In agriculture, the use of measuring instruments is common. From weather stations to refractometers, tensiometers, soil moisture sensors, ceptometers, fluorometers, fruit firmness meters, colorimeters and much more. All this instrumentation is intended to generate numerical data that is then used to evaluate and make improvements in the yield, production and quality of the fruit. Often these values are converted into indices that are considered goals to achieve a final objective.
Despite the above, when we get to the time of cherry harvest, when we analyze in a particular way what happens in a first stage of the post-harvest that goes from when the fruit is harvested until it is received at the processing plant, when the cherry is exposed to high levels of dehydration and deterioration, we realize the dangerous absence of evaluations and measurements, so there are no numbers that allow us to evaluate the process or the condition of the fruit and the environment in which it is found.
When evaluating this stage, we often hear descriptions of the process variables in a qualitative rather than quantitative way. Distances are mentioned as “close” or “far,” the temperature of the fruit is characterized as “fresh” or “hot,” or the time it takes a crew to fill a bin is described as “fast” or “slow.” All of these concepts require a supporting number, which is obtained by implementing evaluations with instruments that will allow the different variables involved to be measured, establishing fluctuation ranges for these values, and making decisions when the numbers go beyond the established limits.
Additionally, there are certain post-harvest management procedures in the field that do not have a numerical basis, but are done out of habit, such as the use of a sponge on the bins inside the truck, or the doubt between using a sponge or a thermal tent on the bins, or the effect of wetting the fruit before it is sent to the plant. These doubts can be easily clarified if the variables involved are measured, such as temperature or weight loss of the fruit.
In previous publications we have talked about the humidity chain, which aims to segment the post-harvest process into stages to define specific strategies in each of them. Thus, in the post-harvest of cherries we can identify:
1) Harvest
2) Field collection
3) Transport to plant
4) Reception plant
5) Raw material chamber
6) Maritime transport
In each of these stages, the variables that will allow the effect of the environment on the cherries to be numerically evaluated must be measured.
There are certain factors in the post-harvest that can be measured in the present and that will be indicators to project the future of the fruit. To do this, it is necessary to measure variables, establish limits, parameterize the measured values and respect them.
Among the factors that will affect the future condition of the already harvested cherry are:
✓ Metabolism: The higher the metabolism, the greater the deterioration of the cherries during post-harvest. Similarly, the higher the temperature of the cherries, the higher their metabolism, as we were able to observe in a study whose results we shared in a previous publication. So, by measuring the pulp temperature we can infer the cherry's respiratory rate at that time. For this we only need a probe thermometer and the routine of monitoring the temperature of the fruit throughout the post-harvest process.
✓ Dehydration: To determine when the cherry is exposed to higher or lower levels of dehydration, we measure the vapor pressure deficit (VPD). To do this, it is necessary to know the air temperature and relative humidity of the environment in which the cherry is located at that time, along with the cherry pulp temperature. To make these measurements we use a thermohygrometer and a probe thermometer. This will indicate the greater or lesser exposure of the fruit to dehydration, however, to know the magnitude of the dehydration of the cherry, it is necessary to monitor its weight. For this, a sample of fruit is taken, its weight is determined in a balance and after a controlled and determined time, the patient is weighed again. This evaluation will determine the weight loss per unit of time (% weight loss per hour).
✓ Ti.e.mpo: The deterioration suffered by the cherry during post-harvest will depend on the time during which it was exposed to the different environmental conditions that we have identified as unfavorable. The dehydration of the fruit is measured per unit of time, and is multiplied by the number of hours during which the fruit was under a certain condition. For example, if we have determined that the cherry under a conventional collection center is dehydrated 0.3% per hour, the dehydration after 5 hours will be 1.5%. If we make the process more efficient and manage to cut the waiting time in half, the dehydration will also be reduced by half, falling to 0.75%.
✓ Concentration of soluble solids: He refractometer It allows to measure the concentration of soluble solids in the fruit (°Brix), an indicator of the level of ripeness of the fruit.
In conclusion, it is important to translate the entire post-harvest process into numbers in order to evaluate and improve it. A number is more precise than a word, so it is essential to use measuring instruments at all stages of the cherry post-harvest process to ensure product quality.
