Many commercially available beverages contain a wide range of nutrients associated with various health benefits. Additionally, these beverages contain a combination of functional components that might be naturally present or formulated to enhance the health benefits of these products.
New strategies are often developed to improve the functional properties of beverages. These can include, for example, the incorporation of beneficial ingredients such as plant extracts, minerals and vitamins or, conversely, the elimination of harmful components such as fats and sugar.
Study: Demonstration of the antioxidant properties of mustard seed protein isolate (Brassica juncea) in orange juice. Image Credit: Irina Ruchushkina / Shutterstock.com
There are three types of functional drinks, including dairy-based drinks like probiotics, vegetable and fruit juices, and sports and energy drinks. These drinks mainly contain chemical components with antioxidant activity (AOX).
Some of the common antioxidants found in these products are polyphenols, carotenoids, and ascorbic acid (AA). Despite the beneficial effect of these functional components, the presence of pro-oxidants (POX) can lead to undesirable effects, since POX are involved in the generation of hydrogen peroxide (H2O2) from mixtures of redox-active constituents such as AA and polyphenols.
Many studies have reported the synthesis of H2O2 beverages rich in polyphenols, including coffee, green tea and cocoa. In addition, a high level of H2O2 has been reported in some sports and energy drinks whose major component is AA.
Recently, researchers reported that an aqueous extract of citrus peel can effectively reduce levels of H2O2 in catechin-enriched green tea. Interestingly, they also found that the levels of H2O2 in orange juice (OJ) are inversely associated with the number of protein, dietary fiber and unsaturated fat.
Proteins have unique potential as AOX additives in foods, as they can scavenge reactive oxygen species (ROS) through several mechanisms, including reduction of hydroperoxides, interactions with free radicals, and chelation of pro-oxidant metals.
H dilute2O2 negatively affects cells in vitro. Moreover, in the presence of transition and light metals, H2O2 is converted to hydroxyl radicals which can propagate radical chain reactions. This reaction can irreversibly alter cellular DNA, lipids and cell membranes.
Typically, the H2O2 levels in AOX-rich functional beverages, such as fruit juices, are not monitored.
About the study
In a recent food chemistry study, the researchers hypothesize that proteins with low nutritional value could be used effectively for the stabilization of AOX in OJ. In this study, scientists prepared a protein-enriched mustard seed extract (Brassica juncea) and assessed its efficacy against the production of H2O2 in fresh and heat-treated juice products.
Protein extracted from mustard seeds is known as mustard protein isolate (MPI). The thaumatin protein, present in many fruit juices, was used as a reference for a comparative study.
H levels2O2 in 16 commercially available fruit and vegetable juices that were labeled as “fresh” and “heat-treated” were analyzed. The researchers estimated the levels of H2O2 be between zero and 7.3 µM in “fresh” juices and between zero and 15.0 µM in processed juices. The highest level of H2O2 was observed in processed mango and pineapple juices, while no H2O2 has been identified in fresh pineapple juice.
MPI contained approximately 51% protein and 6.4 mg GAe/g total solids (TS) total reducible substances, which were assumed to be secondary metabolites such as polyphenols. The dose-dependent suppression of H2O2 was observed in fresh and heat-treated orange juice in the presence of 0.1 mg/mL of MPI after 24 hours. However, such a reduction process did not occur in fruit juices containing the reference protein.
The combination of proteins rich in amino acids containing thiols, such as methionine and cysteine, along with other antioxidant species in MPI, has been shown to effectively inhibit the generation of H through autooxidation.2O2 at OJ. This strategy could also be applied to other commercially manufactured juices.
Mustard seeds. Image Credit: Sunvic/Shutterstock
Low levels of H2O2 were observed in fresh juices, while a high level was found in processed juices. Moreover, an inverse relationship between OJ protein content and H levels2O2 was observed.
The current study reported that MPI can effectively suppress H2O2 properties with the reference protein found in the same juice. Additionally, the MPI preparation used in this study contained additional compounds such as polyphenols and other extracted secondary metabolites that exhibited reducing properties.
The auto-oxidation reaction of functional drinks leading to the production of H2O2 requires immediate attention. The removal or reduction of H2O2 in beverages by the use of MPI with AOX properties presents a promising strategy for industrial purposes.
- Bopitiya, D., Hearn, MTW, Zhang, J. & Bennett, LE (2022) Demonstration of antioxidant properties of mustard seed (Brassica juncea) protein isolate in orange juice. food chemistry. doi:10.1016/j.foodchem.2022.133648.