Keräsalaatin kaasuvarastointi

Authors

• Irma Suhonen Helsingin yliopiston puutarhatieteen laitos, Viik

DOI: https://doi.org/10.23986/afsci.71723

Abstract

Refrigerated gas storage of field grown lettuce was studied in 1963—66 and in 1968. The gas storage method was of a simple type; the carbon dioxide was produced by the respiring lettuces and the concentration of gas was controlled by the ventilation. In 1964—65 three tests were made using NaOH solution as the CO2-absorbent. The gas stores were made of zinc, and their capacity was 336 l. The bins were situated in a refrigerated store where the temperature was 1—2° and the relative humidity 90—95 %. The carbon dioxide content of the bin air was determined with the Riken Keiki gas indicator. The questions studied were; can lettuce be stored in a refrigerated gas store, how big are the gas storage losses, is there any difference between storage losses obtained in cold storage in above mentioned circumstances and in gas storage, is there any difference in the keeping quality of two varieties (Passe Partout and Great Lakes), and what is the influence of different CO2 levels on the wastage. According to the results (Tables 1 to 3, and Figure 1), lettuce could be stored in gas bins. The wastage after gas storage was usually smaller than after cold storage. For example, the average gas storage wastage of Passe Partout was only one half of the cold storage wastage. In gas stores the losses were limited by restricted evaporation and by concentration of gases. In the tests the keeping quality of the variety Passe Partout increased with a higher CO2-content. The above 10 % CO2-concentrations were not studied with the Passe Partout lettuce, because even when the bins were packed full of Passe Partout (15 kg/bin), the CO2-content during the 4 weeks’ storage did not exceed 10 %. On the other hand, when the bins were packed full of Great Lakes (23 kg/bin), the CO2-content of the air during the 4 weeks’ storage rose to 15 %, and the lettuce was injured badly. Measuring the gas concentrations of the air during the tests we noticed that during the first two to three days period the CO2-content rose most quickly. With a lengthening of the storage period, the accumulation of CO2 became slower. This was caused by a natural decrease in respiration, and by a reduction of the O2-concentration. Based on the original weight of stored lettuce, Passe Partout produced quicker CO2 than Great Lakes. Differences in the rates of CO2-accumulation were also noted between different lots of the same variety. In 1968 the difference (Figure 2), for example, seemed to depend on the harvesting temperature, which for test I was 11—14° C and for test II 23—26° C. It was assumed that in the latter temperature the stomata of the lettuce are partly closed, and therefore the rate of the CO2 evolution is reduced.