A near infrared spectroscopic (NIR) approach to estimate quality alterations during prolonged heating of lard

Szabó, A. and Bázár, G. and Andrássy-Baka, G. and Locsmándi, L. and Romvári, R. (2009) A near infrared spectroscopic (NIR) approach to estimate quality alterations during prolonged heating of lard. Acta Alimentaria, 38 (1). pp. 97-106. ISSN 0139-3006

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Abstract

Lard is a preferred frying fat in the Hungarian culinary routine. Our study aimed at measuring conventional fat quality indices and performing NIR-based calibrations of those indices, during prolonged heating. Lard was heated for 4 days at 8 different temperatures (160, 170, 175, 180, 185, 190, 200 and 230 °C) for 8 h a day (n=32+1, i.e. the original sample). Acid value (AV) and carbonyl value (CON) increased in parallel with the duration of heating and heating intensity. Peroxide value (PV) increased in the first 8 h, and decreased back during further treatment. p -Anisidine value (pAV) increased at each heating temperature below 200 °C, while temperatures above 200 °C decreased it. NIR analysis (NIRSystems 6500) was performed on original samples in transflectance mode (400–2500 nm wavelength range, 0.1 mm layer thickness, aluminium-plated reflector). Treatment characteristics (temperature, heat-sum, sampling event) could be estimated effectively. Calibration for AV was robust: R2=0.927; 1-VR=0.786. Weak relationship was found for PV (R2=0.48) and CON (R2=0.109). For pAV, good calibration was gained, expressly below 200 °C, in the 2000–2500 nm wavelength interval (R2=0.912; 1-VR=0.772). Based on calibration and cross-validation results, NIR technique may be a rapid, solvent-free alternative for the estimation of acid value and p-anisidine value of lard below 200 °C.

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