Marisa Di Matteo

Effect of a novel physical pretreatment process on the drying kinetics of seedless grapes

In this paper an alternative physical method for enhancing the drying rate of seedless grapes is proposed. It consists of the superficial abrasion of the grape peel using an inert abrasive material. The effectiveness of this novel process was compared to that of the traditional ethyl oleate dipping process by analysing not only their respective drying times, but also the peel surfaces by scanning electron microscopy. Moreover, the drying kinetics of the above two treatments was reconstructed by using a mathematical model in which the grape pretreatment used was assumed to affect the water diffusivity in the grape peel, but not in the grape pulp. Even though the abrasion method was found to be as effective as the traditional method and gave rise to a darker final product, which is less attractive to consumers, it would allow grape pretreatment thus avoiding the use of chemical additives, and permit safer raisins to be produced.

Evolution of quality parameters during red wine dealcoholization by osmotic distillation

Osmotic distillation technique was used for the total dealcoholization of a red wine (Aglianico grape variety) up to 0.19 vol.%. The dealcoholization process was performed in subsequent cycles which gave rise wine samples at different alcoholic degrees. The effect of processing on the main chemical and physical properties of Aglianico wine was evaluated. Among wine samples, no significant differences (p<0.05) of oenological parameters such as pH, total acidity were found. Similarly, the total phenolic, flavonoids and tartaric esters content and the composition of organic acids did not show significant differences (p<0.05) during the process. On the contrary, colour intensity and tonality of wine samples changed significantly when the alcohol reduction was over the 6.5 vol.%. Finally, the total dealcoholized wine showed properties similar to Aglianico wine except for the volatile compounds, which decreased over 98%. Hence, flavour enrichment may be required to produce a pleasurable and delicious non alcoholic beverage from wine.

A mathematical model of mass transfer in spherical geometry:plum (Prunus domestica) drying

Abstract In this paper the analytical solution of a mathematical model of mass transfer in spherical geometry is presented for boundary conditions useful for simulating drying processes of fruit with near spherical stones. This model is applied to analyse the efficiency of a new pre-treatment for a prune drying processes. The new proposed physical abrasion pre-treatment increases the plum drying rate at 60 °C. The mathematical model here presented allows a complete comparison of the experimental results obtained with this pre-treatment and with traditional ones. In particular the greater efficiency of the new physical pre-treatment appears to be due to the enhancement of the water diffusivity in the plum skin. The dipping pre-treatment with ethyl oleate gives an enhancement of the diffusivity in the skin too, but it have lower efficiency and implies many problems due to the use of chemical additives.

A highly sensitive impedimetric label free immunosensor for Ochratoxin measurement in cocoa beans

In this work the development and optimization of an impedimetric label free immunosensor for the detection of Ochratoxin A (OTA) is reported. Two antibody immobilization methods (oriented and not oriented) were compared highlighting a lower limit of detection (5pg/ml) for the not oriented immobilization but a closer linear range in contrast to oriented anti-OTA immunosensors which showed linearity in the range of 0.01-5ng/mL OTA. The analysis of the Atomic Force Microscopy (AFM) images showed two different nanostructures indicating that the use of oriented immobilization created a more ordered and highly dense antibody surface. Finally the oriented immunosensor was used to quantify OTA in spiked cocoa bean samples and the results were compared with those registered with competitive ELISA kit. The immunosensor was sensitive to OTA lower than 2μg/kg that represents the lower acceptable limit of OTA established by European legislation for the common food products.

Screen printed biosensors for detection of nitrates in drinking water

Amperometric screen printed nitrate reductase by Escherichia coli biosensors have been developed to detect nitrate ions. The effects of two different immobilization procedures of NaR and mediator (Azure A and Methyl viologen MV) to increase the performances (response time, sensitivity, stability) of the nitrate sensor have been studied. The best performances were registered by nitrate biosensor developed with a simultaneous cross-linking of enzyme and MV mixed BSA in in satured glutaraldehyde vapour. This biosensor showed the capability to detect nitrate residue levels lower than the European legislation one for a long storage stability (> 36 days) representing an applicable and cheap method for the analysis of nitrate ions in water and food samples.

Aglianico wine dealcoholization tests

Abstract In the recent years, there has been a growing interest in partial or total dealcoholization of alcoholic beverages. The demand for drinks with low levels of alcohol is attributable both for health reasons and for the desire to reduce alcohol consumption in new generations. This research aims to produce a dealcoholized wine with less than 0.5% alcohol-by-volume from Aglianico. Dealcoholization tests were carried out by plant working on direct osmosis, equipped with a membrane contactor and some temperature sensors and automatic control of the process phases. The fixed alcohol content was achieved with 5 cycles, under mild condition. Chemical-physical and aromatic composition was evaluated in feed (wine) during the dealcoholization process.

