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Influence des stabilisants sur la cristallisation d'un semi-liquide alimentaire : Application à la congélation des sorbets

Abstract : A sorbet is a frozen and aerated dessert made from a mix of concentrated fruit juice, sugars and stabilizers. The most critical step in the manufacturing process of sorbets is the freezing-foaming step that takes place in a scraped surface heat exchanger (SSHE). During this step, ice crystals are generated and air bubbles are introduced while the unfrozen residual solution concentrates in sugars and stabilizers. The quality of the final product is strongly related to the quantity and size of ice crystals formed in the SSHE; they must be numerous and as small as possible. The scientific objective of this thesis is a better understanding of the influence of stabilizers on the microstructure (number and size of ice crystals and air bubbles) formed during the freezing process of a sorbet.The rheological properties of the sorbet mix before freezing and of the unfrozen residual solution were explored and quantified according to the stabilizer added (CMC, HPMC, or LBG). Studies of their surfactant properties and of the diffusion of water molecules were carried out and the thermal equilibrium properties of the mix were analyzed. The microstructure of sorbets was characterized in situ during the freezing process and ex situ at the end of freezing using high-performance characterization tools (FBRM, X-ray micro-computed tomography and Cryo-SEM).This study provides a better understanding of the influence of stabilizers on the establishment of the microstructure of a sorbet and in particular on the size and number of ice crystals and air bubbles. HPMC is the only stabilizer that influences the amount of air incorporated, and also the number and size of ice crystals. It appears that this stabilizer, by increasing the amount of air, decreases the growth of ice crystals. The air bubbles would act as physical barriers during freezing. The viscosities of the mix or the unfrozen residual solution, and water diffusion do not influence the crystallization in these systems.
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Submitted on : Wednesday, February 17, 2021 - 4:00:11 PM
Last modification on : Friday, August 5, 2022 - 2:41:13 PM
Long-term archiving on: : Tuesday, May 18, 2021 - 7:35:52 PM

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  • HAL Id : tel-03144442, version 1

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Véronique Masselot. Influence des stabilisants sur la cristallisation d'un semi-liquide alimentaire : Application à la congélation des sorbets. Génie des procédés. Université Paris-Saclay, 2020. Français. ⟨NNT : 2020UPASB021⟩. ⟨tel-03144442⟩

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