Víctor Falguera

Rheological Behavior of Tomato Juice: Steady-State Shear and Time-Dependent Modeling

IntroductionThe present work has evaluated the time-dependent and steady-state shear rheological properties of tomato juice.Materials and MethodsThree models were compared for describing the shear stress decay during shearing (Figoni–Shoemaker, Weltman, and Hahn–Ree–Eyring), and the parameters of each model were empirically related with the shear rate.ResultThe three evaluated models, as well as their modification as function of shear rate, described well the experimental data of tomato thixotropy. The Herschel–Bulkley and Falguera–Ibarz models have shown to be very adequate to describe the data from steady-state shear. The obtained data are potentially useful for future studies on food properties and process design.

Antioxidant properties of aqueous and ethanolic extracts of tara (Caesalpinia spinosa) pods in vitro and in model food emulsions

BACKGROUND The successful replacement of some synthetic food antioxidants by safe natural antioxidants has fostered intensive search for new vegetable sources of antioxidants. In our study the phenol and flavonoid content of extracts of tara pods was determined. The antioxidant activity was also studied by three different analytical assays: the measurement of scavenging capacity against a radical ABTS⁺ , the oxygen radical absorbance capacity (ORAC) and the ferric reducing antioxidant power (FRAP). RESULTS All analyzed samples showed a good antioxidant capacity, but the use of a solution of ethanol 75% in a 1 h ultrasonic process allowed achieving the greatest quantity of phenolics (0.464 mg gallic acid equivalent (GAE) g⁻¹ dry weight (DW) ) and the highest antioxidant activity measured by the ABTS⁺ and ORAC methods (10.17 and 4.29 mmol L⁻¹ Trolox equivalents (TE) g⁻¹ DW, respectively). The best method for efficient extraction of flavonoids (3.08 mg catechin equivalent (CE) g⁻¹ DW) was a 24 h maceration in cold water. Two extracts obtained with ethanol 75% and water were added to a model food system (oil-in-water emulsion) and the oxidative stability was studied during storage at 38 °C. Oxidation was monitored by determination of the peroxide value. The addition of 48 µg mL⁻¹ ethanol extract to the emulsion delayed oxidation to the same extent as 17.8 µg mL⁻¹ of Trolox, while water extract was only effective in the early stages of the oxidation process. CONCLUSION The results of this study indicate that ethanolic tara extracts may be suitable for use in food, cosmetic and nutraceutical applications.

Kinetic and Multivariate Analysis of Polyphenol Oxidase Inactivation by High Pressure and Temperature Processing in Apple Juices made from Six Different Varieties

The effectiveness of high pressure processing on the inactivation of apple polyphenol oxidase has been widely investigated. However, from an industrial point of view, there is a need for assessing this effectiveness on each one of the different apple varieties that each company uses for their products. This piece of work fills in this gap, studying the effect of the variety on apple juice polyphenol oxidase inactivation. Six varieties were assayed (Braeburn, Fuji, Gala, Golden Delicious, Granny Smith, and Red Delicious), searching for this influence from two different approaches: a kinetic study, finding the best model for each one of them, and a multivariate part consisting of a principal component analysis of data.

Viscoelastic Properties of Tomato Juice: Applicability of the Cox–Merz Rule

Tomato is one of the most important vegetables for the food industry. Rheological characterization of food is important for products, equipments, and unit operations design and evaluation. It is necessary for process optimization and high-quality products assurance. However, the works in literature present variable data, and some rheological characterization, as viscoelastic properties, are still scarce. The present work has evaluated the viscoelastic properties of tomato juice, as well as the applicability of the Cox–Merz rule. Tomato juice has shown dominant elastic properties rather than the viscous ones and could be classified as a weak gel (storage modulus higher then loss modulus). Moreover, due to the low pulp content, it has shown low viscoelastic behavior, with small dependency of oscillatory of the storage modulus. The rheological oscillatory and steady-state shear rheological properties of tomato juice were then correlated by two linear modifications on the Cox–Merz rule. The obtained values are in agreement with those described in the literature for other food products. The obtained data are potentially useful for future studies on food properties and process design.

The Effect of Perilla frutescens Extract on the Oxidative Stability of Model Food Emulsions

The polyphenolic profile of leaves and stalks of Perilla frutescens, was assessed as a source of natural antioxidants. The amount of caffeic and rosmarinic acids, determined by high-performance liquid chromatography (HPLC), were 0.51 mg/g dry weight (DW) and 2.29 mg/g DW, respectively. The measurement of scavenging capacity against the 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical cation, the oxygen radical absorbance capacity (ORAC), and the ferric reducing antioxidant power (FRAP) were 65.03 mg Trolox equivalents (TE)/g DW, 179.60 mg TE/g DW and 44.46 mg TE/g DW, respectively. P. frutescens extracts also showed good antioxidant properties in 10% sunflower oil-in-water emulsions during storage at 32 °C. Perilla extract at 320 ppm was as effective as butylated hydroxyanisole (BHA) at 20 ppm in slowing down the formation of hydroperoxides as measured by peroxide value, thiobarbituric acid reactive substances and hexanal content. The results of this study indicate that extract of P. frutescens may be suitable for use in the food matrix to help achieve potential health benefits.

Relationship between polyphenol oxidase activity and nutrition, maturity and quality parameters in flat peach

BACKGROUND Polyphenol oxidase (PPO) is one of the main factors that determine postharvest stability and therefore commercial possibilities of peach orchards. Since the activity of this enzyme depends on several variables of different nature, stating the relationships among them is essential to manage crop inputs so as to achieve the desired quality. RESULTS Multivariate projection techniques were used to identify these relationships throughout on-tree maturation in flat peach samples that had received different fertilisation doses, but harvested in equal conditions of soluble solids, fruit weight, diameter, firmness and skin and flesh colour. A relatively low fertilisation dose that was enough to avoid any lack of nutrients provided the lowest crop yield, but also with the lowest PPO activity. Fruit N/Ca ratio turned out to be a better indicator of PPO activity than isolated nitrogen or calcium content. Nutrient analyses on leaves did not have strong correlations with any significant parameter. The most useful variables to predict PPO activity before harvest were fruit firmness and skin colour, both of them read at the onset of on-tree maturation. CONCLUSION High fertilisation doses resulted in greater yields, but also with higher PPO activity, which is detrimental for the commercial chances of the fruit.