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UV-C light is a non-thermal technology with potential application in food industries. The objective was to assess UV-C radiation effect (13.44 W/m2) on microbiological decontamination and some quality characteristics of Cantaloupe melon juice, during refrigerated storage. Juice was inoculated with Listeria innocua (non-pathogenic surrogate of L. monocytogenes) and Alicyclobacillus acidoterrestris spores (spoilage indicators) used as indicators of the UV-C treatment efficacy. Total mesophylls and yeasts and molds were also enumerated. Results demonstrated that 5 min of exposure allowed 3.7 ± 0.3 log10 cycles reduction of L. innocua, while for A. acidoterrestris, 20 min were required to decrease 4.7 ± 0.1 log10 cycles. At the end of refrigerated storage for 13 days, UV-C treated juices retained color, total phenolics content and antioxidant activity, and yeast and molds did not grow. Since UV-C process was effective on microbial inactivation and allowed juice quality maintenance, it can be considered as a promising alternative to thermal pasteurization.

Alicyclobacillus acidoterrestris is a spore-forming bacterium, which is responsible for quality degradation of fruit juices. Non-thermal treatments, such as ultraviolet-C radiation (UV-C) and ultrasound (US), are promising methods for microbial inactivation. The main objective was to study the influence of UV-C, ultrasound and combinations of both treatments on A. acidoterrestris spores inactivation in apple juices. A thermal treatment at 95 °C was used as control. Commercial juices artificially inoculated with the bacterium were exposed to the treatments. Results showed that ultrasound had the lowest impact on A. acidoterrestris inactivation. When UV-C radiation was applied, the number of spores decreased drastically after 8 min, being more effective than a 95 °C thermal treatment. In terms of final microbial loads, combination of US and UV-C did not result in synergetic effects. However, inactivation rates of the combined treatments were significantly different from the ones obtained when the treatments were applied individually.

Submitted by Ana Costa (apcosta@porto.ucp.pt) on 2017-05-09T14:36:29Z No. of bitstreams: 1 Combined Effects of Temperature.pdf: 187225 bytes, checksum: 3daf5eb8029aa02e2e3df153a4c13d7a (MD5) Approved for entry into archive by Maria João Pinto (mjpinto@porto.ucp.pt) on 2017-10-12T08:19:19Z (GMT) No. of bitstreams: 1 Combined Effects of Temperature.pdf: 187225 bytes, checksum: 3daf5eb8029aa02e2e3df153a4c13d7a (MD5) Made available in DSpace on 2017-10-12T08:19:19Z (GMT). No. of bitstreams: 1 Combined Effects of Temperature.pdf: 187225 bytes, checksum: 3daf5eb8029aa02e2e3df153a4c13d7a (MD5) Previous issue date: 2016 info:eu-repo/semantics/publishedVersion

Foods are partially crystalline partially amorphous systems. Edible films are considered good models for food systems due to their interesting physical properties, quite straightforward matrices, and easy reproduction. Chitosan is a semicrystalline biopolymer, biocompatible, biodegradable, with antimicrobial activity and filmogenic properties, and it has been thoroughly used in edible films studies. The purpose of this work is to investigate the relationship between the molecular relaxation time in chitosan films, their microstructure (crystallinity) and functional properties. Analyses were carried out using data on chitosan/ glycerol films prepared with different polymer/ plasticisant concentration. In general, results demonstrate that there is a relationship between macroscopic properties and water and glycerol relaxation times. Moreover, results also show that while water is free in the matrix, glycerol is linked to the chitosan polymeric chains, decreasing intermolecular attractions and increasing free volume, thus facilitating molecular migration. Also the data analysis reveals the usefulness of NMR and molecular mobility studies in the matrix for characterisation and development of polymeric structures., Authors Joana F. Fundo and Mafalda A. C. Quintas acknowledge FCT for research grants SFRH/BD/62176/2009 and SFRH/BPD/41715/2007, respectively. The authors acknowledge the Portuguese NMR Network and Strategic Project PEst-C/CTM/LA0025/2013-14 and the support by National Funds from FCT through project PEst-OE/EQB/LA0016/2011.

The effects of storage at different temperatures (2, 5, 10, 15, and 20 degrees C) conditions on whole tomato (Solanum lycopersicum, cv. 'Zinac', fruits harvested at mature-green stage) quality parameters, such as colour, chilling injury, firmness, weight loss and total phenolic content, were investigated during a month period. Storage at all temperatures had significant impact on the quality parameters analysed. Significant alterations in tomato green colour, firmness and weight loss were observed. The results also revealed a slight increase in the total phenolic content, and that refrigeration storage at 2 and 5 degrees C induced chilling injuries. A fractional conversion model fitted well the experimental data on colour parameters (a. and degrees h value), firmness and weight loss. The storage temperature effect was successfully described by the Arrhenius law. These results represent a good predictive tool for tomato quality estimation along the food chain.

