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Journal of Food Science and Technology logoLink to Journal of Food Science and Technology
. 2020 Apr 30;57(11):4182–4192. doi: 10.1007/s13197-020-04456-9

Effect of almond genotypes on fatty acid composition, tocopherols and mineral contents and bioactive properties of sweet almond (Prunus amygdalus Batsch spp. dulce) kernel and oils

Mehmet Musa Özcan 1,✉, Bertrand Matthäus 2, Fahad Aljuhaimi 3, Isam A Mohamed Ahmed 3,✉, Kashif Ghafoor 3, Elfadıl E Babiker 3, Magdi A Osman 3, Mustafa A Gassem 3, Hesham A S Alqah 3
PMCID: PMC7520497  PMID: 33071339

Abstract

Oil content of almond kernels ranged from 36.7% in the cultivar T12 to 79.0% in genotype T27. The major fatty acid in almond oil is oleic (62.43% in T7-76.34% in T4) followed by linoleic (13.97% in T4-29.55% in T3) and palmitic (4.97% in T2-7.51% inT3). The main tocopherol in almond oil was α-tocopherol (44.25 mg/100 g in T25-75.56 mg/100 g in T13) that was 44 folds higher than other tocopherols in the oil. Total tocopherol contents of almond oils ranged between 47.42 mg/100 g (T14) and 80.15 mg/100 g (T16). Among macro minerals, K was the highest (5238–14,683 mg/kg), followed by P (3475–11,123 mgkg), Ca (1798–5946 mg/kg), and Mg (2192–3591 mg/kg), whereas Na was the least (334–786 mg/kg) in almond kernel. The total polyphenol was observed in T16 (98.67 mg GAE/100 g), while the least was found in T24 (23.75 mg GAE/100 g). Antioxidant activity was high in T7 (91.18%) and low in T12 (44.59%).

Keywords: Almond cultivars, Almond oil, Fatty acid, Tocopherol, Mineral, Total phenol, Antioxidant activity, GC-FID, HPLC, ICP-AES

Introduction

Almonds (Prunus amygdalus L.) belong to the Rosaceae family and Prunus genus and can be found in temperate environment around the globe (Moayedi et al. 2011; Izaddost et al. 2013; Čolić et al. 2019). The almonds have numerous nutritional benefits as well as industrial and medicinal importance as they contain good quality oil, protein, fiber, mineral and bioactive compounds. The consumption of nuts is greatly increased globally due to their high health benefits. Among nuts, almonds received great attention around the globe due to their wide food, medicinal, and cosmetic applications. They are frequently used as ingredients in the manufacture of snacks and other processed foods. However, the oil content and composition of food ingredients such as almond in confectionary industry are very important because high oil content reduce the water absorption and affect the product quality. Nutritionally almonds are considered as excellent sources of energy, fats, proteins, essential minerals, carbohydrates, unsaturated fatty acid (linoleic acid and γ-linoleic acids), phenolic compounds and vitamins (Welna et al. 2008). There is lot of work underway to improve the genetic, agronomic and climate adoptability features of almonds. However, the biochemical composition of newly developed almond genotypes yet needed to be explored (Moayedi et al. 2011; Kodad et al. 2008). The ratio of oleic acid to linoleic acid is suggested to be used as a tool for highlighting oil stability and fatty acid profiling of the almond kernels (Kodad et al. 2008). The objective of the current study was to investigate effect of almond genotypes on fatty acid composition, tocopherols and mineral contents and bioactive properties of and oils of thirty-one different sweet almond (Prunus amygdalus Batsch spp. dulce) growing in the Mersin (Büyükeceli-Gülnar) district of Turkey.

Materials and methods

Material

Almond fruits of thirtyone genotypes were collected during the full maturated stage from the Mersin (Büyükeceli-Gülnar) province in Turkey during 2018 season. Precipitation was about 702 mm per year and maximum air temperature around 28–30 °C during the summer months. In 2018, after almond genotypes were selected, almond genotypes were marked as the native population. Almond fruits from each genotype were harvested on September, and samples were collected from each genotype for analysis. About 25 kg almond were collected from each tree. The fruits were dried at 70 °C in hot air oven. The kernels were ground into fine homogeneous powder, and collected in dark colored bottles. Samples were stored at refrigerated temperature (< 5 °C) until analysis.

Methods

Oil content

The hot extraction method using Soxhlet apparatus was used to extract oil from almond seeds. Briefly, 2 g powder was extracted using petroleum ether for 6 h. After the extraction, the solvent was evaporated from the oil at 40 °C and the obtained oil was stored in vials at refrigerated temperature until used for analysis.

Fatty acid composition of almond oil

The fatty acid profile of oil samples extracted from 31 almond genotypes was determined using a gas chromatography system. The system consisted of a CP-Sil 88 capillary column (100 m long, 0.25 mm ID, and film thickness 0.2 μm) attached to a Varian 5890 gas chromatograph. The fatty acid methyl esters of the samples were injected into this system at 250 °C (Matthäus and Özcan 2006) and the individual fatty acid methyl esters were identified by comparing with the retention time of their respective ester standards.

Tocopherol contents in almond oil

Tocopherol contents in oil samples were determined using HPLC system following the method described earlier (Balz et al. 1992). The oil samples (250 mg) were mixed with 20 mL n-heptane. After that, 20 μL of this mixture was directly injected to a Diol phase HPLC column 25 cm × 4.6 mmID (Merck, Darmstadt, Germany) maintaining 1.3 mL/min flow rate.

Mineral contents in almond kernels

The dried almond powder (0.5 g) was digested by using a mixture of 65% HNO3 (5 ml) and 35% H2O2 (2 ml) in a closed system (Cem-MARS Xpress). The digested mixture was then transferred to a volumetric flask and the volume was raised to 20 ml with deionized water. The diluted samples was injected to ICP AES (Varian-Vista, Australia) and the estimation of a particular mineral content in the sample was made by comparing them with the reference mineral solutions provided by the National Institute of Standard and Technology (NIST; Gaithersburg, MD, USA) (Skujins 1998). The working conditions of ICP-AES used during the experiment were: RF Power kept at 0.7–1.5 kw (1.2–1.3 kw for axial); plasma gas flow rate (Ar) was maintained at 10.5–15 L/min (radial) 15 (axial); auxiliary gas flow rate (Ar) was kept at 1.5; the viewing height was 5–12 mm; the copy and reading time was set at 1–5 s (max. 60 s) and the copy time was kept at 3 s (max. 100 s).

Total phenolic content

Total phenolic contents of obtained almond extracts were found by using the Folin-Ciocalteu (FC) reagent as applied by Yoo et al. (2004) with some modifications. 1 ml of FC was added and mixed for five minutes. Following the addition of 10 mL of 7.5% Na2CO3 solution tubes were mixed and the final volume was completed to 25 ml with deionised water. At the end of 1 h, total phenol content was determined as 750 nm wavelength in spectrophotometer. The results were given as mg gallic acid equivalent (GAE)/100 g of fresh weight.

