Evaluation of truck shipment transit hazards in Kenya and the effect of their simulations on the physical quality of bulk-packed black tea as a basis for establishment of a pre-shipment testing protocol for packaged goods to optimize packaging designs

Abstract

Focused transit hazard evaluations of distribution environments have become increasingly important in the recent past. This is due to the realization by businesses such as those in China (Baird et.al.,2004) that pack design optimization can result in reduction of packaging and other related costs, ensuring safe delivery of products as well as enabling companies to comply with global statutory obligations that demand packaging waste reduction via optimal packaging of goods. This work involved focused evaluation of the distribution hazards in truck transport within the bulk packed tea supply chain in Kenya as a basis for establishment of a pre-shipment protocol for packaged goods in order to optimize package designs and protect the physical quality of tea in transit. The parameters addressed included vibrations, shock, and environmental conditions of temperature and relative humidity. The research further examined how above transit conditions may affect important black tea physical quality parameters of density, particle size distribution, colour, and particle morphology. The work also formulated a new a pre-shipment testing protocol for tea (and other goods) moved within this supply channel thus allowing businesses to optimize their packaging designs. Furthermore, such pre-shipment protocols would help in predicting possible failure in transit. The Lasmont’s Saver model 3x90 transit data measuring unit mounted on the truck bed was used to collect transit data while a programmable electrodynamics vibration table was used to simulate the measured transit conditions. Using the specially fabricated rig apparatus for the experiment, analysis of changes of the tea physical properties of particle size distribution, bulk, tapped and compact densities as well as particle morphology and colour were investigated. The results showed that truck transport transit conditions experienced in the Kenyan roads with a composite spectrum of 1.358 (Grms) for the routes measured are more severe than the test standards set by both American Standard Testing Methods (ASTM) and International Safe Transit Association (ISTA) for truck transport conditions of 0.242 and 0,519 (Grms) respectively. This shows Kenyan roads compared to those where both ASTM and ISTA data was derived from are poorer and further confirms that both ASTM and ISTA standard tests may not be appropriate for use in designing optimal packaging for the Kenyan distribution environment. In addition, vibration intensities experienced were relatively higher than average recorded from other similar studies carried out in other parts of the world such as Brazil (0.628 Grms), USA(maximum 0.89 Grms), Spain (0.194Grms) and Indian highways (0.161 Grms). The work revealed how poor Kenyan roads are and that they would lead to damage of delicate physical qualities of tea including particle size distribution for each grade of tea, particle morphology and density unless the right packaging is used. This therefore underpins the importance of carrying out focused pre-shipment testing for a given distribution environment as general test procedures will not allow optimization of packaging designs. Due to the prevailing poor road conditions in Kenya as shown earlier by relatively high vibration and shock impacts, results showed that these hazards together with load compression affected the tea particle integrity in transit leading to breakage of larger tea particles to give rise to smaller particles unless adequate protective distribution packaging has been given due consideration. Equally, particle density as well as the particle surface morphology was affected resulting in undesirable impact on tea physical quality. Consistency in density of tea is an important aspect for the blenders of bulk tea since packing machines often operate within defined density limits. Compressive forces within the pallet load led to the crushing of larger tea particles into smaller ones, thus undermining the desirable black colour tea leaving it greyish which is considered in the tea trade as poor tea quality. In addition, the results confirmed that the effect of compression load on the physical tea quality was more severe than the vibration/shock impact alone. Moreover, the change in physical quality was related to the transit time (vibration period) up to maximum equilibrium level. Density of tea increased with compression load up to a maximum of 350g. The same, however, declined at 400g static load due to resonance conditions of the simulation assembly. Tea morphology measurements indicated that the initial rounded shape of the tea particles gradually changed to an elongated shape with rugged surface. This had an effect of not only damaging the desired black colour but also altered the flow properties of the tea which is an important aspect for bulk tea buyers during their subsequent handling activities of blending and packaging. A new relationship called compact density and compact ratio was established that related elevated tea density in transit due to ‘jamming’ of tea particles upon application of static load pressure on the tea at the lower levels of the pallet load. In addition, a correlation of density against tea powder “stain” travel within the test container containing tea particles, further confirmed that force impulses from the static load on top of tea particles was being transmitted perpendicular down to the bottom of the pallet load. The correlation of both the distance moved by the static load inside the tea container and tea powder “stain” column height on the test tube below the static load with the compact density of tea, brought out further empirical data that could be used by researchers to accurately predict the tea density from both the above parameters. The research further revealed that compressive forces on the tea particles at lower levels of the pallet load had more impact on the damage of tea particles compared to vibration/shock impacts. Finally, there is need for the existing packaging standards for bulk packed black tea to be revised in the light of the newly developed pre-shipment testing protocols from this research.