Development of innovative technologies for fruit products processing

This PhD thesis project dealt with the development of innovative technologies for processing of different type of plant-based products in order to maintain and/or increase their quality and stability. In particular, the technologies studied during PhD project were: pulsed electric field (PEF), ohmic heating (OH), high pressure of homogenization (HPH) and innovative edible coating (EC). Different experimental procedures were set up by performing the following independent case of studies: i) PEF pre-treatment on osmo-dehydrated strawberries; ii) PEF pre-treatment (with or without osmotic dehydration - OD) on kiwifruit slices before air-drying; iii) PEF and OH treatments on carrot and apple mash; iv) HPH application on mandarin and organic kiwifruit juice; v) application of innovative EC on blueberry fruits. Based on the obtained results, the application of PEF treatment at low field strength and the use of trehalose for the osmo-dehydration process seems to be an optimal combination for obtaining a semi-dried strawberry product with quality characteristics similar to the fresh one. Thermal treatment followed by PEF or conducted by OH improve the cell disintegration and juice yield; a controlled application of high temperature may contribute to the inactivation of enzymes, reflected by improved colour and the release of polyphenols. The application of HPH on fruit juice production contributes to guarantee the protecting effect of trehalose on mandarin juice structure during storage and allows obtaining stable kiwifruit juice for more than 40 days under refrigerated storage. For what concern the innovative packaging solutions, the use of different EC showed positive effects on firmness, colour retention and contributed to the increase of antioxidant activity of blueberry fruits. The results of this PhD research work can greatly contribute to obtain high quality fruit/vegetable processed products in an efficient and environmentally sustainable way, thus determining an added value for food companies

Influence of Pulsed Electric Field and Ohmic Heating Pretreatments on Enzyme and Antioxidant Activity of Fruit and Vegetable Juices

The objective of this work was to optimize pulsed electric field (PEF) or ohmic heating (OH) application for carrot and apple mashes treatment at different preheating temperatures (40, 60 or 80 °C). The effect of tissue disintegration on the properties of recovered juices was quantified, taking into account the colour change, the antioxidant activity and the enzyme activity of peroxidase (POD) in both carrot and apple juice and polyphenol oxidase (PPO) in apple juice. Lower ΔE and an increase of the antioxidant activity were obtained for juice samples treated with temperature at 80 °C with or without PEF and OH pretreatment compared with those of untreated samples. The inactivation by 90% for POD and PPO was achieved when a temperature of 80 °C was applied for both carrot and apple mash. A better retention of plant secondary metabolites from carrot and apple mashes could be achieved by additional PEF or OH application. Obtained results are the basis for the development of targeted processing concepts considering the release, inactivation and retention of ingredients

Brewing Quality of Hop Varieties Cultivated in Central Italy Based on Multivolatile Fingerprinting and Bitter Acid Content

The brewing value of hops is mainly affected by the content and composition of humulones (α-acids) and essential oil. Interest in hop plantations is increasing more and more in Italy, in parallel with the rising number of microbreweries and brewpubs, which are strongly oriented towards local production chains. In this context, a selection of 15 international hop varieties were grown, under the same conditions, in an experimental field in the Marche region, Central Italy, with the aim of assessing their suitability for beer production. A multivariate analysis approach to experimental data showed a high content of α- and b-acids and myrcene in the Centennial, Brewer’s Gold, Sterling, Cascade, Nugget, and Columbus varieties; a consistently lower percentages of humulones and a predominance of sesquiterpene hydrocarbons in the cultivars Mount Hood, Northern Brewer, Northdown, Galena, Willamette, and Fuggle; and a desirable high α-acids content and a sesquiterpene-type aroma in cultivars Chinook, Yeoman, and Hallertau. Further studies are needed to assess the environmental adaptability and the yield performance of hop plants in the pedoclimatic conditions of the Central Italy hills

Sustainable Approach for Development Dried Snack Based on <i>Actinidia deliciosa</i> Kiwifruit

