Microstructural modification of papaya tissue during calcium diffusion: Effects on macrostructure level.

The microstructural changes in papaya tissue during calcium diffusion, the effect on drying kinetics and texture parameters were investigated. Calcium pretreatment was applied to papaya samples for 3 h, at a solution concentration of 1.5 g Ca(OH)2/100 mL H2O, and a solution temperature of 25 °C; subsequently, the samples were convectively dried at 70 °C, air flow of 1.5 m/s, and a relative humidity of 5 ± 2%. Calcium content was determined using the Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) technique, the microstructure of the samples was analyzed by High-Resolution Scanning Electron Microscopy (HR-SEM), and the elementary analysis was performed by Energy-Dispersive X-ray Spectroscopy (EDS). Effective diffusivity of calcium (DefCa) and moisture (Defw) were calculated during pretreatment and drying, respectively and texture parameters were determined by double compression using a texturometer. The transport mechanism determined during calcium pretreatment was diffusion with a DefCa = 3.10 × 10-10 m2/s. Also, branched calcium microstructures in the cell walls of tissue were observed due to the calcium effect, it was supported by elemental analysis, which showed an increase of calcium in section restructured compared to non-restructured. During drying, Defw = 1.86 × 10-9 m2/s was higher in pretreated compared to non-pretreated samples with Defw = 1.17 × 10-9 m2/s, indicating a higher drying rate and moisture loss. The texture values changed significantly (α ≤ 0.05) due to calcium pretreatment and drying; the calcium microstructures caused higher cohesiveness, springiness, gumminess, and chewiness. Calcium modifies the microstructure and composition of papaya tissue; therefore, drying kinetics and texture parameters depend on this modification.

Experimental and Numerical Study of a Turbulent Air-Drying Process for an Ellipsoidal Fruit with Volume Changes.

It is common in the numerical simulations for drying of food to suppose that the food does not experience a change of volume. The few numerical studies that include volume changes assume that the shrinkage occurs symmetrically in all directions. Therefore, this effect has not been fully studied, and it is known that not considering it can be detrimental for the accuracy of these simulations. The present study aims to develop a three-dimensional model for the simulation of fruits that includes the volume changes but also takes into consideration the asymmetry of the shrinkage. Physalis peruviana is taken as the subject of study to conduct experiments and imaging analyses that provided data about the drying kinetics and asymmetric shrinkage mode. The effective diffusion coefficient is found to be between 10-12 m2 s-1 and 1.75 × 10-9 m2 s-1. The shrinkage occurs essentially in only one direction, with an average velocity of 8.3 × 10-5 m/min. A numerical modelling scheme is developed that allows including the shrinkage effect in computer simulations. The performance of the model is evaluated by comparison with experimental data, showing that the proposed model decreases more than 4 times the relative error with respect to simulations that do not include volume changes. The proposed model proves to be a useful method that can contribute to more accurate modeling of drying processes.

Combining ultrasound, vacuum and/or ethanol as pretreatments to the convective drying of celery slices.

This work studied three emerging approaches to improve the convective drying (50 °C, 0.8 m/s) of celery. Celery slices of 2 mm thick were pretreated for 5 min using ultrasound (32 W/L, 40 kHz), vacuum (75 kPa vacuum pressure) and ethanol (99.8% v/v, as drying accelerator) applied individually or in combination. To evaluate individual effects of ultrasound and vacuum, the treatments were also performed with distilled water or air medium, respectively. Moreover, the cavitational level was characterized in each condition. Drying kinetics was evaluated tending into account the drying time required by each treatment and the Page's model parameters. In addition, microstructural effects and shrinkage were evaluated. As results, ethanol combined with ultrasound significantly improved drying kinetics reducing drying time by around 38%. However, vacuum pretreatment did not affect drying kinetics even in combination with ethanol and/or ultrasound. Microstructural evaluation did not evidence cell disruption, suggesting changes in intercellular spaces, pores and/or cell wall permeability. The use of ethanol and vacuum showed a greater effect on shrinkage after pretreatment and after drying, respectively. In conclusion, at the studied conditions, the drying acceleration by vacuum and ultrasound is lower compared to the effect produced using ethanol.

