Drying kinetics and physico-chemical quality of mango slices

Mango (Mangifera indica L.) is an important tropical fruit consumed worldwide and grown in Italy only in Sicily, where the areas of the Tyrrhenian coast have proved to be suitable to produce valuable fruits. Mango fruit has a pleasant aroma and taste, which are important qualities for consumer’s sensorial acceptance. However, they are highly perishable, prone to progressive undesired changes if stored untreated, resulting in around 25% postharvest losses, which is further increased during storage and transportation. An alternative for reducing the above-mentioned undesired changes is the dehydration of the cut fruit, which reduce the fruit water activity, thereby avoiding the deteriorative process and extending the shelf-life. This study investigates the effect of dehydration at different temperatures (50, 60 and 70°C) on drying kinetics and volatile compounds of two cultivars (Keitt and Osteen) of mango fruits cultivated in Sicily. Significant losses of volatile constituents of fresh mango occurred at higher temperature, especially for the Osteen cultivar. A diffusion model including the effect of shrinkage is also proposed, which may be used to describe drying behaviour of fruits and to define the optimal drying conditions.. Experimental data of the moisture ratio during drying were well predicted by the model

Experimental Observation of Squeeze Film Damper Executing Offset Circular Whirl

State-of-the-art knowledge about the squeeze film damper (SFD) has been pithily commented in a recent paper [1] putting in evidence the limits that still affect the application to practical cases, despite a sensible quantity of theoretical and experimental work that has been carried out in a long-lasting activity of research in the field [3, 4]. In particular, the heavy influence of film cavitation on SFD performances, with its very likely to set in character that affects most of the common operative conditions, still represents a strong motive for investigation. Many researchers have significantly contributed to clarify, among other aspects, the characteristics of film rupture within SFD (for instance [5, 6]). Recent work [7, 8] has stressed the importance of a common mechanism of cavitation that manifests with air ingestion in the film and consequent formation of bubbly-mixtures. In these conditions, the decaying damping forces can lower till to 15 percent of those pertaining to normal conditions in the absence of cavitation. Under these premises, an experimental work has been carried out about a damper executing offset circular whirl, in line with a previous investigation [2], focusing attention on waveform of pressure signals. Film rupture with vapor cavitation or gaseous cavitation, due to air suction, was observed. The former type was prevailing and frequently accompanied by a region with tensile stresses. Operating conditions with co-presence of both mechanisms of film rupture were also detected

Assessment of drying characterics of berry fruits under physical pretreatment

The drying process of berry fruits, i.e. grapes, cherries, redcurrant and blueberries is a more complex process compared to the dehydration of other agricultural materials. The drying can be difficult due to the wax layer surrounding the fruit (Tarhan S., 2007). The berry fruits are a rich source of phenolic compounds which contributes to their high level of antioxidant activity. However, these compounds of important health benefit will be degraded after the fruit undergo air drying processes because of long exposure to high temperatures (Kalt et al., 2000). Skin pretreatments are considered before drying in order to facilitate water diffusion (Esmaiili et al., 2007). The waxy layer removal has been so far carried out by using several chemical pretreatments. However, they cause heterogeneity in the waxes removal and problems during shelf-life (Carranza-Concha et al, 2012). In this paper an abrasive pretreatment (Cinquanta et al., 2002) for enhancing the drying rate and preserving the samples is applied to berry fruits. The abrasion of the fruit peel is carried out in a motorized shaker, the surfaces of which are covered by abrasive sheets with different grit range. The benefits of the physical pretreatment include low energy cost, low capital cost and no heat damage. We aim at investigating the effect of wax abrasive pretreatment on the convective drying of berry fruits. The factors that are taken into consideration include time, load and rotation speed. The drying characteristics of pretreated and untreated fruits are studied using a convective oven with the air temperature ranging from 40 to 70°C at air velocity of 2.3 ms-1. Fruit quality parameters such as color, texture, moisture content, water activity (aw), skin damage (i.e. by SEM analysis), polyphenols content and antioxidant activity are evaluated to optimize the drying process

