M.A. Ruiz-Cabrera

Spray-Drying of Cactus Pear Juice (Opuntia streptacantha): Effect on the Physicochemical Properties of Powder and Reconstituted Product

ABSTRACT A D-optimal experimental design with three center points was used to evaluate the influence of spray-drying conditions on the physicochemical properties of a powdered product obtained by drying cactus pear juice. Drying was performed in a laboratory spray-dryer (Pulvis GB 22 model) at two inlet air temperatures (205 and 225°C), and two compressor air pressures (0.10 and 0.20 MPa). Commercial maltodextrins (10 and 20 DE) were used as carrier agents at two levels (18 and 23%). Moisture content and hygroscopicity were evaluated in the powder, and vitamin C retention and total color change were measured in the reconstituted product. Analysis of variance (ANOVA) was performed with a confidence level of 95% (p < 0.05). Moisture content of spray-dried powder and vitamin C retention of reconstituted product was mainly determined by the temperature-pressure, T*P, interaction. While for hygroscopicity, the pressure-concentration, P*C, interaction was the most important factor. The reconstituted product showed a slight change of total color (ΔE) with respect to natural juice and a significant effect of the maltodextrin concentration was found in this property.

Study of Enzymatic Hydrolysis of Fructans from Agave salmiana Characterization and Kinetic Assessment

Fructans were extracted from Agave salmiana juice, characterized and subjected to hydrolysis process using a commercial inulinase preparation acting freely. To compare the performance of the enzymatic preparation, a batch of experiments were also conducted with chicory inulin (reference). Hydrolysis was performed for 6 h at two temperatures (50, 60°C) and two substrate concentrations (40, 60 mg/ml). Hydrolysis process was monitored by measuring the sugars released and residual substrate by HPLC. A mathematical model which describes the kinetics of substrate degradation as well as fructose production was proposed to analyze the hydrolysis assessment. It was found that kinetics were significantly influenced by temperature, substrate concentration, and type of substrate (P < 0.01). The extent of substrate hydrolysis varied from 82 to 99%. Hydrolysis product was mainly constituted of fructose, obtaining from 77 to 96.4% of total reducing sugars.

Water Diffusivity and Color of Cactus Pear Fruits (Opuntia Ficus Indica) Subjected to Osmotic Dehydration

This paper details the results of a series of tests whose main purpose was to determinate how osmotic drying influences both water loss and color retention in cactus pear fruits. The dehydration process was performed using a 32 experimental design which involved three different sugar concentration levels (40, 50, and 608Brix) and three different temperatures (25, 40, and 558C). A product/solution ratio of 1/15, cactus pear cylindrical slices 5 mm thick, and ten-hour immersion time spans were used for all the experiments. Modeling of the drying curves was done with Ficks second law and Pages equation, which were used to calculate water effective diffusivity (De), drying constant (k), and the b values respectively. The color parameters (L*, a*, b*) of the samples were measured before and after each test to evaluate total color change (ΔE). An analysis of variance (ANOVA) revealed that water diffusivity and Pages parameter b were affected by temperature and sugar concentration while the drying constant (k) was independent of the drying conditions. The total color change was affected only by the temperature. De and b values varied from 4.06×10−11 to 2.95×10−10 m2/s, and from 0.453 to 0.861 respectively. The best color retention was obtained at 25°C independent of the sugar concentration.

ULTRASONIC ASSISTED PRE-TREATMENT METHOD FOR ENHANCING MASS TRANSFER DURING THE AIR-DRYING OF HABANERO CHILI PEPPER (CAPSICUM CHINENSE)

The ultrasonic pre-treatment method was used for the purpose of reducing the time employed in air-drying of habanero chili pepper. The pre-treatment was performed by immersing the sample in distilled water and applying ultrasonic signals during 30 and 60 min with a 750-Watt ultrasonic processor (20 kHz) operated at different percentages of amplitude (A) ranging between 20 and 100%. The samples immediately underwent air-drying at 60°C in a convection oven with an air velocity of 2 ± 0.2 m/s. A mathematical model that takes into account the influence of the internal resistances to mass transport by diffusion ( ) as well as the resistance of the membrane barrier ( ) promoted by the wax layer of the habanero pepper was proposed to analyze the drying kinetics. The drying time following the ultrasound treatment was reduced from a 25 to a 50% compared to the results obtained in untreated samples. It was found that and were significantly influenced by the ultrasonic pre-treatment (p < 0.05). The highest drying rate was achieved in the amplitude percentage of 80 and 100% with a sonication time of 60 min.

Water Diffusivity and Quality Attributes of Fresh and Partially Osmodehydrated Cactus Pear (Opuntia Ficus Indica) Subjected to Air-Dehydration

Water diffusivity, vitamin C degradation, and color change were assessed in two batches of cactus pear that were dried; one by regular air-drying; and the other one by applying partial osmodehydration followed by air-drying. The drying was done with a convection oven at 40, 50, 60, and 70°C. The pretreatment was performed by immersing the samples for 3 hours in a 40°Brix sucrose solution at 40°C. An analysis of variance (ANOVA) with a confidence level of 95% (p < 0.05) revealed that water diffusivity was mainly affected by the temperature and the pretreatment. Both the vitamin C loss and the color change behaved as a first-order reaction; the set temperature used was found to be the most important factor in the process.

