Hydroponic salad post-harvest introduction

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Introduction

Everybody knows that quality leafy greens is the result of many factors as the variety selection, the cultivation technique, the climate control, the technology and the management in the farm. However, not many people know that to keep the quality we need the right post-harvesting technology and knowledge, especially when we talk about hydroponic production.

Hydroponic lettuce, for example, are harvested after 5 to 6 weeks of cultivation. Then, it is very important to transfer the harvested product to the adequate cold room in order to cool down the salad. Indeed, keeping the optimal temperature (T°C) and relative humidity (RH%) during the correct period with precise technology. In fact, it will ensure the freshness and shelf life of the salad. Moreover, before sending the lettuce to your customer, it is necessary to choose the proper packaging and/or the good washing process that will protect your leafy green from oxidation, dehydration or undesirable taste (due to multiple factors).

How to select the right packaging ?

Firstly, the packaging selection will depend on factors such as: distribution frequency, distance (km and time) between your farm and the market, transportation type (lorry, plane, etc.) and the shelf life (in days) that you expect for your product.

Secondly, other factors which might influence your choice are the appearance of the final product. For example, it can be unwashed head salad, washed head salad or cut and washed salad.

Finally, it will be also important to choose the right washing and drying technique.

In any case it is important to choose a packaging material base on the following items:

• The exchange capacity between the oxygen and CO₂ ;
• The capacity of the material to control the humidity ;
• The inside atmosphere (or modify atmosphere in some cases) ;
• The light protecting, light can accelerate the oxidation of the salads ;
• The resistance of the packaging ;

What is the most important during the washing process?

The washing of the salad will take out all the undesirable insects, particles or even leafs of the fresh harvested salads. Besides, it will help to remove some bacteria that will damage the salad.

A good washing needs the proper water (pH, microbiological quality) with the adequate disinfection product (ppm). Most of the companies are doing more than one washing step using different disinfection products at different concentrations on specific timing. In practice, it will be standardize in function of the salad variety and level of contamination. Nevertheless, it will mostly depend on the desired final product.

What about the drying process?

Regarding the drying process, it is essential to know the resistance of the salad leafs and the desired final humidity. There are different type of technologies using mechanical forces or temperature. The final choice will influence the texture, colour, the shelf life and even the taste of the salad.