Development of novel spray-dried and air-dried formulations of Metarhizium robertsii blastospores and their virulence against Dalbulus maidis.

The present research addressed spray-drying and air-drying techniques applied to Metarhizium robertsii blastospores to develop wettable powder (WP) formulations. We investigated the effect of co-formulants on blastospore viability during drying and assessed the wettability and stability of formulations in water. The effect of oxygen-moisture absorbers was studied on the shelf life of these formulations stored at 26 °C and 4 °C for up to 90 days. Additionally, we determined the virulence of the best spray-dried and air-dried formulations against the corn leafhopper Dalbulus maidis. While sucrose and skim milk played an essential role as osmoprotectants in preserving air-dried blastospores, maltodextrin, skim milk, and bentonite were crucial to attain high cell survival during spray drying. The lowest wettability time was achieved with spray-dried formulations containing less Ca-lignin, while charcoal powder amount was positively associated with formulation stability. The addition of oxygen-moisture absorbers inside sealed packages increased from threefold to fourfold the half-life times of air-dried and spray-dried formulations at both storage temperatures. However, the half-life times of all blastospore-based formulations were shorter than 3 months regardless of temperature and packaging system. Spray-dried and air-dried WP formulations were as virulent as fresh blastopores against D. maydis adults sprayed with 5 × 107 blastospores mL-1 that induced 87.8% and 70.6% mortality, respectively. These findings bring innovative advancement for M. robertsii blastospore formulation through spray-drying and underpin the importance of adding protective matrices coupled to oxygen-moisture absorbers to extend cell viability during either cold or non-refrigerated storage. KEY POINTS: • Cost-effective wettable powder formulations of M. robertsii blastospores were developed. • Bioefficacy of formulations against the corn leafhopper was comparable to fresh blastospores. • Cold storage and dual oxygen-moisture absorber are critical for extended shelf life.

Effect of Ethanol and Ultrasound Pretreatments on Pineapple Convective Drying.

RESEARCH BACKGROUND: Drying represents a viable unit operation for the preservation of food. Convective drying is the most used method for plant materials. However, it can result in negative changes in food nutrient composition, and other quality parameters, besides requiring high energy consumption. Pretreatments can represent an alternative to minimise these negative aspects of dried materials. This work aims to evaluate the use of ethanol and ultrasound before pineapple convective drying and its effect on the product´s colour, water activity, ascorbic acid and total carotenoid contents. EXPERIMENTAL APPROACH: For the pretreatment step, fruit samples were immersed in ethanol solutions of different volume fractions, and experiments were carried out for 10 min with and without using ultrasound (25 kHz). Fruit samples were dried at 60 ºC. A control group (without the pretreatment step) was also dried under the same condition. Semi-theoretical models were used for drying data fitting, and the diffusional model was used to describe the moisture transfer and calculate the effective diffusivity. Water activity, ascorbic acid, total carotenoids and colour analyses were performed. RESULTS AND CONCLUSIONS: The combination of ethanol and ultrasound as a pretreatment reduced the drying time of pineapple. Higher effective moisture diffusivities were obtained when ethanol and ultrasound were applied before drying. The two-term exponential model presented the best fit for drying experimental data. The dried samples had a darker colour than the fresh sample. The pretreatment with ethanol resulted in increased retention of the studied bioactive components. The satisfactory results of this study represent an improvement in the drying process. NOVELTY AND SCIENTIFIC CONTRIBUTION: Ultrasound and ethanol as a pretreatment to convective drying are promising. However, each food matrix has a typical structure and composition. Therefore, the application of the pretreatment in other products or using other conditions is still necessary to deeply understand and explain their effect on the process and the quality of the dried products.

Utilization of Cumbeba (Tacinga inamoena) Residue: Drying Kinetics and Effect of Process Conditions on Antioxidant Bioactive Compounds.