Antioxidant activity

The free radical scavenging activity of almond samples was determined using DPPH(1,1-diphenyl-2-picrylhydrazyl) according to Lee et al. (1998). The extract was mixed with 2 mL methanolic solution of DPPH. The mixture was shaken vigorously and allowed to stand at room temperature for 30 min and the absorbance was recorded at 517 nm by using a spectrophotometer. All determinations were performed in triplicate.

Statistical analysis

All the treatments and measurements were replicated three times and the data was subjected to analysis of variance (ANOVA) using the MSTAT C software (Püskülcü and İkiz 1989). The results were presented as mean ± standard deviation and significance was considered at the probability level of 0.05. Principle component analysis was performed using MULTBIPLOT software as described previously (Vicente-Villardon 2010)

Results and discussion

The oil percentage and fatty acid composition of almond kernels collected from thirty-one genotype of naturally growing almond trees in Mersin province, Turkey are given in Table 1. The results showed high variations in oil contents and fatty acid profiles among almond genotype (P < 0.05). The highest oil content was noticed in the kernel of the cultivar T27 (79%) whereas the lowest value was observed in the cultivar T12 (36.7%). With exception of the genotype T1, T2, T3, T4, T5, T11, T12, T14, T16, and T18, the oil content of all other almond cultivars was higher than 50% suggesting that these almond genotypes are rich sources of vegetable oil. The commercial production of oil from Prunus genus is possibly due to its higher oil yields compared to other commercially used oilseeds such as rapeseed and sunflower seeds (Aşkın et al. 2007).The oil contents found in this study are comparable to those reported previously in different almond species (44.4% in A. Scoparia and 51.4% in A. dulcis (Moayedi et al. 2011). In another study, Kırbaşlar et al. (2012) reported that almond kernel contained 55.86% oil. In addition, Sathe et al. (2008) reported that almond kernels collected from 12 different locations contained 52.51–61.92% oil. Moreover, Martins et al. (2000) stated that the oil of 12 kinds of almond in Portugal ranged between 30.01 and 51%. The cultivation of almond genotypes is restricted to areas with hot and dry conditions where almond trees produce the highest yields of high-quality kernels (Rabadan et al. 2018). Rabadan et al. (2018) reported that although significant variability was reported in almond oils as a result of the crop year and the interaction between crop year and genotype. The variability in the content of oil in nuts was lower than for previous components; but, it was higher in almonds than walnuts and pistachios. The genotypes were considered for the nuts as the main source of variability for this parameter (Rabadan et al. 2019). Apparently the variation in oil contents between these studies could be attributed to the differences in almond genotype, growing conditions, and environmental factors. Zhu et al. (2015) stated that the humid depressed almond kernel lipid synthesis regardless of the imposed deficit treatment. In addition, in average season like that 2011/2012, with generally higher lipid content, moderate water deficiency was not detrimental to almond lipid content but severe deficit irrigation was (Zhu et al. 2015).

Table 1.

Oil content and fatty acid composition of different almond kernel and oils (%)