Reduction of Ageing Time of Bovine Meat by Intermittent Thermal Treatments

Semimembranosus and Semitendinosus muscles (one day after slaughter) were used to study intermittent thermal treatments of 4–20 and 4–25°C as an alternative method to reduce ageing time and improve beef tenderness. A number of samples thermostated at 4°C were used as the basis for comparison. The evolution of muscle tenderness with storage time was measured by the compression method using an INSTRON 4442 machine at 20% deformation. At the end of the thermal treatment process, weight loss in muscle was determined and a sensory evaluation of meat was carried out. It was found that intermittent thermal treatment reduced the ageing time by 50–70% in relation to studies done at 4°C. However, muscle weight loss was elevated, varying from 10 to 15% compared to 5% observed on the samples treated at 4°C. The results of the sensory evaluation indicated that meat tenderness treated at 4–20 and 4–25°C was comparable to samples treated at 4°C (p < 0.10).

Experimental and simulated thermal properties and process time for canned escamoles (Liometopum apiculatum) under sterilization conditions

Sterilization process of canned pickled escamoles and canned brined escamoles was studied in order to analyze the heat transfer mechanisms as well as to calculate the thermal properties and process time. Sterilization process was performed using water immersion and saturated steam at 115°C and 121°C. Transient temperature changes in the cold point inside of the can containing either pickled or brined escamoles were determined experimentally and compared with simulation results. Additionally, the physicochemical, nutritional and sensory quality properties of sterilized escamoles were also evaluated. Uniform and conductive heating profiles were observed in both products. The thermal conductivity (k), specific heat (Cp) and density (ρ) were significantly affected (p < 0.05) by the temperature and by the heating medium. Results also showed that maximum quality retention and the lowest process times were achieved for canned pickled escamoles.

Sugars and Fructans Separation by Nanofiltration from Model Sugar Solution and Comparative Study with Natural Agave Juice

The fructan separation from a model sugar solution and natural agave juice was studied using a stirred-cell nanofiltration unit operated in concentration mode. Hydrophilic cellulose membrane with MWCO of 1000 Da was used. The experimental conditions were varied to predict the influence of pressure (0.14–0.350 MPa) and feed concentration (0.15–0.25 g/mL) on the initial permeate flux and solute retained fraction (SRF) values of the process. Response surface plots (p < 0.05) showed that the permeate flux and SRF increased significantly with the pressure and decreased with feed concentration. The permeate flux varied from 0.5 to 4.1 L · h−1 · m−2. The fructan retained fraction in model sugar solution varied from 0.85 to 0.97 whereas fructose, glucose and sucrose presented similar SRF values ranging from 0.38 to 0.65. Promising results were obtained when natural agave juice was used.

Experimental and CFD Modeling Study of Inulin-Type Fructan Purification from a Model Solution by Diafiltration on a Pilot-Scale Unit

Nanofiltration of a model inulin-sucrose solution has been studied using a pilot cross-flow unit. The aim of this work was to evaluate two operation modes: total recycle nanofiltration and diafiltration. Experiments were performed at transmembrane pressures from 0.4 to 1.45 MPa and two inlet flow rates. It was found that inulin purification is feasible within the range of the process conditions set. Furthermore, the sucrose retention coefficient is highly affected by the transmembrane pressure but the inlet flow rate does not affect this parameter significantly. Experimental results were simulated by Computational Fluid Dynamics (CFD) and a good agreement was observed between the predicted and the experimental values.

Structural and physicochemical changes due to proteolytic deterioration of escamoles (Liometopum apiculatum) a traditional Mexican food

Entomophagy or consumption of insects has significantly increased worldwide, either for pleasure or to satisfy the food needs in developing countries. There are approximately 2,000 species of edible insects distributed in 120 countries. From these 2,000 species, about 540 are located in Mexico; one of the most consumed are the escamoles. Escamoles are larvae and pupae of the ant Liometopum apiculatum. Escamoles are nutritious because of their high content of protein, fat, carbohydrates and vitamin. However, during storage the quality of escamoles changes rapidly which affects the acceptability by the consumer. This loss of quality is probably a result of proteolytic activity of endogenous proteases. Therefore, the objectives of this study were to identify the classes of proteases in escamoles as well as to evaluate the effect of proteolytic activity on physicochemical and structural changes during storage. Proteases identification was conducted using specific inhibitors; structural changes, texture, and proteolytic activity were monitored at different days of storage. The highest proteolytic activities (P<0.05) were observed at pH 8, 9 and 10 and at 37 and 50 °C. Proteases were mainly inhibited by iodoacetic acid and soybean trypsin inhibitor showing that cysteine and serine proteases were dominant. High proteolytic activity, significant (P<0.05) reduction in texture and weight loss was observed during storage. The deterioration of escamoles was evident in analyses of images, where initial structure was lost during storage. These results indicate that different groups of proteases are associated with rapid deterioration of escamoles.