The sensory characteristics of almonds can be described by an array of attributes. Distinctive texture attributes can include roughness, crunchiness, hardness, particulate mass, cohesiveness and adhesiveness, and be crispy and chewy. Typical almond aroma/flavor attributes can include overall intensity, fruity, marzipan (benzaldehyde), dark chocolate, nutty, woody, toasty and earthy.
A sensory lexicon is like a vocabulary of terms that can be used to describe and document the attributes of a product. In very simple terms, texture is evaluated for the almond surface, the various chewing stages, and the residual attributes after chewing. Aroma is evaluated by smelling the almonds before chewing. Flavor is evaluated as the in-mouth flavor impact as the nuts are chewed.
In a study at the University of Minnesota, researchers evaluated the sensory texture attributes of five types of almond forms (natural whole, dry-roasted whole, blanched whole, blanched slivered and natural sliced) at different moisture levels. Some of their findings about almond texture are listed below.
Natural raw whole almonds are high in crunchiness, hardness, and cohesiveness while dry-roasted almonds are generally harder, crispier, crunchier and produce more loose particles. Natural almonds are harder, crisper and crunchier than blanched almonds. Compared with whole almonds, sliced and slivered almonds have less hardness, crunchiness, cohesiveness and tooth packing, and require fewer chews and swallows to consume. Compared with slivered almonds, sliced almonds are more powdery and have more surface roughness and loose particles, as well as less hardness, moistness, and cohesiveness of mass and fatty film. Sliced almonds broke into fewer pieces and required fewer chews and swallows to consume than did slivered almonds.
Almond texture is closely correlated with moisture. Sensory testing of texture showed that as moisture increases, moistness of mass and cohesiveness of mass increase. Crispness, hardness, crunchiness, persistence of crunch, and particulate mass decrease with increasing moisture content. Consumers like crispness, crunchiness, and persistence of crunch.
Texture can also be measured with instruments by using compression or bending tests. Read more about texture measurements and moisture.
Volatile compounds are responsible for the aroma and flavor attributes of foods. The almond lexicon study showed that the intensities of aroma/flavor attributes in raw almonds are relatively low, ranging between 0 and 5, which is indicative of mild-flavored products. The major California almond varieties evaluated show a range of inherent variability in aroma/flavor attributes. This variability within an almond variety also may be influenced by crop years and growing regions.
A wide range of volatile compounds exists in raw, aged, and roasted almonds. But the dominant flavor compound in raw almonds is benzaldehyde. Other volatile compounds in raw almonds include short-chain branched alcohols, aldehydes, and ketones. Benzaldehyde is a breakdown compound released from the hydrolysis of amygdalin (download PDF below), a compound responsible for bitterness in almonds. California almonds are sweet varieties that contain only trace amounts of amygdalin. Roasting diminishes the benzaldehyde intensity, which then may not be perceivable from sensory evaluation.
Flavor volatiles in roasted almonds are dominated by volatiles such as pyrazines and branched aldehydes and ketones generated during the browning reaction (also known as the Maillard reaction). The degree of roasting dictates the flavor intensity of roasted almonds.
Researchers at the University of California, Davis, have evaluated the volatile compounds in raw and roasted almonds (download PDF below).
Development of an almond lexicon to assess the sensory properties of almond varieties. Civille, G.V., K. Lapsley, G. Huang, S. Yada, J. Seltsam. Journal of Sensory Studies, 2010, 25(1):146–162.
Impact of almond form and moisture content on texture attributes and acceptability. Vickers, Z., A. Peck, T. Labuza, G. Huang. Journal of Food Science, 2014, 79(7):S1399–S1409.
HS-SPME GC/MS characterization of volatiles in raw and dry-roasted almonds (Prunus dulcis). Xiao, L., J. Lee, G. Zhang, S.E. Ebeler, N. Wickramasinghe, J. Seiber, A.E. Mitchell. Food Chemistry, 2014, 151:31–39.