Almonds Oil Palmitic Palmitoleic Stearic Oleic Vaccenic Linoleic Linolenic Arachidic Eicosenoic Total
T1 45.0 ± 1.13*l 6.17 ± 0.11 g 0.27 ± 0.01ı 1.97 ± 0.17e 63.15 ± 0.71i 0.95 ± 0.05 g 27.49 ± 0.37b –*** – – 100.0
T2 43.1 ± 0.98n** 4.97 ± 0.07i 0.26 ± 0.03ı 1.46 ± 0.21ı 72.28 ± 1.16e 1.43 ± 0.11b 17.25 ± 0.61j 1.42 ± 0.11a 0.15 ± 0.03a 0.28 ± 0.09a 99.51
T3 48.6 ± 0.62j 7.51 ± 0.21a 0.39 ± 0.05e 1.56 ± 0.13 h 58.89 ± 1.11 k 1.31 ± 0.09c 29.55 ± 0.43a 0.20 ± 0.03b 0.12 ± 0.01c 0.12 ± 0.05b 99.64
T4 46.3 ± 0.76 k 5.92 ± 0.14f 0.37 ± 0.01f 2.22 ± 0.24c 76.34 ± 0.38a 1.02 ± 0.07f 13.97 ± 0.27n 0.16 ± 0.01c – – 100.00
T5 46.7 ± 1.23 k 5.37 ± 0.09ı 0.38 ± 0.07f 2.41 ± 0.19b 74.51 ± 0.21c 1.06 ± 0.03f 15.76 ± 1.18 l 0.11 ± 0.01e 0.14 ± 0.01b 0.11 ± 0.03c 99.85
T6 55.4 ± 1.17ef 5.57 ± 0.07ı 0.35 ± 0.01ef 1.62 ± 0.09 h 72.72 ± 0.56e 1.14 ± 0.01e 18.05 ± 0.98i 0.14 ± 0.03d 0.10 ± 0.01 0.11 ± 0.07c 99.80
T7 54.4 ± 1.21 g 7.34 ± 0.03c 0.46 ± 0.09d 1.98 ± 0.11e 62.43 ± 0.74j 1.21 ± 0.09e 26.36 ± 1.32c 0.10 ± 0.01e – – 99.89
T8 55.8 ± 1.11ef 6.64 ± 0.15f 0.52 ± 0.11c 1.58 ± 0.17 h 71.62 ± 0.89f 1.41 ± 0.07b 17.64 ± 1.35j 0.10 ± 0.03e 0.08 ± 0.01 g 0.08 ± 0.01f 99.67
T9 53.3 ± 1.09 h 5.49 ± 0.11ı 0.33 ± 0.01 g 1.61 ± 0.07 h 73.48 ± 0.81d 1.12 ± 0.05e 17.33 ± 0.67j 0.10 ± 0.01e 0.11 ± 0.03d 0.10 ± 0.03d 99.68
T10 54.6 ± 2.56 g 6.92 ± 0.07d 0.35 ± 0.03 g 1.63 ± 0.05 h 66.75 ± 0.93 h 1.16 ± 0.11e 22.21 ± 0.86f 0.07 ± 0.01 g 0.10 ± 0.01e 0.10 ± 0.01d 99.29
T11 44.3 ± 1.78 m 6.64 ± 0.21f 0.63 ± 0.13a 2.01 ± 0.27d 70.78 ± 0.67 g 1.35 ± 0.17c 17.85 ± 0.71j 0.10 ± 0.03e 0.11 ± 0.05d 0.09 ± 0.01e 99.56
T12 36.7 ± 0.87ö 7.49 ± 0.18ab 0.46 ± 0.09d 1.85 ± 0.18f 62.88 ± 0.82j 1.20 ± 0.19e 25.60 ± 1.29d 0.08 ± 0.01f 0.09 ± 0.01f 0.07 ± 0.01 g 99.71
T13 55.6 ± 1.61ef 6.52 ± 0.15f 0.30 ± 0.07 g 2.32 ± 0.21b 63.93 ± 0.98i 0.91 ± 0.03 g 25.55 ± 0.89d 0.08 ± 0.01f 0.12 ± 0.03c 0.08 ± 0.01f 99.80
T14 44.5 ± 0.55 m 5.44 ± 0.21ı 0.39 ± 0.03e 1.89 ± 0.11f 75.49 ± 0.54b 1.10 ± 0.07e 14.82 ± 0.75 m – 0.09 ± 0.01f 0.09 ± 0.03e 99.31
T15 57.3 ± 0.61d 6.06 ± 0.16 g 0.34 ± 0.01 g 1.57 ± 0.13 h 72.60 ± 0.39e 1.13 ± 0.13e 18.03 ± 0.68i – 0.10 ± 0.03e 0.10 ± 0.05d 99.92
T16 44.5 ± 0.83 m 5.85 ± 0.09hf 0.33 ± 0.05 g 1.76 ± 0.32 g 65.68 ± 0.43ı 1.12 ± 0.15e 24.77 ± 1.27e 0.14 ± 0.05d 0.10 ± 0.03e 0.10 ± 0.01d 99.85
T17 53.2 ± 0.78 h 5.73 ± 0.07ı 0.35 ± 0.07 g 2.26 ± 0.21c 71.78 ± 0.48f 0.95 ± 0.03 g 18.49 ± 1.13i 0.08 ± 0.03f 0.11 ± 0.07d 0.08 ± 0.01f 99.84
T18 44.4 ± 0.96 m 6.67 ± 0.14e 0.52 ± 0.09c 1.74 ± 0.27 g 69.19 ± 0.51 h 1.28 ± 0.07d 20.33 ± 1.19 h – 0.11 ± 0.01d 0.08 ± 0.03f 99.90
T19 59.7 ± 1.33d 6.58 ± 0.21e 0.50 ± 0.05c 1.89 ± 0.18f 69.01 ± 0.37 h 1.28 ± 0.03d 20.42 ± 1.32 h 0.06 ± 0.01 g 0.09 ± 0.03f 0.08 ± 0.03f 99.91
T20 63.5 ± 1.27c 6.21 ± 0.17 g 0.52 ± 0.03c 2.09 ± 0.21d 67.42 ± 0.73 g 1.27 ± 0.05d 22.23 ± 1.56f – 0.10 ± 0.05e 0.08 ± 0.03f 99.92
T21 56.1 ± 1.16e 5.37 ± 0.13ı 0.41 ± 0.07d 2.08 ± 0.13d 74.14 ± 0.69c 1.06 ± 0.01f 16.65 ± 1.63 k – 0.11 ± 0.01d 0.09 ± 0.01e 99.91
T22 59.6 ± 1.18d 6.90 ± 0.19d 0.52 ± 0.13c 2.02 ± 0.17d 70.11 ± 0.81 g 1.29 ± 0.07d 18.86 ± 0.58i – 0.12 ± 0.03c 0.08 ± 0.03f 99.90
T23 52.1 ± 1.56ı 5.31 ± 0.22ı 0.29 ± 0.03 h 1.80 ± 0.19f 74.23 ± 0.48c 0.97 ± 0.03d 17.13 ± 0.27j – 0.09 ± 0.01f 0.09 ± 0.01e 99.91
T24 50.2 ± 0.77i 7.37 ± 0.05c 0.63 ± 0.11a 1.09 ± 0.07i 68.07 ± 0.54f 1.57 ± 0.09a 20.90 ± 0.38 h 0.08 ± 0.01f 0.11 ± 0.03d 0.09 ± 0.03e 99.90
T25 52.6 ± 0.68ı 7.12 ± 0.03 cd 0.55 ± 0.03b 2.72 ± 0.05a 62.83 ± 0.72j 1.19 ± 0.03d 25.41 ± 0.46d – 0.11 ± 0.01d – 99.92
T26 56.7 ± 0.94e 5.91 ± 0.17 h 0.31 ± 0.05 g 2.25 ± 0.03c 69.29 ± 0.84 h 0.93 ± 0.07 g 21.30 ± 0.75 g – – – 100.00
T27 79.0 ± 2.71a 6.91 ± 0.32d 0.48 ± 0.01d 1.99 ± 0.11e 69.74 ± 0.43 h 1.24 ± 0.05d 19.53 ± 0.36ı – 0.11 ± 0.03d – 100.00
T28 54.8 ± 1.32 g 6.93 ± 0.18d 0.60 ± 0.13ab 1.70 ± 0.09 g 63.78 ± 0.48i 1.41 ± 0.06b 25.34 ± 1.43d – 0.07 ± 0.01 h 0.07 ± 0.01 g 99.91
T29 53.8 ± 1.19 h 7.01 ± 0.34 cd 0.46 ± 0.03d 2.50 ± 0.21b 64.58 ± 0.51i 1.09 ± 0.03f 24.07 ± 1.38e – 0.13 ± 0.05c 0.08 ± 0.01f 99.92
T30 67.4 ± 2.58b 5.97 ± 0.13 h 0.42 ± 0.03d 1.78 ± 0.27 g 71.25 ± 0.67f 1.21 ± 0.07d 19.01 ± 0.85ı 0.05 ± 0.01 h 0.11 ± 0.01d 0.10 ± 0.03d 99.91
T31 57.6 ± 1.53d 5.85 ± 0.09hf 0.37 ± 0.01 g 1.66 ± 0.18 h 73.36 ± 0.86d 1.13 ± 0.09e 17.25 ± 0.77j 0.08 ± 0.01f 0.11 ± 0.03d 0.10 ± 0.01d 99.91
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*Standard deviation; **values within each column followed by different letters are significantly different at p < 0.05; ***nonidentified