The residue generated from the processing of Tacinga inamoena (cumbeba) fruit pulp represents a large amount of material that is discarded without proper application. Despite that, it is a raw material that is source of ascorbic acid, carotenoids and phenolic compounds, which are valued in nutraceutical diets for allegedly combating free radicals generated in metabolism. This research paper presents a study focused on the mathematical modeling of drying kinetics and the effect of the process on the level of bioactive of cumbeba residue. The experiments of cumbeba residue drying (untreated or whole residue (WR), crushed residue (CR) and residue in the form of foam (FR)) were carried out in a fixed-bed dryer at four air temperatures (50, 60, 70 and 80 °C). Effective water diffusivity (Deff) was determined by the inverse method and its dependence on temperature was described by an Arrhenius-type equation. It was observed that, regardless of the type of pretreatment, the increase in air temperature resulted in higher rate of water removal. The Midilli model showed better simulation of cumbeba residue drying kinetics than the other models tested within the experimental temperature range studied. Effective water diffusivity (Deff) ranged from 6.4890 to 11.1900 × 10-6 m2/s, 2.9285 to 12.754 × 10-9 m2/s and 1.5393 × 10-8 to 12.4270 × 10-6 m2/s with activation energy of 22.3078, 46.7115 and 58.0736 kJ/mol within the temperature range of 50-80 °C obtained for the whole cumbeba, crushed cumbeba and cumbeba residue in the form of foam, respectively. In relation to bioactive compounds, it was observed that for a fixed temperature the whole residue had higher retention of bioactive compounds, especially phenolic compounds, whereas the crushed residue and the residue in the form of foam had intermediate and lower levels, respectively. This study provides evidence that cumbeba residue in its whole form can be used for the recovery of natural antioxidant bioactive compounds, mainly phenolic compounds, with the possibility of application in the food and pharmaceutical industries.

Producing non-traditional flour from watermelon rind pomace: Artificial neural network (ANN) modeling of the drying process.

An artificial neural network (ANN) model was developed to simulate the convective drying process of watermelon rind pomace used in the fabrication of non-traditional flour. Also, the drying curves obtained experimentally were fitted with eleven different empirical models to compare both modeling approaches. Lastly, to reduce the required fossil fuel in the convective drying process, two types of solar air heaters (SAH) were presented and experimentally evaluated. The optimization of the ANN by a genetic algorithm (GA) resulted in an optimal number of neurons of nine (9) for the first hidden layer and ten (10) for the second hidden layer. Also, the ANN performed better than the best fitted empirical model. Simulations with the trained ANN showed very promising generalization capabilities. The type II SAH showed the best performance and the highest air temperature it reached was 45 °C. The specific energy consumption (SEC) needed to dry the watermelon rind at this temperature and the CO2 emissions were 609 kWh.kg-1 and 318 kg CO2.kWh-1, respectively. Using the type II SAH, this energy amount would be saved without CO2 emissions. To reach higher drying temperatures the combination of the SAH and the electrical convective dryer is possible.

Enhancing carrot convective drying by combining ethanol and ultrasound as pre-treatments: Effect on product structure, quality, energy consumption, drying and rehydration kinetics.

Ultrasound was combined with ethanol to improve different aspects of carrot convective drying, evaluating both processing and product quality. The ultrasound in water treatment resulted in cellular swelling and small impact on texture. Differently, the ultrasound in ethanol and ethanol treatments modified both carrot microstructure (cell wall modifications of parenchymatic tissue) and macrostructure (shrinkage and resistance to perforation). Pre-treatments with ultrasound in ethanol and ethanol improved the drying kinetics, reducing the processing time (~50%) and the energy consumption (42-62%). These pre-treatments also enhanced rehydration, whose initial rate and water retention were higher than the control. In addition, the carotenoid content was preserved after drying, for all the treatments. Any impact on shrinkage was observed. A mechanistic discussion, based on structural modification (microstructure and macrostructure) and physical properties of water and ethanol, was provided. As conclusion, this work not only described positive aspects of combining the technologies of ultrasound and ethanol as pre-treatments to convective drying, but also proposed mechanisms to explain the phenomena.

2-Furoylmethyl amino acids as indicators of Maillard reaction during the elaboration of black garlic.

