Massimo Migliori

Filled-snacks production by co-extrusion-cooking. Part 3. A rheological-based method to compare filler processing properties

Abstract Filled snacks are new industrial co-extruded products made by a dough shell and an internal filler constituted by salty or sweet cream. Due to different rheological characteristics of fillers and dough, it is difficult to choose operational variables capable of guaranteeing a complete filling. This work aims to determine the optimal rheological properties of both filler and dough to make an optimal product without undesired voids. A typical dough and several fillers have been considered and rheologically characterised by means of dynamic oscillation, steady shear flow and creep tests. A dynamic temperature ramp test at 1 Hz was performed to determine temperature dependency of the tested material. A time–temperature shifting technique based on a modification of the Cox–Merz rule and on weak gel model was applied to extend the flow curve range and to overcome temperature experimental difficulties. The obtained data, expressed by a power law correlation, were inserted in a numerical algorithm previously developed, and the internal swelling of the dough followed by a recovery was computed during mixed flow inside the extrusion head. It was suggested that a greater recovery implies a better filling capability because the filler may follow the dough during swelling. Simulations indicated that a complete filling was obtained only for the materials exhibiting a quite stable network during the flow. The experimental results obtained by preparing different industrial filled snacks confirmed the simulative predictions. Quantification of the network shear stability was determined by comparing the loss modulus (G″) and shear viscosity (η) values. In particular G″ versus frequency and η versus shear rate were fitted by a power law model and the best fillers must present a ratio between their exponents close to 1.

HMF etherification using NH4-exchanged zeolites

The properties of BEA, MFI and Silicalite-1 zeolites in the ammonium and protonic forms are studied in the etherification of HMF (5-hydroxymethylfurfural) in anhydrous ethanol and compared with FTIR data on ammonium ion siting and displacement by competitive adsorption, as well as data on ammonium ion dissolution in aqueous solution. For the first time it is demonstrated that ammonium-exchanged zeolites are active and show better performances (particularly for the BEA structure) in the acid-catalyzed etherification reaction. This behavior is associated to a reversible dissociation of NH4+ ions, which is favored by the BEA zeolite structure. A critical condition for enhanced catalytic performances is that dissociated ammonia remains in the zeolite cages, and may be reversibly re-adsorbed. It is thus likely that the dissociated ammonia participates in the reaction or induces a confinement effect.

Rheological Characterisation of Dairy Emulsions For Cold Foam Applications

Dairy foams are complex aerated materials where the liquid matrix is an emulsion made by oil droplets dispersed in a water system. An innovative application of these systems leads to an interesting product derived from instant whipped creams that are stored and consumed at low temperatures (typically between −4 and −18°C) like an ice cream. This novel product requires a specific texture due to the particular conditions related to its consumption. In the present work, the effects of some relevant ingredients (emulsifiers, sugars, and fats) on rheological properties and freezing temperature of dairy emulsions were investigated. Samples were prepared on lab scale and it was found that structure extension is affected strongly by stabilizers (carrageenan and guar gum) and in a lower measure by fat content. As far as freezing point is concerned a significant effect only of sugars (type and amount) and fats was measured. A formulation having interesting properties for low temperature applications was obtained and it was prepared on a pilot plant scale to investigate the potential effects of the industrial production. These samples exhibited a relevant reduction in both viscosity and elasticity; it was speculated that this effect could be attributed to the whey protein thermal damage (induced by the UHT treatment) and to the homogenisation conditions, different from those adopted on lab scale.

Influence of Fat Content on Chocolate Rheology

Molten chocolate is a suspension having properties strongly affected by particle characteristics including not only the dispersed particles but also the fat crystals formed during chocolate cooling and solidification. Even though chocolate rheology is extensively studied, mainly viscosity at high temperature was determined and no information on amount and type of fat crystals can be detected in these conditions. However chocolate texture and stability is strongly affected by the presence of specific crystals. In this work a different approach, based on creep test, was proposed to characterize chocolate samples at typical process temperatures (approximately 30 °C). The analysis of compliance, as time function, at short times enable to evaluate a material “elasticity” related to the solid‐like behavior of the material and given by the differential area between the Newtonian and the experimental compliance. Moreover a specific time dependent elasticity was defined as the ratio between the differential area, ...

CO2 Recycling to Dimethyl Ether: State-of-the-Art and Perspectives

This review reports recent achievements in dimethyl ether (DME) synthesis via CO2 hydrogenation. This gas-phase process could be considered as a promising alternative for carbon dioxide recycling toward a (bio)fuel as DME. In this view, the production of DME from catalytic hydrogenation of CO2 appears as a technology able to face also the ever-increasing demand for alternative, environmentally-friendly fuels and energy carriers. Basic considerations on thermodynamic aspects controlling DME production from CO2 are presented along with a survey of the most innovative catalytic systems developed in this field. During the last years, special attention has been paid to the role of zeolite-based catalysts, either in the methanol-to-DME dehydration step or in the one-pot CO2-to-DME hydrogenation. Overall, the productivity of DME was shown to be dependent on several catalyst features, related not only to the metal-oxide phase—responsible for CO2 activation/hydrogenation—but also to specific properties of the zeolites (i.e., topology, porosity, specific surface area, acidity, interaction with active metals, distributions of metal particles, …) influencing activity and stability of hybridized bifunctional heterogeneous catalysts. All these aspects are discussed in details, summarizing recent achievements in this research field.