The fatty acids profiles also differed significantly (p < 0.05) among the almond genotype. The major fatty acid in almond genotypes was oleic (62.43% in T8 to 76.34% in T4), followed by linoleic (13.97% in T4 to 29.55% in T3), and palmitic (4.97% in T2 to 7.51 in T3), whereas the lowest proportion was found for arachidic acid (0.07% in T28 to 0.15% in T2). The palmitic, palmitoleic, stearic, oleic, vaccenic, and linoleic acids were observed in all almond cultivars with different quantities, whereas, linolenic, arachidic and eicosenoic acids were not detected in some genotypes. These findings suggested that the fatty acid composition of almond oil depends mainly on the genotype as all these genotypes were collected from same location. Previous studies indicated that fatty acid composition of almond differed among genotype and growing environments. It was observed statistically significant differences among fatty acid compositions of almond kernel oils (p < 0.05). Kırbaşlar et al. (2012) studied the fatty acid compositions of the almond oil and found palmitic (0.39%), palmitoleic (0.56%), stearic (1.20%), oleic (71.98%), linoleic (20.37%) acids as the main fatty acids in almond oil. In addition, Sathe et al. (2008) reported that oleic acid content of eight almond genotype varied between 57.54% and 73.94%. The oleic acid content in almond oils in the current study was in agreement with those reported previously by Maguire et al. (2004) and Mehran and Filsoof (1974) for different types of commercially available almonds. Piscopo et al. (2010) reported the presence of higher oleic and lower linoleic acid in an almond variety in the month of August. The oleic acid content of some of the of almond species have been reported to be in between 66.7 and 69.7%, and the linoleic acid content has been detected in the range of 18.2–23.0% (Moayedi et al. 2011). Karatay et al. (2014) reported 74.46% oleic, 0.70% palmitoleic, 17.89% linoleic, 5.34% palmitic, 0.85% stearic and 0.75% linolenic acid as an average of a total of 32 different almond varieties. The presence of oleic (72.5–79.9%), linoleic (13.5–19.8%) and palmitic (5.9–6.7%) acids have been reported in different cultivars of almonds (Özcan et al. 2011). In another report about different cultivars of almond oils, oleic contents ranged between 50.41 and 81.20%, linoleic between 6.21 and 37.13%, palmitic between 5.46 and 15.78%, stearic 0.80 and 3.83% and palmitoleic between 0.36 and 2.52% (Aşkın et al. (2007). The oleic acid contents have been reported to be 60.9%, 62.9% and 61.0% in different studies carried out with domestically used almonds. Still higher oleic acid contents have been reported by Nanos et al. (2002) (72–80%) and Kodad et al. (2008) (69–78%) for domestically used kernels. Karatay et al. (2014) reported that average palmitic, palmitoleic, stearic, oleic, linoleic and linolenic acid amounts of 32 almond oils were found 5.34%, 0.70%, 0.85%, 74.46%, 17.89% and 0.75%, respectively. Rabadán et al. (2017) determined 5.87–7.64% palmitic, 0.54–0.86% palmitoleic, 1.97–3.21% stearic, 48.19–56.88% oil, 65.37–72.99% oleic, 16.90–23.54% linoleic acids in almond kernels. Zhu et al. (2015) determined 48.99–54.55% and 50.64–57.32% oil, 6.76–7.04% and 6.80–7.60% palmitic, 61.85–62.80% and 57.13–64.30% oleic and 25.32–26.09% and 24.03–30.23% linoleic acids in the oils of almonds collected in 2010/2011 and 2011/2012 harvest seasons, respectively. The almond oil fatty acid compositions do not vary widely such as for the results about A. scorparia almond oils as reported by Farhoosh and Tavakoli (2008). Different type of reports about oils obtained from almond kernels pointed out that the oleic and linoleic acids are the predominant fatty acids in almond oils. There is a wide variation in fatty acid composition of oils obtained from different almond seeds and the presence of some characteristic fatty acids can help in differentiating different plant species and their respective families (Aitzetmuller 1993). There are various factors that can affect the fatty acid composition of oils obtained from different almond seeds and these factors include species, variety, cultivation and climatic conditions, and the harvesting time and conditions (Kritsakis and Markakis 1984). Rabadán et al. (2017) reported that almond oil yield was similar for all the selected 10 cultivars, and significant differences were observed in fatty acid profile, including essential fatty acids of main nutritional interest. Linoleic acid contents illustrate high variability (13.97–29.55%), becoming a parameter of main nutritional interest as it is the main essential fatty acid found in almond oil. On the other hand, stearic and palmitic acids are the most common saturated fatty acids in almond oil, with percentages in our samples below 2.72 and 7.11%, respectively. Rabadán et al. (2017) reported that the nutritional value of almond oil is highly influenced by the high presence of unsaturated fatty acids and although all cultivars show a health fatty acid profile. Nanos et al. (2002) reported that oleic acid levels were higher in irrigated than non-irrigated almonds (Ferragnes and Texas cv).

The results in Table 2 show the tocopherol contents in 31 almond genotypes. The results showed significant variations in tocopherol contents and composition among almond genotype. The total tocopherols content was ranged between 47.42 mg/100 g in T14 and 80.15 mg/100 g in T16. Among all detected tocopherols, α-tocopherol was the highest (44.25 mg/100 g in T5 to 75.56 mg/100 g in T13), followed by γ-tocopherol (0.63 mg/100 g in T10 to 7.51 mg/100 g in T20). With few exceptions, most of the almond kernel oils were found to have more than 50.0% of the α-tocopherol contents. α-Tocotrienol contents of almond oils varied between 0.44 mg/100 g (T22) and 1.35 mg/100 g (T 28). β-tocopherol contents of almond oils were varied between 0.48 mg/100 g (T31) and 1.73 mg/100 g (T26). γ-Tocotrienol contents (0.23 and 0.46 mg/100 g) were found in only T17 and T27 almond oil, while δ-tocopherol (0.24 mg/100 g) was found only in T27 almond oil. It was observed statistically significant differences were observed among tocopherol contents of almond kernel oils (p < 0.05). Several researchers have also reported similar ranges of tocopherols in almond oils from different locations (Sathe et al. 2008; Moayedi et al. 2011; Gupta et al. 2012). The concentration of α-tocopherols was reported between 187 and 490 g/kg of almond oil (Kodad 2017). The range of variability for the different tocopherol homologues is of 335–657 mg/kg of almond oil for α-, 2–50 for γ-, and 0.1–22 for β-tocopherol (Kodad et al. 2018). Almond oil contained 97.3 mg/kg α-tocopherol and 2.8 mg/kg γ-tocopherol as reported by Fernandes et al. (2017). In another study by Lopez Ortiz et al. (2006), the α, γ and γ-tocopherol have been detected in the ranges of 23.5–44.9, 2.90–6.15 and 1.27–8.06 mg/100 g, respectively. Kornsteiner et al. (2006) reported that almond oil had 24.2 mg/100 g α-tocopherol content. According to Kodad et al. (2006), concentration of α-tocopherol in almond oil varied between 187 and 490 mg/kg of oil. The higher content of α- and γ-tocopherol contents in the almond oil could likely enhanced the oil resistance to oxidation because tocopherols can helps to protect the peroxidation of polyunsaturated fatty acids (Beringer and Dompert 1976; Kamal-Eldin and Andersson 1977). The oil products having higher amount of fatty acids and tocopherols are considered good from the health point of view (Oomah et al. 2000). Kodad et al. (2008) reported that environmental factors like temperature have significant effects on the concentration of tocopherols in almond. It is thought that higher concentration of tocopherols in almond oil helps its long term storage with no adverse effects on the quality of oil (Filsoof et al. 1976; Garcia-Pascual et al. 2003). One of the parameters greatly affected by genotype, crop year and the interaction of both was the energy value of nuts (Rabadan et al. 2019).

Table 2.

