Changes in Quinoa Seed Fatty Acid Profile Under Heat Stress Field Conditions

Abstract

The nutritional quality of quinoa is often related to the high protein content of their seeds. However, and despite not being an oilseed crop, the oil composition of quinoa seeds is remarkable due to its profile, which shows a high proportion of polyunsaturated fatty acids (PUFAs), particularly in essential fatty acids such as linoleic (ω-6) and α-linolenic (ω-3). In line with this, this study aimed at evaluating the effect of elevated temperatures on the oil composition of different quinoa cultivars grown in the field in two consecutive years (i.e., 2017 and 2018). In 2017, heat stress episodes resulted in a reduced oil content and lower quality linked to decreased ratios of oleic acid:linoleic acid, larger omega-6 (ω-6) to omega-3 (ω-3) ratios, and lower monounsaturated fatty acid (MUFA) and higher PUFA contents. Furthermore, the correlations found between mineral nutrients such as phosphorous (P) and the contents of oleic and linoleic acids emphasize the possibility of optimizing oil quality by controlling fertilization. Overall, the results presented in this study show how the environmental and genetic factors and their interaction may impact oil quality in quinoa seeds.

Keywords: erucic acid; fatty acids; heat stress; quinoa; seed nutritional quality; seed oil content; ω6/ω3 ratio.

FIGURE 1

Seed oil content of five quinoa varieties harvested in 2 years (2017 and 2018). Total seed oil content is expressed as percentage (%). Error bars correspond to the SDs. Bars that do not share the same letters show statistically significant differences following an ANOVA test and Tukey’s post hoc test at a p-value < 0.05.

FIGURE 2

Fatty acid composition of seeds harvested from five quinoa varieties grown in 2 years (2017 and 2018) on field experiments. Mean values are shown for each fatty acid quantified, and the values are presented as percentage (%). The fatty acids detected included the following: myristic—C14:0, palmitic—C16:0, palmitoleic—C16:1, margaric—C17:0, margaroleic—C17:1, stearic—C18:0, oleic—C18:1, linoleic acid—C18:2, α-linolenic—C18:3, gadoleic—C20:1, behenic—C20:1, and erucic—C22:1.

FIGURE 3

Major fatty acid contents of quinoa seeds obtained from five varieties and 2 cultivation years (2017 and 2018). Error bars correspond to the SDs. Bars that do not share the same letters show statistically significant differences following an ANOVA test and Tukey’s post hoc test (C16:0, C18:1, C18:2, and α-C18:3) at a p-value < 0.05.

FIGURE 4

Erucic acid (C22:1) content in quinoa seeds obtained from five varieties and 2 cultivation years (2017 and 2018). Error bars correspond to the SDs. Bars that do not share the same letters show statistically significant differences following a Welch’s ANOVA test followed by a Games–Howell post hoc test at a p-value < 0.05.

FIGURE 5

Average content of polyunsaturated fatty acids (PUFA), monounsaturated fatty acids (MUFAs), and saturated fatty acids (SFA) in seeds of five quinoa varieties harvested in 2 years (2017 and 2018).

FIGURE 6

Polyunsaturated fatty acid, MUFA, and SFA contents in quinoa seeds obtained from five varieties and 2 cultivation years (2017 and 2018). Vertical bars mean SD. Bars that do not share the same letters show statistically significant differences following an ANOVA test and Tukey’s post hoc test (SFA) and a Welch’s ANOVA test followed by a Games-Howell post hoc test (MUFA, PUFA) at a p-value < 0.05. SFA: C14:0 + C15:0 + C16:0 + C17:0 + C18:0 + C20:0 + C22:0. MUFA: C16:1 + C17:1 + C18:1 + C20:1 + C22:1. PUFA: C18:2 + C18:3.

FIGURE 7

Ratio of omega-6 (ω-6) to omega-3 (ω-3) essential fatty acid (EFA) contents in quinoa seeds obtained from five varieties and 2 cultivation years (2017 and 2018). Error bars correspond to the SDs. Bars that do not share the same letters show statistically significant differences following an ANOVA test and Tukey’s post hoc test at a p-value < 0.05. Total (ω-3): α-linolenic—C18:3. Total (ω-6): linoleic acid—C18:2.

FIGURE 8

Correlogram of variables measured. Pearson’s correlation coefficients (r) are given when the correlation between variables is statistically significant (p < 0.05). Red cells indicate negative correlations, and blue cells show positive correlations. The variables considered in the correlogram were as follows: seed fatty acid contents (palmitic—C16:0, stearic—C18:0, oleic—C18:1, linoleic acid—C18:2, α-linolenic—C18:3, and erucic—C22:1), the PUFA, MUFAs, and SFAs, the ratio of omega-6 (ω-6) to omega-3 (ω-3) (ω-6/ω-3), seed yield, seed ash and oil, seed carbohydrates (CH), seed fiber, protein and N, P, K, Ca, and Mg contents, straw yield, harvest index (HI), straw protein, ash, and fiber contents (FB), straw neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), hemicellulose (HEM), cellulose (CEL), and P, K, Ca, and Mg contents (31).