The effectiveness of ozone in aqueous solution treatment on microbial inactivation was studied for three combinations microorganism/food: Listeria innocua/red bell peppers (artificially inoculated), total mesophiles/strawberries, and total coliforms/watercress, with two concentrations (0.3 and 2.0 ppm). Blanching treatments (50-60 degrees C) were also individually applied and in combination with ozone, for studying possible synergistic effects. In relation to ozone treatments, the highest microbial reductions were obtained for the highest concentration with the highest treatment time (3 min). Under those conditions. L. innocua/peppers, total mesophiles/strawberries and total coliforms/watercress were reduced respectively 2.8 +/- 0.5, 2.3 +/- 0.4 and 1.7 +/- 0.4 log-cycles. However, a substantial portion of the microbial populations were reduced by water washing alone, and the presence of ozone generally added an additional reduction of 0.5-1.0 log-cycles. If ozone at the highest concentration is used, the treatment impacts on L. innocua/peppers and total mesophiles/strawberries load reductions were equivalent to a blanching at 50 degrees C (for the same treatment times). Combining blanching and ozone did not generate synergistic effects, and in some situations microbial reductions were lower than the ones observed when treatments were applied independently.

Sucrose solutions, with concentrations near or superior to saturation, present high potentialities for the candy and pastry industries. The development of colour in a neutral and highly concentrated sucrose solution (16.32%(w/w) water content) subjected to isothermal heat treatment (in the 100-160 °C range) was investigated. Under such conditions, sucrose degrades through caramelisation and 5-hydroxymethylfurfural (HMF) is formed. Colour development was monitored through lightness/darkening (L/L0) and total colour difference (TCDH) changes during reaction course. Kinetic behaviour was mathematically described using modified Gompertz equations. The effect of temperature on the reaction was described by an Arrhenius type dependency. Colour development and sucrose degradation kinetic parameters were compared and similar lag phases were found. However, the same was not observed for reactions rate, indicating that not only sucrose degradation contributes to colour development. To investigate the colour development/HMF content relationship, a fractional conversion and a power law models where successfully proposed to express, respectively, L/L0 and TCDH dependence on HMF content.

Watercress (Nasturtium officinale) colour changes due to blanching by heat and a combined treatment of heat/ultrasound (thermosonication) were studied in the temperature range of 82.5 to 92.5 °C. The application of thermosonication was intended to enable less severe blanching treatments and, therefore, improve the quality of the blanched product. The thermosonication blanching processes promoted changes of the green colour (an parameter) at a higher rate (P < 0.05), when compared with the heat blanching processes. No significant differences (P > 0.05) were detected between heat and thermosonication blanching processes in terms of the colour parameters Ln, bn and TCD changes. In both treatments, a fractional first order model fitted well the experimental data for Ln, an and bn (RH2 = 0.99; RTs2 = 0.99) and TCD (RH2 = 0.92; RTs2 = 0.96) colour parameters. The chlorophylls content showed no significant differences (P > 0.05) between thermally treated and thermosonicated watercress samples. The present findings will help to evaluate the effectiveness of thermosonication as a novel process to replace the classical heat treatment. Industrial relevance: Conventional blanching commonly results in severe losses or destruction of nutrients due to process intensity and extended process times. Consequently, the attempts to use the synergistic effects of heat and ultrasound (at least) for enzyme inactivation are of high relevance. The results, although not conclusive, indicate, that they may aid optimization of blanching processes.

Sucrose solutions, with concentrations near or superior to saturation, present high potentialities for the candy and pastry industries. Creep measurements under small stresses were done to obtain the rheological properties of highly concentrated sucrose solutions, since such solutions could be in a metastable state and tend to crystallise. The viscosities of these solutions, from 70.0% to 85.2% (w/w), were determined experimentally at different temperatures, from 0 to 90 °C. The temperature dependence of viscosity was studied using experimental and published data for, respectively, high and low concentrations (

The objective of this study was to assess the impact of a training programme, designed to make preschool-age children’s invented spelling evolve, on their phonemic awareness. The participants were 90 children who were divided into 3 experimental and 3 control groups based on the nature of their invented spelling. Children’s phonemic skills were evaluated in a pre-test and a post-test. In between the experimental groups underwent the training program. The experimental groups achieved greater progress in the phonemic tests than the control groups. The training’s impact on those tests differed depending on the level of the children’s invented spelling. 2006 Elsevier Ltd. All rights reserved.

