# How Hydrogen (H\({}_{2}\)) Can Support Food Security: From Farm to Fork
## 5 Incorporating H\({}_{2}\) in the Packaging Environment of Food  
Historically, the packaging of food had the sole intention of providing a physical barrier between the environment and the contents to prevent external contamination. Innovation in the food packaging industry is broadly focused on the incorporation of active components such as ethylene scavengers (e.g., potassium permanganate) into the package, which can maintain, or extend, product quality, sensory attributes and shelf-life [63]. Currently, to improve the quality and longevity of produce, many fresh products are distributed and displayed in plastic packages containing a modified atmosphere composed of carbon dioxide (CO\({}_{2}\)) and Nitrogen (N\({}_{2}\)) [9]. This O\({}_{2}\)-depleted environment inhibits cellular oxidative mechanisms and microbial activity, restricting senescent processes and preserving the contents. However, with compounding stresses on food security and distribution networks, any improvements which can enhance the longevity of fresh produce will be highly valued. As with the utilisation of H\({}_{2}\) gas in thermal drying discussed previously, incorporating H\({}_{2}\) into the packaging atmosphere should be relatively simple. Nevertheless, unless the gas is used as it is produced, through water electrolysis, for example, the same safety concerns over the storage of pressurised gas and flammability apply. Therefore, stringent safety procedures in food processing and manufacturing environments will be necessary. On the other hand, the benefits of introducing non-explosive (<4% \(v/v\)) amounts of H\({}_{2}\) into packaging atmospheres may well outweigh any required investment in safety measures. Although the precise mechanisms behind H\({}_{2}\) activity in cells have yet to be elucidated, the ability of H\({}_{2}\) to act as an effective antioxidant in plants and produce is now well-documented [8; 64; 65; 66]. One of the primary functions of H\({}_{2}\) utilization in both agricultural and clinical settings is as an antioxidant, first demonstrated by [PERSON] et al. (2007), in a rodent model of ischemia/reperfusion injury [38]. The highly influential study describes the selective reduction in the highly reactive \({}^{\bullet}\)OH radical and ONOO\({}^{-}\) molecules, but no reduction in the important signalling molecules hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)) and nitric oxide (NO\({}^{\bullet}\)). Either as a result of, or in addition to, selectively neutralising the most detrimental reactive oxygen/nitrogen species, the upregulation and increased expression of such antioxidant proteins and peptides CAT, nuclear erythroid factor-2 (Nrf-2) and SOD are often reported [34]. Upregulation of such endogenous antioxidants is known to enhance tolerance to such environmental stressors as diseases, salinity, drought and temperature stress, and to confer a level of microbial resistance [23; 24; 25]. Such antioxidant activity is also demonstrated when H\({}_{2}\) is incorporated into the packaging atmosphere. Recently, several studies have identified that adding up to 4% H\({}_{2}\) gas into such packaging environments can markedly improve both the sensory qualities and shelf-life of fresh produce (Table 3). It can be seen from Table 3 that the addition of H\({}_{2}\) in the packaging atmosphere of animal and animal-derived products, including cheese, eggs and fish, was able to inhibit both lipid oxidation and the decomposition of amino acids by decarboxylase enzymes, whilst concomitantly reducing microbial growth and spoilage. As with the pre-harvest and processing applications of H\({}_{2}\) (Tables 1 and 2, respectively), the preservation of endogenous antioxidant activity may account for many of the effects noted in Table 3. Furthermore, in addition to being utilised as a preservative gas, H\({}_{2}\) gas can be used to detect flaws in food packages such as mis-sealing, tears, and small holes [71].