# How Hydrogen (H\({}_{2}\)) Can Support Food Security: From Farm to Fork
## 4 H2 in Food Processing  
A more practical and viable way of treating plant and animal produce can be envisaged during the packaging and processing stages, where H2 can be applied without much \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Product** & **Application** & **Process** & **Mechanism** & **Outcome** & **Ref(s)** \\ \hline Banana (_Musa_ spp. _AAA cv._ _Baxijiao_) & HRW (0.4 mM) & 26-day storage & Reduced ethylene production and respiratory rate & Delayed ripening & [45] \\ \hline Chive (_Allium tuberosum_) & H2 gas (3\%) & 8-day storage & Increased antioxidant activity APx, CAT, GSH, POD and SOD & Increased shelf-life (100\%) & [34] \\ \hline Kiwi (_Actinidia chinensis_) & HRW (0.6 mM) & 16-day storage & Increased antioxidant capacity (SOD) and reduced cellulase, PG and PME activity & Reduced respiration and rotating & [46] \\ \hline Kiwi (_Actinidia chinensis_) & HRW (0.15 mM) & 10-day storage & Increased antioxidant capacity APx, CAT, POD and SOD; reduced activity of \(\beta\)-Gal, Cx, PG, PL and PME & Delayed ripening & [47] \\ \hline Mushrooms (_Hynesizygus_ (0.1–0.4 mM) & HRW 12-day storage & Increased antioxidant capacity (APx, CAT, GR, SOD); increased the contents of polysaccharides, protein, total sugar and amino acids & Extended shelf-life & [22; 48] \\ \hline Okra (_Abelmoschus esculent_ L.) & HRW (0.22 mM) & 15-day storage & Increased biosynthesis of pectin, hemicellulose and cellulose & Delayed ripening & [49] \\ \hline Pak Choi (_Brussica Chintensis_) & HRW (0.21 mM) & 4-day storage & Delayed chlorophyll degradation; preserved phenolic content & Delayed & [50] \\ \hline Tomato (_Solantum Lycopersicum_) & HRW (0.2 and 0.6 mM) & 16-day storage & Prevented nitrite accumulation & Increased vitamin C levels & [51] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Identifies the benefits of H2 application to animal and plant products, noting the mechanism of action and overall effects on fresh produce. APx—ascorbate peroxidase; \(\beta\)-Gal—\(\beta\)-galactosidase; CAT—catalase; Cx—connexin; GR—glutathione reductase; GSH—glutathione; PG—peptidoglycan hydrolase; PL—pectate lyase; PME—pectin methylesterase; POD—peroxidase; SOD—superoxide dismutase. adaptation to current preservation methods. H2 gas can be easily incorporated into numerous preservation techniques, including drying, fermentation, extraction and preparation of foods (Table 2). Dairy products are particularly susceptible to oxidation-related spoilage which can shorten the shelf-life. For example, oxidative reactions in butter lead to the destruction of essential fatty acids and vitamins. The foremost oxidative decomposition products formed in animal-derived produce such as butter are unstable hydroperoxides (R-OOH), molecules which are further decomposed into rancidity-inducing compounds (e.g., aldehydes (R-CH=O), ketones (R-C=O), alcohols (R-C-OH)) [61]. Introducing H2 in the form of HRW when washing raw butter [58; 60] was demonstrated to improve the quality attributes (e.g., acidity, colour), decrease the accumulation of heavy metals, prevent spoilage by inhibiting microbial decarboxylase activity, and retard the growth of yeasts and moulds, prolonging the shelf-life. Adding H2 into the preparation stages of such dairy products as butter and yoghurt is shown to inhibit microbial spoilage whilst also promoting microbial fermentation. Similarly, dissolving H2 gas into the pickling media of vegetable produce was noted to enhance the fermentation process and reduce lactic-acid-bacteria-associated biogenic amine formation. The authors demonstrated that using HRW during the fermentation phase and replacing the medium with freshly infused H2-enriched brine before pasteurisation was most effective in reducing levels of such biogenic amines as 2-phenylethylamine, putrescine andryptamine [55]. Dissolving H2 into solvent fluids used for the extraction of phytochemicals can increase the yields of anthocyanins, flavonoids and polyphen