Quality Attributes of Low-Alcohol Top-Fermented Beers Produced by Membrane Contactor

The practice of dealcoholization is used nowadays to reduce the alcohol content in beverages, and osmotic distillation seems to be a convenient membrane process due to its mild operating conditions. The focus is on the quality of final beverage which may lack in taste, flavor, and body. The aim of this work was to evaluate the quality attributes of low-alcohol beers, dealcoholized by osmotic distillation and using stripping solutions specific for the beverage composition. Two types of top-fermented beer were used: Weiss beer, with a very fruity aroma and strong phenolic content, and Bitter beer, with a malt aroma. Regarding the stripping solutions, they were obtained by dilution of the original beer with water, in order to limit the volatile compound loss during the process. Moreover, low-alcohol Weiss beer was also produced by using carbonated stripping solutions (i.e., saturated with CO2 at ambient pressure). The results highlighted that color, bitterness, total phenols, and antioxidant activity were unchanged in the low-alcohol beers but volatile compounds were reduced to a different extent. The lower vapor pressure of some volatile compounds (i.e., 2-phenylethanol, aldehydes) can explain their retention in beer. The carbonation of stripping solutions did not significantly reduce CO2 loss, but aldehydes and total alcohols were better retained in low-alcohol Weiss beer. Esters and other volatile compounds were reduced so that the low-alcohol beer may result with a weak sensory profile, which can be compensated by a re-addition of CO2 before bottling.

Investigation of Osmotic Distillation Technique for Beer Dealcoholization

A growing demand for low-alcohol drinks, due to health and social benefits resulting from lower alcohol consumption, has given rise to the development of techniques for alcohol reduction or elimination in beverages. The main difficulty is the development of a low alcohol content product with sensory properties similar to the original one. This work presents a preliminary study on the production of alcohol free beer (alcohol content = 0.5 %vol) by osmotic distillation technique, which allows to operate at low temperature and atmospheric pressure, using water as ethanol stripping agent. To this goal, a lab-scale plant equipped with a commercial membrane contactor with hollow fibers was set up. The effect of different stripping agents for ethanol removal on dealcoholization kinetics and on chemical and physical properties of the dealcoholized beer (i.e alcohol content, colour, pH, polyphenols, antioxidant activity) was investigated. Finally, the ethanol mass flux through the membrane during the dealcoholization process was measured and theoretically calculated with a good agreement.

Effect of bug damage and mold contamination on fatty acids and sterols of hazelnut oil

Fatty acid and sterol content of oil from nuts (cv Tonda di Giffoni) affected by two different biotic damages were characterized. Hazelnuts were sorted by a visual inspection of the kernels in three different samples (cimiciate, apparently healthy and moldy). The oil was extracted and analyzed by gas–liquid chromatography coupled to a flame ionization detector for fatty acid and sterol composition. The higher level of total polyunsaturated fatty acids (PUFA) in cimiciato oil compared to apparently healthy nuts was associated with the decrease in total monounsaturated fatty acids, resulting in a higher unsaturated/saturated acid ratio, while the PUFA content in moldy nut oil was lower than in apparently healthy nut oil. In both damaged samples, the appearance of four new chromatography peaks could be due to the presence of hydroperoxides, as proved by carrying out a TLC analysis. The overall phytosterol amount decreased in both cimiciato and moldy nut oils compared to the apparently healthy nut oil, and the main differences were observed in terms of sitosterol, campesterol and clerosterol.

Effect of Abrasive Pretreatment on Hot Dried Goji Berry

Goji (Lycium barbarum L.) is a Solanaceous deciduous shrub that grows in China, Tibet and other parts of Asia. Nowadays, goji berries are known as being very rich in nutrients with high antioxidant capacity, fact for which they were included in the novel category of “superfruits”. Goji berries contain high amounts of antioxidants, carotenoids, vitamin A and zeaxanthin. Most of goji berries produced are dried because they are very delicate fruits. Drying process improves fruit stability, since it decreases considerably the water activity of the food, reduces microbiological and enzymatic activity and minimizes physical and chemical reactions during storage. However, drying of goji berries can be difficult due to the wax layer surrounding the fruit and the health properties may be reduced by long exposure to high temperatures.In this study, a physical wax abrasive pretreatment was used to carefully remove the wax layer and reduce drying time. The abrasion of the goji peel was carried out in a motorized drum lined inside with sandpaper. The rotating time was optimized to reduce the damage to the fruits. The drying characteristics of pretreated and untreated fruits were studied using a convective oven at 60 °C and air velocity of 2.1 m/s.The drying kinetics and fruit quality parameters such as colour, sugars and antioxidant activity were evaluated before and after drying. The results showed that the dried fruit were obtained in less time when they were pretreated (from 21 h for untreated samples to 15 h for pretreated samples), preserving better the colour, increasing the antioxidant activity and maintaining the same sugar content with respect to the untreated case.