Integrated Model-based Design of Horticultural Produce Packaging

T.R. Robertson and J.E. Bronlund

Horticultural produce grown in New Zealand (Table1) is extensively exported, often over long distances, to key markets in Europe, Japan, North America and Australia. Some horticultural produce is stored for long periods where potential quality deterioration is controlled by appropriate grading, storage, packaging and distribution systems.

Table 1: Fruit and vegetables exported from New Zealand in 2007

Shelf life is a complex function of initial quality and variations in temperature, surrounding gas composition and relative humidity during storage which influence produce physiology, extent of water loss and microbial spoilage. As such, full scale shelf life trials are complex, expensive and time consuming. These factors have lead to the use of mathematical modelling approaches to predict produce quality and to design packaging and distribution systems for fresh horticultural produce.

Initially modelling was used to predict the heat load during chilling and storage of horticultural produce to optimise the design of the refrigerated storage (e.g. Cleland and Cleland 1989). This modelling was extended to include the contribution of the fruit and the packaging to the heat loads used in design of refrigerated storage (e.g. Tanner et al. 2002a). Other studies have investigated prediction of air flows in cool stores, shipping holds and containers (e.g. Smale 2004) and air flow within cartons (Zou et al. 2006a,b). Models have been used to characterise heat (Bronlund and Robertson 2006) and moisture transfer through corrugated paperboard used to pack the produce. It is through the integrated understanding of product and package heat and moisture transfer achieved in this work that lead to design of packaging that meets the requirements of both pre-cooling and long term storage.

To complement the understanding of heat and moisture flow in bulk produce, research on predicting produce quality from environmental conditions has been carried out (Hertog and Nicholson 2003, Hertog et al. 2004, East et al. 2009). By combining these models for weight loss, firmness loss, chilling injury and rot, with heat and mass transfer models, insights have been gained into packaging and distribution system design (Tanner et al. 2002b).

The search for technologies to increase the storage life of high quality produce has lead to the development of controlled volatile release systems. To avoid trial and error, models have been developed to predict the impact of antimicrobial component (single and multiple) release such as hexanal and ethanol from packaging material into the package atmosphere (Utto et al. 2008, Figure 1). This models the rates of release required to maintain the produce quality over the required shelf life. These design tools provide clear targets for new research on manufacture of polymer films to release active compounds at the required rates.

Figure 1. Modelling hexanal release into a MAP tomato system at 20C (lines represent model predictions, symbols represent experimental data points). Taken from Utto (2008)

The approach of model-based design of packaging and distribution systems has been widely used in the New Zealand horticultural export industry. It is clear that to gain significant improvements in product quality in the market place, design of these systems must integrate produce quality models, packaging design and cold-chain systems. Through the use of modelling and extending it into developing areas such as active packaging and nanotechnology, future improvements of quality and potential export of other horticultural products is possible.

References

Bronlund, JE and Robertson, TR (2006) Modelling of heat transfer through corrugated cardboard packaging. Proceedings of the International Institute of Refrigeration (IIR) Institute of Refrigeration, Heating and Air Conditioning Engineers of New Zealand (IRHACE) International Conference. Auckland, 16-18 February 2006; Paper 85.

Cleland, DJ and Cleland, AC (1989). Appropriate level of model complexity in dynamic simulation of refrigeration systems. Refrig. Sci. Technol. 1:261 – 268.

East, AR, Araya, XIT, Hertog, MLATM, Nicholson, SE and Mawson, AJ (2009) The effect of controlled atmospheres on respiration and rate of quality change in 'Unique' feijoa fruit. Postharv. Biol. Technol. 53(1-2): 66-71.

Hertog, MLATM and Nicholson, SE (2003) Modelling product quality in MA systems: the missing link. Acta Horticult. 600: 639-646.

Hertog, MLATM, Nicholson, SE and Jeffery, PB (2004) The effect of modified atmospheres on the rate of firmness change of 'Hayward' kiwifruit. Postharv. Biol. Technol. 31(3): 251-261.

Tanner, DJ, Cleland, AC, Opara, LU and Robertson, TR (2002a) A generalised mathematical modelling methodology for design of horticultural food packaging exposed to refrigerated conditions : Part 1, formulation. Internat. J. Refrig. 25(1): 33 – 42.

Tanner, DJ, Cleland, AC and Robertson, TR (2002b) A generalised mathematical modelling methodology for design of horticultural food packaging exposed to refrigerated conditions: Part 3, mass transfer modelling and testing. Internat.J. Refrig. 25(1): 54 – 65.

Utto. W (2008) Mathematical modelling of active packaging systems for horticultural products. PhD Thesis, Massey University, Palmerston North, New Zealand.

Utto, W, Mawson, AJ and Bronlund, JE (2008) Hexanal reduces infection of tomatoes by Botrytis cinerea whilst maintaining quality. Postharv. Biol. Technol. 47(3): 434-437.

Zou, Q, Opara, LU and McKibbin, R (2006a) A CFD modelling system for airflow and heat transfer in ventilated packaging for fresh foods: I. Initial analysis and development of mathematical models. J. Food Eng. 77(4): 1037-1047.

Zou, Q, Opara, LU and McKibbin, R (2006b) A CFD modelling system for airflow and heat transfer in ventilated packaging for fresh foods: II. Computational solution, software development, and model testing. J. Food Eng. 77(4): 1048-1058.

T. R. Robertson is a Senior Lecturer in Packaging Technology (e-mail: t.r.robertson@massey.ac.nz) and Dr J. E. Bronlund is an Associate Professor in Process Engineering (e-mail: j.e.bronlund@massey.ac.nz) in the School of Engineering and Advanced Technology, Massey University, Palmerston North, New Zealand.