Distribution of polyamines in kernel tissues of Canadian barley cultivars and their association with protein content

Polyamines are nitrogen-containing compounds that naturally occur in barley grain and are known to have beneficial effects on human health. This study investigated the distribution of polyamines in barley grains from two covered and two naked Canadian barley cultivars. Five pearling fractions were collected at 5% intervals of kernel weight for all cultivars. Grains from covered cultivars were dehulled before pearling, followed by consecutive sieving to recover the germ, fine hull (<0.5 mm), and coarse hull (>0.5 mm) fractions. The levels of putrescine, spermidine, and spermine in barley kernels with 25% kernel weight removed were 69–76, 55–64, and 21–41% lower than those in unpearled kernels. Dehulled and pearled kernels were enriched in spermine and depleted in putrescine. The barley germ showed a notably high total polyamine content (52.0–65.5 mg/100 g). The protein and total polyamine content in the fine hull fraction were 2.8–3.5 and 2.1–3.3 fold higher, respectively, compared to the coarse hull fraction, reflecting differences in their histological composition as shown by microscopic examination. Correlation analysis revealed positive and significant correlations between polyamine and protein content at the sub-kernel level ( r = 0.769–0.839), suggesting a potential chemical and physiological synchronization between these components during barley seed development and germination. The insights provided by this study on the obtainment of polyamine-rich fractions from barley grains could be valorized for nutraceutical purpose. The understanding about polyamine–protein relationship in barley tissues could aid the selection of cultivating or processing conditions for different uses. • Outer layers of barley kernel obtained by pearling had increased polyamine content. • Pearling and dehulling resulted in spermine enrichment and putrescine depletion. • Barley germ contained the highest total polyamine content among all fractions. • Fine hulls showed higher protein and polyamine level than coarse hulls. • Polyamine and protein level were significantly correlated at the sub-kernel level.