The aim of this study was to evaluate the method of producing shelf-stable snacks based on kiwifruit with the objective of obtaining an appealing snack with good taste, color, and nutritional value. Less valuable kiwifruits for size and shape were utilized in order to reduce kiwifruit production waste. To obtain the snacks, two drying methods were used: freeze-drying and hot air drying. Physical and chemical analyses were conducted. Furthermore, a sensory evaluation was undertaken. The results showed that both hot-air and freeze-drying methods are suitable for obtaining a good quality snack, which was attractive to consumers. However, the freeze-dried snack was better assessed than hot-air dried. Moreover, consumers preferred snacks with additional sucrose or trehalose to those without it. It was observed that products produced using the freeze-drying process had lower water content, and lower water activity, were brighter, had a more saturated color, and had similar or higher antioxidant activity, especially for samples made from kiwi, fennel, and spinach. The drying process allows for obtaining a snack that can be stored at room temperature. Freeze drying better preserved bioactive compounds compared to air drying. The freeze-dried samples were more appreciated by consumers than the air-dried and those containing sweetener

Sustainable Approach for Development Dried Snack Based on Actinidia deliciosa Kiwifruit

The aim of this study was to evaluate the method of producing shelf-stable snacks based on kiwifruit with the objective of obtaining an appealing snack with good taste, color, and nutritional value. Less valuable kiwifruits for size and shape were utilized in order to reduce kiwifruit production waste. To obtain the snacks, two drying methods were used: freeze-drying and hot air drying. Physical and chemical analyses were conducted. Furthermore, a sensory evaluation was undertaken. The results showed that both hot-air and freeze-drying methods are suitable for obtaining a good quality snack, which was attractive to consumers. However, the freeze-dried snack was better assessed than hot-air dried. Moreover, consumers preferred snacks with additional sucrose or trehalose to those without it. It was observed that products produced using the freeze-drying process had lower water content, and lower water activity, were brighter, had a more saturated color, and had similar or higher antioxidant activity, especially for samples made from kiwi, fennel, and spinach. The drying process allows for obtaining a snack that can be stored at room temperature. Freeze drying better preserved bioactive compounds compared to air drying. The freeze-dried samples were more appreciated by consumers than the air-dried and those containing sweetener

Clotting Properties of Onopordum tauricum (Willd.) Aqueous Extract in Milk of Different Species

Plant proteases used in cheesemaking are easily available and could increase the acceptability of cheeses, otherwise hindered by ethical issues (e.g., religions, dietary habits, aversion to genetically engineered food and food ingredients). The milk clotting potential of Onopordum tauricum (Willd.) aqueous extract as an alternative to animal rennet was assessed for the first time in milk of different species (ewe, goat, cow). Among the aerial anatomical parts, i.e., receptacle, leaves, stems, and flowers, only the latter ones showed clotting properties. A response surface methodology (RSM) was used to explore the effects of three independent variables (temperature, pH, volume of coagulant) on the milk clotting activity (MCA) of the flower extract. A second-order polynomial model adequately described the experimental data and predicted a temperature value of 55 &deg;C, a pH value of 4.9&ndash;5.7, and a volume of coagulant of 300&ndash;500 &mu;L (added to 5 mL of milk) as optimal conditions to maximize the MCA. At a 35 &deg;C temperature and natural milk pH of 6.7&ndash;6.8, the estimated MCA of the O. tauricum extract was 72&ndash;87, 69&ndash;86, and 75&ndash;151, in goat&rsquo;s, ewe&rsquo;s, and cow&rsquo;s milk, respectively. In comparison, the MCA of calf rennet was 5.4&ndash;4.9, 3.3&ndash;14.7, and 4.9&ndash;16.7 times higher than that of the plant extract in goat&rsquo;s, ewe&rsquo;s, and cow&rsquo;s milk, respectively

Multi-Analytical Approach to Study Fresh-Cut Apples Vacuum Impregnated with Different Solutions

