Oat sprouts analysis

A research group published two 2020 studies on sprouting oat seeds. Their first study produced evidence over a range of germination parameters (hulled / dehulled seeds of two varieties, for 1-to-9 days, at 12-to-20°C):

“The aim was to investigate the influence of germination period and temperature on protein profile, bioactive potential (β-glucan and phenolic contents), antioxidant capacity, and on activity of enzymes (α-amylase, protease and lipase) from hulled and dehulled oat varieties. Multi-response optimization was used to identify optimal germination conditions that maximize sprouted oat flour quality.

  • Hulled (variety Barra) and dehulled (variety Meeri) germination was performed in dark at different temperatures (12, 14, 16, 18, and 20 ◦C) and duration (24, 60, 96, 156, and 216 h).
  • Germination at 16 ◦C for 216 h and 20 ◦C for 96 h produced the highest protein accumulation in varieties Barra and Meeri, respectively.
  • Germination for short periods (24–96 h) combined with medium temperatures (12–16 ◦C) retained β-glucan levels, but longer germination times (156–216 h) caused reductions of 47–64%. Endogenous β-glucanases increase activity during germination, causing hydrolysis of β-glucan.
  • Free phenolic compound content was between 1.6-fold and 2.8-fold higher when germination took place at high temperatures (16–18 ◦C) for longer times.
  • Antioxidant capacity was between 1.4 and 4.5-fold higher. High temperatures (16–18 ◦C) and longer germination times (156–216 h) positively influenced antioxidant capacity.

The effect of germination conditions strongly depended on genetic diversity and presence/absence of hull.

Optimal germination conditions maximize contents of β-glucan, free phenolic compounds, protease activity, and antioxidant capacity, and minimize activity of undesirable enzymes α-amylase and lipase. For variety Meeri, that corresponded to 18 ◦C and time 120 h.”

https://www.sciencedirect.com/science/article/abs/pii/S0023643820309440 “Changes in protein profile, bioactive potential and enzymatic activities of gluten-free flours obtained from hulled and dehulled oat varieties as affected by germination conditions” (not freely available)

Their second 2020 study analyzed properties of 4-day-old oat sprouts. Dehulled oat seeds (variety Meeri) were soaked at room temperature for 4 hours, then germinated in darkness at 18°C with humidity ≥ 90%.

“Sprouted oat powder was an excellent source of protein (10.7%), β-glucan (2.1%), thiamine, riboflavin, and minerals (P, K, Mg and Ca). It presented better amino acid and fatty acid compositions, and levels of γ-aminobutyric acid [GABA], free phenolics, and antioxidant capacity than control.

Protein content (g/100 g) and amino acid profile (g/100 g protein). Different letters within a row indicate p ≤ 0.05 statistical differences.

During germination, proteins are partially hydrolyzed increasing availability of free amino acids. Activity of glutamate decarboxylase enzyme is enhanced.

However, no significant reduction of glutamate content was observed. Glutamate is used for GABA and protein synthesis, but it is also produced by protein hydrolysis, glutamine synthetase-glutamate synthase cycle, and GABA transaminase reactions.

Sprouted oat powder exhibited 2.5-fold higher SPC [soluble (free) phenolic compounds] levels. De novo synthesis of phenolic compounds or liberation of phenolic compounds that are linked to macromolecules due to cell wall dismantling during germination could explain enhancement of SPC.

Sprouted oat powder displayed a 3-fold higher antioxidant capacity. Release of bound phenolic compounds and de novo synthesis of avenanthramides might be responsible.

Hydrolysis of β-glucan might also cause an increase in oxygen radical absorbance capacity. β-glucan oligosaccharides exhibit high radical scavenging activity and reducing power, and that could be related with exposure of their active hydroxyl groups and decrease of intermolecular hydrogen bonding during germination.”

https://www.sciencedirect.com/science/article/abs/pii/S0308814620318343 “Sprouted oat as a potential gluten-free ingredient with enhanced nutritional and bioactive properties” (not freely available)

Both studies started germination by:

“Twenty grams of oat seeds were used for germination. Soaking (1:6 ratio, w/v) was performed at room temperature (20 ◦C ±2 ◦C) for 4 h.”

Neither study included estimates of germination rates. I contacted the corresponding coauthor for that information, and they replied:

“The germination rate in hulled oat varieties was around 95% and in
dehulled one around 55-70% depending on the germination conditions.”

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