 for A vs t curve.

(ln k) vs temperature (1/T inK) [2]
The value of b slope used was based on the reaction order that had been determined. A linear formula of y = a + bxor ln k = ln ko -(Ea/R) (1/T), which is called Arrhenius equation, in which ln kowas the intercept, Ea/R was the slope, Eawas activation energy, and R was the ideal gas constant (1.986 cal/mol K).

Calculating the Activation Energy [2]
The activation energy (cal/mol) was calculated from the b value from the Arrhenius equation multiplied with R.

Predicting Shelf Life [2]
Reaction rate (k) at certain temperature was determined by the Arrhenius Equation. The prediction of shelf life was obtained from the difference the quality changes after and before storage. The formula to determine the shelf life is: = Initial Quality Attributed Value (day 0) At = Final Quality Attributed Value (day t) k = Quality Reduction Constant

The effects of lecithin concentration and storage length of mango on the weight loss
In post-harvest processing of mango, coating fruits with wax, or waxing, can reduce the respiration rate, and therefore, this treatment can be a good option to prolong the shelf life.
Waxing can decrease the respiration process in harvested fruits, which in turn suppresses the chemical changes. The slow down on the respiration rate can therefore delay the fruit ripening process [3].
Weight loss is one of the perimeters to measure the degree of freshness in fruits. This phenomenon is a manifestation of the respiratory processes taking place in the harvested fruits. Weight loss is the result of water evaporation and glucose breakdown into CO2 and water. In addition, weight loss is also related to the reduction of firmness, in which connections among cells in the fruit have been weakened by the loss of water [12].
The results showed that the smallest weight loss was achieved from samples treated with beeswax coating containing 0.25% vegetable oil-based lecithin was 7.25%. Whereas the highest weight loss took place in uncoated or control mangoes at 20.62%. Figure 1shows that cooling reduced weight loss. This result corresponds to other study [7]. The largest weight loss occurred in mangoes stored at room temperature. In this condition, fruits undergo active respiration and transpiration processes in the fruits. Cooling can reduce those processes and therefore decrease the rate of weight loss [7]. Table 1 shows changes in the the quality of mangoes for 5 weeks at room and cooler temperature. In most fruits, the first sign of ripening is the loss of green coloration caused by the reduction of chlorophyll contents. Table  1 demonstrates that mangoes without coating stored at room temperature underwent ripening in the first week and rotted completely in the second week. Whereas the beeswax-coated  The color change on coated mangoes stored in the cooler was more stable. Mangoes remained green with a little browning. No rotting was observed throughout the five-week trial period.

Analyses on the Shelf Life Prediction using ASLT method, Arrhenius equation
The length of shelf life can be predicted using weight loss curves. The data on weight loss on mangoes during this five-week trial are presented on Table 2.
Each treatment in this trial exhibited a different pattern of weight changes from others. If the rate of changes is constants, the reaction can be categorized into zero order. However, if the rate is not constant, logarithmic, or exponential, the reaction can be categorized into first order.
Determining the reaction order is the method for predicting the shelf life [1].
For zero order, the formula is obtained by plotting the data on to a curve with y axis representing mango weight and x axis representing length of storage. Whereas the formula for first order reaction is obtained by plotting the data on a curve with ln mango weight on y axis and length of storage on x axis.
The reaction order is determined based on the greater value of R2of the corresponding curves [1]. The determining values (R2) on weight loss on mangoes obtained in this trial were higher in zero order reaction than those in first order (Table 3). It can be concluded that the kinetic reaction in weight loss on mango in storage follows a zero-order reaction.
The gradient or slope value (k) describes the relation between change of quality/weight and length of storage. Negative values of k indicate that there were weight reductions during storage was shown on Table 3.
By calculating the slope of the regression formula for ln mango weight and length of trial at two storage temperatures, the quality change value (k) could be determined. These values are presented in Table 5. In summary, k at each storage temperature could be calculated using the resulting Arrhenius Equations for each beeswax coating [1].
For example, using the Arrhenius equation for 0.25% lecithin of Ln k= -5613.x(1/T) +19.25 (Table 5), the shelf life for mangoes stored at 286oK would yield ln k = -0.395 or k = 0.673. This means that there is 0.673 gram weight reduction per day.
The plot of the values of ln k and 1/T in the changes in mango fruit weight were shown in Figure 2.
The results presented in Table 5 show that the smallest k value occurred in mangoes coated with 0.25% lecithin. The control mangoes exhibited the highest k value, which meant that this sample lost the most weight during storage.     The parameter that can be used to detect sensitivity to temperature changes is the activation energy (Ea). Lower Ea indicates higher weight-change stability [6]. In this trial, mangoes coated with beeswax containing 0.25% plant-based lecithin exhibited the lowest Ea at 11147.4 cal/mol ( Table 5).
The analyses for predicting the shelf life using ASLT method and Arrhenius Equation are presented in Table 5. Mangoes treated with beeswax coating containing 0.25% plant-based lecithin exhibited the longest shelf life an average of 36.91 days or 1.23 month for both storage temperatures, derived from the Arrhenius Equation for this treatment of y = -5613.x+19.25.

CONCLUSIONS
The conclusions that can be drawn from these results are mango fruits coated with beeswax containing plant-based lecithin exhibited smaller weight loss than the uncoated fruits stored in both room 301 o K and cooler temperatures 286 o K; the smallest weight losses occurred in mangoes coated with beeswax containing 0.25% plant-based lecithin at the value of 7.25%; and the prediction of shelf life for mangoes coated with 0.25% plant-based lecithin using the Arrhenius equation yielded 36.91 days.