Comparative analysis of marine oligosaccharides on strawberry quality formation: The mechanism of mannuronate oligosaccharides which obtained by screening to promote coloration

To optimize the application of marine oligosaccharides in the strawberry industry, the effects of pre-harvest treatments with chitosan oligosaccharides, alginate oligosaccharides (AOS), carrageenan oligosaccharides, and agar oligosaccharides on quality improvement were compared. For the most effective oligosaccharides, more research on the structure-function relationship and regulating systems was conducted. The findings revealed that AOS improved the soluble sugar content, aroma, and nutritious elements of strawberries, especially enhancing the strawberry coloration. Mannuronate oligosaccharide (mAOS) was the most effective AOS for improving the coloration with a greater M/G ratio and a lower molecular weight. AOSs were observed to localize to the cell membrane and infiltrate strawberry cells. Higher M/G ratios enhanced AOSs' propensity for binding with strawberry protoplasts. The color-enhancing effect of mAOS depended critically on the jasmonic acid pathway. By modulating the expression levels of FaMYB10, FabHLH33, and FaMYB5 through the JA synthesis, AOS induced anthocyanin production, hence enhancing strawberry coloration.