This study reports the formation of 2-furomethyl-amino acids (2-FM-AA) as indicators of Maillard reaction (MR) in black garlic elaboration, followed by the determination of furosine by ion-pair RP-HPLC-UV. The method was assessed for accuracy, repeatability and detection and quantitation limits indicating its adequacy. Traditional procedure of black garlic obtainment and the inclusion of convective drying (CDP) and ohmic heating (OHP) were assayed. For comparison purposes, three commercial black garlic samples were used. Together with furosine (2-FM-lysine), 2-furoylmethyl-γ-aminobutyric acid and 2-FM-arginine were detected. Levels of furosine were higher in CDP (46.6-110.1mg/100g protein) than in OHP (13.7-42.0mg/100g protein) samples, probably due to the most severe processing conditions used in the former. These results highlight the suitability of 2-FM-AA as chemical indicators to monitor the process of black garlic elaboration in order to obtain high quality products.

Chemical and sensory comparison of fresh and dried lulo (Solanum quitoense Lam.) fruit aroma.

The odour-active volatile compounds of lulo fruit (Solanum quitoense Lam.) were isolated by solvent extraction followed by solvent-assisted flavour evaporation (SAFE). GC-O and GCMS analyses as well as quantitation by internal standard method showed that (Z)-3-hexenal, ethyl butanoate, 3-sulphanylhexyl acetate, and ethyl hexanoate were key aroma compounds in this fruit. Other odorants with relevance because their contribution (high OAVs) to the overall aroma were 4-hydroxy-2,5-dimethyl-3(2H)-furanone, methyl benzoate, (E)-2-hexenal, and hexanal. Lulo fruit pulp in presence of maltodextrin DE-20 was dried by using four different types of drying methods: hot air-drying (HD), spray drying (SD), lyophilisation (LD), and ultrasonic convective hot air-drying (HUD). LD sample exhibited the highest sensory rank (lulo-like) in comparison with fresh fruit pulp. Hot-air drying processes (HD and HUD) changed adversely the aroma of lulo fruit pulp.

Fruits and vegetables with osmotic dehydration pretreatment / A desidratação osmótica como pré-tratamento para frutas e hortaliças

Osmotic dehydration is a crucial operation unit used for transforming the perishable vegetal product into the new produces containing an added nutritional value and much longer shelf life. This process is responsible for removing the water from fruits and vegetables. Accordingly, the fruits and vegetables are subjected to the immersion into a hypertonic solution which causes a high osmotic pressure in the system. The present study aimed at presenting a review on the osmotic dehydration involving the process definition, the process variables and the desirable and undesirable changes in procedures carried on in products of vegetable source.(AU)

A desidratação osmótica é uma operação importante para transformar os alimentos de origem vegetal perecíveis em novos produtos com valor agregado e com maior vida de prateleira. Este processo é responsável pela remoção de água, em que as frutas e hortaliças são submetidas à imersão em solução hipertônica que tenha alta pressão osmótica. O presente trabalho apresenta uma revisão sobre a desidratação osmótica abrangendo-se a definição do processo, as variáveis e as alterações desejáveis e indesejáveis nos procedimentos realizados com os produtos de origem vegetal.(AU)

Condições de secagem de uma pasta de anchoita modificada enzimaticamente na oxidação lipídica, lisina disponível e atividade antioxidante do produto / Drying conditions of an enzymatic modified paste of anchovy in the lipid oxidation, available lisina and antioxidant activity of the product

O objetivo do trabalho foi analisar as condições da secagem convectiva de uma pasta de anchoita (Engraulis anchoita) modificada enzimaticamente, através da metodologia de superfícies de resposta, sendo as respostas consideradas: a oxidação lipídica (TBA), a redução da lisina disponível e a perda da atividade antioxidante específica. A pasta de anchoita modificada foi obtida por hidrólise enzimática da fração muscular (filés) do pescado por Neutrase®. Foram avaliadas na operação de secagem, a temperatura do ar (60, 70 e 80°C) e a espessura das amostras (1,5; 2,5 e 3,5mm). A análise estatística da secagem mostrou efeitos significativos da temperatura do ar e da espessura das amostras (P<0,05) nas respostas. A melhor condição de secagem foi obtida na temperatura do ar de 60°C e espessura das amostras de 2,5mm. Nessa condição, o índice de TBA foi de 0,93mgMDA kg-1, redução da lisina disponível de 16% e perda da atividade antioxidante específica de 20,2%.

