Introduction

Fruit and vegetable juices are widely used due to their convenience and method of consumption, high concentrations of functional ingredients, and represent an appropriate medium for functional component dissolution (^{Wootton-Beard & Ryan, 2011}). Cranberry juice is the second fruit juice of interest due to its health benefits, after citrus juices (^{Wootton-Beard & Ryan, 2011}; ^{Shidfar et al., 2012}; ^{Hyson, 2015}). With various clinical studies that support its use, cranberry has established itself in the market of dietary supplements since the last decade of the twentieth century (^{Blumberg et al., 2016}).

The cranberry belongs to the Vaccinium genus (Ericaceae), is cosmopolitan and has 450 species (^{Abreu et al., 2014}) of which the most used to produce commercial juices is V. macrocarpon, a shrub species native to North America (^{Brown & McNeil, 2006}). As one of the first functional foods in America, cranberry juice has been popular for many years for treating and preventing Urinary Tract Infections (UTIs) and cardioprotective effects attributed to its phenolic compounds. Its activities have been evaluated in reproductive-age women (^{Bass-Ware et al., 2014}), adults (^{Chen et al., 2013}), children (^{Salo et al., 2012}), and pregnant women (^{Heitmann et al., 2013}). According to epidemiological studies, cranberry and cranberry juices consumption is related to a decrease in the inflammatory response associated with non-communicable diseases (cancer, diabetes, renal diseases) (^{Babu et al., 2012}; ^{Pagonas et al., 2012}; ^{Weh et al., 2016}). Besides, cranberry juice is beneficial in stomach ulcer prevention (^{McKay et al., 2015}) because it inhibits Helicobacter pylori adhesion in the gastric mucous membrane (^{Lin et al., 2011}).

Cranberries are popular with consumers because of their tart taste and their health benefits (^{McKay et al., 2015}). These effects are attributed to a variety of compounds with antioxidant capacities such as tannins, flavonoids (including flavonols, flavan-3-ols, anthocyanins, and proanthocyanidins), anthocyanins, procyanidins, phenolic acids (including benzoic, hydroxycinnamic, and ellagic acids), triterpenes, iridoids, and organic acids (^{Pappas & Schaich, 2009}). The antioxidant capacity of cranberry juices in humans has been reported in numerous studies. These effects are attributed to the vitamin C increase and phenols in plasma. Also, it has been reported that cranberry juice consumption for two weeks decreased circulating oxidized LDL (^{Vinson et al., 2008}).

It has been proven that fruit juices stored at room temperature have a significantly shorter shelf life than those at a lower temperature (^{Teleszko et al., 2016}). There are studies for the antioxidant activity analysis of medicinal or edible plants. However, analysis of the antioxidant activity of foods consumed daily by the population is currently scarce. Packaged juices are among the most popular foods in the population. However, proper storage temperature is a requirement to maintain the packaged juices quality. The purpose of this study was to evaluate the antioxidant capacity of cranberry juices available on markets of San Luis Potosí, México, before and after storage al low temperature (4°C). The antioxidant capacity was evaluated by 2,2’-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical cation (ABTS•), 1,1-diphenyl-2-picrylhydrazyl radical (DPPH•), and (ferric reducing ability of plasma) FRAP methods.

1. Materials and methods

2. Results and discussion

All juices showed antioxidant activity, the highest activity recorded at 60 minutes (p = 0.001). Significant differences were found between D1 and D2 (p < 0.05), with D1 the highest VCEAC for the three methods (figure 1), as well as a higher percentage of inhibition of free radicals (table 1). The antioxidant activity of the cranberry juices is due to the phenolic compounds, which act as reducing agents’ hydrogen donors, and some have metal chelation potential ^{(Vinson et al., 2008}; ^{Côté et al., 2011}).

Studies on the antioxidant activities of plants and their components have typically used more than two different methods and recommended a combination of assays for scavenging electrons or radicals DPPH•, ABTS•, and FRAP, the most widely used (^{Moon & Shibamoto, 2009}). In our study, antioxidant activity was different in the three methods in the brands evaluated. With ABTS•, the SO showed the highest VCEAC and inhibition percentage (91.1%). Juice JX was the lowest (table 1). With DPPH•, HC was the highest at (96.9%) (figure 1), and OD was the lowest (table 1). With the FRAP method, the OD showed the highest VCEAC and percentage of inhibition (94.1%) (figure 1), and JX presented the lowest (table 1).

Studies have evaluated the antioxidant capacity of cranberry fruits (^{Taruscio et al., 2004}; ^{Ehala et al., 2005}; ^{Skrovankova et al., 2005}) and the effect of storage temperature on the antioxidant capacity of the fruits. The recommended storage temperature for blueberry fruit to maintain its antioxidant capacity is 2 to 4 °C (^{Wang & Stretch, 2001}). This temperature coincides with the present study since the antioxidant activity of the juices analyzed was higher at 4 °C.

Source: Own elaboration. Note: a) ABTS•, b) DPPH•, and c) FRAP at 30 min and 60 min days 1 y 2. All analyses were performed in triplicate.

