Compressive mechanical cracking of pili (Canarium ovatum Engl.) nuts: Concept and mechanism design

A mechanical pili nut cracker that used gradual compression for cracking was proposed and developed. This was a deviation from the traditional practice of applying impact for cracking pili nuts. The cracking unit of the machine accomplishes gradual compression by a rotating assembly of discs and compression bars travelling along an arrangement of cam rails. The cracker’s performance was established using pili nuts at different moisture levels.  The tests followed a single-factor three-level experiment where the response variables included cracking capacity, cracking efficiency, cracking recovery, whole kernel recovery, kernel damage, kernel losses and purity of output. The machine performed satisfactorily using nuts dried for three days after depulping (moisture content wet basis = 11.6%). At this moisture level, the machine showed consistent and satisfactory performance in terms of cracking capacity (25 kernels min-1), cracking efficiency (74.0%), cracking recovery (62.6%) and whole kernel recovery (84.3%). Modifications were recommended to further reduce kernel damage (30.6%) and kernel losses (37.4%) and to improve the purity of output (46.8%). It was successfully demonstrated that gradual compression can be used for cracking pili nuts. It is recommended that the operating characteristics of the machine should be optimized to improve its performance.  Furthermore, a dedicated feeding assembly and a more suitable separation method should be explored to further enhance the performance of the cracker

An investigation into the drying of apricots using solar energy : A thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Agricultural Engineering at the University of Canterbury, New Zealand

In this thesis a drying model APRICOT_DRYING was developed using an empirical equation for drying constant k derived from a set of detailed experiments. The preliminary model verification produced some reasonable results for the assumptions considered. Solar drying was found to remove a significant amount of moisture during the simulated apricot drying. Initially, a resolution IV two-level fractional factorial experimental design was used to identify relevant variables affecting the drying time of apricots by estimating their main effects and interactions between any two of them. The variables considered and the levels of each were air temperature, 50 and 60°C; relative humidity, 30 and 40% ; air speed, 2 and 5 m/s; sulphiting duration, 50 and 90 minutes; fruit size, 50 and 60 mm diameter; blanching, 30 seconds and none at all; and microwaving, with and without. Out of these seven variables, only microwaving was eliminated in succeeding experiments for lack of significance. The drying time to 25 % moisture content wet basis increased with the increase in relative humidity, fruit size, and air speed. On the other hand, an increase in air temperature and sulphur content shortened the drying time. Blanching and microwaving decreased the drying time as well. The effect of air speed on the drying time of apricots was further investigated for the range of 1.985 to 4.955 m/s during the '88-'89 apricot season. This was triggered by the seemingly uncharacteristic trend observed from the previous experiments. It seemed to appear that an optimum air speed which may produce the shortest drying time lies somewhere between 2 and 3.5 m/s for relative humidity range of 30 to 40 % at 55°C dry bulb temperature. In another set of trials during the same season and using a modified tumble dryer, the generalized thin-layer drying equation was developed by studying the drying characteristics of apricots for an air temperature range of 35 to 55°C, initial moisture content of 85.7% wet basis, and air speed range of 0.75 to 2.0 m/s. A significant function expressing the drying constant k in terms of air temperature and speed was derived