Luciano Cinquanta

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.

Production of functional probiotic, prebiotic, and synbiotic ice creams

In this work, 3 types of ice cream were produced: a probiotic ice cream produced by adding potentially probiotic microorganisms such as Lactobacillus casei and Lactobacillus rhamnosus; a prebiotic ice cream produced by adding inulin, a prebiotic substrate; and a synbiotic ice cream produced by adding probiotic microorganisms and inulin in combination. In addition to microbial counts, pH, acidity, and physical and functional properties of the ice creams were evaluated. The experimental ice creams preserved the probiotic bacteria and had counts of viable lactic acid bacteria after frozen storage that met the minimum required to achieve probiotic effects. Moreover, most of the ice creams showed good nutritional and sensory properties, with the best results obtained with Lb. casei and 2.5% inulin.

Effect on orange juice of batch pasteurization in an improved pilot-scale microwave oven.

The effects on orange juice batch pasteurization in an improved pilot-scale microwave (MW) oven was evaluated by monitoring pectin methyl-esterase (PME) activity, color, carotenoid compounds and vitamin C content. Trials were performed on stirred orange juice heated at different temperatures (60, 70, 75, and 85 degrees C) during batch process. MW pilot plant allowed real-time temperature control of samples using proportional integrative derivative (PID) techniques based on the infrared thermography temperature read-out. The inactivation of heat sensitive fraction of PME, that verifies orange juice pasteurization, showed a z-value of 22.1 degrees C. Carotenoid content, responsible for sensorial and nutritional quality in fresh juices, decreased by about 13% after MW pasteurization at 70 degrees C for 1 min. Total of 7 carotenoid compounds were quantified during MW heating: zeaxanthin and beta-carotene content decreased by about 26%, while no differences (P < 0.05) were found for beta-cryptoxanthin in the same trial. A slight decrease in vitamin C content was monitored after MW heating. Results showed that MW heating with a fine temperature control could result in promising stabilization treatments.

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.

Kinetics of carotenoids degradation and furosine formation in dried apricots (Prunus armeniaca L.)

The kinetics of carotenoid and color degradation, as well as furosine formation, were investigated in apricot fruits during convective heating at 50, 60 and 70°C. Degradation of carotenoids and color, expressed as total color difference (TCD), followed a first and zero order kinetic, respectively. The activation energy (Ea) for carotenoids degradation ranged from 73.7kJ/mol for 13-cis-β-carotene to 120.7kJ/mol for lutein, being about 91kJ/mol for all-trans-β-carotene. Violaxanthin and anteraxanthin were the most susceptible to thermal treatment. The furosine evolution was fitted at zero order kinetic model. The Ea for furosine formation was found to be 83.3kJ/mol and the Q10 (temperature coefficient) varied from 1.59 to 4.14 at the temperature ranges 50-60°C and 60-70°C, respectively.

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.

Rapid Assessment of Gray Mold (Botrytis cinerea) Infection in Grapes with a Biosensor System

Botrytis cinerea is the causative agent of gray mold disease, which causes considerable economic losses to winemakers. The extent of gray mold infection of winegrapes is commonly visually estimated, a method that is prone to assessor bias. Here, we used rapid and simple enzyme-based screening consisting of carbon-electrode, screen-printed amperometric biosensors to estimate gluconic acid and glycerol concentration in winegrapes infected with different degrees of B. cinerea. The lower limits of quantification of the screen-printed amperometric biosensors were 3 mg/L for gluconic acid (corresponding to an infection rate of less than 1%) and 35 mg/L for glycerol; the response times with a flow rate of 0.5 mL/min were in a range of 0.5 to 2 min in the linear ranges of the two assays. This study demonstrates the efficacy of amperometric biosensors for rapid analysis of gluconic acid and glycerol in grapes. The measurements confirmed that concentrations of both compounds are highly correlated with the rate of B. cinerea infection (R2 = 0.98). Thus, the biosensor developed to measure gluconic acid in grapes (or must) was more precise and gave a faster response than methods that currently exist for determining the rate of B. cinerea infection of grape berries.

The Quality of Orange Juice

Orange juice (OJ) is defined in the European Union: “the fermentable but unfermented product obtained from Citrus sinensis (L.) Osbeck, which is sound and ripe, fresh or preserved by chilling, having the characteristic color, flavor, and taste typical of the juice of the fruit from which it comes. Flavor, pulp, and cells from the juice which are separated during processing may be restored to the same juice. The fruit juice must come from the endocarp with minimum 11.2°Brix.” In the United States OJ is also obtained by the citrus hybrid commonly called “Ambersweet.” OJ is prepared by mechanically squeezing of fruits: it is always 100 % fruit juice. Nectar is also made from citrus fruit but presents at least 50 % juice content and usually has added sugar. Still drinks contain some juice and a lot of sugar.