Hélène Simonin

Effect of high pressure and salt on pork meat quality and microstructure.

The interaction of salt (0%, 1.5%, and 3% in the final product) and a high-pressure treatment (500 MPa, 20 °C, 6 min) was investigated using pork biceps femoris muscle. The Warner-Bratzler shear force and the water holding capacity (WHC) were assessed and linked to the microstructure evaluation by environmental scanning electronic microscopy (ESEM). Pressure-treated and cooked samples showed a high Warner-Bratzler shear force with a low WHC compared to control cooked samples. These negative effects could be linked to the general shrinkage of the structure as observed by ESEM. The addition of 1.5% salt was sufficient to improve the technological properties of the high-pressure-treated samples and to counteract the negative effect of high pressure on texture and WHC. This phenomenon could be linked to the breakdown in structure observed by ESEM. This study states that it is possible to produce pressurized pork products of good eating quality by adding limited salt levels.

Optimization of nutrient-induced germination of Bacillus sporothermodurans spores using response surface methodology

Spores of Bacillus sporothermodurans are known to be contaminant of dairy products and to be extremely heat-resistant. The induction of endospore germination before a heat treatment could be an efficient method to inactivate these bacteria and ensure milk stability. In this study, the nutrient-induced germination of B. sporothermodurans LTIS27 spores was studied. Testing the effect of 23 nutrient elements to trigger an important germination rate of B. sporothermodurans spores, only D-glucose, L-alanine, and inosine were considered as strong independent germinants. Both inosine and L-alanine play major roles as co-germinants with several other amino acids. A central composite experimental design with three factors (L-alanine, D-glucose, and temperature) using response surface methodology was used to optimize the nutrient-induced germination. The optimal rate of nutrient-induced germination (100%) of B. sporothermodurans spores was obtained after incubation of spore for 60 min at 35 °C in presence of 9 and 60 mM of D-glucose and L-alanine, respectively. The results in this study can help to predict the effect of environmental factors and nutrients on spore germination, which will be beneficial for screening of B. sporothermodurans in milk after induction their germination. Moreover, the chosen method of optimization of the nutrient-induced germination was efficient in finding the optimum values of three factors.

The combined effect of nisin, moderate heating and high hydrostatic pressure on the inactivation of Bacillus sporothermodurans spores

To investigate the combined effect of hydrostatic pressure (HP), moderate temperature and nisin on the inactivation of Bacillus sporothermodurans spores which are known to be contaminant of dairy products and to be extremely heat‐resistant.

Pasting properties of high-pressure-treated starch suspensions

High pressure (HP) applied to starch suspensions is a promising technology as an alternative to conventional thermal treatment. It may allow the development of new textures which may retain flavors and nutrients while providing food safety. The properties of corn starch and two waxy starch suspensions, rice and corn, were studied after or during HP treatments at 500 MPa. Waxy starches lost their granular structure during the pressure treatment, whereas corn starch granules swelled gradually. Waxy rice starch was the more pressure sensitive among the studied starches. After 10 min at 500 MPa, the granular structure disappeared totally and the gel obtained reached its maximal viscosity. It was more viscous than the two corn starch suspensions. Viscosity of both corn starch gels increased gradually during 30 min at 500 MPa, but waxy starch gave the more viscous gels. This study demonstrates the high potential of waxy starches for HP applications in food.

Methodology assessment on melting and texture properties of spread during ageing and impact of sample size on the representativeness of the results

A large number of methods and instruments have been used for measuring the melting and texture properties of margarine and spread. All these methods assume that margarine or spreads are isotropic materials. Depending on the scale of the sample, such statement is sometimes questionable in particular when using miniaturized samples. This paper gives an overview of the methods adopted and evaluates its suitability to analyze the melting and textural characteristics of spreads. Differential Scanning Calorimetry (DSC) was used to analyze the melting property of spread. Textural evaluation was carried out on spread with cone penetration, creep analysis and compression test using cylinder. DSC was found to be not reproducible due to the small size of the sample; larger sample are recommended. Creep analysis by DMA was found to be a sensitive method in detecting the differences in textural attributes of spread.