Tocopherol contents of different almond type kernel oils (mg/100 g)

Almonds α-tocopherol α-tocotrienol β-tocopherol γ-tocopherol β-tocotrienol P8 γ-tocotrienol δ-tocopherol Total
T1 56.94 ± 0.67*i 0.52 ± 0.09ı 0.74 ± 0.03 h 3.33 ± 0.37c 0.61 ± 0.03 g – – – 62.15
T2 49.79 ± 0.81l** 0.65 ± 0.05g 0.82 ± 0.09g 1.08 ± 0.19f 2.94 ± 0.11a – – – 55.28
T3 62.54 ± 0.47fg 1.10 ± 0.13d 0.87 ± 0.01g 5.00 ± 0.21b 2.68 ± 0.18b 1.27 ± 0.13a – – 73.46
T4 47.18 ± 0.24m 0.75 ± 0.09g 0.90 ± 0.13f 1.37 ± 0.15ef 0.15 ± 0.03i 0.38 ± 0.05 h – – 50.74
T5 44.25 ± 0.32n 1.01 ± 0.07d 1.12 ± 0.09e 1.07 ± 0.09f 0.32 ± 0.07ı 0.50 ± 0.09f – – 48.26
T6 44.95 ± 0.51n 0.45 ± 0.01i 0.80 ± 0.07 g 0.96 ± 0.13 g 0.58 ± 0.09 h – – – 47.74
T7 59.93 ± 0.63h 0.66 ± 0.03g 1.27 ± 0.03cd 2.48 ± 0.32d 2.28 ± 0.17c – – – 66.61
T8 48.94 ± 0.88lm 0.83 ± 0.11f 1.26 ± 0.09 cd 1.21 ± 0.19ef 1.51 ± 0.21e 0.31 ± 0.03ı – – 54.06
T9 50.68 ± 0.76kl 0.53 ± 0.07 h 0.91 ± 0.07f 2.09 ± 0.27de 1.82 ± 0.23d – – – 56.03
T10 51.11 ± 0.62k 0.69 ± 0.03g 1.01 ± 0.03e 0.63 ± 0.03h 1.12 ± 0.18f – – – 54.56
T11 60.58 ± 0.54g 0.72 ± 0.09g 1.33 ± 0.17c 2.49 ± 0.11d –*** – – – 65.12
T12 68.63 ± 0.29e 0.90 ± 0.12e 1.23 ± 0.19cd 2.55 ± 0.33d – – – – 73.32
T13 75.56 ± 0.31a 0.68 ± 0.11g 1.10 ± 0.03e 2.31 ± 0.28d – 0.28 ± 0.01j – – 79.92
T14 44.72 ± 0.47n 0.83 ± 0.17f 0.84 ± 0.15g 0.67 ± 0.09 h – 0.36 ± 0.03h – – 47.42
T15 69.84 ± 0.98dg 0.80 ± 0.15f 1.02 ± 0.09e 3.02 ± 0.42c – – – – 74.67
T16 74.38 ± 0.77b 1.15 ± 0.09c 1.62 ± 0.21b 2.31 ± 0.19d – 0.68 ± 0.05d – – 80.15
T17 60.19 ± 0.69g 0.88 ± 0.13f 1.20 ± 0.18 cd 1.36 ± 0.21ef – 0.27 ± 0.09k 0.23 ± 0.07b – 64.13
T18 58.61 ± 0.81ıı 0.58 ± 0.07 h 1.28 ± 0.13cd 1.62 ± 0.27e – – – – 62.09
T19 54.64 ± 0.95j 0.95 ± 0.19e 0.52 ± 0.09ı 1.07 ± 0.09f – – – – 57.19
T20 56.34 ± 0.47i 1.16 ± 0.07c 1.23 ± 0.07cd 7.51 ± 0.39a – 0.28 ± 0.03j – – 66.81
T21 54.19 ± 0.27j 0.64 ± 0.03 g 1.20 ± 0.03cd 1.79 ± 0.25e – 0.22 ± 0.07l – – 58.05
T22 53.24 ± 0.13jk 0.44 ± 0.03i 1.50 ± 0.11b 2.23 ± 0.17d – – – – 57.40
T23 61.34 ± 0.38g 0.76 ± 0.09 g 1.37 ± 0.09c 1.00 ± 0.09f – 0.81 ± 0.09b – – 65.28
T24 57.08 ± 0.17i 0.47 ± 0.01i 0.96 ± 0.03f 2.78 ± 0.18d – 0.73 ± 0.07c – – 62.01
T25 63.55 ± 0.21f 0.67 ± 0.03 g 0.64 ± 0.15ı 5.23 ± 0.46b – 0.26 ± 0.03f – – 70.34
T26 70.69 ± 0.28c 0.94 ± 0.15e 1.73 ± 0.27a 2.17 ± 0.38d – 0.50 ± 0.03f – – 76.03
T27 69.30 ± 0.43d 1.18 ± 0.13b 1.20 ± 0.18cd 3.15 ± 0.23c – 0.45 ± 0.01g 0.46 ± 0.03a 0.24 ± 0.03 75.97
T28 64.92 ± 0.86f 1.35 ± 0.17a 0.59 ± 0.07ı 5.14 ± 0.38b – 0.62 ± 0.09e – – 72.62
T29 62.24 ± 0.84fg 0.70 ± 0.09 g 0.79 ± 0.11h 0.83 ± 0.03g – 0.60 ± 0.07e – – 65.16
T30 45.62 ± 0.57mn 0.54 ± 0.03 h 0.68 ± 0.09ı 1.55 ± 0.11e – 0.31 ± 0.01i – – 48.70
T31 45.59 ± 0.65mn 0.58 ± 0.07 h 0.48 ± 0.03i 1.11 ± 0.07f – 0.50 ± 0.09f – – 48.26
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*Standard deviation; **values within each column followed by different letters are significantly different at p < 0.05; ***nonidentified