Home storage is the final step of the frozen foods distribution chain, and little is known on how it affects the products quality. The present research describes frozen green beans (Phaseolus vulgaris, L.) quality retention profile during the recommended ‘star marking’ system dates, at the storage temperatures of +5, −6, −12 and −18 °C (along 1, 4, 14 and 60 days, respectively). The quality profile was assessed by a simulation system. Simulations were set by a response surface methodology to access the effect of different packaging materials (thermal conductivities and thickness), surface heat transfer coefficient, and refrigerator dynamics (effect of refrigeration cycles at the different storage temperatures) on the average retentions of Ascorbic Acid, total vitamin C, colour and flavour. Green beans quality losses along frozen storage are significantly influenced by temperature, refrigerator dynamics and kinetic properties. Quality is also highly dependent on packaging materials thermal insulation (e.g. at temperatures above the melting point). Temperature cycles inside frozen chambers have a long term effect, and at the higher storage temperatures (e.g. T>−6 ° C ) are detrimental to frozen green beans quality after shorter periods.

Frozen green beans ( Phaseolus vulgaris , L.) thermal conductivity ( k ) and heat capacity ( C p ) were determined experimentally by a one dimensional finite difference (transient method) and differential scanning calorimetry, respectively. Thermal properties were also estimated by the inverse problem methodology (IPM). Heat capacity and thermal conductivity behaviour with temperature were modelled by the Schwartzberg equations and linear relationship, respectively below and above the melting point. These equations were used inside a finite element model (FEM) to simulate green beans phase transition under thawing conditions. The sequential simplex method was used to minimise the error vector of the FEM inverse problem, to estimate thermal capacity and thermal conductivity. The accuracy of thermal-physical properties estimated by the two methodologies was compared with data from literature. The thermo-physical properties estimated by the IPM converged for physically meaningful values. Important conclusions were obtained about errors in model predictions. Furthermore, the IPM thermal properties increased the accuracy of simulations, especially during phase transition.

Colour changes and chlorophyll degradation of frozen green beans (Phaseolus vulgaris, L., variety bencanta) were studied during 250 days of storage at 7, 15 and 30 C. Chlorophyll a and b losses and colour Hunter a and b coordinates and total colour difference (TCDH) changes were successfully described by first order and reversible first order models, respectively. The temperature effect was described by the Arrhenius law. Disagreement between the colour co-ordinates and chlorophyll content was obtained. Therefore, chlorophyll content is not a good colour index of frozen green beans. The results emphasise that colour is a more important parameter to assess frozen green beans visual quality. # 2002 Elsevier Science Ltd and IIR. All rights reserved.

Submitted by Anabela Morais (ajmorais@porto.ucp.pt) on 2016-02-22T16:48:57Z No. of bitstreams: 1 Food Structure Design- Innovation in food structure-properties relationships.pdf: 205995 bytes, checksum: a1a8783be152adda3610b5211211720a (MD5) Approved for entry into archive by Maria João Pinto (mjpinto@porto.ucp.pt) on 2016-04-21T08:38:33Z (GMT) No. of bitstreams: 1 Food Structure Design- Innovation in food structure-properties relationships.pdf: 205995 bytes, checksum: a1a8783be152adda3610b5211211720a (MD5) Made available in DSpace on 2016-04-21T08:38:34Z (GMT). No. of bitstreams: 1 Food Structure Design- Innovation in food structure-properties relationships.pdf: 205995 bytes, checksum: a1a8783be152adda3610b5211211720a (MD5) Previous issue date: 2015 info:eu-repo/semantics/publishedVersion

A computer program was developed to model heat sterilization of one-dimensional conduction-heated foods with negligible surface resistance to heat transfer. The optimal sterilization temperature, defined as the processing temperature that results in a food product with minimum surface cook-value after achieving the desired degree of sterility, was calculated as a function of food properties (thermal diffusivity, Z-value of the quality factor), processing conditions (dimensions and geometry of the food or container, initial temperature of the product, heating medium come-up-time) and processing criteria (target F0-value). The initial temperature of the food and the heating medium come-up-time have a minor effect on the optimal temperature. Generalized (semi)-empirical formulae relating optimal sterilization temperatures and all relevant variables were developed.

Mathematical methods available to optimize heat sterilization of prepackaged foods are critically reviewed. Heat transfer models, with special relevance to those considering external resistance to heat transfer, are discussed. Different optimization methods and constraints are analysed and their applicability is evaluated. Several objective functions suggested in the literature to minimize quality degradation, energy consumption or economic costs are presented along with their impact on optimum conditions. The use of variable heating medium time temperature profile in order to improve sterilization conditions, both interms of mass average and surface quality retention, is also extensively reviewed. The review suggests that sufficient experimental evidence is lacking. Most models do not provide experimental validation and it is thought that this impairs the potential applications that would arise.