Publications

JOURNAL ARTICLES

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Comparative study of the stability of multiple emulsions containing a gelled or aqueous internal phase

Perez-Moral N., Watt S., Wilde P. J.

Food Hydrocolloids (2014) 42 p215-222

Water in Oil in Water (WOW) multiple emulsions have, for many years, been studied in order to utilise their functionality in food and pharmaceuticals, for reduced fat formulation, drug delivery and taste masking applications. However, their complex structure is susceptible to a broader range of instabilities than conventional emulsions. In this study we investigate the role of different emulsifiers and a simple, novel approach to gel the internal aqueous droplets to improve the stability to heat, shear, and the presence of salt. Changes in salt concentration can be detrimental to multiple emulsions, as this will induce swelling or shrinkage of the internal water droplets. Polyglycerolpolyricinoleate (PGPR) was the preferred low HLB emulsifier, and its presence dominated the stability of the WOW emulsions, irrespective of the high HLB emulsifier. However, lecithin was found to be the most stable high HLB emulsifier to heating. Gelling the internal water droplets with either alginate or carrageenan reduced the size of the water droplets, probably due to reduced recoalescence rates. The multiple Gel in Oil in Water (GOW) emulsions were more stable to the addition of up to 1% salt to the external phase than WOW emulsions. In addition, the presence of xanthan in the external phase further improved the stability to the addition of salt. Therefore GOW emulsions show potential to be used in a realistic food processing environment, showing stability to shear, temperature and changes in salt concentration.

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Effect of gelation of inner dispersed phase on stability of (w1/o/w2) multiple emulsions

Oppermann A.K.L., Renssen M., Schuch A., Stieger M., Scholten E.

Food Hydrocolloids (2015) 48 p17-26

The use of water-in-oil-in-water (w1/o/w2) multiple emulsions offers a method for the reduction of oil in foods. In this study we investigated the influence of osmotic pressure tailoring and gelation of the inner dispersed w1 water droplets on the stability and yield of multiple emulsions. Yield is defined as the percentage of water retained in the inner dispersed phase w1 after preparation, storage, heat or shear treatment. Differential scanning calorimetry (DSC) was used to determine the yield. Gelation of the inner aqueous phase w1 by gelatin or whey protein isolate increased stability and yield of multiple emulsions after preparation, storage (after 7 days at 20 °C), shear (5 min at 10,000 rpm) and heat treatment (30 min at 97 °C) by 20%–50% compared to reference emulsions. Yield and emulsion stability were correlated to oil droplet sizes and the mechanical properties of the gelled inner dispersed droplets. Yield increased with increasing fracture stress and modulus of gelled w1 droplets. We conclude from the present study that stable food-grade multiple (w1/o/w2) emulsions can be prepared by gelling the inner dispersed phase. These multiple emulsions are able to withstand shear and heat treatments. This provides opportunities to use these emulsions as potential fat replacers in foods.

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Binding of Na⁺ ions to proteins: Effect on taste perception

Mosca A.C., Andriot I., Guichard E., Salles C.

Food Hydrocolloids (2015) 51 p33-40

This study investigated the relationship between the ionic binding of sodium and salty perception in protein matrices. Protein type (i.e. gelatin, milk protein and soy protein), protein concentration and pH were varied to obtain matrices with distinct compositions and rheological properties. ²³Na NMR spectroscopy was used to determine the ratio of sodium ions bound to proteins and the mobility of sodium ions. The results showed that protein type, concentration and pH affected the rheological properties of the protein matrices, the ionic binding of sodium ions and taste intensity. As the protein concentration increased, the mobility of sodium ions decreased and the ratio of bound sodium ions increased. Gelatin matrices displayed the greatest mobility of total sodium ions and the smallest amount of bound sodium. Soy protein had a larger amount of bound sodium than milk protein. Lowering the pH of milk protein matrices tended to decrease the ratio of bound sodium and increase sodium mobility. We suggest that sodium ionic binding is related to the presence of negatively charged groups in proteins. Although changes in matrix composition modified sodium ionic interactions, taste perception was mainly affected by the rheological properties of the protein matrices. As the values of fracture stress or viscosity increased, firmness intensity increased and saltiness intensity decreased. The observed effects of texture on taste could be explained by cross-modal texture-taste interactions and by differences in the oral breakdown behavior of protein matrices.

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Effect of Combined Salt and Animal Fat Reductions on Physicochemical and Biochemical Changes During the Manufacture of Dry-Fermented Sausages 

Safa H., Gatellier P., Lebert A., Picgirard L., Mirade P.-S.

Food and Bioprocess Technology (2015) 8(10) p2109-2122

Reducing salt and fat contents in dry-fermented sausages could benefit consumer health. This study aimed to quantify, from an experimental design, the effects of salt and fat contents and combined salt and fat reductions on the time-course of several physicochemical (product weight loss, mean water activity and pH values) and biochemical (proteolysis, lipolysis and lipid and protein oxidations) parameters. Statistical analyses found that time, salt and fat contents had a very significant impact on weight loss and a w and that time and salt content (not fat content) had a significant impact on pH. Biochemical results indicated that proteolysis was salt-content-dependent and amplified by combined salt and fat reductions. Intensity of lipolysis was mainly dependent on fat content. Lipid and protein oxidations were more intense in higher-fat formulations. Combined salt and fat reductions in dry-fermented sausages increased acidification, weight losses and a w, leading to more proteolysis, less lipolysis and less oxidation. Sensory studies are now required to investigate consumer acceptability of these healthier sausages. However, the present results constitute a valuable set of data for helping professionals wishing to reduce salt and fat contents in dry-fermented sausages.