High-Pressure Processing of Meats and Seafood

Meat and seafood products represent a high proportion of the applications of high-pressure processing (HPP) in the world. Mainly used for decontamination purposes, this innovative process has proved to be a reliable technology for ensuring food safety and extending the shelf life of these perishable and fragile foods. However, meat and seafood may experience quality alterations under pressure. This chapter focuses on the effect of HPP on meat and seafood organoleptic quality (texture, color, aroma, taste…). The physicochemical processes responsible for these changes are also reviewed to provide a better understanding of the mechanisms involved. This chapter ends with an overview of current commercial applications and other potential applications.

Effect of high pressure–high temperature process on meat product quality

High pressure/high temperature (HPHT) processing is an innovative way to sterilize food and has been proposed as an alternative to conventional retorting. By using elevated temperatures and adiabatic compression, it allows the inactivation of vegetative microorganisms and pathogen spores. Even though the microbial inactivation has been widely studied, the effect of such process on sensorial attributes of food products, especially meat products, remains rare. The aim of this study was to investigate the potential of using HPHT process (500 MPa/115 °C) instead of conventional retorting to stabilize Toulouse sausages while retaining high organoleptic quality. The measurements of texture, color, water-holding capacity and microbial stability were investigated. It was possible to manufacture stable products at 500 MPa/115 °C/30 min. However, in these conditions, no improvement of the quality was found compared with conventional retorting.

Gelatinization kinetic of waxy starches under pressure according to ionic strength

High pressure is a potential technology for the texturization of food products at ambient temperature. In this area, waxy starches are particularly interesting because they gelatinize quickly under sufficient pressure. However, gelatinization may be influenced by other components in the food matrix. Here, we investigate the influence of increasing ionic strength on gelatinization rate and kinetics at 500 MPa for waxy corn and waxy rice starches. We show that increasing ionic strength strongly retards and inhibits starch gelatinization under pressure and leads to heterogeneous gels with remnant granules.

Model-Based Settings of a Conveyorized Microwave Oven for Minced Beef Simultaneous Cooking and Pasteurization

Abstract A major drawback of microwave processing is the heterogeneity of treatment, which prevents from a plenty benefit of its flexibility and rapidity. Most of time, this operation is realized in continuous processes, composed of a series of microwave generators with adjustable power. In this paper is proposed a methodology leading to an optimal setting of these powers in order to warrant the expected microorganisms’ inactivation during simultaneous cooking and pasteurization, while preserving quality. It consists in minimizing a multicriteria formulation including hottest and coldest points on the first hand, and final logarithmic inactivation on the other one. The simulation model is composed of a reduction of the heat equation via a finite volume scheme with a source term deduced from appropriate closed-form solutions of the Maxwells equations, whereas the non-isothermal inactivation is described by the Geeraerd model. The methodology is carried out by considering treatment of minced beef.

Membrane integrity of Campylobacter jejuni subjected to high pressure is pH-dependent

Our study focuses on a foodborne pathogen, Campylobacter, which is responsible for the most frequent bacterial enteritis worldwide. Membrane integrity of Campylobacter jejuni NCTC 11168 cells treated at high pressure (300 MPa, 20°C, 10 min) at pH 7.0 and pH 5.6 was measured by fluorescence spectroscopy of propidium iodide (PI) uptake. The percentage of membrane-damaged cells by high pressure, in which PI is allowed to penetrate, was determined using two calibration methods based on the PI fluorescence signal obtained with cells killed either by a heat treatment (80°C for 15 min) or by a pressure treatment (400 MPa, 20°C, 10 min). Both calibrations were shown to be statistically different (P<0.05), particularly at acidic pH, suggesting that a difference in the penetration of PI into bacterial cells might depend on the mode of cell inactivation. These results corroborate the fact that the mechanism of microbial inactivation by high pressure is pH-dependent.