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Comparison of the Kjeldahl and dry combustion methods for the determination of nitrogen and protein content in 'Lovran marron' fruits from Croatia

Chestnut cultivars grown for high-quality fruits are known as marrons. ‘Lovran Marron’ is the only known traditional Croatian variety of the sweet chestnut. It is grown on private estates in the Lovran surroundings, on the eastern slopes of Mount Učka, where the oldest plantations are several hundred years old. The aim of this study was to compare two methods of nitrogen and protein analysis in ‘Lovran Marron’ fruits. Fruits were collected in October 2019, in the environs of Lovran (Croatia). In order to compare total nitrogen (N) content in marron fruits by the Kjeldahl and dry combustion methods (ISO 13878, 1998), 70 samples of ‘Lovran Marron’ fruits were analyzed. Protein content was calculated by multiplying nitrogen content by factor of 5.30. The Kjeldahl method was performed using Kjeltec 8200 (FOSS, Denmark), using 1 g of grounded raw fruits, previously frozen. The dry combustion method was performed on the NC Soil Flash 2000 Thermo Scientific device (Thermo Fisher Scientific, USA), using 20 mg of grounded and dried raw fruit. Descriptive statistics and analysis of variance were applied to evaluate the differences between the results obtained by these two analytical methods.

dry combustion method ; Kjeldahl method ; marrons ; nitrogen content ; protein content

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