prunus_dulcis_mill._d._a.

Prunus dulcis (Mill.) D. A. Webb - syn.Amygdalus communis L.; Prunus amygdalus Batsch; Amygdalus amara Duhamel - Rosaceae
almond, Mandelbaum, Mandel, Bittermandel

Tree or shrub, 3-6m tall, native to Central and Southwest Asia. Cultivated varieties of almonds have been named for whether the seeds are sweet (var.dulcis) or bitter (var.amara) and whether the endocarp is hard or fragile (var.fragilis). http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200010606

„Almond, Amygdalus communis L., is an ancient crop of south west Asia. Selection of the sweet type marks the beginning of almond domestication. Wild almonds are bitter and eating even a relatively small number of nuts can be fatal. How man selected the sweet type remains a riddle. Also, the wild ancestor of almond has not been properly identified among the many wild almond species. Breeding experiment, which is the most critical test for identifying the wild progenitors of other crops, is ineffective in almond, because it is interfertile with many wild taxa. The so-called wild A. communis of central Asia cannot be regarded as a genuine wild form, but as a feral form, or remains of old afforestation. The wild taxa morphologically akin to almond, A. korshinskyi (H.-M.) Bomm. and A. webbii Spach, are also feral types occurring in the Middle East and southern Europe, respectively. The taxon A. fenzliana (Fritsch) Lipsky is the most likely wild ancestor of almond for three reasons: 1. It is a genuine wild type forming extensive thickets of large trees young seedlings and all the intergradations between them in nature; 2. Its morphology, and particularly the partially pitted grooved nut-shell are within the range of variation of almond, and 3. A. fenzliana is native of Armenia and western Azerbaijan in the Middle East where almond was apparently domesticated.“
[On the origin of almond., Ladizinsky, G., Genetic Resources and Crop Evolution, vol.46(2), 1999, 143-147]

„Bitter flavour of the almond kernel is due to the cyanoglucoside amygdalin and has been the first characteristic considered in breeding programmes. In such programmes, the seedlings from sweet-kernelled parents were used to study the transmission of bitterness, which was shown to be a monogenic characteristic, the sweet flavour being dominant. The aim of this work was to investigate more deeply the inheritance of bitterness in almond, by studying for 2 consecutive years the bitter flavour in 169 seedlings of 9 families (obtained exclusively for this purpose), one or both parents being bitter-kernelled. With the exception of the presence of slightly bitter seedlings, the results support the hypothesis of monogenic inheritance of this trait, the bitter flavour being recessive, although other factors could have a slight influence on the expression of this characteristic. Heterozygous individuals showed sweet, slightly bitter or year-changeable (sweet-slightly bitter) phenotypes. Our results demonstrated the possibility of using as parents bitter-kernelled individuals with some outstanding characteristic desirable for transmission to the progeny, always in combination with a homozygous sweet progenitor.“
[Use of recessive homozygous genotypes to assess genetic control of kernel bitterness in almond., Dicenta, F., Ortega, E., Martínez-Gómez, P., Euphytica, Vol.153(1-2), 2007, 221-225]

