The influence of the storage conditions heat and humidity on conformation, state transitions and degradation behaviour of dried pectins

Thermal and structural study of guava (Psidium guajava L) powders obtained by two dehydration methods

“…This complex endothermic peak involves the volatilization processes of water, melting of pectin contained in guava 13,20 and a possible demethoxylation, dehydroxylation and decarboxylation of pectin and other polysaccharides. 19 A slight shift of discussed peaks toward lower temperature values is observed for the G-HA sample (Figure 1d), probably due to a higher water content 20 and its lesser thermal stability. In addition, almost a double intensity of G-HA peak regarding G-LF peak is clearly observed, and so a larger flow of heat, revealing more significant changes on the G-HA sample and thereby a lower thermal stability of this material.…”

“…This drop of mass can be assumed as water loss during the temperature rise. The third region (350-470 ºC) in the TGA analyses shows a more stable stage after volatilization of water and other compounds: between 150 and 350 ºC dehydroxylation, demethoxylation and decarboxylation reactions should be occurring on pectin 19 and similar polysaccharides (pectin is the main component of dehydrated guava). The total loss of weight for samples (63% for G-LF and 67% for G-HA) indicates that freeze drying is a technique slightly more suitable to give more thermally stable solids.…”

Characterisation and performance assessment of guava (Psidium guajava L.) microencapsulates obtained by spray-drying

“…The mass of the MD sample is very stable until 160°C, but a pronounced loss of mass was observed after 200°C for both MD and AGMD-1 samples. Loss of mass in these materials along this temperature range can be understood as a possible degradation or thermal decomposition of one or more components (polysaccharides) and their subsequent volatilization (Mothé & Rao, 2000;Einhorn-Stoll & Kunzek, 2009;Pereira, Carmello-Guerreiro, & Hubinger, 2009). So, it is very important that MD sample surpasses the 100°C without loss of mass, because this is a typical temperature for sterilisation processes in food industries.…”

Physicochemical property of starch–pectin conjugates with resistance to enzymatic activity

“…As exhibited in Fig. , all DSC curves display the transition from an endothermic peak to an exothermic peak with peak values ( T p ) ranging from 261.32°C to 286.49°C, which could be derived from the combustion of carbon and the combustive volatiles in the process of conjugates degradation . Moreover, the endothermic DSC peaks start earlier than the corresponding exothermic DTG peaks for all conjugates, and it can be due to conformation transformation before the degradation weight loss, which needs more energy than that released by the beginning thermal degradation.…”

“…2, all DSC curves display the transition from an endothermic peak to an exothermic peak with peak values (T p ) ranging from 261.32 • C to 286.49 • C, which could be derived from the combustion of carbon and the combustive volatiles in the process of conjugates degradation. 18 Moreover, the endothermic DSC peaks start earlier than the corresponding exothermic DTG peaks for all conjugates, and it can be due to conformation transformation before the degradation weight loss, which needs more energy than that released by the beginning thermal degradation. The conformation conversion might be the transformation from the stable 4 C 1 chair conformation of the glucose ring via a 1,4 B conformation to the inverse 1 C 4 chair conformation that has higher free energy, G. Additionally, with the exception of SPC1, other SPCs show another endothermic peak at about 200 • C, owing to the presence of pectin in the starch-pectin conjugates.…”