Figure 1 Antioxidant capacity equivalent to vitamin C (VCEAC) of the cranberry juices 

Regarding pH measurements, all values were below 5.0 with an average of 2.76, being HC the most acidic (2.58) and GH the least (3.03) in the D1. In D2, the pH increased but remained below 5.0; GH was the most acidic on both days (table 2). The acidity of the cranberry is attributable to the polyphenols; its low pH and astringency is due to low levels of sugars but high levels of organic acids, mainly citric, malic, and quinic acids (^{Lu et al., 2017}). However, polyphenols are sensitive to changes in pH because they present oxidative degradation in alkaline media, while at a pH below 5.0 they have better stability (^{Zeng et al., 2017}).

One of the main findings of the study was a significant difference (p < 0.05) in the antioxidant activity during the two evaluations. Samples in D1 have the highest percentage of inhibition and the highest rate of VCEAC. On the other hand, for D2 after refrigeration at 4 °C by 24 h, possibly the antioxidant effect decreased since the phenolic compounds were oxidized. It has been observed that phenolic compounds are susceptible to degradation by heat, light, and dissolved oxygen (^{Côté et al., 2011}; ^{Zeng et al., 2017}). Besides, heating, separation, and storage techniques can result in oxidation, thermal degradation, and leaching to surrounding water can increase or decreases the antioxidant activity (^{Wootton-Beard & Ryan, 2011}). Also, the pH change modified the antioxidant capacity of the juices registered in D2. It is recommended to store the cranberry juice at 4 °C to avoid contamination with pathogens (^{Sewlikar & D’Souza, 2017}). However, when juices are stored at a low temperature (i. e., 4 °C), the polyphenol content decreased (^{Tembo et al., 2017}).

It has been suggested that juices stored at −1.5 °C possessed higher polyphenol contents, fewer color alterations, and less aroma and taste loss than at 25 °C (^{Gou et al., 2019}). However, frozen juice requires thawing before consumption, during which time it may become contaminated with microorganisms. Understanding how processing and storage alter the cranberries’ polyphenolic compounds, it is crucial to avoid them and maximize the health benefits of cranberry juice (^{White et al., 2011}).

The compounds with antioxidant capacity present in the commercial juices of cranberry confer benefits to human health (^{Babu et al., 2012}; ^{Dang et al., 2012}; ^{Duffey & Sutherland, 2015}). Several studies reported increases in the antioxidant capacity of plasma following consumption of cranberry juice (^{Liu et al., 2015}; ^{Liu et al., 2017}). For these reasons, currently, cranberry juice is popular among the population and is known as a beverage that brings health benefits. Commercial juices are a source of antioxidants and may increase the consumption of fruits and vegetables to re-equate the balance between recommendations and actual intake due to their high levels of polyphenolic compounds, which have health benefits (^{Wootton-Beard & Ryan, 2011}). It is important to note that commercial cranberry juices are high in sugars and calories. In Mexico, there is front-of-food labeling that allows consumers to identify foods with higher sugars, calories, and fat content. Therefore, commercial cranberry juice should be consumed according to the recommended portions for each age group to obtain its benefits as a functional food.

Cranberry juice is an option to increase the consumption of functional foods in a scenario where there is an increase in the incidence of diseases associated with inflammatory processes (cancer, diabetes, cardiopulmonary diseases) and a low intake of fruits and vegetables.

Our understanding of how cranberry juice has beneficial effects on human health is a challenge because of the range of product formulations and the amount of cranberry juice on the market. Especially in the Mexican population, the challenge is to register the consumption frequency and amount consumed of cranberry juicy because they are unknown. In this regard, it is crucial to carry out studies about the content of phenolic compounds, their bioavailability, antioxidant activity, and consumption of available cranberry juices to know their nutritional contribution to the Mexican diet.

Prospective

Studies on the antioxidant activity of medicinal plants and functional foods have been carried out. However, studies on commercial foods and beverages commonly consumed by the population are scarce. Cranberry juice is among the most popular due to its beneficial health effects related to its antioxidant activity. Beverage-appropriate storage and foods are essential to maintain their properties and safety. The present study found that the temperature at which cranberry juice is stored affects its antioxidant activity. Packaged juices are an alternative to improve the intake of fruits and vegetables and their bioactive compounds. However, juices must be handled and stored adequately. It is advisable to drink cranberry juices at room temperature and not to store them since this decreases their antioxidant activity. Antioxidant consumption from functional foods has been increasing due to their effect on health. The general population is looking for alternatives for their health, especially in an era of infectious diseases related to the pandemic as COVID-19, where self-care and good nutrition have become fundamental. Epidemiological studies related to the consumption of cranberry juice in Mexico are needed to know which population consumes it, as well as to disseminate information on the appropriate storage of the juices consumed by the people.

Conclusions

The compounds in cranberry juices give them antioxidant effects with great benefits for health. However, these compounds are easily degraded and significantly decrease their antioxidant activity once the container is opened. For this, we recommend consuming cranberry juice once the package is opened, along with attention to the conditions used to preserve it to guarantee the consumption of the compounds responsible for their beneficial effects on health. Fruit and vegetable juices are a rich source of antioxidants, which have health benefits. Cranberry juice is an option to increase the consumption of functional foods in a scenario where there is an increase in the incidence of diseases associated with inflammatory processes and a low intake of fruits and vegetables, especially in the Mexican population.