„The secondary metabolite amygdalin is a cyanogenic diglucoside that at high concentrations is associated with intense bitterness in seeds of the Rosaceae, including kernels of almond (Prunus dulcis (Mill.), syn. Prunus amygdalus D. A. Webb Batsch). Amygdalin is a glucoside of prunasin, itself a glucoside of R-mandelonitrile (a cyanohydrin). Here we report the isolation of an almond enzyme (UGT85A19) that stereo-selectively glucosylates R-mandelonitrile to produce prunasin. In a survey of developing kernels from seven bitter and 11 non-bitter genotypes with polyclonal antibody raised to UGT85A19, the enzyme was found to accumulate to higher levels in the bitter types in later development. This differential accumulation of UGT85A19 is associated with more than three-fold greater mandelonitrile glucosyltransferase activity in bitter kernels compared with non-bitter types, and transcriptional regulation was demonstrated using quantitative-PCR analysis. UGT85A19 and its encoding transcript were most concentrated in the testa (seed coat) of the kernel compared with the embryo, and prunasin and amygdalin were differentially compartmentalised in these tissues. Prunasin was confined to the testa and amygdalin was confined to the embryo. These results are consistent with the seed coat being an important site of synthesis of prunasin as a precursor of amygdalin accumulation in the kernel. The presence of UGT85A19 in the kernel and other tissues of both bitter and non-bitter types indicates that its expression is unlikely to be a control point for amygdalin accumulation and suggests additional roles for the enzyme in almond metabolism.“
[A seed coat cyanohydrin glucosyltransferase is associated with bitterness in almond (Prunus dulcis) kernels., Franks, T.K., Yadollahi, A., Wirthensohn, M.G., Guerin, J.R., Kaiser, B.N., Sedgley, M., Ford, C.M., Functional plant biology, Vol.35(3), 2008, 236-246]

The main volatile compound identified in oil extracts from simultaneous distillation solvent extraction of Almond oil was benzaldehyde, minor components were hexanal, nonanal, and (E,E)-2,4-decadienal.
[Caja, M. M., Del Castillo, M. R., Alvarez, R. M., Herraiz, M., & Blanch, G. P. (2000). Analysis of volatile compounds in edible oils using simultaneous distillation-solvent extraction and direct coupling of liquid chromatography with gas chromatography. European Food Research and Technology, 211(1), 45-51.] in Tree Nuts: Composition, Phytochemicals, and Health Effects, 111

benzaldehyde

„A robust HS-SPME and GC/MS method was developed for analyzing the composition of volatiles in raw and dry-roasted almonds. Almonds were analyzed directly as ground almonds extracted at room temperature. In total, 58 volatiles were identified in raw and roasted almonds. Straight chain aldehydes and alcohols demonstrated significant but minimal increases, while the levels of branch-chain aldehydes, alcohols, heterocyclic and sulfur containing compounds increased significantly (500-fold) in response to roasting (p < 0.05). Benzaldehyde decreased from 2934.6 ± 272.5 ng/g (raw almonds) to 315.8 ± 70.0 ng/g (averaged across the roasting treatments evaluated i.e. 28, 33 and 38 min at 138 °C) after roasting. Pyrazines were detected in only the roasted almonds, with the exception of 2,5-dimethylpyrazine, which was also found in raw almonds. The concentration of most alcohols increased in the roasted samples with the exception of 2-methyl-1-propanol, 3-methyl-1-butanol and 2-phenylethyl alcohol, which decreased 68%, 80%, and 86%, respectively.“
[HS-SPME GC/MS characterization of volatiles in raw and dry-roasted almonds (Prunus dulcis)., Xiao, L., Lee, J., Zhang, G., Ebeler, S.E., Wickramasinghe, N., Seiber, J., Mitchell, A.E., Food chemistry, Vol.151, 2014, 31-39]

„Results of AEDA indicated that 1-octen-3-one and acetic acid were important aroma compounds in raw almonds. Those predominant in dry roasted almonds were methional, 2- and 3-methylbutanal, 2-acetyl-1-pyrroline and 2,3-pentanedione; whereas, in oil roasted almonds 4-hydroxy-2,5-dimethyl-3(2H)-furanone, 2,3-pentanedione, methional and 2-acetyl-1-pyrroline were the predominant aroma compounds. Overall, oil roasted almonds contained a greater number and higher abundance of aroma compounds than either raw or dry roasted almonds.“
[Erten, Edibe S., and Keith R. Cadwallader. „Identification of predominant aroma components of raw, dry roasted and oil roasted almonds.“ Food chemistry 217 (2017): 244-253]

Prunus dulcis as Prunus amygdalus
Kohl, F.G., Die officinellen Pflanzen der Pharmacopoea Germanica, t.98 (1891-1895)
http://plantillustrations.org/species.php?id_species=1265448