EFFETTO DELLA TEMPERATURA SULLA QUALITÀ DI MELANZANE ESSICCATE MEDIANTE MICROONDE

La richiesta da parte dei consumatori di alimenti con elevate caratteristiche qualitative spinge l’industria alimentare alla ricerca di nuove tecnologie di stabilizzazione capaci di mantenere inalterate la qualità del prodotto fresco. Nel caso dei vegetali essiccati questi effetti sono associati alla perdita di composti aromatici, variazione del colore, della texture e diminuzione del valore nutrizionale, dovuti ai prolungati tempi di trattamento ad elevate temperature. Il rapido riscaldamento, associato all’impiego delle microonde contribuisce a minimizzare il danno termico laddove si riesca ad effettuare un controllo della temperatura del prodotto durante l’essiccamento. In questo lavoro si è valutato l’effetto dell’essiccamento a microonde a tre diverse temperature (50 e 60°C), sui principali parametri qualitativi (colore, polifenoli, capacità di reidratazione), di melanzane essiccate. Il controllo della temperatura durante il processo di essiccamento è stata eseguita attraverso termografia ad infrarossi.Drying of vegetables is the oldest and widely used preservation method. It involves reduction of as much water as possible from foods to arrest enzyme and microbial activities hence stopping deterioration. Nevertheless, shrinkage, fading of natural color or discoloration, decreased flavor and unappetizing texture are the most evident deficiencies of dry products of drying on food. The aim of this paper is to study the drying processes of eggplant by means of microwave. The effects of two technologies (conventional hot air drying and microwave drying) at different temperatures of process were investigated on the physical and chemical properties of the dried eggplant (cv Longo)

Shelf life study of dried pumpkin in biopolymeric films by accelerated shelf life test

In the context of consumers’ increasing demand for high-quality food, the development of strategies to prolong the shelf-life of these products can attract the interest of the food industry and the processed food field. Moreover, consumers’ awareness on environmental sustainability is increasing and leads to choose alternative packaging for food products. Bio-based polymeric films are eco-friendly and good alternatives of traditional plastic packaging [1]. Pumpkin is widely cultivated in Italy throughout many regions and in many temperate climate areas of the world. It has high nutritional value because it is rich in antioxidants, vitamins, minerals, fibres and is recommended in diets because of its low calories content [2]. After harvesting, pumpkins are stable for 1-3 months; after peeling they are more perishable and rapidly lose organoleptic quality for microbial spoilage, softening, moisture loss and colour changes. For this reason, pumpkin is generally processed to obtain juice, pomace, pickles, dried products in many countries worldwide [3]. Drying is a suitable technique for preserving nutritional value and prolonging the shelf life of pumpkin. Moreover drying combined with a pretreatment is a efficient method for reducing changes in colour and antioxidant activity and for improving preservation [4]. In this study the shelf life of dried pumpkin slabs, Cocurbita moschata, packed in a polyethylene bag and in a biopolymeric bag in PLA, polylactic acid polymer from corn starch, was investigated. The objective was to evaluate the efficiency of the bio-packaging for the preservation of dried pumpkin compared to the plastic packaging (PE). The shelf life of dried foods, when properly stored, lasts from 4 to 12 months. Accelerated Shelf-life Test (ASLT) was performed in order to determine the shelf life in a relatively shorter time. By this method, the product is stored under high stress conditions, such as high temperature, to accelerate the deterioration process. During the trial, the total microbial aerobic count, weight loss, pH and colour of the packed dried pumpkin have been monitored at 30°C every 3 days for 12 days, at 40 °C every 3 days for 9 days at 50 °C and 25°C every 2 days for 6 days. In particular the colour was expressed in terms of polar coordinate Chroma that indicates the dullness/vividness of the product. The results obtained showed that the shelf life of dried pumpkin, packed in PLA and PE bags, can be predicted using the ASLT by selecting an index of quality