I.I. Ruiz-López

Moisture and temperature evolution during food drying: effect of variable properties

Theoretical moisture and temperature evolution during carrot slab drying were estimated with non-steady heat and mass transfer equations using constant and variable properties. Experimental drying kinetics of carrot slabs were obtained in order to compare with estimations. The results showed that moisture evolution, estimated for constant properties, reproduces approximately the experimental one, with deviations of experimental shape. Moisture evolution estimation for variable properties reproduces the experimental shape, but numerical effort is considerably increased. Temperature evolution is sensitive with respect to properties functions. This paper shows that constant properties assumption has application for engineering purposes and variable properties gives more phenomenological information for further predictions.

Effect of Osmotic Dehydration on Air-Drying Characteristics of Chayote

In this study the effect of osmotic dehydration (OD) on the air-drying kinetics of chayote (Sechium edule (Jacq.) Swartz) fruits was investigated. Fresh and osmotically dehydrated chayote parallelepipeds (1 × 1 × 2 and 4 × 4 × 2 cm) were subjected to convective drying at air temperatures of 50 and 60°C, with air velocities of 1.5 and 2.5 m/s. The OD pretreatments were performed in 10 and 25% NaCl solutions (w/w) at 25°C during 3 h using a solution-to-fruit mass ratio of 4:1. The use of higher air velocities notably accelerated drying rates as manifested through significantly higher drying rate constants estimated with Pages model, whereas no effect of temperature was observed. A previously reported analytical solution that considers both product shrinkage and variable diffusivity was generalized to describe the drying kinetics of food products with parallelepiped geometry. Selected drying experiments were then fitted to this solution using six different sets of model assumptions. Results indicated that product shrinkage is the main factor to be considered in order to estimate reliable values for diffusion coefficients. The OD pretreatments produced a significant reduction of the initial moisture content of chayote slabs before drying, thus allowing shorter drying time, which may lead to reduced energy consumption.

Evaluation of physical and chemical properties of carrots dried by Refractance Window drying

ABSTRACT The Refractance Window™ (RW) technique was used to dry carrot slices (3 cm diameter; 0.2 and 0.4 cm thickness) at 74 and 94°C. Moisture loss, texture, color, total polyphenol content (TPC), and antioxidant activity (AA) were evaluated as response variables and were compared with the values of a control (fresh carrot) and the slices dried via convective drying (C) at the same temperatures. The RW method produced a reduction of drying time of 26–51% (p < 0.05) when compared to convective drying. The color, TPC, and AA values for the RW treatment did not differ (p > 0.05) compared with the control. The texture values showed a difference with respect to the control for the two drying methods used. However, between the two drying methods there was no difference in the texture (p > 0.05). The results suggest that the RW technology can be used to develop products with better functional properties compared with those obtained via conventional air-drying methods.

Significant improvement of Geobacillus thermoleovorans CCR11 thermoalkalophilic lipase production using response surface methodology.

The medium optimization for the production of the Geobacillus thermoleovorans CCR11 thermoalkalophilic lipase was carried out in shake flask cultures using safflower high oleic oil. In the first step of optimization, a two level fractional factorial design allowed the identification of the concentration of nutrient broth and temperature as the main variables significantly affecting lipase production (P<0.05). In a second step, a D-optimal design was applied to determine the variables optimal values, defined as those yielding maximal lipase production in shaken flasks, thus demonstrating that the optimal concentration of nutrient broth was 3.8 g/l and the optimal culture temperature was 39.5°C. The model was experimentally validated, yielding a lipase production of 2283.70 ± 118.36 U/mL which represents a 6.7-fold increase in comparison to the non-optimized medium.

Ultraviolet-C light effect on physicochemical, bioactive, microbiological, and sensorial characteristics of carrot (Daucus carota) beverages

The aim of this research was to evaluate the effect of ultraviolet-C light on physicochemical, bioactive, microbial, and sensory characteristics of carrot beverages. Beverages were formulated with different concentrations of carrot juice (60, 80, and 100% [v/v]) and treated with ultraviolet-C light at different flow rates (0, 0.5, 3.9, and 7.9 mL s−1) and times (5, 10, 15, 20, and 30 min), equivalent to ultraviolet-C dosages of 13.2, 26.4, 39.6, 52.8, and 79.2 J cm−2. Total soluble solids, pH, and titratable acidity were not affected by the ultraviolet-C light treatment. Ultraviolet-C light significantly affected (p < 0.05) color parameters of pure juice; however, at low concentration of juice, total color change was slightly affected (ΔE = 2.0 ± 0.7). Phenolic compounds (4.1 ± 0.1, 5.2 ± 0.2, and 8.6 ± 0.3 mg of GAE 100 mL−1 of beverage with 60, 80, and 100% of juice, respectively) and antioxidant capacity (6.1 ± 0.4, 8.5 ± 0.4, and 9.4 ± 0.3 mg of Trolox 100 mL−1 of beverage with 60, 80, and 100% of juice, respectively) of carrot beverages were not affected by ultraviolet-C light treatment. Microbial kinetics showed that mesophiles were mostly reduced at high flow rates in carrot beverages with 60% of juice. Maximum logarithmic reductions for mesophiles and total coliforms were 3.2 ± 0.1 and 2.6 ± 0.1, respectively, after 30 min of ultraviolet-C light processing. Beverages were well accepted (6–7) by judges who did not perceive the difference between untreated and Ultraviolet-C light treated beverages.

