Encapsulation and pigmenting potential of betalains of pitaya (Stenocereus pruinosus) fruit.

Betalains of pitaya (Stenocereus pruinosus) fruit can be used as natural pigment, but they are susceptible to deterioration by temperature, pH, and presence of sugars. In this work, a refined extract (Er) of betalains was obtained through aqueous two-phase extraction, which reduced significantly sugar and mucilage contents. In order to favor stability, the encapsulation of the refined extract was evaluated, with native potato starch that was modified through phosphorylation or succinylation and reactive extrusion. Starches were evaluated in terms of degree of substitution, Fourier transform infrared spectroscopy, scanning electron microscopy, and viscous behavior. Microcapsules were formed by spray drying and their stability was evaluated at 40 °C for 39 days and by using them as pigmenting agent of yogurt at 4 °C during 32 days. The behavior of modified starches during encapsulation was superior to that of commercial N-Lok® starch. Microcapsules based on modified starches showed better pigmenting potential and higher stability than Er and microcapsules based on N-Lok® starch. The separation of betalains from pitaya fruit may be a good alternative for adding value to this plant genetic resource.

Physical, chemical, and antioxidant activity characterization of pitaya (Stenocereus pruinosus) fruits.

Fruits with red and orange flesh of the columnar cactus pitaya (Stenocereus pruinosus) were studied to evaluate physical characteristics, total soluble solids, betalains and soluble phenols content, and antioxidant activity. Fruits had, in average, weight of 179.0 g, 9.8 °Brix, 9.4 % carbohydrates, 1.25 % protein, 0.11 % ethereal extract, 0.60 % crude fiber, and 0.62 % ash. Also, fruits resulted rich in Fe (22.8-27.8 mg/kg). Hue angle and contents of betacyanins, betaxanthins (µg/g dry sample), and total soluble phenols (mg GAE/g fresh sample) were 19.8°, 2860.0, 3210.0, and 1.6 in the red material, and 28.9°, 470.0, 2670.0, and 1.2, respectively, in the orange fruit. The antioxidant capacity was higher in the red material, since the ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)) technique reported 1090.6 and 735.4 µmol of Trolox equivalents/g fresh flesh in red and orange fruits, respectively, while the oxygen radical absorbance capacity (ORAC) assay reported 7.84 and 5.16 µmol of Trolox equivalents/g fresh flesh, respectively. The chromatographic profile showed five betalains in red fruits, but only four of them were observed in those orange fleshed.

Modeling temperature variations in a pilot plant thermophilic anaerobic digester.

A model that predicts temperature changes in a pilot plant thermophilic anaerobic digester was developed based on fundamental thermodynamic laws. The methodology utilized two simulation strategies. In the first, model equations were solved through a searching routine based on a minimal square optimization criterion, from which the overall heat transfer coefficient values, for both biodigester and heat exchanger, were determined. In the second, the simulation was performed with variable values of these overall coefficients. The prediction with both strategies allowed reproducing experimental data within 5% of the temperature span permitted in the equipment by the system control, which validated the model. The temperature variation was affected by the heterogeneity of the feeding and extraction processes, by the heterogeneity of the digestate recirculation through the heating system and by the lack of a perfect mixing inside the biodigester tank. The use of variable overall heat transfer coefficients improved the temperature change prediction and reduced the effect of a non-ideal performance of the pilot plant modeled.

Effect of moderate thermal treatments on the inactivation of a strain of Listeria monocytogenes and physicochemical properties of soursop pulp.

Soursop (Annona muricata L.) is a commercially important tropical fruit, whether fresh or processed as a pasteurized or frozen pulp used to prepare juice, drinks, nectar, ice cream, popsicles, and desserts. Besides preserving quality, another preoccupation in the processing of fruit pulps is product safety. Several studies show the association between pulp processing and the development of various microorganisms; however, few have focused on the association between L. monocytogenes and the pulp of sour fruits. The objective was to evaluate the effect of moderate thermal treatments on the inactivation of L. monocytogenes and the physicochemical properties in soursop pulp in order to determine the best processing conditions that will allow to maintain quality as well as to achieve an adequate level of safety. Thermal inactivation kinetics were obtained for L. monocytogenes inoculated in soursop pulp at five levels of temperature (50, 52.5, 55, 57.5, and 60 ℃) and different exposure times (0-60 min). The survival curves did not suggest a log-linear relationship, and were, consequently, fitted to the modified Gompertz equation. The results indicated that the modified Gompertz equation provided an acceptable goodness of fit. Five-log10 cycles reductions of L. monocytogenes were achieved at 50 ℃/60 min, 52.5 ℃/16 min, 55 ℃/10 min, 57.5 ℃/5 min, and 60 ℃/1.25 min. These 5-log10 treatments applied to the soursop pulp indicated that the soursop pulp showed changes in the color parameters and a decrease in the content of total sugars, reducing sugars, ascorbic acid, total phenols, and pH.

Betalains and phenolic compounds profiling and antioxidant capacity of pitaya (Stenocereus spp.) fruit from two species (S. Pruinosus and S. stellatus).

Pitaya fruits (Stenocereus spp.) contain betalains and phenolic compounds that have not been completely characterized. Fruits of two ecotypes of S. pruinosus, red-fleshed (SpR) and orange-fleshed (SpO), and two of S. stellatus, red-fleshed (SsR) and white-fleshed (SsW), were characterized in their betalains and phenolic compounds. The chromatographic profile of betalains was similar in SpR, SpO, and SsR, where indicaxanthin, gomphrenin I, phyllocacthin, and their isomers predominated. Betaxanthins content was higher than betacyanins and ranged from 17,706.7±1128.1 to 22,053.6±328.1µg/g dry sample. The identified phenolics mostly corresponded to hydroxycinnamoyl derivatives, flavonols and flavanones. The phenolics content was higher in S. stellatus than in S. pruinosus. The ecotype SsW, that had flesh without color, showed the highest concentration. The antioxidant capacity varied within 9.21±0.84 and 2.41±0.36µmolTrolox/g fresh sample, as determined by the ABTS assay. By its phytochemical composition, the fruits of pitaya can be a good source of antioxidant compounds.

Effect of heating strategy on power consumption and performance of a pilot plant anaerobic digester.

The effect of heating strategy on power consumption and performance of a pilot plant anaerobic digester treating chicken litter, under thermophilic conditions, has been studied. Heating strategy was evaluated using three different spans (0.2 degrees C, 0.6 degrees C, and 1.0 degree C) for triggering the temperature control system from target temperature (56.7 degrees C). The hydraulic retention time in the pilot plant digester was in the range of 32 to 37 days, varying the total solids concentration fed from 5% to 6%. The results showed that under the experimental conditions, heating was the most energy-demanding process with 95.5% of the energy used. Increments up to 7.5% and 3.8%, respectively, on mechanical and heating power consumption, were observed as the span, for triggering the temperature control system from target temperature, was increased. Under the experimental conditions studied here, an increment of 30.6% on the global biodigester performance index was observed when a span of 1.0 degree C was compared to the one of 0.2 degrees C.