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The influence of cheese composition and microstructure on the diffusion of macromolecules: A study using Fluorescence Recovery After Photobleaching (FRAP)

Chapeau A.L., Silva J.V.C., Schuck P., Thierry A., Floury J.

Food Chemistry (2016) 192 p660-667

In cheese technology, the diffusion phenomena are crucial during ripening. The technique of Fluorescence Recovery After Photobleaching was applied for the first time on real cheese, in order to investigate the relationships between molecular diffusion and the cheese composition and/or its microstructure. Measured effective diffusion coefficients in soft and hard cheese of a group of dextrans (10–500 kDa) were found to be in the same order of magnitude with values observed when using a comparable non-fat model cheese (∼0.1–20 μm2 s−1). Diffusion of the dextrans was mainly dependent on the fraction of "free" aqueous phase present in the cheese, closely which is linked to cheese-making technology and ripening stage. Diffusion coefficients were modeled by a power law relationship as a function of dextran molecular weight, which allowed some study of the cheese microstructure. A tighter protein network will require some deformation of those flexible macromolecules with a higher molecular weight (>250 kDa), in order to diffuse through the pores of such cheese structures. 

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Reducing salt and fat while maintaining taste: An approach on a model food system

Syarifuddin A., Septier C., Salles C., Thomas-Danguin T.

Food Quality and Preference (2016) 48(A) p59-69

Unbalanced diets contribute to chronic pathologies. Therefore, global healthcare organisations encourage the food industry to reduce the salt, fat and sugar contents in food. Different strategies to achieve this goal have been investigated. One strategy relying on cross-modal sensory compensation aims to maintain the saltiness and fat perception in low-fat and low-salt food using congruent aromas. Our main objective is to evaluate the effect of cross-modal interactions (odour–taste–texture) on salt and fat perception in cheese-like solid food products.
Model cheeses were prepared according to a full-factorial design with two levels of fat, salt and pH at renneting and were flavoured with either a sardine aroma (associated to salt) or a butter aroma (associated to fat) or were not flavoured (control). Taste, texture and aroma attribute intensities and consumer liking were rated by thirty-one panellists.
The results confirmed that the modification of salt, fat content and pH value induced changes in texture perception. In addition, a significant saltiness enhancement and fat content perception enhancement was induced by the congruent aroma only. These findings confirmed that the use of aromas can be an efficient strategy to compensate for the reduction of fat and salt content in food products. However, the effect of the composition and structure of products on odour-induced salt and fat perception enhancement appeared to be complex and mostly unpredictable at this stage, suggesting a combined influence of stimuli release dynamic and perceptual interactions.

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PhD THESIS

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PhD title: Multi sensory integration as a strategy to compensate for sodium and fat reduction in food

by Adiansyah Syarifuddin 

Defended on the 29th June 2015 at the University of Burgundy – Franche Comté, Dijon, France

Abstract: In recent years, health authorities worldwide advise for a reduction of salt and fat in daily food consumption. However, foods with reduced salt and fat content are often not appreciated by consumers, Therefore, the formulation of low-salt-fat foods that maintain acceptability is a major concern in food research. In this thesis, the multi-sensory integration and release kinetics of flavor compounds were explored as strategies to compensate for salt and fat reduction in cheese products (model cheeses and real cheeses). The objective was to better understand the mechanisms leading to aroma and salt release during mastication and to evaluate how the matrix composition and structure influence salt and aroma release profile.

Multisensory integration approach to compensate for salt and fat reduction was studied in a first step. The structure and sensory perception of 24 cheese models varying in composition (2 levels of fat, 2 salt, 2 pH at renneting) and flavored with either a sardine aroma (associated to salt), a butter aroma (associated to fat) or not flavoured (control) were characterised by rheological measurements (uniaxial compression) and sensory evaluation (descriptive analysis). The results demonstrated an influence of the composition on the products structure and perceived texture. Furthermore, a significant saltiness enhancement was induced by sardine aroma while significant fat perception enhancement was induced by butter aroma. However, this influence of the aroma on other sensory dimensions depends on the texture of the products thus on their composition and structure. These results have been extended to real cheeses but with specificities. If the sardine flavor enhanced the perception of salt, only butter-sardine-flavor enhanced the perception of fat.

In a second step, a physico-chemical approach was developed to explore the release kinetic of flavor compounds during in vitro breakdown using a chewing simulator. The aim was to use these data to explain the influence of the structure of model cheeses and real cheeses and their breakdown during chewing on sensory effects observed in the first step. Volatile compounds release was monitored by connecting the chewing simulator to a proton transfer reaction-mass spectrometry (PTR-MS), while salt release was monitored using a conductivity probe. Results showed that product composition and structure (fat, salt and pH at renneting) influenced aroma release, which however depends on the nature of the aroma: the more hydrophobic compounds are less sensitive to variations in fat content and more sensitive to variations in pH and therefore to the products structure. The salt release kinetic during in vitro chewing was also influenced by the composition and structure of the products. Indeed, beyond salt content which determined the amount of salt released, fat content and the pH at renneting modulated the release kinetic. In conclusion, this work showed a significant impact of the flavor compounds release kinetic and probably of temporality of sensations on the overall perception of salt and fat when consuming a complex food.

Keywords: salt, fat, flavor compounds, perception, multisensory integration, release kinetic, in vitro chewing, cheese