Suitability of various onion (allium cepa) varieties for drying and long-term storage
¹National University of Life and Environmental Sciences of Ukraine, 15 Heroyiv Oborony Str., UA 03041 Kyiv, Ukraine
²Estonian University of Life Sciences, Institute of Technology, 56 Kreutzwaldi Str., EE 51006 Tartu, Estonia
In the paper, the results are presented obtained in the research into the fresh bulbs and the dried products of 9 onion varieties cultivated in the conditions of the Ukrainian Forest Steppe area with regard to their economical biology, biochemical, marketability and organoleptic indices. The varieties that are most suitable for convection drying and long-term storage have been identified. It has been established that the marketability of both the fresh bulbs and dried products depends on the masses of the bulbs. The Bronze d’Amposta and Harmony varieties deliver the greatest amount of marketable output (94.0 and 93.2%) featuring marketable bulbs with masses of 67.4 g and 70.4 g, respectively (r = 0.82). As the bulb mass increases, the amount of non-standard (r = –0.81) and small (r = –0.76) particles in the dried product decreases substantially. It has been found that the content of solid matter and sugars in fresh bulbs has effect on the yield and quality of the dried and reconstituted products. The Harmony and Skvirskaya varieties, the bulbs of which during the vegetation season build up 12.9% and 13.8% of solid matter, respectively, are distinguished by the highest dry product yield – 17.1 and 16.8%, respectively. Correlation has been established between the contents of solid matter and sugars in fresh bulbs (r = + 0.58). During the tasting of reconstituted onion products, the highest scores were awarded to the samples produced from the Skvirskaya and Harmony varieties – 7.0 points each on the 9-point scale, as their bulbs had accumulated over 7.0% of sugars (total). Judging by the aggregate of the researched indices, the Harmony and Skvirskaya varieties of onions are the most suitable for convection drying. It has been established that the preservation of onions in the conditions of stationary buried storage without artificial cooling depends on the duration of storage and the specific varietal features. Within the five months of the test storage, the preservation of bulbs of all the varieties was high and varied within the range of 80–93%. Longer storage is expedient only in case of the Harmony, Skvirskaya and Gospodinya, for which the bulb preservation rates for a seven month storage period has been shown to be equal to 90.2, 88.4 and 87.2%, respectively. It has been proved that the quantity of healthy bulbs depends to a significant extent on the solid matter content in the bulbs (r = 0.93).