Mineral contents of 31 almond samples collected from Mersin province, Turkey are presented in Table 3. Significant variations in mineral contents and composition were observed among several almond genotype suggesting the influence of genetic makeup on the mineral composition of almond kernels. Noticeably, there are big variations in the macro and trace mineral content in almond genotypes. Among macro minerals, potassium (5238 mg/kg in T6–14,683 mg/kg in T27) represent the highest followed by phosphorous (3475 mg/kg in T31–11,123 mg/kg in T27), calcium (1798 mg/kg in T24–5946 mg/kg in T27) and magnesium (2192 mg/kg in T22–3591 mg/kg in T27), whereas sodium showed the lowest content (334 mg/kg in T18–786 mg/kg in T27). Among the trace minerals, zinc (32.9 mg/kg in T6–87.4 mg/kg in T27) was the major mineral in almond kernel, followed by iron (34.7 mg/kg in T5–83.5 mg/kg in T31), aluminum (7.0 mg/kg in T30–28.0 mg/kg in T11), copper (6.6 mg/kg in T31–26.6 mg/kg in T27), and manganese (6.2 mg/kg in T15–24.7 mg/kg in T27), while, chromium (0.19 mg/kg in T23–0.58 mg/kg in T27) was found as the least trace mineral in almond kernel. Interestingly, with view exceptions, the cultivar T27 outscores all other genotypes in quantity of most minerals indicating that the kernel of this cultivar is of great importance from nutritional stand point. It was observed statistically significant differences were observed among mineral contents of almond kernels (p < 0.05). Özcan et al. (2011) reported that some almond kernels contained 2.98-4.04 mg/g Mg, 0.29-0.38 mg/g Na, 7.93–9.38 mg/gP, 13.14–15.10 mg/g K, 1.83–2.94 mg/g Ca, 0.20–0.27 mg/g Fe and 0.04–0.06 mg/g Zn. In a previous study, almond kernels contained 1546–1685 mg/100 g K, 253–259 mg/100 g P, 640–678 mg/100 g Ca, 447–496 mg/100 g Mg, 24.30–25.80 mg/100 g Cu, 76.33–80.50 mg/100 g Zn, 54.83–65.33 mg/100 g Fe and 37.67–37.83 mg/100 g Mn (Barbara et al. 1994). Aslantas et al. (2001) reported values of 98.5-187.00 mg/100 g Ca, 360.8-513.4 mg/100 g Mg, 403.9-800 mg/100 g P, 1677.3-2051.1 mg/100 g K, 39.77-146.35 mg/100gFe, 77.86-88.44 mg/100 g Zn, 29.0-33.95 mg/100gMn, 16.0-23.0 mg/100 g Cu and 56.66-103.88 mg/100 g Na in selected almond cultivars naturally grown in Kemaliye district of Erzincan in Turkey. Schirra et al. (1994) determined 1050 mg/100 g K, 300 mg/100 g P, 467 mg/100 g Ca, 30 mg/100 g Mg, 5 ppm Cu 34 ppm Zn and 70 ppm Fe in Texas almonds during fruit growth and ripening. Significant differences were observed in the mineral composition of almonds by several researchers (Saura Calixto et al. 1981; Özcan et al. 2011). The difference in mineral contents and composition between the almond fruits may be due to the kind and genetic structure of the fruit, variety, genetic factors, ecological conditions and different ripening stages. In addition, harvesting time is generally affects the chemical contents of almond kernel. The current investigations showed that the almond kernels were found to be rich in most of the essential elements. The mineral elements present in the dry nuts have a pivotal role in human nutrition. The high levels of macro (Ca, K, P, Mg, and Na) and micro (Zn, Fe, Cu, and Mn) elements demonstrated that almond kernels in the current study could serve as excellent sources of these essential minerals in the human diet.

Table 3.

Mineral contents of different almond type kernels (mg/kg)

