Use of microbial models to evaluate the effect of UV-C light and trans-cinnamaldehyde on the native microbial load of grapefruit (Citrus × paradisi) juice.

The aim of this research was to evaluate the storage stability (5 °C), and microbial modeling, of Rubi red grapefruit (Citrus × paradisi) juice treated with ultraviolet-C (UV-C) light (0, 10 and 20 min), alone or in combination with trans-cinnamaldehyde (trans-CAH) (0, 25 and 50 µg/mL). A 32 factorial design was used and data modeled with the Weibull, Modified Gompertz and Logistic models. A response surface model was used to evaluate the effect of modeling parameters for suggesting the optimum treatment conditions. Treated and some untreated juice lasted up to 9 days without physicochemical and microbial changes. At the higher combination of UV-C light and trans-CAH, the microbial load of grapefruit juice was maintained below 100 CFU/mL up to 15 days. For mesophiles, the three predictive models indicated that the parameters n and Nmax decreased and the parameters λ and tc increased as the combination of UV-C light and trans-CAH increased. The response surface modeling of the parameters obtained by the predictive models showed acceptable correlation for mesophiles (R2 = 0.815-0.977) but not for yeasts (R2 = 0.618-0.815). The three predictive models showed that, the concentration of trans-CAH had more effect on stopping the microbial growth than the UV-C light treatment.

Antioxidant characteristics of extracts of Hibiscus sabdariffa calyces encapsulated with mesquite gum.

This study compared the stability of extracts of H. sabdariffa calyces microencapsulated with different concentrations of mesquite gum during storage. Dry Roselle calyces were mixed with 50:50 (v/v) ethanol:water solution to obtain 18°Bx concentrate. This Roselle extract concentrate was mixed with purified mesquite gum (100:1-100:5 v/w). The Roselle extract concentrate-gum (RECG) was spray dried at inlet and outlet temperatures of 180 ± 2 and 104 ± 2.3 °C, respectively, at an air flow rate of 38 m3/h. Encapsulated Roselle powders (ERP) were analyzed for moisture content, total monomeric anthocyanins (differential pH), phenolic compounds (Folin and Ciocalteu method), antioxidant capacity (ABTS), and color parameters ([Formula: see text], and [Formula: see text]) after 5 weeks and 1 year of storage. Sorption properties (isotherms) and micrographs of powders were also obtained. The average yield of RECG powders was 15.27 ± 0.81 g/100 mL. During storage, ERP showed average values of phenolic compounds, antioxidant capacity, and anthocyanins of 3.43 ± 0.25 g gallic acid equivalents/100 g, 9.34 ± 1.4 g Trolox equivalents/100 g, and 318.7 ± 20.6 mg cyanidin-O-glycoside/100 g, respectively. Color parameters remained constant along the storage time.

Determination of absolute threshold and just noticeable difference in the sensory perception of pungency.

Absolute threshold and just noticeable difference (JND) were determined for the perception of pungency using chili pepper in aqueous solutions. Absolute threshold and JND were determined using 2 alternative forced-choice sensory tests tests. High-performance liquid chromatography technique was used to determine capsaicinoids concentration in samples used for sensory analysis. Sensory absolute threshold was 0.050 mg capsaicinoids/kg sample. Five JND values were determined using 5 reference solutions with different capsaicinoids concentration. JND values changed proportionally as capsaicinoids concentration of the reference sample solutions changed. Weber fraction remained stable for the first 4 reference capsaicinoid solutions (0.05, 0.11, 0.13, and 0.17 mg/kg) but changed when the most concentrated reference capsaicinoids solution was used (0.23 mg/kg). Quantification limit for instrumental analysis was 1.512 mg/kg capsaicinoids. Sensory methods employed in this study proved to be more sensitive than instrumental methods. Practical Application: A better understanding of the process involved in the sensory perception of pungency is currently required because "hot" foods are becoming more popular in western cuisine. Absolute thresholds and differential thresholds are useful tools in the formulation and development of new food products. These parameters may help in defining how much chili pepper is required in a formulated product to ensure a perceptible level of pungency, as well as in deciding how much more chili pepper is required in a product to produce a perceptible increase in its pungency.