Physicochemical Characterization of Jordanian Air Dried Olive Fruits

Abstract

The effect of indoor air drying on the mass of irrigated and rain-fed green and black olives has been investigated in the present study. Mass loss data were collected over a drying period of about four months. Several measurements were carried out on the pit and pulp fractions of the dried samples. These measurements included the determination of:  Mass percentages of pits and pulp fractions, mineral and fat contents, percentages of carbon, hydrogen and nitrogen, gross and net calorific values. Results based on using simultaneous thermogravimetry and differential thermal analysis, derivative thermogravimetry and differential scanning calorimetry are reported for pits derived from rain-fed green and black olives. The maximum average % mass loss was found to be 78.99% for irrigated green olives while the minimum average % mass loss was found to be 34.48% for rain-fed black olives. The percentages of pulp and pits for dry green olives fall in the range 57.59 - 65.18% and 33.91 - 39.98%, respectively. The corresponding ranges for the dry black olives are 65.13 - 76.70 and 20.65 - 33.76% for pulp and pits fractions. The gross calorific values are 21.609 and 21.745 kJ/g on dry basis for pits of rain-fed green and black olives. Soxhlet extraction with n-hexane of rain-fed olives gave extractives percentages of 23.39 and 21.84% for pits of green and black olives and 46.43 and 51.80% for pulp fraction of green and black olives, respectively. The pyrolysis thermograms gave residual masses of 0.29 and 0.27 at 600°C for pits of green and black rain-fed olives. Three peaks were identified on the derivative curves. Peak value, peak temperature and % remaining mass at the peak temperature were determined. The differential scanning calorimetric curves of the studied samples showed a series of exothermic humps in addition to the endothermic moisture peak.