Almonds Al Ca B Cr Cu Fe K
T1 8.6 ± 0.3*k 2485 ± 261 13.0 ± 0.2h 0.34 ± 0.02f 13.0 ± 1.3f 41.0 ± 1.2 m 7798 ± 169de
T2 12.7 ± 0.1g** 2292 ± 140 13.9 ± 1.1h 0.34 ± 0.05f 13.2 ± 1.1f 39.7 ± 1.6ö 7574 ± 74ef
T3 12.5 ± 0.0g 3940 ± 29 14.6 ± 0.5g 0.33 ± 0.01f 11.0 ± 0.0h 45.7 ± 0.3j 7692 ± 52e
T4 10.9 ± 0.9i 2216 ± 134 19.1 ± 0.3c 0.39 ± 0.02f 11.2 ± 1.1h 39.3 ± 2.8ö 7402 ± 5f
T5 9.3 ± 0.9j 3286 ± 150 17.1 ± 1.1d 0.29 ± 0.01g 13.0 ± 0.6f 34.7 ± 2.2 s 9324 ± 57b
T6 8.4 ± 1.0k 2866 ± 186 12.4 ± 0.9ı 0.36 ± 0.02f 12.2 ± 1.4g 40.3 ± 3.7n 5238 ± 132 m
T7 8.8 ± 0.3k 2585 ± 175 11.8 ± 0.0i 0.47 ± 0.08c 14.8 ± 0.8e 41.5 ± 1.8 m 7082 ± 43g
T8 8.8 ± 0.7k 2148 ± 122 14.4 ± 0.3g 0.32 ± 0.04f 14.4 ± 0.6e 37.4 ± 0.9p 6777 ± 81g
T9 14.4 ± 0.4e 2637 ± 22 16.9 ± 0.1e 0.49 ± 0.11c 17.0 ± 0.0b 46.4 ± 1.4i 6200 ± 1i
T10 16.7 ± 0.0c 2612 ± 150 11.1 ± 0.4i 0.51 ± 0.08b 16.7 ± 0.1c 64.8 ± 5.6d 6336 ± 42ı
T11 28.0 ± 1.6a 3092 ± 80 15.1 ± 1.0f 0.46 ± 0.05d 13.9 ± 0.5f 42.7 ± 2.3l 7124 ± 347 fg
T12 13.1 ± 0.8f 2695 ± 236 20.3 ± 1.2b 0.41 ± 0.07e 11.8 ± 0.8h 44.2 ± 1.7k 5704 ± 350l
T13 13.2 ± 0.7f 3307 ± 191 21.9 ± 0.9a 0.41 ± 0.04e 11.6 ± 0.7h 39.0 ± 1.5ö 6743 ± 307g
T14 9.3 ± 0.7j 4252 ± 95 16.1 ± 0.8e 0.37 ± 0.01f 9.8 ± 0.4j 39.2 ± 0.4ö 7987 ± 282 cd
T15 12.4 ± 0.2g 2021 ± 36 10.6 ± 0.4j 0.34 ± 0.02f 14.0 ± 0.2e 45.6 ± 1.2j 7167 ± 130 fg
T16 12.0 ± 1.2g 3118 ± 206 6.8 ± 0.1l 0.27 ± 0.02g 12.9 ± 0.4g 42.1 ± 1.2l 6763 ± 74g
T17 14.2 ± 1.0e 3490 ± 38 16.6 ± 0.1e 0.40 ± 0.0e7 15.1 ± 0.3d 48.1 ± 3.0g 7613 ± 303e
T18 8.0 ± 1.1k 3770 ± 120 12.8 ± 0.7ı 0.21 ± 0.02ı 10.4 ± 0.3i 52.8 ± 5.3f 8072 ± 194d
T19 12.6 ± 0.2g 3739 ± 200 14.4 ± 0.7g 0.45 ± 0.04c 12.5 ± 1.1g 47.2 ± 1.1h 7929 ± 404 cd
T20 8.9 ± 0.1k 2590 ± 3 11.0 ± 1.2i 0.41 ± 0.02e 15.2 ± 0.1d 42.8 ± 1.8l 6404 ± 91h
T21 15.1 ± 0.5d 2946 ± 53 12.9 ± 0.0ı 0.43 ± 0.04c 9.4 ± 0.1j 56.9 ± 2.0e 6691 ± 104gh
T22 12.8 ± 1.1g 2037 ± 144 4.6 ± 0.1n 0.41 ± 0.01e 10.5 ± 0.5i 36.9 ± 4.0r 7536 ± 34ef
T23 12.8 ± 0.2g 2754 ± 37 6.1 ± 0.5l 0.19 ± 0.01h 13.7 ± 0.1f 95.0 ± 1.2a 6083 ± 71k
T24 10.7 ± 0.3i 1798 ± 133 12.4 ± 1.0ı 0.32 ± 0.03f 15.9 ± 0.9d 40.8 ± 0.1n 6243 ± 14j
T25 17.8 ± 4.0b 2504 ± 128 5.7 ± 0.7 m 0.41 ± 0.07e 13.7 ± 0.2f 47.4 ± 2.3h 9154 ± 130b
T26 17.3 ± 5.6b 3493 ± 229 4.6 ± 0.6n 0.40 ± 0.04e 13.2 ± 0.1 47.9 ± 1.8h 6744 ± 622g
T27 15.7 ± 0.1d 5946 ± 21 15.0 ± 0.3f 0.58 ± 0.02a 26.6 ± 0.2a 70.9 ± 0.2c 14,683 ± 69a
T28 8.3 ± 1.0k 2538 ± 33 10.2 ± 0.8 0.31 ± 0.04f 17.5 ± 1.6b 37.8 ± 4.1p 7626 ± 487e
T29 11.6 ± 0.4h 1906 ± 93 8.8 ± 0.5j 0.38 ± 0.02f 9.2 ± 0.8j 44.0 ± 4.4k 7539 ± 425ef
T30 7.0 ± 0.6l 1970 ± 62 7.8 ± 0.4k 0.27 ± 0.03g 8.6 ± 0.0k 37.4 ± 2.8p 6254 ± 327j
T31 9.3 ± 0.1j 2040 ± 17 7.0 ± 0.6k 0.45 ± 0.04c 6.6 ± 0.2l 83.5 ± 4.1b 8494 ± 562c
Almonds Mg Mn Na P S Zn
T1 2514 ± 40 11.4 ± 0.2f 563 ± 7d 4507 ± 42l 1232 ± 23d 51.1 ± 0.9b
T2 2502 ± 29b 15.4 ± 1.0b 632 ± 41c 5621 ± 465c 1338 ± 32c 47.6 ± 0.8d
T3 2631 ± 15b 14.9 ± 0.2c 710 ± 5b 5848 ± 77b 1332 ± 1c 48.3 ± 0.1 cd
T4 2572 ± 33b 15.9 ± 0.1b 530 ± 40d 5185 ± 30h 1378 ± 11c 39.3 ± 2.1j
T5 2442 ± 8c 15.3 ± 0.1b 527 ± 17d 5163 ± 437h 1345 ± 11c 37.1 ± 1.2k
T6 2338 ± 68d 8.0 ± 0.5i 555 ± 53d 4458 ± 170 m 975 ± 27g 32.9 ± 2.9n
T7 2395 ± 59d 6.9 ± 0.3k 630 ± 42c 5506 ± 101d 871 ± 6j 36.6 ± 0.1lm
T8 2473 ± 34c 9.7 ± 0.2h 489 ± 47e 5975 ± 109a 908 ± 21i 37.8 ± 1.9k
T9 2424 ± 10c 7.0 ± 0.1j 527 ± 5d 5118 ± 20h 1210 ± 19 39.5 ± 0.2j
T10 2384 ± 3d 10.1 ± 0.3g 540 ± 23d 4596 ± 229l 1256 ± 46d 37.7 ± 0.1k
T11 2279 ± 81e 10.5 ± 0.2g 556 ± 52d 5517 ± 464d 1113 ± 79e 38.0 ± 1.4jk
T12 2546 ± 91b 9.0 ± 0.0h 535 ± 29d 5098 ± 357i 1221 ± 52d 42.1 ± 1.7g
T13 2462 ± 70c 10.9 ± 0.5g 539 ± 22d 5968 ± 179a 1178 ± 60e 38.0 ± 1.9l
T14 2234 ± 61e 12.3 ± 0.0e 525 ± 5d 5981 ± 191a 1469 ± 48b 46.5 ± 0.2e
T15 2510 ± 34b 6.2 ± 0.1k 484 ± 9f 5103 ± 139h 936 ± 17h 35.1 ± 0.4lm
T16 2293 ± 9e 11.9 ± 1.4f 678 ± 14c 4642 ± 16k 1114 ± 0e 42.2 ± 2.5g
T17 2356 ± 33d 8.8 ± 1.2i 709 ± 14b 5824 ± 318b 1531 ± 12ab 48.2 ± 2.0 cd
T18 2383 ± 52d 12.7 ± 0.4e 334 ± 10f 5213 ± 185g 1046 ± 36f 42.0 ± 0.7g
T19 2319 ± 46d 15.0 ± 0.2b 572 ± 17d 5101 ± 431h 1060 ± 40f 41.5 ± 0.1h
T20 2435 ± 56c 6.5 ± 0.5k 527 ± 41d 5353 ± 79f 1066 ± 23f 42.3 ± 0.4g
T21 2564 ± 39b 13.8 ± 0.3d 562 ± 9d 5843 ± 129b 1137 ± 11e 47.9 ± 0.6d
T22 2192 ± 9f 6.5 ± 0.4k 542 ± 14d 5894 ± 11b 1152 ± 0e 39.1 ± 4.8j
T23 2508 ± 34b 10.7 ± 0.2g 349 ± 4f 4755 ± 105j 1346 ± 28c 40.7 ± 0.4i
T24 2474 ± 22c 12.9 ± 0.8e 522 ± 42d 5511 ± 116d 1562 ± 24a 42.0 ± 0.2g
T25 2437 ± 11c 15.7 ± 1.9b 520 ± 20d 5483 ± 39e 1238 ± 39d 49.5 ± 0.9c
T26 2324 ± 36d 10.2 ± 1.0g 643 ± 17c 5397 ± 420f 1274 ± 80d 40.3 ± 2.9i
T27 3591 ± 29a 24.7 ± 0.0a 786 ± 5a 11,123 ± 127 2594 ± 23a 87.4 ± 0.4a
T28 2332 ± 74d 12.6 ± 1.9e 532 ± 12d 5357 ± 145f 1423 ± 18b 47.2 ± 3.7d
T29 2448 ± 65c 10.6 ± 0.7g 526 ± 11d 5910 ± 463a 1441 ± 23b 47.2 ± 4.5d
T30 2440 ± 17c 8.6 ± 0.6i 561 ± 37d 5419 ± 244e 1265 ± 22d 43.3 ± 3.6f
T31 2585 ± 80b 12.1 ± 1.3e 636 ± 92c 3475 ± 314n 1275 ± 40d 41.2 ± 0.9h
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*Standard deviation; **values within each column followed by different letters are significantly different at p < 0.05

Total phenol and antioxidant activity values of almond kernels collected from naturally growing almond trees in Mersin province are given in Table 4. Significant differences among total phenol and antioxidant activity values were observed among almond kernels (P < 0.05). The total phenol and antioxidant activity values of almond kernels different depending on almond genotype. The highest value of total phenolic was found in T16 (98.67 mg GAE/100 g), whereas the lowest value was observed in T24 (23.75 mg GAE/100 g). The antioxidant activity of almond cultivars ranged from 44.59% (T12) to 91.18 (T23). Statistically significant differences were observed between total phenolic contents and antioxidant activity values of almond kernel (p < 0.05). In previous study, Yıldız et al. (2014) reported that total phenolic contents of almond kernels changed between 45.58 (cv. Primorski) and 93.64 mg GAE/g (cv. Garrigues), respectively. Esfahlan and Jamei (2012) reported total phenolic content of 10 wild almond species kernel extracts between 184 mg GAE/g (A. urumiensis) and 482 mg GAE per g extract for (A. pabotti). T23 genotype in general showed the highest antioxidant activity values in all almonds. In other study, almond extract scavenged 89.50% of the ABTS radical, 66.77% of the hydroxyl radical, and 87.30% of the DPPH radical (Keser et al. 2014). Ten different almond kernels were collected from Spanish almond varieties in the same plot to remove the environmental and agricultural management effects on almond chemical traits (Rabadán et al. 2017). A wide differences of antioxidant activity of almond kernel types were found.

