How packaging shapes GABA and lactic acid levels in broccoli rabe florets

Freshness is central to the nutritional and sensory quality of vegetables, yet the conditions of storage and packaging can alter the pathways that govern nutrient content. A new study reveals how minimally processed organic broccoli rabe florets undergo profound metabolic and transcriptomic shifts during storage. Researchers found that carbohydrate reserves decline significantly in packaged samples, while stress-responsive amino acids and organic acids increase. Most notably, under low-oxygen conditions, florets redirect carbon into γ-aminobutyric acid (GABA) and lactic acid (LA) accumulation—compounds with known health relevance. By linking gene expression changes with metabolite profiles, the study maps the molecular routes that drive these alterations, offering insights for both quality preservation and consumer health.

Broccoli rabe (Brassica rapa subsp. sylvestris), a traditional leafy vegetable in Italy and beyond, is valued for its pungent taste, resilience in organic farming, and richness in bioactive nutrients. Consumer demand for organic produce has surged, and minimally processed “fresh-cut” vegetables now represent a growing segment in retail markets. However, packaging and modified atmosphere storage can change internal gas balances, leading to nutrient loss or the buildup of unwanted volatiles. Past studies showed that post-harvest treatments may trigger the synthesis of stress metabolites such asγ-aminobutyric acid (GABA) and LA. Due to these problems, it is necessary to conduct in-depth research on how storage and packaging influence the nutritional pathways of broccoli rabe.

The study, conducted by scientists at the National Research Council of Italy and collaborators, was published (DOI: 10.1093/hr/uhae274) on 28 September 2024 and typeset on 1 January 2025 in Horticulture Research. It investigated two genotypes of organic broccoli rabe across two production years, comparing freshly harvested florets with those stored fresh or packaged for four days. Using untargeted nuclear magnetic resonance profiling and RNA-seq, the team aimed to unravel the metabolic and gene expression changes that occur in different storage conditions, focusing particularly on the pathways leading to GABA and LA accumulation.

The researchers quantified 25 water-soluble compounds, including amino acids, carbohydrates, and organic acids, and performed principal component analysis to track differences among freshly harvested, stored fresh, and packaged florets. Packaged samples showed the sharpest divergence, with carbohydrate levels dropping by more than 50%, while amino acids such as phenylalanine and valine rose by over 30%. Stress-related organic acids including succinic acid and α-ketoglutaric acid increased by more than 75%. Crucially, GABA levels surged to over 8 mg/g dry weight in packaged florets, compared with negligible amounts in freshly harvested samples. Lactic acid, absent in fresh tissues, also accumulated under packaging conditions, reflecting hypoxia-induced fermentation. RNA-seq analysis revealed more than 8,000 differentially expressed genes in packaged versus fresh florets. Weighted gene co-expression network analysis linked these shifts to transcription factors in the bZIP, WRKY, and ERF families, which regulate enzymes such as GAD and LDH in GABA and LA biosynthesis. A detailed gene–metabolite map of 175 genes and 14 metabolites was constructed, providing a molecular blueprint of the stress-driven reprogramming. The authors conclude that low-oxygen packaging conditions trigger a carbohydrate sink into GABA and LA pathways, underscoring both nutritional opportunities and quality management challenges.

“Our findings highlight how a common post-harvest practice—packaging—fundamentally reshapes the metabolism of organic broccoli rabe,” said Donato Giannino, senior author of the study. “The rise in GABA and lactic acid is a double-edged sword. On one hand, these compounds are associated with beneficial effects such as blood pressure regulation and gut health. On the other, the metabolic reprogramming reflects stress conditions that could shorten shelf life if unmanaged. Our gene–metabolite network provides a valuable resource for designing better storage solutions while safeguarding both nutritional and sensory quality.”

The study offers immediate relevance for organic farming, food processing, and consumer health. By clarifying how packaging conditions accelerate GABA and lactic acid accumulation, the research guides improvements in modified atmosphere packaging to balance nutrient enhancement with freshness preservation. Producers may leverage these insights to tailor packaging strategies that maintain flavor while boosting health-promoting compounds. For consumers, the results explain why minimally processed organic vegetables can differ from fresh harvests in nutrient profiles. Longer term, the identified transcription factors and metabolic pathways could inform breeding programs for stress-resilient varieties with naturally elevated levels of functional nutrients.

###

References

DOI

10.1093/hr/uhae274

Original Source URL

https://doi.org/10.1093/hr/uhae274

Funding information

This work was funded by projects Top of the Crops (A0375-2020-36731) - Progetti Gruppi di Ricerca 2020 – Regione Lazio; NUTRAGE - CNR project FOE-2021 DBA.AD005.225.

About Horticulture Research

Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.