Impact of Ultrasound Pretreatment on Juice Yield and Bioactive Content in Juice Produced from Selected Berries Fruit.

The aim of the work was to investigate the effect of ultrasound application during juice pressing. The impact on pressing yield and extraction of bioactive compounds during production of juice from strawberry, blackcurrant and raspberry was evaluated. Juice pressing was carried out after four kinds of mash pretreatment. The tested objects were heated to 55 °C, treated by ultrasound, and/or macerated with an enzyme. The obtained juices were analyzed for the content of bioactive compounds and compared to the 'Control' sample, which was the juice pressed without any pretreatment. Although the results presented here do not conclusively show that enzymatic maceration can be completely replaced by the use of ultrasound, in the case of strawberry and raspberry fruit, juice yield after ultrasound treatment increased almost as much as after enzymatic maceration. Additionally, in the case of raspberry fruit, the antioxidant activity of the juice samples was definitely improved when ultrasound was used. The results from this experiment also showed that it is possible to separate the effect of temperature from the effect of mechanical and chemical actions in ultrasound treatment.

In Vitro Propagation Method for Production of Phenolic-Rich Planting Material of Culinary Rhubarb 'Malinowy'.

Culinary rhubarb is a popular vegetable crop, valued for its long, thickened stalks, very rich in different natural bioactive ingredients. Tissue cultures are a useful tool for vegetative propagation of virus-free rhubarb plants and rapid multiplication of valuable selected genotypes. The aim of this study was to develop an effective method for in vitro propagation of selected genotypes of Polish rhubarb 'Malinowy' characterized by high yield and straight, thick and intensive red stalks. Identification and quantification of anthocyanins and soluble sugars by the HPLC method in shoot cultures and ex vitro established plantlets were also performed. Shoot cultures were established from axillary buds isolated from dormant, eight-year-old rhizomes. Effective shoot multiplication of rhubarb 'Malinowy' was obtained in the presence of 6.6 µM benzylaminopurine or 12.4 µM meta-topolin. Both cytokinins stimulated shoot formation in a manner that depended on sucrose concentration. Increasing the sucrose concentration from 59 to 175 mM decreased the production of shoots and outgrowth of leaves by 3-fold but enhanced shoot length, single shoot mass and callus formation at the base of shoots. This coincided with increased accumulation of soluble sugars (fructose, glucose) and anthocyanins-cyanidin-3-O-rutinoside (max. 208.2 mg·100 g-1 DM) and cyanidin-3-O-glucoside (max. 47.7 mg·100 g-1 DM). The highest rooting frequency (94.9%) and further successful ex vitro establishment (100%) were observed for shoots that were earlier rooted in vitro in the presence of 4.9 µM indole-3-butyric acid. Our results indicated that anthocyanin contents in leaf petioles were influenced by developmental stage. Under in vitro conditions, it is possible to elicit those pigments by sucrose at high concentration and meta-topolin.

Impact of Innovative Technologies on the Content of Vitamin C and Its Bioavailability from Processed Fruit and Vegetable Products.

Nowadays, thermal treatments are used for extending the shelf-life of vegetable and fruit products by inactivating microorganisms and enzymes. On the other hand, heat treatments often induce undesirable changes in the quality of the final product, e.g., losses of nutrients, color alterations, changes in flavor, and smell. Therefore, the food industry is opening up to new technologies that are less aggressive than thermal treatment to avoid the negative effects of thermal pasteurization. Non-thermal processing technologies have been developed during the last decades as an alternative to thermal food preservation. Processing changes the structure of fruit and vegetables, and hence the bioavailability of the nutrients contained in them. In this review, special attention has been devoted to the effects of modern technologies of fruit and vegetable processing, such as minimal processing (MPFV), high-pressure processing (HPP), high-pressure homogenization (HPH), ultrasounds (US), pulsed electric fields (PEF), on the stability and bioavailability of vitamin C.

The Influence of Ultrasound and Cultivar Selection on the Biocompounds and Physicochemical Characteristics of Dried Blueberry (Vaccinium corymbosum L.) Snacks.

The aim of the study was to characterize physical and chemical composition of four highbush blueberry cultivars ("Bluecrop," "Late Blue," "Chandler," and "Elliot"). The assessment of ultrasound influence at the osmotic dehydration step and during hybrid drying on mass transfer and the nutritional quality of all cultivars was also done. The experiment consisted of two stages: (1) initial: optimization of osmotic dehydration procedure, (2) the main experiment including all stages of dried blueberry production (pretreatment, osmotic dehydration chosen in the initial stage, and drying). In both parts, the effect of US and cultivar were considered as factors influencing the most important quality indices. The osmotic dehydration, in the mixture (1:1) of sucrose solution and apple juice concentrate (65°Bx) at a fruit to syrup ratio 1:4, was carried out in water bath fitted with ultrasonic transducers (25 kHz, 27.8 W/L) at a temperature of 40°C for 150 min. After pretreatment osmo-dehydrated fruits were subjected to drying in hybrid (microwave-ultrasound-convective) drum dryer. Regardless of the cultivar US had positive influence on mass transfer (up to 22% for intact and 12% for mechanically scratched) at the osmotic dehydration stage. Unfavorably, its action tend to decrease phenolic compounds content. The final effect, however, was strongly influenced by the choice of cultivar. With regard to ultrasound applied at the drying step, no explicit effect, either on the drying process efficiency or on final product quality, was identified. In the same processing conditions "Elliot" turned out to be the most promising to produce ready-to-eat fruit snacks in terms of the final product stability and bioactives content. PRACTICAL APPLICATION: Hybrid drying was proposed as a novel approach in blueberry drying. Ultrasound application as a part of abovementioned drying technique is considered an efficient way of shortening drying time due to mass transfer intensification and the interaction with dehydrated tissue. However, no experiments studying the impact of ultrasound on various cultivars within one species were carried out. This study contributes to the understanding that appropriate cultivar selection in the production of ready-to-eat dried blueberry fruit is just as important as process parameters in obtaining an attractive product with a high level of natural bioactive compounds.

Effects of Ultrasound Assistance on Dehydration Processes and Bioactive Component Retention of Osmo-Dried Sour Cherries.

Despite having numerous health benefits, dried sour cherries have proven to be more acceptable to consumers when infused with sugar or other sweeteners to enhance their flavor, which, in turn, leads to serious anthocyanin losses. For this reason, a consideration was made for the application of ultrasound to accelerate solid gain and shorten drying time, thus favoring bioactive component retention. To determine the usefulness of ultrasound as a tool for sour cherry osmotic infusion enhancement, the effect of sonication time on dehydration effectiveness, as well as the stability of bioactive components during osmotic treatment and consecutive convective drying, was investigated. Fruits were osmo-dehydrated using a 60% sucrose solution for 120 min (40 °C), during which, ultrasound of 25 kHz (0.4 W/cm(2) ), was applied for 0, 30, 60, 90, and 120 min, after which, the fruits were convectively dried. In the range of the applied ultrasound energy no significant effect of sonication on mass transfer intensification was observed; moreover, longer acoustic treatment seemed to retard moisture removal during subsequent convective drying, which can be related to the breakdown of the parenchyma cell walls caused by the prolonged ultrasound (US) action. It was concluded that although US assistance could be considered neutral for bioactive component retention, excessive sonication time can lead to some anthocyanin deterioration. According to high-performance liquid chromatography analysis, the particular anthocyanin alterations, both during dehydration and final drying, occurred in a similar way. Sonication time prolongation caused approximately 10% more bioactive compound deterioration, than earlier, shorter trials.