Pulsed electric fields–processed orange juice consumption increases plasma vitamin C and decreases F2-isoprostanes in healthy humans

Abstract

Orange juice, a rich source of vitamin C, accounts for 60% of all fruit juices and juice-based drinks consumed in western Europe. Orange juice preservation is currently accomplished by traditional pasteurization. Pulsed electric fields (PEF) have been studied as a nonthermal food preservation method. Food technology needs in the area of processing are driven by nutrition. Therefore, the objectives of this study were to assess the bioavailability of vitamin C from pulsed electric fields–treated orange juice in comparison with freshly squeezed orange juice and its impact on 8-epiPGF_2α concentrations (biomarker of lipid peroxidation) in a healthy human population. Six subjects consumed 500 mL/day of pulsed electric fields–treated orange juice and six subjects consumed 500 mL/day of freshly squeezed orange juice for 14 days, corresponding to an intake of about 185 mg/day of ascorbic acid. On the first day of the study, subjects drank the juice in one dose, and on days 2–14 they consumed 250 mL in the morning and 250 mL in the afternoon. Blood was collected every hour for 6 hours on the first day and again on days 7 and 14. In the dose-response study, the maximum increase in plasma vitamin C occurred 4 hours postdose. Vitamin C remained significantly higher on days 7 and 14 in both orange juice groups. Plasma 8-epiPGF_2α concentrations was lower at the end of the study (P < 0.001) in both groups. Plasma levels of vitamin C and 8-epiPGF_2α were inversely correlated. Pulsed electric fields–preservation of orange juice retains the vitamin C bioavailability and antioxidant properties of fresh juice with a longer shelf-life.

Introduction

Epidemiological evidence suggests the protective effects of plant-based diets on certain cardiovascular diseases and other chronic diseases [1], [2]. Two large cross-sectional studies in the United States, the National Health and Nutrition Examination Survey (NHANES) II and III, showed an association between high serum vitamin C concentration and a decreased prevalence of stroke [3], [4]. Recent studies suggest that intake of orange juice, a rich source of vitamin C, improve HDL-cholesterol plasma levels in subjects with moderate hypercholesterolemia [5].

Orange juice accounts for 60% of all fruit juice and juice-based drinks consumed in western Europe [6]. Hydrosoluble nutrients such as vitamin C that are present in orange juice are susceptible to degradation by heat [7]. Thus, preservation of food quality with little depletion in the hydrosoluble vitamin contain is a main concern [8], [9]. New approaches involve nonthermal processing technologies that offer full or partial alternatives to heat for the inactivation of micro-organisms and enzymes [10], [11]. Pulsed electric fields (PEF) treatment involves applying very short electric pulses (μs) at high electric field intensities (typically pulse duration within the interval of 10–1000 μs; electric field strength within 20–80 kV/cm). During the PEF procedure, energy loss due to heating of foods is minimized, thereby reducing nutritional depletion and changes in the physical properties of foods [12], [13].

Recent studies have confirmed that PEF-processed orange juice retains many of the characteristics of fresh juice. PEF-treated orange juice retains all the physical properties, along with a 97.5% of vitamin C, and a reduction of 92.7% in the pectinmethylesterase activity required to prevent cloudiness in the juice. In addition, PEF treatment improves the microbial shelf-life and browning index during storage at 4°C compared with heat pasteurization (96.4°C for 30 s) [6], [14], [15], [16]. Until now, research has been focused on the sensory attributes and shelf-life of PEF-treated juices, but there are no studies assessing the impact of PEF technology on the health benefits of orange juice. Specifically, it is known that PEF application to vegetable foods results in effective permeabilization of cellular membranes and in some cases disruption of their structural integrity [17]. However, whether these structural changes in the cell walls of the orange juice sacs affect the intestinal absorption of the bioactive compounds contained in PEF-treated products remains to be elucidated.

Antioxidant vitamins are important for the cardiovascular system [18]. Vitamin C contributes to preserving a healthy vasculature through the regulation of collagen synthesis, prostacyclin production, and maintenance of nitric oxide levels [19], [20], [21]. Fruits and vegetables are the main sources of vitamin C, but 25% of women and about 33% of men in US eat less than 2.5 servings of fruits and vegetables daily to provide about 80 mg/day of vitamin C [22], [23]. Data retrieved from the Data Food Networking (DAFNE) databank concluded that, on average, more than 64% of the households are likely to consume less than the recommended daily fruit and vegetable intake of five servings per day [24].

A substantial body of evidence indicates that the measure of isoprostanes provides a reliable noninvasive approach to assess lipid oxidation in vivo in humans [25]. One of the isoprostanes, the 8-epiPGF_2α, has been shown to act as a vasoconstrictor [26] and to be associated with the hepatorenal syndrome [27] and pulmonary oxygen toxicity [28]. Previous studies showed high concentrations of F2-isoprostanes in presence of low levels of antioxidants and chronic diseases [29].

Elevated serum uric acid concentration appears to be an important risk factor predicting myocardial infarction [30]. In addition, hyperuricemia may have a direct injurious effect on the endothelium, altering endothelial cell function and reducing nitric oxide bioavailability, relevant in the development of vascular dysfunction and cardiovascular risk.

Therefore, the objectives of this study were to assess the bioavailability of vitamin C and levels of 8-epiPGF_2α after the consumption of PEF-treated in comparison with freshly squeezed orange juice in a healthy human population.