The aim of this study was to evaluate the effect of different solutions for vacuum impregnation (VI) of fresh-cut (FC) apples through an innovative multi-analytical approach. In particular, the individual and synergistic effects of ascorbic acid and calcium lactate on the preservation of freshness of FC apples was assessed through color, texture, microscopy, isothermal calorimetry, and time-domain nuclear magnetic resonance (TD-NMR) evaluations. The analysis was performed immediately after VI and after 24 h of refrigerated storage. The obtained results showed a good preservation of color and higher firmness in the impregnated samples. Concerning the metabolic heat production, a decrease following the VI treatment was observed, especially when the combined solution was used for the impregnation. The TD-NMR studies showed higher changes in terms of signal intensity and transversal relaxation time T2 after 24 h of storage, evidencing the meta-stability of the plant material for its dynamic tissue nature, and the dewatering/impregnation processes evolution until the achievement of dynamic equilibrium

Effect of PEF pre-treatment on drying kinetics and quality parameters of kiwifruit chips

Nowadays, product diversity, longer shelf-life and great volume reduction are the reasons for the popularity of dried fruits and vegetables, and this could be further expanded with the improvements in product quality and process applications. In particular, osmotic dehydration (OD) and/or pulsed electric field (PEF) combined with air drying allow to obtain dried products by accelerating mass transfer phenomena. The aim of this work was to investigate the effect of PEF and OD pre-treatment on the drying kinetics, texture, color, polyphenol content, vitamin C, antioxidant activity and sensorial analysis of dried kiwifruit. Kiwifruits slices (5 mm thick) were subjected to OD process (40% trehalose, 35\ub0C, 2.5h). PEF treatment was applied before and/or after OD by using electric field strength of 200 V/cm and 100 near-rectangular shaped pulses, with fixed pulse width of 100 \u3bcs and repetition time of 10 ms. The differently treated samples were subjected to air drying at 70\ub0C. The results showed that the application of OD process reduced the drying time and further combining the PEF application. All treated samples maintained a good crispiness as well as non-treated kiwifruits (control) while better retention of hue color parameter was observed for OD pre-treated samples. Kiwifruit snacks treated with OD showed a better preservation of antioxidant activity, polyphenol and vitamin C content; on the contrary for PEF kiwifruit slices was noticed a reduction in comparison to the other samples. Panelists appreciated more kiwifruit slices pre-treated with a combination of PEF and OD compared to control ones. Based on the results the combination of PEF and OD allowed to reduce drying time for the production of kiwifruit slices whit high quality characteristics

Application of non-thermal pre-treatments (PEF and/or OD) to develop yellow kiwifruit dried snack with high nutritional functionality

Currently, the fruits with lesser value in terms of size and shape are considered waste, and poorly paid as they are used in the production of fruit juices or in the energy supply chain. The production of snacks with high nutritional functionality could be a valid alternative to use the kiwifruit waste, with positive economic impact on the entire production chain. Therefore, in this work, osmotic dehydration (OD) and pulsed electric field (PEF) were combined as pre-treatments for the subsequent air drying to obtain snacks with a high functional content. Yellow kiwifruits slices (5 mm thick) were subjected to OD process (40% trehalose, 35\ub0C, 2.5h). PEF pre-treatment was performed by using lab-scale PEF unit (Model S-P7500, Alintel, Italy), with the electric field strength of 200 V/cm and 1000 near-rectangular shaped pulses, with fixed pulse width of 10 \u3bcs. PEF was applied before and/or after OD. The differently treated samples were subjected to air drying at three different temperatures 50, 60 and 70\ub0C. The total polyphenol content, vitamin C content and antioxidant activity (DPPH and ABTS method) were investigated. The results showed that all measured parameters were strongly depended on the type of pre-treatment applied and, on the drying temperature. Vitamin C content was the highest in non-treated and PEF treated kiwifruit samples when dried at low temperature. Total polyphenol content and antioxidant activity by DPPH were the highest at the temperature of 60 \ub0C in non-treated and OD treated samples. However, when lower (50\ub0C) and higher (70\ub0C) temperatures were used the antioxidant activity of PEF and PEF/OD treated samples were at a comparable level as control samples. Concerning the antioxidant activity measured by ABTS the samples treated with PEF and PF/OD showed the highest values of this parameters, suggesting the contribution of other bioactive compounds with high antioxidant activity