Production of Pectin-based edible film/coating in a Pilot Scale to Extend Shelf Life of Citrus Fruits

Use of edible films/coatings has been considered to be an important element in preservation concepts. In the commercial preparation of fruit, such as citrus fruit, for market, it is common to treat the fruit with an aqueous coating to replace the emulsion which is removed during the washing process, thereby serving to protect the fruit during periods of storage and handling, during transit to market, and ultimately, to enhance the appearance of the fruit at the marketplace. Once this coating has been applied, it is desirable to dry the fruit to facilitate handling, packing and shipping. The focus of this project was to develop a pectin - based edible films to apply on citrus fruits and extend the shelf life these commodities. To accomplish this goal, some preliminary research was carried on to provide a drying apparatus for drying of fruits that has been coated with a coating emulsion. First, the heat transfer calculations were done to determine the required data to design the apparatus. Then plots were prepared and the construction of the instrument was started. The apparatus included a hopper to be filled with coating emulsion, some hookers to lift the fruits to the dryer, a conveyor and a zone after the dryer for cooling the fruit. An electrical heater (9 kw) was provided and fans that circulated drying air. Fruits were firstly dipped in coating emulsion in hopper and then transferred to the dryer. The dryer included a housing that was divided into two distinct zones, above and below the conveyor. The conveyor was being moved in 0.2 m/min. The air at 40ΊC was blown across the fruit conveyor to dry the fruits. After passing about 16 min in the dryer, fruits were moved to a zone in which cool air was blown across the fruits to decrease fruit surface temperature. The final temperature of fruit surface after cooling was 25ΊC and the time that fruit was passed through the conveyor was 19.2 min. The capacity of the apparatus was designed as 40 kg/hr.Some experiments were done to apply the coating emulsion on the lime fruits in the coating apparatus and fruit quality were evaluated during storage at 4, 15 and 25ΊC.To optimize the film formulation pectin films were developed and some experiments were done to determine the proper type and concentration of pectin, lipids and plasticizers in the film. The effects of pectin, oil and glycerol concentration on water vapor permeability, mechanical properties and opacity of the films were evaluated using response surface methodology. To study the effect of drying conditions (temperature and air flow), a CCRD was used to combine this two parameters and characterize the related responses (elasticity, tensile strength and drying time of the film). Results of experiments confirmed that coating could reduce undesirable changes in lime fruit during storage. The respiration rate, moisture loss, firmness, chemical parameters and color changed in a lower rate in coated fruits as compared with the control. Results of studies on film structure revealed that water vapor permeability increased by pectin and glycerol concentration and was decreased by oil concentration. Mechanical properties were mainly affected by pectin and glycerol concentration. Oil was the most influential factor that affected opacity which increased with increasing oil concentration. Results of drying of films revealed that increasing temperature and increasing air flow led to lower elongation at break and higher tensile strength, while increasing temperature and decreasing air flow resulted in shorter drying time of the film.