Four almond cultivars (Marcona, Guara, Garrigues and Butte) have been classified using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and gas chromatography (GC) data. The data were obtained by completing the first stages of a thermal oxidative degradation process. The degradation process was monitored by using the variations in the main fatty acid methyl esters (FAME) content determined by GC and to changes in the infrared spectra recorded using the ATR-FTIR technique. In order to classify the almond cultivars, a stepwise linear discriminant analysis was applied to the data. The results indicated that, although the four almond oils evaluated here have a similar fatty acid composition, differences in linoleic acid content may be linked to oxidative stability. Butte cultivar samples had higher linoleic acid content and were more prone to oxidative deterioration.

Almonds show a great variability in their chemical composition. This variability is a result of the existence of a diverse range of almond cultivars, the self-incompatibility of most almond cultivars, and the heterogeneous harvesting conditions found around the different locations where almons are grown. In the last years, the discrimination among almond cultivars has been the focal point of some research studies to avoid fraud in protected geographical indications in almond products and also for selecting the best cultivars for a specific food application or the most interesting ones from a nutritional point of view. In this work, a revision of the recent research works related to the chemical characterization and classification of almond cultivars from different geographical origins has been carried out. The content of macronutrients, tocopherols, phytosterols, polyphenols, minerals, amino acids, and volatile compounds together with DNA fingerprint have been reported as possible cultivar and origin markers. The analysis of the results showed that no individual almond compound could be considered a universal biomarker to find differences among different almond cultivars. Hence, an adequate selection of variables or the employment of metabolomics and the application of multivariate statistical techniques is necessary when classification studies are carried out to obtain valuable results. Meanwhile, DNA fingerprinting is the perfect tool for compared cultivars based on their genetic origin.

Protected designations of origin ''Alicante'' and ''Jijona'' nougats are manufactured products produced using raw materials from Eastern Spain. In order to avoid adulteration practices, determination of volatile compounds from three different almond cultivars (Spanish Guara and Marcona and, from the USA, Butte) was performed to obtain a set of parameters for discrimination between Spanish and American cultivars. Factorial experimental design was applied for the development of a headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) analytical method for isolation and determination of the volatile compounds in almond oils. Main HS-SPME variables optimized were extraction temperature, extraction time, and stirring speed. Several volatile compounds including aldehydes, alkanes, alcohols and aromatic hydrocarbons were identified. Multivariate techniques were applied for classification and discrimination of the different almond cultivars studied. Specifically, cluster and stepwise linear discriminant analysis (LDA) were used, with LDA showing the best performance. The results obtained demonstrated that the proposed method combined with multivariate statistical analysis can be successfully applied for discrimination among different almond cultivars.

Known statistical techniques have been applied to the free amino acid composition of 107 samples from 10 different almond cultivars (Marcona, Desmayo-Largueta, Guara, Tuono, Ferragnes, Masbovera, Non Pareil, Titan, Texas, and Primorskyi) cultivated in seven different locations and growing conditions. It is concluded that free amino acid composition can constitute a basis for classifying and typifying these cultivars into five groups: (1) Marcona and Texas, (2) Ferragnes and Masbovera (and probably Primorskyi), (3) Tuono and Guara, (4) Non Pareil (and probably Titan), and (5) an isolated cultivar (Desmayo Largueta). As a result, an easy decision tree is proposed to discriminate the cultivar of an almond flour, as used in confectionery, if it consists of a single cultivar.

Almonds are subjected to thermal processes in the production of processed food and this can affect their thermal stability and lead to oxidation processes. In this work, almond samples from three different cultivars (Spanish Guara and Marcona, and American Butte) were characterized by using Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) at different heating rates. Crystallization and melting parameters were determined by DSC; whereas thermal stability was studied by TGA, showing no apparent degradation for all samples up to around 290°C. Butte samples showed the lowest DSC values and TGA initial degradation temperature. These results were linked with differences in fatty acid profiles between Butte and Spanish almond cultivars, Butte presenting higher linoleic acid content. Successful discrimination was obtained for samples analyzed at 2 and 10°C min -1 heating rates for DSC and TGA, respectively, by applying multivariate stepwise linear discriminant analysis (LDA). The results obtained proved the suitability of thermal analysis techniques combined with LDA for an easy and fast discrimination among different almond cultivars to control eventual adulteration in food processing.