The effect of temperature, time and the use of ultrasonic waves on the process of Deiri dates hydration in Khuzestan

Document Type : Research Paper

Authors

• Maedeh Benitorfizadeh ¹
• Yaghoob Mansoori ²
• Ahmad Mostaan ³

¹ Department of Biosystems Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran

² Department. Of Biosystems Engineering, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Iran

³ . Date Palm and Tropical Fruits Research Institute, Ahvaz, Iran.

Abstract

Keywords

• Date
• Deiri
• Hydration
• Response surface method
• Ultrasound

Main Subjects

• after harvest

The effect of temperature, time and the use of ultrasonic waves on the process of Deiri dates hydration in Khuzestan

EXTENDED ABSTRACT

Introduction:

Dates are one of Iran's major horticultural crops being exported all over the world. Dairi is considered a very popular dry date variety Khuzestan province. In addition to domestic consumption, Dairi also has its own fans abroad. So far, over 500,000 seedlings of commercial dairi cultivars have been produced and distributed among the country's palm-growing provinces. The Dairi dates are easily transported due to the dry texture of the fruit. On the other hand, increasing the hardness of its tissue during storage is the first problem of the processing industries. Regarding the high volume of date production in Khuzestan and the need for investigation the methods affecting preservation and improvement of its quality, the effect of hydration process on the quality of Dairi date fruits was studied.

Materials and Methods:

The study was carried out at Shahid Chmaran university of Ahvaz. Dairi Palm samples, uniform in appearance and weight, were purchased from a local palm grove. After separating the damaged fruits, healthy fruits were divided into 25 fruit packs. The hydration applied with a water bath at five temperature levels (30, 40, 50, 60 and 70 degrees Celsius), five soaking durations (40, 55, 70, 85, and 100 minutes) and two condition of ultrasonic waves (ie, with and without ultrasonic). Fruits without undergoing moisturizing process were considered as control. The dependent qualitative parameters measured in this study were moisture content, color, fruit texture, and sugar content. In ultrasonic assisted hydration, date fruit samples were weighed then placed inside the ultrasonic bath containing distilled water at the desired temperature under a constant ultrasonic wave frequency of 28 kHz. Whenever each treatment's time period elapsed, the samples were removed from the machine, their surface water was taken off using a filter paper, then their qualitative parameters were measured. For samples under the hydration process without ultrasonic waves, this process was the same but the ultrasonic wave generator was off. To calculate the percentage of weight gain of fruits from each treatment, 10 fruits were randomly selected, their initial pre-treatment weight (w_i) and final post-treatment weight (w_f) were determined. The color of the fruit was determined using the HunterLab color meter (Konica MINOLTA, INC). Color attributes include three indicators L, a, and b. For texture analysis, the TPA test was conducted using QTS Farnell25 texture analyzer. Total and inverted sugar of the samples determined according to the fehling test. Response surface method (RSM) with central composite design (CCD) was used to investigate the effect of independent variables (namely temperature (A), time (B), ultrasound (C)) on the above mentioned dependent qualitative variables of Dairi fruits.

Results and Discussion:

The results showed that the proposed regression models were significant in determining the effect of hydration on moisture content, reduced and total sugar, color indicators L, E, hardness, chewiness, gumminess and springiness of the treated samples. study showed that the effect of hydration with ultrasound on moisture content and reduced sugar content of the samples was 7.47 percent and 1.34 timest more than the corresponding amount in hydration without ultrasound, which showed the greater effect of ultrasound on the samples. According to the results, the effect of temperature and time levels applied in the current study (and not necessarily all possible temperature and time duration) on other qualitative traits such as color indicators a, b significant difference (at the level of 5 percent) were not observed. Based on the optimization, the temperature level of 40 degrees Celsius and the time of 85 minutes with the application of ultrasound can be stated as the optimal conditions for the hydration process of the Dairi date fruits under test. The use of ultrasonic waves, despite the effect on some traits, should also be economically justified.

Conclusion:

 This study showed that water temperature level of 40 degrees Celsius and the time duration of 85 minutes along with applying ultrasounic waves can be considered as an optimal set point. Although ultrasonic application was effective on some traits, the cost of the equipment and economy should be considered for its use.