María J. Esteve

Analytical Methods for Determining Bioavailability and Bioaccessibility of Bioactive Compounds from Fruits and Vegetables: A Review

Determination of bioactive compounds content directly from foodstuff is not enough for the prediction of potential in vivo effects, as metabolites reaching the blood system may be different from the original compounds found in food, as a result of an intensive metabolism that takes place during absorption. Nutritional efficacy of food products may be ensured by the determination of bioaccessibility, which provides valuable information in order to select the appropriate dosage and source of food matrices. However, between all the methods available, there is a need to establish the best approach for the assessment of specific compounds. Comparison between in vivo and in vitro procedures used to determine bioaccessibility and bioavailability is carried out, taking into account the strengths and limitations of each experimental technique, along with an intensive description of actual approaches applied to assess bioaccessibility of bioactive compounds. Applications of these methods for specific bioactive compounds bioaccessibility or bioavailability are also discussed, considering studies regarding the bioavailability of carotenoids, polyphenolic compounds, glucosinolates, vitamin E, and phytosterols.

Ascorbic acid is the only bioactive that is better preserved by high hydrostatic pressure than by thermal treatment of a vegetable beverage.

Variations in levels of antioxidant compounds (ascorbic acid, total phenolics, and total carotenoids), total antioxidant capacity, and color changes in a vegetable (tomato, green pepper, green celery, onion, carrot, lemon, and olive oil) beverage treated by high hydrostatic pressure (HHP) were evaluated in this work. The effects of HHP treatment, four different pressures (100, 200, 300, and 400 MPa) and four treatment times for each pressure (from 120 to 540 s) were compared with those of thermal treatment (90-98 °C for 15 and 21 s). High pressure treatment retained significantly more ascorbic acid in the vegetable beverage than thermal treatment. However, no significant changes in total phenolics were observed between HHP treated and thermally processed vegetable beverage and unprocessed beverage. Color changes (a*, b*, L, chroma, h°, and ΔE) were less for pressurized beverage than thermally treated samples compared with unprocessed beverage.

Determination of ascorbic and dehydroascorbic acids in blood plasma and serum by liquid chromatography

A liquid-chromatography (LC) method with ultraviolet detection for measuring ascorbic (AA) and dehydroascorbic acid (DHA) in human blood and serum was studied. The method used an ODS reversed-phase column and cetyltrimethyl ammonium bromide as an ion-pairing agent. AA was measured before and after the reduction of DHA with dithiothreitol. The absence of interferences resulting from hemolysis products was verified and also the stability of the ascorbic acid in metaphosphoric acid extracts. The analytical parameters, linearity (1-80 micrograms/ml), accuracy (recovery, 96.7-100.7%) and precision (C.V. = 3.1%), show that the method is reliable and adequate for measuring the total vitamin C content in serum and plasma.

Study of Antioxidant Capacity and Quality Parameters in An Orange Juice–Milk Beverage After High-Pressure Processing Treatment

The aim of this study was to obtain a beverage with a high content of bioactive compounds. Therefore, a mixture of orange juice and milk was prepared. The effect of high-pressure processing (HPP), four different pressures (100, 200, 300, and 400xa0MPa), four treatment times for each pressure (120, 300, 420, and 540xa0s) on antioxidant compounds, and quality parameters was studied. The effects of HPP treatment were compared with those of thermal treatment (90xa0°C for 15, 21xa0s and 98xa0°C for 15, 21xa0s). Ascorbic acid retention in the orange juice–milk beverage was higher than 91% in all cases after HPP. There was a significant increase (pu2009<u20090.05) in phenolic compounds at 100xa0MPa/420xa0s, however at 400xa0MPa/540xa0s, it was observed a non-significant decrease. Total carotenoid content was significantly higher in all samples treated by HPP when treatment time was 420 and 540xa0s. Color changes increased when pressure and treatment times were higher, with the highest difference appearing at 400xa0MPa/540xa0s, but HPP had a smaller effect on total color changes than thermal processing. A 5-log reduction of Lactobacillus plantarum CECT 220 was obtained in the orange juice–milk beverage after HPP (200xa0MPa, 300xa0s), and this was compared with treatment at 90xa0°C (15xa0s), the heat treatment most effective at preserving ascorbic acid.

Determination of liposoluble vitamins in cooked meals, milk and milk products by liquid chromatography

A method for the simultaneous determination of liposoluble vitamins in cooked meals was established. Saponification was performed with 50% (w/v) KOH at 80 degrees C, and ascorbic acid was added as antioxidant. The subsequent extraction was carried out with diethyl ether. This was followed by a liquid chromatographic separation on a reversed-phase C18 column with methanol-water (94:6, v/v as the mobile phase. Retinyl acetate was used as the internal standard. The analytical parameters linearity, detection limit (0.19 and 8.33 microg/100 g for retinol and alpha-tocopherol, respectively), precision of the method (RSD=5.24 and 6.99% for retinol and alpha-tocopherol, respectively) and recovery assays (95.6 and 96.5% for retinol and alpha-tocopherol, respectively) show that the method studied is useful for measuring these compounds in foods and cooked meals.