Table 4.

Total phenol and antioxidant activity values of almond kernels

Almonds Total phenol mgGAE/100 g) Antioxidant activity (%) Almonds Total phenol mgGAE/100 g) Antioxidant activity (%)
T1 54.18 ± 1.17*hı 49.15 ± 0.87no T17 37.93 ± 0.53n 79.83 ± 3.56g
T2 38.29 ± 2.37m** 64.82 ± 3.28jk T18 51.28 ± 1.32i 81.29 ± 2.87f
T3 41.57 ± 1.76kl 59.33 ± 1.76k T19 57.61 ± 1.17ı 83.47 ± 1.61de
T4 64.98 ± 2.51f 47.19 ± 2.13o T20 49.63 ± 0.76j 85.46 ± 1.19c
T5 44.71 ± 3.64jk 51.28 ± 1.18n T21 59.38 ± 0.33fg 78.32 ± 2.65g
T6 39.11 ± 0.89m 73.42 ± 1.78ı T22 47.19 ± 0.45j 65.38 ± 1.43j
T7 56.83 ± 0.63h 65.37 ± 2.65j T23 28.34 ± 0.51p 91.18 ± 3.76a
T8 71.19 ± 1.34d 54.28 ± 2.88 lm T24 23.75 ± 1.15r 87.35 ± 2.98b
T9 47.61 ± 1.71j 76.29 ± 1.89gh T25 42.89 ± 1.13k 48.53 ± 1.17ö
T10 67.82 ± 1.57e 82.38 ± 1.63e T26 37.21 ± 2.38n 55.38 ± 0.98lm
T11 88.49 ± 3.87b 67.17 ± 2.54i T27 56.81 ± 1.68h 49.21 ± 0.86no
T12 65.51 ± 1.64f 44.59 ± 1.35p T28 74.17 ± 3.27c 56.71 ± 1.67lm
T13 43.26 ± 1.29k 71.37 ± 1.08ı T29 43.82 ± 1.56k 66.98 ± 2.31i
T14 53.28 ± 0.81ıi 46.83 ± 2.27o T30 59.48 ± 1.87g 75.25 ± 3.48h
T15 41.19 ± 0.45kl 71.87 ± 3.18ı T31 34.63 ± 0.98ö 59.77 ± 1.83k
T16 98.67 ± 1.09a 65.23 ± 3.76j
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*Standard deviation; **values within each column followed by different letters are significantly different at p < 0.05

Principle component analysis results clearly indicated the interrelationship between the genotype and their influence on the biochemical composition of almond kernel and oils (Fig. 1). In the HJ-biplot, the short distance between the genotypes indicated their similarity based on the biochemical composition, while long distance indicated dissimilarity. In this sense, the genotype were group into three groups, in which, T27 formed separate group and other genotype formed two groups with some interaction between them. Regarding the traits, the cosine of the angle between the vectors specifies correlations, where, acute angle indicate positive correlation, obtuse and strait angles shows negative correlations, and right angle show no correlations (Yan and Fregeau-Reid, 2008). In this regard, strong positive correlations were observed among minerals, tocopherols, and fatty acids. The first group (upper left, circle symbol) composed of the cultivar T27 which is characterized by high levels of minerals (mainly Mn, S, Mg, K, Ca, Zn, P, Na, Cu, Cr, and Al), oil, γ-tocotrienol, δ-tocopherol, P8, and α-tocotrienol. The second group (upper right, squire symbols) is consisted of the cultivars T2, T4, T5, T6, T8, T9, T10, T14, T15, T17, T18, T19, T21, T22, T23, T30 and T31. This group is characterized by high levels of antioxidant, Fe, oleic, linolenic, arachidic, eicosenoic, and β-tocotrienol. Within this group, the cultivars T2 and T6 contributed more to these parameters than other cultivars. The third group (lower of the graph, tringle symbol) consisted of the cultivars T1, T3, T7, T11, T12, T13, T16, T20, T24, T25, T26, T28, and T29. This group is characterized by great contents of total polyphenols (TPC), tocopherols (α-, β-, and γ- tocopherols), stearic, palmitic, linoleic, palmitoleic, and vaccenic acids. Among this group, the cultivars T3, T7, T12, T25, and T28 contributed more to these biochemical properties than other cultivars. Overall, PCA suggested that the genotypes T2, T3, T6, T7, T12, T25, T27 and T28 contains considerable amounts of nutritional compounds and they could thus be recommended for human consumption. Within these cultivars, T27 has a higher nutritional quality than the other genotypes.

Fig. 1.

Fig. 1

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The HJ-biplot based on principal component analysis for biochemical properties of 31 almond genotypes collected from Mersin district of Turkey

Conclusion

In the present study, the biochemical composition and antioxidant activity of 31 almond genotypes wildly grown in Turkey was investigated. The results of the present study indicate that the almond kernels constitute a viable source of certain health-beneficial phytochemical compounds. The results showed wide variations in oil contents, fatty acid composition, tocopherols, minerals, phenolics and antioxidant activity among the kernels and oils of almond genotype. Obtained results from analyzing fatty acid profile revealed that, almond oils contained high amounts of polyunsaturated fatty acids. The oil products having higher amount of good fatty acids and higher tocopherols contents are considered good from the health point of view. The high levels of macro (Ca, K, P, and Mg,) and micro (Zn, Fe, and Cu) minerals in the kernels of almond genotype indicated that they could serve as excellent sources of these elements in the human diet. The current investigations showed that the almond kernels were found to be rich in most of the essential elements. Almond kernels had high total phenolic contents. The total phenol and antioxidant activity values of almond kernels differed depending on almond genotype.

Acknowledgments

The authors extend their appreciation to the Deanship of Scientific Research at King Saud University for funding this work through research group no. (RG-1439-080).

Compliance with ethical standard

Conflict of interest

The authors declare that there are no conflicts of interest.

Footnotes

Publisher's Note

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Contributor Information

Mehmet Musa Özcan, Email: mozcan@selcuk.edu.tr.

Isam A. Mohamed Ahmed, Email: iali@ksu.edu.sa

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