The aim of the work was to analyze the conditions of the convective drying of an enzymatic modified paste of anchovy (Engraulis anchoita) through the response surfaces methodology, and the responses were the lipid oxidation (TBA), reduction of the available lisina and loss of the specific antioxidant activity. The modified paste of anchovy was obtained through enzymatic hydrolysis of the fish muscular fraction (fillets) by Neutrase®. In drying operation the air temperature (60, 70 and 80°C) and the samples thickness (1.5, 2.5 and 3.5mm) were studied. The statistical analysis of the drying showed significant effects of the air temperature and samples thickness (P<0.05). The best drying condition was obtained in the air temperature of 60°C and samples thickness of 2.5mm. In this condition the TBA index was of 0.93mgMDA kg-1, available lisina reduction of 16% and loss of the specific antioxidant activity of 20.2%.

ASSESSMENT OF THE OSMO-CONVECTIVE DEHYDRATION ON THE QUALITY ATTRIBUTES AND CENTESIMAL COMPOSITION OF YACON (Smallanthus sonchifolius)

This work has studied the application of the osmo-convective dehydration on yacon roots, regarding its composition and quality attributes. Slices of yacon were submitted to osmotic treatment with sucralose solution followed by convective dry. The experiments followed a complete 23 factorial design to assessthe effect of three variables of the process (temperature, stirring rate of the osmotic solution and drying temperature) over four quality attributes (moisture content, color, luminosity and soluble solid content). The application of the osmotic treatment before convective drying provided quality gains to the dried product, such as low browning and shrinkage rates, and reduction of the structural damages towards angular distortions and fissures, in comparison to the samples dried directly on the tray dryer. The effect of osmotic treatment over the centesimal composition of yacon have resulted on absorption of sucralose and water loss without a significance compromise of its nutritional attributes. The obtained product presented different contents of moisture, but similar levels of darkening and color alteration at diverse experimental conditions.

Investigou-se a aplicação da desidratação osmo-convectiva em raízes de yacon, com relação à sua composição centesimal e atributos de qualidade. Fatias de yacon foram submetidas ao tratamento osmótico em solução de sucralose e depois à secagem convectiva. Os experimentos seguiram planejamento fatorial completo (2

Condições de secagem de uma pasta de anchoita modificada enzimaticamente na oxidação lipídica, lisina disponível e atividade antioxidante do produto

The aim of the work was to analyze the conditions of the convective drying of an enzymatic modified paste of anchovy (Engraulis anchoita) through the response surfaces methodology, and the responses were the lipid oxidation (TBA), reduction of the available lisina and loss of the specific antioxidant activity. The modified paste of anchovy was obtained through enzymatic hydrolysis of the fish muscular fraction (fillets) by Neutrase®. In drying operation the air temperature (60, 70 and 80°C) and the samples thickness (1.5, 2.5 and 3.5mm) were studied. The statistical analysis of the drying showed significant effects of the air temperature and samples thickness (P 0.05). The best drying condition was obtained in the air temperature of 60°C and samples thickness of 2.5mm. In this condition the TBA index was of 0.93mgMDA kg-1, available lisina reduction of 16% and loss of the specific antioxidant activity of 20.2%.

O objetivo do trabalho foi analisar as condições da secagem convectiva de uma pasta de anchoita (Engraulis anchoita) modificada enzimaticamente, através da metodologia de superfícies de resposta, sendo as respostas consideradas: a oxidação lipídica (TBA), a redução da lisina disponível e a perda da atividade antioxidante específica. A pasta de anchoita modificada foi obtida por hidrólise enzimática da fração muscular (filés) do pescado por Neutrase®. Foram avaliadas na operação de secagem, a temperatura do ar (60, 70 e 80°C) e a espessura das amostras (1,5; 2,5 e 3,5mm). A análise estatística da secagem mostrou efeitos significativos da temperatura do ar e da espessura das amostras (P 0,05) nas respostas. A melhor condição de secagem foi obtida na temperatura do ar de 60°C e espessura das amostras de 2,5mm. Nessa condição, o índice de TBA foi de 0,93mgMDA kg-1, redução da lisina disponível de 16% e perda da atividade antioxidante específica de 20,2%.