Study of oil uptake during deep-fat frying of Taro (Colocasia esculenta) chips

The effects of a water blanching pretreatment (BP, 85°C for 3 min), sample thickness (1 and 2 mm), oil temperature (180 and 200°C), and frying time (1 and 3 min) on the oil uptake (OU) behavior during the deep-fat frying of pre-dried (oven dried at 70°C for 20 min) taro (Colocasia esculenta) chips were investigated. Results demonstrated that using short frying times and high oil temperatures causes OU to decrease in both blanched and non-blanched samples (p < 0.01). In addition, higher product thicknesses were found to increase OU in non-blanched taro chips, while the opposite trend was found for the blanched slices (p < 0.01). BP also affected the OU, yielding lower fat contents (up to 80% of OU reduction) (p < 0.05), thus allowing the development of a fried taro product with reduced fat content (less than 30% fat content in dry basis).

Drying of Food Products Shaped as Longitudinal Sections of Solid and Annular Cylinders: Modeling and Simulation

A mass transfer model was proposed to describe the moisture evolution during drying of longitudinal sections of solid and annular cylinder-shaped food products. The dimensionless form of the model was numerically solved under the resulting combinations of two geometrical parameters (inner radius and angular cuts) to produce longitudinal sections of solid and annular cylinders. In addition, average drying curves were calculated from the volume integration of local moisture values. A mixed theoretical and numerical approach was used to develop the dimension similarity between the studied geometries and a simpler flat slab-shaped product in order to obtain an approximate analytical solution to the original, non-steady-state mass transfer problem, while an exact solution was also developed to highlight problem complexity. In order to validate actual results during water diffusivity estimation, potatoes were chosen as the food model, as this product can be easily shaped into either studied or traditional geometry with known solution. Different cuts (parallelepiped and longitudinal sections of both solid and annular cylinders) were obtained and air-dried (80°C, 2.5 m/s). In this regard, a simple method to estimate diffusion coefficients in 2D or 3D geometries is also presented. Under the described experimental conditions, water diffusivities for each geometry were estimated in the narrow range of 1.27–1.52 × 10−9 m2/s, demonstrating the applicability of the proposed approach to solve mass transfer problems in products described by geometries lacking simple analytical solutions.

Sorption of BTEX on a nanoporous composite of SBA-15 and a calcined hydrotalcite

Benzene, toluene, ethylbenzene, and p-xylene (BTEX) are hazardous volatile organic compounds mostly released from fuel combustion, paint gas emissions, and biomass burning. In this work, it is studied the BTEX sorption influence on the surface reactivity of a new kind of nanoporous composite, prepared via an in situ functionalization of SBA-15 with a Mg–Al calcined hydrotalcite (HTC). During its preparation, Mg/Al mixed oxides are indeed formed and dispersed on the SBA-15 surface with non-blockage porosity. Furthermore, the physicochemical surface properties are exalted from its precursors and it is synergistically favorable for the BTEX sorption at low pressure and temperature.

Chemical, physical and sensory properties of Vienna sausages formulated with a starfruit dietary fiber concentrate

The use of a starfruit dietary fiber concentrate (SDFC) as a novel ingredient in Vienna sausages was investigated. A constrained mixture design was followed to evaluate the effect of different proportions of SDFC (0–10%), pork meat (0–100%) and turkey meat (0–100%) on the shear force, shrinkage, color, residual nitrite, moisture and polyphenol contents of sausages. Moreover, a chemical, physical and sensory characterization of the optimized formulations was performed. The cubic model equations demonstrated that the SDFC in mixture with pork or turkey meat had a reducing effect on nitrites, moisture, shear force and shrinkage, while there was an increase on the polyphenol concentration as the increase of SDFC proportion in the formulations. The optimization resulted in Vienna-type sausages formulated with a ternary mixture of pork/turkey meat and high SDFC proportion (7.4–8.4%). These products had high total dietary fiber content (11.04–17.79%) and antioxidant polyphenols, low residual nitrite content, shrinkage and red color. They presented good taste, color and texture attributes, and were sensory acceptable. This study demonstrated that enrichment of Vienna-type sausages with SDFC in mixture with pork/turkey meat is a way to obtain potential functional meat products with high antioxidant dietary fiber content, reduced in nitrites, and good physical and sensory properties.

Production, chemical, physical and technological properties of antioxidant dietary fiber from pineapple pomace and effect as ingredient in sausages

ABSTRACT In this study, fresh and steamed under pressure (SPP) pineapple pomace were used to produce dietary fiber concentrates (DFCs) dried by freeze-drying or hot air-drying. Chemical, physical and technological properties were determined to select one pineapple DFC (PDFC) and to evaluate its mixture effect with meats on characteristics of Vienna-type sausages. The PDFC produced from SPP and hot air-dried (SPDFC-HD) had the highest content of DF, carotenoids, polyphenols such as gallic, cinnamic and p-coumaric acids, antioxidant capacity and hydration properties. Microstructural analysis evidenced a cell wall disruption of the PDFCs matrix by the effect of processing. The cubic model equations showed that with the increase in SPDFC-HD in the ternary mixture, a reducing effect on nitrites, moisture, shear force and shrinkage was obtained in sausages, while carotenoids and antioxidant polyphenols increased. This study demonstrated that SPDFC-HD was produced with characteristics to be used as ingredient in potential functional sausages.