Time-Dependent and Time-Independent Rheological Characterization of Date Syrup

Ibrahim O Mohamed,Eihab Hassan

doi:10.5539/jfr.v5n2p13

Abstract

The time-dependent and time-independent rheological properties of Barhi date syrup have been investigated. Rheological measurements were performed with a rotational viscometer with parallel plate geometry. The date syrup showed thixotropic behavior and a first order exponential decay model characterized the time-dependent behavior. The rate constant of the structure breakdown was found to be a function of shear rate. The steady shear flow measurements showed that the date syrup is a non-Newtonian material fit the power law model (p &lt;0.001). The Arrhenius model described the effect of temperature on consistency coefficient; the estimated parameters from the Arrhenius equation were used to develop a prediction rheological model for the apparent viscosity. The model accurately predicts the experimental data even when extrapolating beyond parameter estimation temperature range. The time-independent viscosity model was satisfactory for modeling date syrup despite the presence of thixotropic behavior.

Highlights

The fruit of the date palm (Phoenix dactylifera L.) is one of the most economically important fruit in the Middle East and North African countries
The Arrhenius model described the effect of temperature on consistency coefficient; the estimated parameters from the Arrhenius equation were used to develop a prediction rheological model for the apparent viscosity
Date syrup is an aqueous extract from date fruits that is concentrated under vacuum commercially to 70 – 78 oBrix

Summary

Introduction

The fruit of the date palm (Phoenix dactylifera L.) is one of the most economically important fruit in the Middle East and North African countries. Dates are important for human nutrition because they are a rich source of carbohydrates, proteins, minerals, dietary fiber and some vitamins in addition to being a source of rapid energy (Jasim Ahmed, Almusallam, & Al-Hooti, 2013; Al-Hooti, Sidhu, Al-Saqer, & Al-Othman, 2002; Al-Shahib & Marshall, 2003; El-Nagga & Abd El–Tawab, 2012). Dates are mostly consumed as a whole fruit or in processed form such as date paste or date syrup. Date syrup is one of the major processed forms of the dates. Date syrup is not produced like fruit juice by pressing but produced by the addition of potable water to the dates to dissolve sugars and other components, which is subjected to a series of purification and concentration steps. Demand for date syrup in the food industry as a natural sweetener packed with nutrients is growing, and there is much potential for new food products that contain date syrup

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