The relationships between headspace gases in canned apple sauce and storage time and temperature, food pH and consistency, and headspace vacuum and volume were studied. The apple sauce processing method used essentially duplicated commercial procedures. Canned apple sauce was stored at l00°F for 7 or 10 months, and sampled for headspace gases with a modified Zahm air tester. Procedures were developed for sampling for chromatographic analysis gas from cans with high vacuum and small headspace, and for calculating gas volumes. A minimum headspaoe hydrogen was observed in samples within the pH range 3.45-3.75, in products of consistency within the range common to the Virginia commercial apple sauce, and in cans with higher vacuum. Maximum carbon dioxide content was noted in samples having a pH value of 3.45. Samples with more fluid consistency had more headspaoe carbon dioxide than those of higher consistency. Variations in headspaoe carbon dioxide content occurred in direct proportion to headspace size, and trends could not be associated with can vacuum. Oxygen was generally 1.2-1.9 percent of the headspace gas. Carbon monoxide was present in all samples in very small amounts. / Master of Science

Ph. D.

Applesauce prepared for the US military is processed as MRE (meals-ready-to-eat) in several forms including Type VI - Applesauce with raspberry puree, and Type VII - Carbohydrate enriched applesauce. Production of MRE applesauce starts with commercially prepared and thermally processed applesauce that is further processed by a military contractor. The further processing includes adjusting pH, ºBrix, and ascorbic acid level, packaging into pouches, and again thermally processing. Both types of the MRE applesauce are very much liked by troops, but under stress storage applesauce darkens and its consumption is drastically reduced. The overall goal of this project was to identify additives to be used during further processing in order to slow darkening when exposed to elevated temperatures during shipping and storage. The specific objective was to determine whether different types of ascorbic acid, calcium salts, or addition of chelators can reduce deterioration under stress storage. Applesauce (AS), applesauce with raspberry puree (RPAS), MRE AS (Type VII) and MRE RPAS (Type VI) for all experiments were provided by Sopakco, Bennettsville S.C. The research was carried out in three phases. From the Phase 1, we learned that Type VII and Type VI darkened at faster rates at the beginning of the storage, but the effects of storage at 50°C for more than 2 weeks overcame any differences caused by further processing. Phase 2 helped us determine the formulations for the processing on the industrial scale. The formulations were: 0.15% L-ascorbic-acid (AA), and 0.15% AA with 300 ppm EDTA for both AS and RPAS, with 0.83% calcium lactate gluconate (CLG) for AS, and 0.15% ascorbyl-palmitate for RPAS. The results from the Phase 3 indicated that AS with addition of CLG and RPAS with total of 0.18% AA had the least total color change. In all samples, accumulation of HMF was related to amount of ascorbic acid with exception of samples with Pal which had the lowest HMF content. Our results indicate that current MRE Types VI and VII may have better stability at stress storage if the level of AA is limited to 0.18% and 0.83% CLG is added to the AS formulation.

