Microwave and ultrasound pre-treatments for ‘Rocha’ Pear: impact on drying kinetics and selected quality attributes

Rocha’pear (Pyruscommunis L.) is the main cultivar produced in Portugal, and is classified as protected designation of origin (PDO).This pear fruit is characterized by its own typical and specific properties, such as pleasant flavor, crispness and also sweetness.Pears are rich in polyphenols with strong antioxidant activity,offering health promoting benefits. In order to extend its shelf life and increase availability along the year, drying processes are widely applied as a good alternative method for fruits preservation. Drying is used to improve food stability, decrease moisture content and microbial activity, and minimize physico-chemical changes during storage. However, drying process conditions (i.e. air temperature, time, and velocity) usually may lead to food quality degradation in terms of physico-chemical and nutritional attributes. In this context, drying combined with pre-treatments have been proposed in order to reduce the drying impact on products quality. The objective of this work was to evaluate the use of microwave and ultrasound pre-treatments on ‘Rocha’ pear drying kinetics and quality attributes (water activity, color, shrinkage, total phenolics, antioxidant activity, and texture and rehydration behavior of dried slabs).Three different samples were compared: a) Control, b) Microwave Pre-treatment (1540 MW, 4 min) (MW), and c) Ultrasound Pre-treatment (35 kHz, 10 min, 25°C) (US). Drying experiments were conducted on pear slabs (thickness and diameter of 6 and 38 mm, respectively) in a tray dryer with an air temperature of 60°C and a fixed velocity of 0.75 m/s. Pear samples pre-treated with MW had shorter drying time than control and ultrasound treated ones.Pear samples pre-treated with US showed the lowest colour changes and shrinkage, higher total phenolics and antioxidant activity, the highest rehydration capacity, and similar drying time to the control. This study contributes with information for the development of new drying pre-treatment conditions of ‘Rocha” pear fruits, as an alternative to traditional drying in an industrial context.info:eu-repo/semantics/publishedVersio

Microwave and ultrasound pre-treatments for drying of the “Rocha” Pear: impact on phytochemical parameters, color changes and drying kinetics

The objective of this research was to evaluate the effect of drying temperature and innovative pre-treatments (i.e., microwave and ultrasound) on “Rocha” pear drying behavior and quality characteristics, such as color, total phenolic content and antioxidant activity. Experiments were carried out with pear slabs subjected to microwaves (2450 MHz, 539 W, 4 min, microwave oven) and ultrasounds (35 kHz, 10 min, in an ultrasonic bath) as well as control samples. The drying process was conducted in a tray dryer at three different temperatures (50, 55 and 60 °C) and a fixed air velocity of 0.75 m/s. Microwave technology resulted in a higher quality deterioration in dried pear samples compared to those of controls and ultrasound pre-treated samples. The combined application of ultrasound pre-treatment and the higher drying temperature of 60 °C was characterized by the lowest color changes (ΔE = 3.86 ± 0.23) and higher preservation of nutritional parameters (total phenolic content, TPC = 345.60 ± 8.99; and antioxidant activity, EC50 = 8.80 ± 0.34). The drying characteristics of pear fruits were also analyzed by taking into account empirical models, with the Page model presenting the best prediction of the drying behavior. In conclusion, ultrasound application is a promising technology to obtain healthy/nutritious dried “Rocha” pear snacks as dietary sources for consumers.info:eu-repo/semantics/publishedVersio

Microwave and ultrasound pre-treatments for ‘Rocha’ pear: impact on drying kinetics and selected quality attributes

info:eu-repo/semantics/acceptedVersio

Micro structural approach of potato and pumpkin drying and rehydration

The food structure is subjected to a change of the integrity during dehydration which will affect rehydration. Changes in the underlying microstructure of this deformation and rehydration generally fails in restoring the integrity and quality of the food material to the original status. In this context, there are not many studies performed which correlate cellular structural changes to the desorption-sorption behaviour of food materials after dehydration. This study was undertaken to understand desorption-sorption behaviour of food considering potato (cv Sebago) and pumpkin (cv ecotype) as the model materials during drying and further explanations on rehydration. Pumpkin was used to construct only for dehydration and rehydration graphs. For potato SEM images were taken for dehydration and rehydration. Corresponding behaviours show the irreversible trend of dehydration-rehydration exists and changes to the scenario of relationship of the cellular structure

Drying kinetics of two grape varieties of Italy

Two varieties of grapes, white grape and red grape grown in the Campania region of Italy were selected for the study of drying characteristics. Comparisons were made with treated and untreated grapes under constant drying condition of 50o C in a conventional drying system. This temperature was selected to represent farm drying conditions. Grapes were purchased from a local market from the same supplier to maintain the same size of grapes and same properties. An abrasive physical treatment was used as pretreatment. The drying curves were constructed and drying kinetics was calculated using several commonly available models. It was found that treated samples show better drying characteristics than untreated samples. The objective of this study is to obtain drying kinetics which can be used to optimize the drying operations in grape drying