Rheological Study of O/W Concentrated Model Emulsions for Heavy Crude Oil Transportation

Abstract The oil-in-water emulsion is increasing in popularity as a cost-reducing method for “heavy” crude oil transportation. In order to analyze the effect of oil-in-water ratio and emulsifier amount on the viscosity of the final emulsion, concentrated model-emulsion of oil-in-water were rheologically characterized. Two emulsification methods were investigated: batch and “in-flow” in a lab scale plant. Comparison revealed the effect of the emulsifier amount both on the viscosity decay during time and on the final emulsion viscosity. Qualitative microscopy results revealed a rather wide drop size distribution for systems exhibiting a lower viscosity value.

Olive Oil Based Emulsions in Frozen Puff Pastry Production

Puff pastry is an interesting food product having different industrial applications. It is obtained by laminating layers of dough and fats, mainly shortenings or margarine, having specific properties which provides required spreading characteristic and able to retain moisture into dough. To obtain these characteristics, pastry shortenings are usually saturated fats, however the current trend in food industry is mainly oriented towards unsatured fats such as olive oil, which are thought to be safer for human health. In the present work, a new product, based on olive oil, was studied as shortening replacer in puff pastry production. To ensure the desired consistency, for the rheological matching between fat and dough, a water‐in‐oil emulsion was produced based on olive oil, emulsifier and a hydrophilic thickener agent able to increase material structure. Obtained materials were characterized by rheological dynamic tests in linear viscoelastic conditions, aiming to setup process and material consistency, and...

Biomethane production by biogas with polymeric membrane module

Abstract Biogas is one of the most important biofuels that can be produced by biomass owing to its simple and consolidated process. Until the past decade it was used for power production, but because of the direction of European Union policy issues that have drawn attention to the possibilities offered by upgrading biogas to biomethane, currently there are the important conditions for the dynamic growth of this industry. The aim of this chapter is to underline the end uses of biogas compared with its upgrade, with a focus on the gains and limitations of using polymeric membranes for biomethane purification.

A simple rheological model to predict filled fresh pasta failure during heat treatment

The production of filled fresh pasta was studied with particular emphasis to the importance of the rheological properties of the used dough. A model capable of simulating the biaxial extension of the products during pasteurisation has been developed to predict the possible occurrence of rupture leading to very poor quality. The deformation and stress field were approximated by means of membrane deformation and a quasi-stationary hypothesis. Two commercial flours (00-grade and semolina) were tested and the viscoelastic rheological behaviour was modelled with a unique relaxation time that was experimentally determined by means of a time cure test at 1 Hz. Rupture was measured by means of a simple laboratory device and the work of deformation was measured to establish the breakage criterion. Simulations of the deformation process occurring during two different heating treatments were done and analysed in terms of stress, thickness, deformation and deformation work. The results confirmed the capability of the proposed model to predict rupture conditions and were found to be in agreement with what was industrially expected.

Direct versus acetalization routes in the reaction network of catalytic HMF etherification

The etherification of HMF (5-hydroxymethylfurfural) to EMF (5-(ethoxymethyl)furan-2-carbaldehyde) is studied over a series of MFI-type zeolite catalysts containing different heteroatoms (B, Fe, Al), aiming to understand the effect of different isomorph substitutions in the MFI framework on the reaction pathways of HMF conversion. The rate constants in the reaction network are determined for these different catalysts and analyzed with respect to the amount of Bronsted and Lewis acid sites determined by FT-IR pyridine adsorption. Two different pathways of EMF formation, i.e. direct etherification and via acetalization, were evidenced. The Lewis acid sites generated from the presence of aluminum are primarily active in catalyzing direct HMF etherification to EMF, which has a rate constant about one order of magnitude lower than the etherification of the corresponding acetals. This behaviour is due to the competitive chemisorption between hydroxyl and aldehyde groups (both present in HMF) on the Lewis acid sites catalyzing the etherification. A cooperation phenomenon between Bronsted and Lewis acid sites is observed for the HMF acetal etherification to EMF acetal. In the reactions of direct HMF acetalization and deacetalization of the EMF acetal, the turnover frequencies for Silicalite-1 and B-MFI samples are about twice those for Fe-MFI and Al-MFI samples. This is attributed to the different reactivity of strong silanol groups associated with surface defects on the external surface in Silicalite-1 and B-MFI. These sites are also responsible for the EMF-to-EOP (ethyl 4-oxopentanoate) reaction step. In the deacetalization reaction of the EMF acetal, the behavior is determined from the presence of water (product of reaction) favouring the back reaction (aldehyde formation).