Influence of germination on the protein content, total phenolic content, and antioxidant capacity of quinoa (Chenopodium quinoa Willd.): a systematic review and meta-analysis

The germination process has emerged as a promising biotechnological strategy to enhance the nutritional and functional properties of quinoa (Chenopodium quinoa Willd.). However, scientific consensus regarding its effects on protein content, total phenolic content, and antioxidant capacity remains limited and controversial. To systematically review and meta-analysis the scientific evidence on germination effects on protein content, total phenolic content, and antioxidant capacity across white, red, and black quinoa varieties. A comprehensive literature search was conducted in Scopus, ScienceDirect, and Google Scholar databases (June 2019–March 2025). The MINORS scale was used to judge the level of bias and quality of evidence. Pooled and variety-specific subgroup analyses were performed using ratio of means (ROM) with 95% confidence intervals 95% CI. Heterogeneity was evaluated through I² statistics. Statistical analyses were conducted using R 4.5.0 software. Twenty-one studies met inclusion criteria. Germination significantly increased protein content by ~ 9% (ROM = 1.09 95% CI: 1.04–1.14; z = 3.789, p < 0.001), with white variety showing the highest increment (~ 12%). Total phenolic content increased by ~ 44% (ROM = 1.44 95% CI: 1.30–1.60; z = 6.849, p < 0.001), with red variety exhibiting the greatest enhancement (~ 51%). Antioxidant capacity improved by ~ 28% (ROM = 1.28 95% CI: 1.16–1.42; z = 4.729, p < 0.001), with black variety demonstrating superior response (~ 36%). Germination significantly enhances protein content, total phenolic content, and antioxidant capacity in quinoa, with variety-dependent differential responses that suggest genotype-specific optimization potential. Most included studies lacked adequate sample size calculations and consistently employed three replicates, potentially constraining meta-analysis robustness and generalizability of findings.