Condições de secagem de uma pasta de anchoita modificada enzimaticamente na oxidação lipídica, lisina disponível e atividade antioxidante do produto

The aim of the work was to analyze the conditions of the convective drying of an enzymatic modified paste of anchovy (Engraulis anchoita) through the response surfaces methodology, and the responses were the lipid oxidation (TBA), reduction of the available lisina and loss of the specific antioxidant activity. The modified paste of anchovy was obtained through enzymatic hydrolysis of the fish muscular fraction (fillets) by Neutrase®. In drying operation the air temperature (60, 70 and 80°C) and the samples thickness (1.5, 2.5 and 3.5mm) were studied. The statistical analysis of the drying showed significant effects of the air temperature and samples thickness (P 0.05). The best drying condition was obtained in the air temperature of 60°C and samples thickness of 2.5mm. In this condition the TBA index was of 0.93mgMDA kg-1, available lisina reduction of 16% and loss of the specific antioxidant activity of 20.2%.

O objetivo do trabalho foi analisar as condições da secagem convectiva de uma pasta de anchoita (Engraulis anchoita) modificada enzimaticamente, através da metodologia de superfícies de resposta, sendo as respostas consideradas: a oxidação lipídica (TBA), a redução da lisina disponível e a perda da atividade antioxidante específica. A pasta de anchoita modificada foi obtida por hidrólise enzimática da fração muscular (filés) do pescado por Neutrase®. Foram avaliadas na operação de secagem, a temperatura do ar (60, 70 e 80°C) e a espessura das amostras (1,5; 2,5 e 3,5mm). A análise estatística da secagem mostrou efeitos significativos da temperatura do ar e da espessura das amostras (P 0,05) nas respostas. A melhor condição de secagem foi obtida na temperatura do ar de 60°C e espessura das amostras de 2,5mm. Nessa condição, o índice de TBA foi de 0,93mgMDA kg-1, redução da lisina disponível de 16% e perda da atividade antioxidante específica de 20,2%.

Condições de secagem de uma pasta de anchoita modificada enzimaticamente na oxidação lipídica, lisina disponível e atividade antioxidante do produto

The aim of the work was to analyze the conditions of the convective drying of an enzymatic modified paste of anchovy (Engraulis anchoita) through the response surfaces methodology, and the responses were the lipid oxidation (TBA), reduction of the available lisina and loss of the specific antioxidant activity. The modified paste of anchovy was obtained through enzymatic hydrolysis of the fish muscular fraction (fillets) by Neutrase®. In drying operation the air temperature (60, 70 and 80°C) and the samples thickness (1.5, 2.5 and 3.5mm) were studied. The statistical analysis of the drying showed significant effects of the air temperature and samples thickness (P 0.05). The best drying condition was obtained in the air temperature of 60°C and samples thickness of 2.5mm. In this condition the TBA index was of 0.93mgMDA kg-1, available lisina reduction of 16% and loss of the specific antioxidant activity of 20.2%.

O objetivo do trabalho foi analisar as condições da secagem convectiva de uma pasta de anchoita (Engraulis anchoita) modificada enzimaticamente, através da metodologia de superfícies de resposta, sendo as respostas consideradas: a oxidação lipídica (TBA), a redução da lisina disponível e a perda da atividade antioxidante específica. A pasta de anchoita modificada foi obtida por hidrólise enzimática da fração muscular (filés) do pescado por Neutrase®. Foram avaliadas na operação de secagem, a temperatura do ar (60, 70 e 80°C) e a espessura das amostras (1,5; 2,5 e 3,5mm). A análise estatística da secagem mostrou efeitos significativos da temperatura do ar e da espessura das amostras (P 0,05) nas respostas. A melhor condição de secagem foi obtida na temperatura do ar de 60°C e espessura das amostras de 2,5mm. Nessa condição, o índice de TBA foi de 0,93mgMDA kg-1, redução da lisina disponível de 16% e perda da atividade antioxidante específica de 20,2%.