Application of chemometric tools for the comparison of volatile profile from raw and roasted regional and foreign almond cultivars (Prunus dulcis)

Abstract

In almonds, volatile compounds are major contributors to flavour, being scarce the current knowledge about their volatile profile. Hence, this work intended to characterize the volatile profile, using headspace solidphase microextraction and gas chromatography-mass spectrometry, in raw and roasted almond cultivars (regional cvs. Amendoão, Bonita, Casanova, Molar and Pegarinhos and foreign cvs. Ferragnès and Glorieta). Overall, 35 compounds were identified, with major chemical classes being alcohols and aldehydes. In raw fruits, benzaldehyde and 3-methyl-1-butanol were key compounds, with roasting changing volatile profiles, increasing release of compounds, with predominance of hexanal and benzaldehyde. Cultivars Glorieta and Molar didn't show significant increase in aldehyde content after roasting, which may indicate higher resistance to heat-caused oxidation. The use of linear discriminant analysis and principal components analysis permitted the recognition of patterns in the volatile profiles, that can be useful for cultivars identification. This work allowed the characterization and monitoring changes caused by roasting of volatile components of less studied almond cultivars, identifying some that can withstand roasting procedures with reduced formation of compounds associated with off-flavours.

Variability of Chemical Profile in Almonds (Prunus dulcis) of Different Cultivars and Origins

“…This trend is similar to other scientific works that presented the amounts of C5-C8 aldehydes as useful predictors of rancidity in roasted almond samples [ 89 , 90 ]. Changes caused by roasting of volatile components of nine cultivars (Amendoao, Molar, Pegarinhos, Bonita, Casanova, Pegarinhos, and Refego, Ferragnès and Glorieta) were monitored by HS-SPME-GC-MS analysis [ 91 ]. LDA results obtained from raw samples showed that only seven volatiles had statistical significance (benzyl alcohol, 3-penten-2-ol, guaiacol, benzaldehyde, limonene, 2-heptanol, and 3-methyl-1-pentanol) explaining about 58% of the data that allowed the classification of all cultivars.…”

Effects of Different Processing Treatments on Almond (Prunus dulcis) Bioactive Compounds, Antioxidant Activities, Fatty Acids, and Sensorial Characteristics

“…In the north of Portugal, there is a large area of almond cultivation which has been assigned a Protected Designation of Origin (PDO) status: Amêndoa Douro. The cultivars grown in Amêndoa Douro have been the subject of few scientific studies [ 13 , 14 , 15 ]. Preliminary data indicate that these cultivars are low-yielding due to unsuitable soils and environments as well as poor management practices [ 13 ].…”

Genetic characterization of an almond germplasm collection and volatilome profiling of raw and roasted kernels

“…This investigation supports the use of PTR-ToF-MS as an accurate and objective phenotyping tool to evaluate the VOC profile of almonds. Indeed, most of the molecules that were previously identified on a limited number of almond accessions by gas chromatographic analysis 33 , 35 , 36 were detected in this broad germplasm collection.…”

“…All steps of measurements were automated by an adapted GC autosampler (MPS Multipurpose Sampler, GERSTEL) coupled to PTR-ToF-MS. After the PTR-ToF-MS measurement of fresh almonds, each vial, without cup, was transferred into an oven (WTB Binder, Germany) at 150 °C for 15 min to achieve a medium roast. These roasting conditions were decided based on literature information 35 , 36 and on preliminary tests performed on almond kernel genotypes, characterized by different shapes and sizes profile of roasted almonds was assessed in the same way of fresh samples.…”