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Technological evaluation of the plum and pear suitability for drying and freezing

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The quality of processed products depends primarily on the quality of fruits and berries, their chemical composition, and consequently from selected varieties. In St. Petersburg State Agrarian University the suitability of some plum and pear varieties were investigated in terms of their subsequent freezing and drying: Pavlovskaya yellow, a Gift to Saint-Petersburg, Carmine, Chizhovsky, Leningrad, Petrovka cotton. In the experiment two ways of processing were used: freezing fresh plums and pears in the dry state and the drying of plums and pears in infrared dryer. Tasting of frozen fruits showed that the most delicious and aromatic were Pavlovskaya yellow and Carmine cherry-plum varieties – 4.7 or 4.8 points and Chizhovsky and Leningrad pear varieties – 4.4 or 4.5 points. The highest content of sugars was in the frozen fruits of Carmine plum – 11.5% and Chizhovsky pear – 11.2%. The highest content of ascorbic acid was in the frozen Pavlovskaya yellow plum – 15.6 mg/100 g and in the Peter cotton pear – 12.6 mg/100 g. The following varieties of plums had the richest chemical composition of the frozen fruits: Pavlovskaya yellow and Carmine as well as Chizhovsky and Peter cotton pears. Frozen plums and pears preserved their amount of dry substances and sugars almost completely, frozen honeysuckle berries retaining from 90 to 95% of ascorbic acid (% of fresh berries). Organoleptic assessment of the dried plum revealed the best varieties: Pavlovskaya yellow – 4.7 points and Carmine – 4.6; for pears they are Chizhovsky and Leningrad – 4.8 points. The highest sugar content was observed in dried Carmine plum – 42%, and Leningrad pear. Drying decreases ascorbic acid content drastically, but nevertheless, dried plum had its adequate content of 28–40 mg/100 g and dried pear does 22–36 mg/100 g. Pavlovskaya yellow and Carmine plums as well as Peter cotton and Leningrad pears had the richest chemical content in dried fruits. Loss of sugars during drying amounted to 14–20%, losses of ascorbic acid – from 45 to 60% for plum and 40–50% for pear (depending on variety). The following varieties are recommended for freezing: Pavlovskaya yellow and Carmine plums, Chizhovsky pear. Pavlovskaya yellow and Carmine plums, and Leningrad pear are recommended for drying.

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