Drying kinetics, quality changes and shrinkage of two grape varieties of Italy

Two varieties of grapes, white grape and red grape grown in the Campania region of Italy were selected for the study of drying characteristics, moisture diffusion, quality changes (colour) and shrinkage behaviour. Comparisons were made with treated and untreated grapes under constant drying condition of 50o C in a conventional drying system. This temperature was selected to represent farm drying conditions. Grapes were purchased from a local market from the same supplier to maintain the same size of grapes and same properties. An abrasive physical treatment was used as pretreatment. The drying curves were constructed and drying kinetics was calculated using several commonly available models. It was found that treated samples shows better drying characteristics than untreated samples. The objective of this study is to obtain drying kinetics which can be used to optimize the drying operations in grape drying

Effects of Passive Modified Atmosphere Packaging on Physico-Chemical Traits and Antioxidant Systems of ‘Dottato’ Fresh Fig

Fig is a very perishable fruit with short postharvest life. Low-cost postharvest techniques should be employed to reduce fresh fig postharvest losses. The purpose of this study was to design a passive modified atmosphere packaging (PMAP) to extend the shelf-life of fresh ‘Dottato’ figs stored at 4 °C for 21 days. Physico-chemical traits and enzymatic and non-enzymatic antioxidant systems were evaluated. Storage in PMAP reduced the losses of fruit weight as well as maintained physico-chemical traits and nutraceutical traits such as polyphenol and flavonoid contents and the antioxidant activity in fresh figs. PMAP reduced oxidative stress, inducing the activities of antioxidant enzymes such as ascorbate peroxidase and catalase, involved in reactive oxygen species scavenging. A reduction in browning process due to polyphenol oxidase and guaiacol peroxidase activities was observed in PMAP samples. Multivariate analysis indicated that storage conditions and storage time affected the responses of qualitative and enzymatic traits. Fig fruit storage in PMAP was suitable to delay its postharvest decay and to preserve nutraceutical traits and antioxidative enzymes during 21 days of cold storage

Effects of Passive Modified Atmosphere Packaging on Physico-Chemical Traits and Antioxidant Systems of ‘Dottato’ Fresh Fig

Fig is a very perishable fruit with short postharvest life. Low-cost postharvest techniques should be employed to reduce fresh fig postharvest losses. The purpose of this study was to design a passive modified atmosphere packaging (PMAP) to extend the shelf-life of fresh ‘Dottato’ figs stored at 4 °C for 21 days. Physico-chemical traits and enzymatic and non-enzymatic antioxidant systems were evaluated. Storage in PMAP reduced the losses of fruit weight as well as maintained physico-chemical traits and nutraceutical traits such as polyphenol and flavonoid contents and the antioxidant activity in fresh figs. PMAP reduced oxidative stress, inducing the activities of antioxidant enzymes such as ascorbate peroxidase and catalase, involved in reactive oxygen species scavenging. A reduction in browning process due to polyphenol oxidase and guaiacol peroxidase activities was observed in PMAP samples. Multivariate analysis indicated that storage conditions and storage time affected the responses of qualitative and enzymatic traits. Fig fruit storage in PMAP was suitable to delay its postharvest decay and to preserve nutraceutical traits and antioxidative enzymes during 21 days of cold storage

Multifunctional Role of Chitosan Edible Coatings on Antioxidant Systems in Fruit Crops: A Review

Chitosan-based edible coatings represent an eco-friendly and biologically safe preservative tool to reduce qualitative decay of fresh and ready-to-eat fruits during post-harvest life due to their lack of toxicity, biodegradability, film-forming properties, and antimicrobial actions. Chitosan-based coatings modulate or control oxidative stress maintaining in different manner the appropriate balance of reactive oxygen species (ROS) in fruit cells, by the interplay of pathways and enzymes involved in ROS production and the scavenging mechanisms which essentially constitute the basic ROS cycle. This review is carried out with the aim to provide comprehensive and updated over-view of the state of the art related to the effects of chitosan-based edible coatings on anti-oxidant systems, enzymatic and non-enzymatic, evaluating the induced oxidative damages during storage in whole and ready-to-eat fruits. All these aspects are broadly reviewed in this review, with particular emphasis on the literature published during the last five years

The influence of abrasive pretreatment on hot air drying of grape

The drying of grapes is a more complex process compared to the dehydration of other agricultural materials due to the necessity of a pretreatment operation prior to drying. Grape drying to produce raisins is a very slow process, due to the peculiar structure of grape peel, that is covered by a waxy layer.Its removal has benn so far carried out by using several chemical pre-treatments. However, they cause heterogeneity in the waxes removal and create microscopic cracks. In this paper an abrasive pretreatment for enhancing the drying rate and preserving the grape samples is proposed. Two cultivars of grape were investigated: Regina white grape and Red Globe red grape. The drying kinetics of untreated and treated samples were studied using a convective oven at 50 C. Fruit quality parameters such as sugar and organic acid contents, shrinkage, texture, peel damage (i.e. by SEM analysis) and rehydration capacity were studied to evaluate the effectiveness of abrasive pretreatment on raisins. Abrasive pretreatment contributed to reduce drying time and rehydration time. The treated and untreated dried grapes were significantly different (p<0.05) in sugar and in tartaric acid content. On the contrary, no significant differences (p<0.05) in malic and citric acids in texture peoperties between untreated and treated samples were observed