Blanching treatment

Long-time blanching treatments such as that of 50°C for 80 min and 70°C for 45 min resulted in the lowest levels of acrylamide formation (342 and 538 p.g/kg as average values for the three frying temperatures tested). These two blanching treatments after fiying at 190°C, lead to the lowest acrylamide contents (564 and 883 p.g/kg, respectively). 

Figure 4. Effect of blanching and freezing on texture. UF refers to tissue which Is not frozen after the blanch treatment, F/T to tissue which has undergone a freeze thaw cycle after the blanch treatment.

The extent of the reaction converting chlorophylls into pheophytins is directly related with the temperature and the time that the blanching treatment lasts [132]. Blanching at low temperature (65°C-80°C) favors activation of the enzyme chlor-ophyllase, and thus the formation of dephytylated chlorophyll derivatives (chloro-phyllides and pheophorbides). At higher temperatures (around 100°C), the enzyme is partially inactivated, but is favored the parallel reaction of pheophytinization. The extent of chlorophyllide and pheophorbide formation will depend not only on the specific conditions of the technological treatment, but also on the level of chlorophyllase activity in the plant material [133]. 

DEVECE C, RODRIGUEZ LOPEZ J N, FENOLL L G, TUDELA J, CATALA J M, DE LOS REYES E and GARCIA CANOVAS F (1999) Enzyme inactivation analysis for industrial blanching applications comparison of microwave, conventional, and combination heat treatments on mushroom polyphenoloxidase activity , J g-nc Food Chem, 47 (11) 4506-11. 

Maharaj, V. and Sankat, C.K., Quality changes in dehydrated dasheen leaves effects of blanching pre-treatments and drying conditions. Food Res. bit., 29, 563, 1996. 

The structural features of ceU wall polysaccharides of carrots have been studied by Stevens and Selvendran (1984) and Massiot et al.(1988). Plat et al.(1991), Ben Shalom et al.(1992) and Massiot et al.(1992) investigated the changes in pectic substances of carrots after blanching, dehydration and extended heat treatment. Data on the changes in ceU waU polysaccharides of canned carrots are lacking. This study aims to investigate the effect of preheating time at low temperature and the addition of CaCL on texture and on the composition of various pectin fractions of carrots canned by conventional and by a new process. 

Same dust treatment, then washed and blanched for freezing 2.6... 

Unheated carrot juices produced from carrots blanched at 80°C for lOmin were devoid of di-isomers, and further pasteurization or sterilization process formed only 13-d.v-P-carotene, respectively, at 2% and 5% (Marx et al. 2003). However, extensive carrot blanching (100°C for 60min) caused the losses of 26%-29% in total P-carotene content, along with an increased 13-d.s-P-carotene content up to 10% after pasteurization (Tmax 95°C, F = 3) and to 14% after sterilization (Tmax 121°C, F = 5) (Marx et al. 2003). The addition of grape oil to carrot juice before heat treatment enhanced the 13-di-P-carotene formation (18.8%) as compared to the control (6.0%) (Marx et al. 2003). This fact is probably due to the partial dissolution of crystalline carotene, present in the intact carrot in lipid droplets, since the solubilization of carotenes during blanching is a prerequisite for the formation of di-isomers. 

Escriche, I., Chiralt, A., Moreno, J., and Serra, J.A. 2000. Influence of blanching-osmotic dehydration treatments on volatile fraction of strawberry. J. Food Sci. 65, 1107-1111. 

Clair, Catalogue, 44, no. 57 Portrait de Joueurs d echecs, Blanche 11. The image was obviously significant for Duchamp as several preparatory studies exist, beginning in October 1911 (nos. 51-56). An earlier treatment on the same theme. 

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