Changes in Quality and Nutritional Parameters During Refrigerated Storage of an Orange Juice–Milk Beverage Treated by Equivalent Thermal and Non-thermal Processes for Mild Pasteurization

The effects of high-pressure (HP) treatment (400u2009MPa at 42xa0°C for 5xa0min) and pulsed electric field (PEF) processing (25xa0kV/cm at 57xa0°C for 280xa0μs) on ascorbic acid, total carotenoids, total phenolic compounds and total antioxidant capacity (TEAC and ORAC) of an orange juice–milk (OJ-M) beverage along the storage time at 4xa0°C were compared with a conventional heat preservation technology used in industry (90xa0°C for 15xa0s). During storage, ascorbic acid, total carotenoids and antioxidant capacity (TEAC) depleted with time regardless of the treatment applied. Instead, total phenolic content and antioxidant capacity measured by the ORAC method increased at the end of the storage. Non-thermal-treated beverage had less non-enzymatic browning than the thermally pasteurized one. There were no significant variations in the hidroxymethylfurfural (HMF) content of the HP- and PEF-treated OJ-M, whilst a significant increase was obtained after thermal treatment. During refrigerated storage, HMF was always below the maximum values established. The HP treatments reduced the L* value of the treated beverages immediately after processing and during refrigerated storage and induced an increase in total colour differences of beverages treated by HP compared with PEF and thermally processed orange juice–milk. Hence, alternative methods such as HP and PEF may give new opportunities to develop orange juice–milk with an equivalent shelf life to that of thermally treated orange juice mixed with milk in terms of microbial, physicochemical and nutritional characteristics.

A Comparative Study of the Analysis of Antioxidant Activities of Liquid Foods Employing Spectrophotometric, Fluorometric, and Chemiluminescent Methods

The antioxidant profile of liquid foods is complex and includes different lipid and water-soluble compounds. These should be considered when assessing total antioxidant capacity (TAC) of these beverages, since it may act synergistically rather than individually. This study describes and compares the use of spectrophotometric methods (Trolox equivalent antioxidant capacity, TEAC and 2,2-diphenyl-1-picrylhydrazyl, DPPH), fluorometric (oxygen radical antioxidant capacity, ORAC), and photochemiluminescence (PCL) for the measurement of the TAC of different liquid foods (fruit juice mixed with milk and vegetables beverage). An evaluation was also made for the influence of certain compounds (ascorbic acid, phenolic compounds, total carotenoids, and tocopherols) with antioxidant capacity that was present in the samples studied. The different methods studied allow the determination of the TAC of the analyzed foods in a precise and accurate way. The TAC values in the studied samples differ from the applied method. An overall antioxidant potency composite index was calculated by assigning each tests equal weight. When an index score was applied, ORAC method had the higher antioxidant capacity values in the analyzed liquid foods in comparison with the other methods. The correlations among the different methods used for the determination of the antioxidant capacity depend on food, that is, mainly due to compounds (lipid and water soluble) of the different food matrix. In addition, ascorbic acid was the main contributor to antioxidant capacity of fruit juice mixed with milk beverages measured with the different methods. However, in vegetables beverages, phenolic compounds were found to correlate more significantly with antioxidant capacity values.

Stevia rebaudiana Bertoni as a natural antioxidant/antimicrobial for high pressure processed fruit extract: Processing parameter optimization

Response surface methodology was used to evaluate the optimal high pressure processing treatment (300-500 MPa, 5-15 min) combined with Stevia rebaudiana (Stevia) addition (0-2.5% (w/v)) to guarantee food safety while maintaining maximum retention of nutritional properties. A fruit extract matrix was selected and Listeria monocytogenes inactivation was followed from the food safety point of view while polyphenoloxidase (PPO) and peroxidase (POD) activities, total phenolic content (TPC) and antioxidant capacity (TEAC and ORAC) were studied from the food quality point of view. A combination of treatments achieved higher levels of inactivation of L. monocytogenes and of the oxidative enzymes, succeeding in completely inactivating POD and also increasing the levels of TPC, TEAC and ORAC. A treatment of 453 MPa for 5 min with a 2.5% (w/v) of Stevia succeeded in inactivating over 5 log cycles of L. monocytogenes and maximizing inactivation of PPO and POD, with the greatest retention of bioactive components.

Determination of vitamin B6 (pyridoxamine, pyridoxal and pyridoxine) in pork meat and pork meat products by liquid chromatography

A liquid chromatographic method for determining vitamin B6 compounds in pork meat and pork meat products is examined. It uses the same extraction procedure as that applied for thiamin and riboflavin determination, followed by a liquid chromatographic separation on a reversed-phase C18 column with 0.01 M H2SO4 as mobile phase at 30 degrees C. 4-Deoxypyridoxine is used as internal standard. The analytical parameters linearity, precision of the method (R.S.D. = 7.3 and 6.9% for pyridoxamine and pyridoxal, respectively) and accuracy obtained by recovery assays (99 and 85.1% for pyridoxamine and pyridoxal, respectively) show that the studied method is useful to measure these compounds in pork meat.

Refrigerated fruit juices: quality and safety issues.

Fruit juices are an important source of bioactive compounds, but techniques used for their processing and subsequent storage may cause alterations in their contents so they do not provide the benefits expected by the consumer. In recent years consumers have increasingly sought so-called fresh products (like fresh products), stored in refrigeration. This has led the food industry to develop alternative processing technologies to produce foods with a minimum of nutritional, physicochemical, or organoleptic changes induced by the technologies themselves. Attention has also focused on evaluating the microbiological or toxicological risks that may be involved in applying these processes, and their effect on food safety, in order to obtain safe products that do not present health risks. This concept of minimal processing is currently becoming a reality with conventional technologies (mild pasteurization) and nonthermal technologies, some recently introduced (pasteurization by high hydrostatic pressure) and some perhaps with a more important role in the future (pulsed electric fields). Nevertheless, processing is not the only factor that affects the quality of these products. It is also necessary to consider the conditions for refrigerated storage and to control time and temperature.