High‐Pressure‐Freezing Effects on Textural Quality of Carrots

Abstract

Raw or 3 min blanched carrots were pressurized for 45 min at Ϫ18ЊC ϳ Ϫ20ЊC and then thawed at 20ЊC. When carrots were frozen at 100MPa (ice I), firmness decreased and strain increased. Textural values of carrots pressurized at 200MPa (liquid), 340MPa (ice III), 400MPa (ice V) at ca. Ϫ20ЊC were acceptable. When pressure was increased above 500MPa, the strain increased. Release of pectin and histological damage in carrots pressurized at 200, 340 and 400MPa were less than carrots frozen at 100 and 700MPa (ice VI). After pressurization at 200 and 340MPa at Ϫ20ЊC, carrots were stored in a freezer (Ϫ30ЊC). Firmness decreased and strain increased, but textural values were higher and histological structure were more intact than those frozen at Ϫ30ЊC (0.1MPa) then stored. Thus, high-pressure-freezing at 200, 340 and 400MPa appeared to be effective in improving both the texture and histological structure of frozen carrots.

Ice Morphology: Fundamentals and Technological Applications in Foods

“…150 After pressure release, PSF proceeds like the classical freezing process and the temperature profiles follow the same course as conventional freezing curves. 151 In practical terms, the use of high-pressure facilitates supercooling, promotes uniform and rapid ice nucleation, and produces smaller crystals, 148 as has been demonstrated for several foods products including gelatine gels 152 and starch gels, 153 meat pieces, 154 tofu, 155 fish, [156][157][158] and fruit and vegetables like carrots, 159,160 peach and mango, 161 and potatoes [162][163][164] These results suggest that high-pressure freezing is the best known method to preserve the microstructure of large pieces of food.…”

Chromoplasts ultrastructure and estimated carotene content in root secondary phloem of different carrot varieties

“…We used an alternative method, high pressure freezing (HPF), during the fixation process but this method also failed to retain carotene in the cells. Nevertheless, the use of HPF minimizes damage to sub-cellular structures that may occur with chemical fixation (Fuchigami et al 1997), and has greatly enhanced the visualization of the pre-fixation sites of carotene accumulation at the sub-cellular level. (109); e, f secondary xylem (409).…”

“…The fibrous nature of the carrot root and the extraction of carotenoids by the fixation solvents present challenges to sample preparation for TEM studies. Recent developments in TEM sample preparation, for example high pressure freezing (HPF) (Fuchigami et al 1997;Van Buggenhout et al 2005) may offer the opportunity to reexamine the subcellular localization of carrot root carotenoids, and to compare the potential ultrastructural differences between different carrot varieties with respect to carotene accumulation. Vasquez-Caicedo et al (2006) examined ultrastructural changes of chromoplasts in ripening mango mesocarp using light microscopy and TEM, and only briefly compared these results to chromoplast structure in carrot roots.…”

Optimización experimental del proceso de liofilización de uchuva adicionada con componentes activos

“…Por lo tanto espacios más porosos en muestras liofilizadas tienen como resultado una textura más suave y mayor capacidad de rehidratación. Acevedo et al (2008) (48) analizaron por SEM manzana liofilizada con diferentes velocidades de congelación, confirmándolo como un factor responsable de los cambios en los tejidos (49). En general, las velocidades de congelación rápidas generan productos con mejor calidad y estructura (50), pero generar mayor cantidad de poros con más sitios efectivos para la adsorción de agua.…”