Potential of near infrared spectroscopy for the analysis of volatile components in cheeses I. González-Martín a, * , J.M. Hernández-Hierro a , C. González-Pérez a , I. Revilla b , A. Vivar-Quintana b , I. Lobos Ortega a a Departamento de Química Analítica, Nutrición y Bromatología, Facultad de Ciencias Químicas, C/ Plaza de la Merced s/n, 37008 Salamanca, Spain b Área de Tecnología de los Alimentos, Escuela Politécnica Superior de Zamora, Avda Requejo 33, 49022 Zamora, Spain article info Article history: Received 17 September 2010 Received in revised form 24 December 2010 Accepted 2 October 2013 Keywords: NIRS Volatile compounds Cheeses Determination abstract Near Infrared Spectroscopy (NIRS) was used for the determination of volatile compounds in cheeses allowed to ripen for different times using a remote fibre-optic reflectance probe. To do so, cheeses with known and varying percentages of cow’s, ewe’s, and goat’s milk were elaborated and used as reference material. The volatile compounds determined were: acetaldehyde, ethanol, 1-propanol, 2-butanol, 2- pentanol, 3-methyl-1-butanol, 2-butanone, 2-pentanone, 2-heptanone and 2-nonanone. The regres- sion method employed was the modified partial least squares (MPLS). The calibration results using 67 e72 samples of cheese had a correlation coefficients (RSQ) between 0.600 for the 3-methyl-1-butanol and 0.903 for the 2-nonanone. The robustness of the method was confirmed by applying it to twenty new samples of different compositions and ripening times which did not belong to the calibration group. Likewise, the correlations between the factors of influence studied and the volatile compounds were carried out. The results of the NIRS method are comparable with those of the purge-and-trap-gas chromatography-mass spectrometry. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The volatile compounds found in cheese are the result of a complex combination of microbial and biochemical activities throughout manufacture and ripening process (Pillonel, Ampuero, Tabacchi, & Bosset, 2003). Among these, proteolysis, lipolysis and lactose fermentation are major biochemical events (Fox & Wallace, 1997). Degradation of amino acids leads to amines, aldehydes, al- cohols, acids and sulphur compounds. Breakdown of fatty acids produces esters, methyl ketones and secondary alcohols. The importance of volatile compound determinations is due to their correlation with the flavour, which depends on the ripening, time, cheese-technology, seasonality, etc. The volatile fractions of some Iberian Peninsula cheeses such as Manchego (Gómez-Ruiz, Ballesteros, González, Cabezas, & Martínez-Castro, 2002), Roncal (Izco & Torre, 2000), Zamorano (Fernández-García, Carbonell, Gaya, & Nuñez, 2004) and Serra da Estrela (Dahl, Tavaria, & Malcata, 2000; Tavaria, Dahl, Carballo, & Malcata, 2002; Tavaria, Tavares, Silva-Ferreira, & Malcata, 2006; Villaseñor, Valero, Sanz, & Martí- nez-Castro, 2000) have been studied as a response to the growing interest in the characterisation of traditional products protected by a Denomination of Origin. Volatile compound analysis is usually carried out by gas chro- matography, but it is necessary to use several techniques for * Corresponding author. Tel./fax: þ34 923 294483. E-mail address: inmaglez@usal.es (I. González-Martín). * This important reference establishes correlations between the sensory attri- butes of cheese and different volatiles. The n-Butanoic acid and branched chain acids contributed to higher scores for sharp, rennet and brine odours, and rancid and rennet flavours in Idiazabal cheese than in Zamorano, Roncal and Manchego cheeses. On the other hand, acetic acid, methyl ketones and their reduction prod- ucts contributed to the higher scores for buttery and toasty odours. ** Work on the fundamentals of the near-infrared spectroscopy (NIR) and how to develop quantitative models applicable from the spectral information and chemometrics. y Relates how the evolution experienced during ripening and the seasonal vari- ation of the volatile fraction of Zamorano cheese were studied by using purge and trap extraction and GC-MS analysis. It states that the concentrations of acetalde- hyde, propanal and branched chain aldehydes, 2-methyl ketones, higher molecular weight alcohols, and most esters increased significantly with ripening. z This reference exemplifies the use of the NIR (near infrared spectroscopy) methodology in the establishment of the origin of milk used in making cheeses. x This work establishes the ranges that are taken as reference in the prediction capability (RPD) of the equations obtained by near infrared spectroscopy. From these RPD values it can be inferred if the models developed using NIR are applicable to unknown samples. Contents lists available at ScienceDirect LWT - Food Science and Technology journal homepage: www.elsevier.com/locate/lwt 0023-6438/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.lwt.2013.10.008 LWT - Food Science and Technology 55 (2014) 666e673