Gianni Bertolo

Osmotic pre-treatments in fruit processing : chemical, physical and structural effects

Over the last few decades wide prospects for osmotic dehydration have arisen as a pre-step to further processing. The distinctive aspect of this process, when compared with other dehydration methods, is the direct formulation achievable through the selective incorporation of solutes, without modifying the food integrity. By balancing the two main osmotic effects, water loss and solid uptake, the functional properties of the fruit could be adapted to many different food systems. The role of an osmotic step mainly related to improvement of processed fruit quality characteristics, such as texture, and pigment, vitamin and aroma content, is analysed.

Partial removal of water before freezing: cultivar and pre-treatments as quality factors of frozen muskmelon (Cucumis melo, cv reticulatus Naud.)

Abstract The influence of both the cultivar and the dehydration method, applied before freezing, on quality characteristics of dehydrofrozen muskmelon spheres has been studied. Water was removed from muskmelon cultivar Mirado and Rony, prior to freezing, by Dewatering–Impregnation–Soaking in concentrated solution (DIS) for 1 h, air dehydration and combined DIS-air dehydration to a final 50% weight reduction. The results of the analysis of exudate loss, texture, colour, aroma composition and sensory characteristics ascertained the crucial importance of the cultivar which had a great influence on the quality of the end products. Moisture reduction prior to freezing reduced exudate loss and improved texture at thawing. All the pre-treatments caused the loss of ethyl esters, namely “positive” aroma compounds, while the alcohols, “negative” aroma compounds, increased in air dehydrated fruits and remained stable in the DIS-treated ones. This finding could explain the higher sensory acceptability of the DIS-treated fruit when compared with those pre-air dehydrated.

Steam-Blanched Highbush Blueberry (Vaccinium corymbosum L.) Juice : Phenolic Profile and Antioxidant Capacity in Relation to Cultivar Selection

High-quality standards in blueberry juice can be obtained only taking into account fruit compositional variability and its preservation along the processing chain. In this work, five highbush blueberry cultivars from the same environmental growing conditions were individually processed into juice after an initial blanching step and the influence was studied of the cultivar on juice phenolic content, distribution and relative antioxidant activity, measured as scavenging capacity on the artificial free-radical 2,2-diphenyl-1-picrylhydrazyl (DPPH*). A chromatographic protocol was developed to separate all main phenolic compounds in berries. A total of 15 glycosylated anthocyanins, catechin, galactoside, glucoside, and rhamnoside quercetin 3-derivatives, and main benzoic and cinnamic acids were identified. The total content and relative distribution in anthocyanins, chlorogenic acid, and quercetin of each juice were dependent upon cultivar, and the total content was highly correlated (rxy=0.97) to the antioxidant capacity. A selective protective effect of berry blanching in juice processing can be observed on more labile anthocyanin compounds.

Functional properties of reduced moisture fruits as ingredients in food systems

Abstract Fruit pieces of some species have been processed to be used as ingredients in various food systems, either by partial dehydration alone or by osmosis and partial dehydration, to achieve different levels of water activity and solids contents in the final products. The relationships existing among processing, phase composition after processing and functional properties of the products have been assessed within a useful range of water content and water activity. The functional properties are expressed as diagrams relating the phase composition (soluble solids, insoluble solids and water) to the range of consistencies obtainable at various water activities. These diagrams provide a useful tool for preparing fruit ingredients suitable for specific food systems.

Modification of glass transition temperature through carbohydrates addition and anthocyanin and soluble phenol stability of frozen blueberry juices

Abstract To evaluate the influence of carbohydrate addition on anthocyanin and soluble phenol stability, blueberry juices were added with 20% (wt/wt) of maltose, sorbitol and a mixture (1:1) of glucose and fructose. A juice without addition of carbohydrates was used as a control. The juices were frozen and stored up to six months at −10, −20 and −30 °C. The transition temperatures T m ′ correlated with those of the added sugars. The glass transition was shifted to higher temperatures by addition of maltose and no significant changes in the transition temperatures were noticed with storage time. Anthocyanin and soluble phenol changes were mainly influenced by storage temperature and storage time: the lower the temperature, the shorter the storage time, the lower the changes. Sugar addition had no influence on anthocyanin content.

Freezing effect on some quality parameters of transgenic parthenocarpic eggplants

Abstract Parthenocarpy is the development of fruits in the absence of fertilization. It confers advantages to horticultural crops; the most important are fruit production under adverse environmental conditions and seedless fruits. Parthenocarpy has been obtained in eggplant by genetic engineering using a chimeric gene and an ovule-specific promoter which allows the plant to increase the content and/or the activity of indol-3-acetic acid. Two transgenic hybrids, P 1 and P 2, were compared with the corresponding control hybrids C 1 and C 2 in open field. All parthenocarpic hybrids were seedless, so increasing fruit quality. In order to evaluate the quality of transgenic eggplants, particularly their suitability for freezing, analyses on colour, texture and pectic composition were carried out on raw fruits and after 15 months of frozen storage at −20 °C. Fresh and frozen parthenocarpic eggplants showed a slower browning of the pulp with respect to the controls. Texture data showed a higher decrease of firmness for the transgenic, while pectin analysis suggests that there are lower molecular weight fragments in the transgenic eggplants than in the controls.