The Effects of Seaweed and Humic Acid Seed Treatments on the Phytochemical Composition and Storage Stability of Wheatgrass Juice Derived from Different Triticum Species

Wheatgrass juice is a prominent functional food; however, the comparative potential of ancient wheat species and the role of biostimulant seed priming in determining phytochemical stability during storage remain insufficiently defined. This study investigated the effects of seaweed extract and humic acid seed priming on the phytochemical composition and storage stability of wheatgrass juice derived from Triticum aestivum, Triticum sphaerococcum, Triticum macha, and Triticum spelta. Seeds were primed for 24 h with seaweed extract or humic acid (200 mg 100 g⁻¹ seed), grown for 10 days, and juice was obtained by cold pressing. Phytochemical attributes (total phenolic content, total flavonoid content, antioxidant capacity, vitamin C, and titratable acidity) were quantified in fresh samples and after 7 days of storage at 4°C and −20°C. Stability was defined as the percentage retention of bioactive compounds during storage. Data were analyzed using a completely randomized factorial design (three replicates) with analysis of variance, and mean comparisons were performed using Tukey’s test. Biostimulant treatments increased total phenolic content by up to 69% and antioxidant capacity by up to 7% compared to the control, with T. macha and T. sphaerococcum showing the strongest response, particularly under seaweed priming. During storage at 4°C, antioxidant capacity decreased by 49–87%, while total phenolic content declined by 84–94%. Whereas, flavonoids and vitamin C decreased by 12–21% and 25–34%, respectively. In contrast, storage at −20°C preserved flavonoids up to 99%, while mean retention rates of antioxidant capacity and total phenolic content were approximately 63% and 76%, respectively, across all genotypes and treatments. The improved retention of phytochemicals in primed samples may be associated with enhanced initial metabolite accumulation and reduced oxidative degradation. Among the evaluated genotypes, T. macha exhibited the highest phytochemical content and retention capacity. These findings demonstrate the interactive effects of genotype, biostimulant priming, and storage conditions on wheatgrass juice quality, and indicate that frozen storage is more effective than refrigeration for preserving bioactive compounds.