Les purées de fruits sont considérées ici comme des dispersions concentrées de particules végétales déformables et insolubles dans une phase continue aqueuse ou sérum riche en sucre et contenant des pectines solubles. La phase dispersée est constituée de cellules ou d'amas de cellules de parenchyme dont les parois insolubles ne représentent qu'une très faible masse (un peu plus de 1 % p/p) dispersées dans un sérum dont elle sont remplies. La constitution et les propriétés rhéologiques des purées vont dépendre de plusieurs facteurs internes tels que la variété de fruit et l'état de maturité et de facteurs externes tels que les paramètres liées au procédé de transformation (traitement mécanique et thermique). Par ailleurs, la texture est l'un des principaux attributs de qualité des purées et constitue à ce titre une source potentielle importante dans le développement de produits nouveaux. L'objectif général de ce travail a été de mieux comprendre les relations entre les propriétés rhéologiques, structurales et sensorielles des purées de pomme dans la perspective d'identifier des leviers d'action pour le pilotage « à façon » de la texture des produits. La stratégie de recherche a consisté à réaliser l'ensemble de l'étude à partir d'une même lot d'une purée issue d'une seule variété de pomme : Golden Delicious et à identifier les axes majeurs permettant de créer des structures et textures variées. Les trois paramètres structuraux qui ont été modifiés sont : la concentration en parois cellulaires (liée à la quantité de particules de pulpe), la taille des particules et la viscosité de la phase continue. Une technique de séparation - reconstitution couplée à un traitement de broyage ainsi que l'augmentation de la viscosité du sérum ont permis d'obtenir une large gamme de textures et de structures. La construction de deux plans expérimentaux a permis de maîtriser la préparation des produits pour l'étude des relations entre la structure, la rhéologie et la texture des purées. La caractérisation physique et sensorielle a mis en évidence l'importance des paramètres structuraux sur le comportement rhéologique et la perception de la texture des purées. Ainsi la concentration en particules a un effet de premier ordre, suivi par la granulométrie et la viscosité du sérum. L'augmentation de la teneur en particules se traduit directement au niveau de l'état d'encombrement du milieu qui dépend de leur taille. Un traitement mécanique entraîne la séparation des amas des cellules de parenchyme en cellules individualisées, ce changement de structure implique des modifications marquées de propriétés. La caractérisation rhéologique et structurale a permis d'établir des modèles rhéologiques et de mieux comprendre le comportement, l'état et le rôle des particules (molles et déformables) sur la structuration du milieu ainsi que le volume occupé par celles-ci. Cette approche a été complétée et validée par l'observation des dispersions par différentes techniques microscopiques. Les différents régimes de concentration, du régime dilué à l'état d'encombrement et de compaction du régime concentrée des purées ont pu être mis en évidence. Les deux axes principaux qui suffisent à décrire la texture sensorielle d'une purée sont la « consistance » et la « granulosité ». La viscosité de la phase continue a un impact sur la perception de la « granulosité » comme sur la cohésion du réseau particulaire. Les résultats montrent que la texture des dispersions végétales peut être « pilotée » à partir de la maîtrise de quelques grandeurs clés : la concentration en parois cellulaires (pulpe) et la granulométrie des particules complété par la viscosité de la phase continue. De grandes possibilités d'innovation sont ouvertes en jouant sur ces leviers notamment à partir des possibilités offertes au niveau des paramètres du procédé de fabrication. / Fruit purees are considered as concentrated dispersions of deformable and insoluble particles in a continuous phase or serum rich in water, sugar and soluble pectin. The dispersed phase consists of cells or cell clusters of parenchyma tissue and the insoluble cell wall material dispersed in the serum represents a very low weight (~ 1% w/w). The structure and the rheological properties of purees will depend on many internal factors such as the variety and ripeness of the fruit and external factors occurring during the processing (mechanical and thermal treatment). Texture is a key quality attribute of purees and thus constitutes an important potential source for new product development. The main objective of this study was to better understand the relationship between the rheological, structural and sensory properties of apple puree, in order to pilot and control the texture of the products. The study was performed with a single batch of apple puree prepared industrially from fresh mature Golden Delicious. In order to create purees with varied structure and texture, three structural parameters were identified and modified: the cell walls concentration (related to the amount of pulp), the particle size and the viscosity of the continuous phase. A separation-reconstitution strategy joined to a grinding step and the modification of the serum viscosity allowed us to obtain a wide range of products with different structures and textures. The construction of two experimental designs made it possible the controlled preparation of the products so as to study the relatioins between structure, rheology and texture of the apple puree. Physical and sensory characterization highlighted the importance of structural parameters on the rheological behaviour and perception of the texture of the puree. Thus, the concentration of particles is the main parameter influencing these properties, followed by the particle size and the serum viscosity. The increase in particle content translates directly at the “overcrowding” that also depends on the particle size. Mechanical treatment leads to the separation of clusters of parenchyma cells in to individual cells; this change in structure involves marked changes of properties. Rheological and structural characterization made it possible the generation of rheological models and the better understanding of the behaviour, the state and the role of particles (soft and deformable) on the structure of the medium and the volume occupied by them. This approach has been completed and validated by the observation of dispersions by various microscopic techniques. The different regimes of concentration were identified. Texture perception of apple puree can be described basically by their “consistency” and their “graininess”. The viscosity of the continuous phase has an impact on the perception of “graininess” and in the cohesion of the particle network. Our results show that the texture of plant food dispersions can be “mastered” by controlling a few selected key parameters: the concentration of cell walls (pulp) and particle size, completed by the viscosity of the continuous phase. High possibilities for innovation are opened by playing on these parameters that can be modified during the processing.