*Rheological Stability, Enzyme Activity, and Incorporation of Pseudocereal Powder… DOI: http://dx.doi.org/10.5772/intechopen.101890*

amylopectin-amylopectin chains that lessen amylase leaching and decrease setback viscosity. From **Table 2**, it can be observed that all HMT of modified-amaranth (*A. caudatus*) starches and modified-buckwheat starches decreases in peak viscosity and breakdown viscosity as compared with native starch. It indicates that the modified starches are more stable as compared with native one. Meanwhile, Sindhu and his team [22] found the contradict results, which increase in peak, breakdown, and setback viscosity that reflects the poor stability of modified starches and starch retrogradation occurred. All physical treatments aim to modify the granular structure of native starch and convert it to cold-dissolvable starch or crystallization of starch.

The hydrothermal treatment of native starch reduced its ultimate viscosity at lower temperatures (85 and 100°C), but increased it significantly at higher temperatures (120°C). The eventual viscosity of all starch samples was lower than the peak viscosity, which could be due to some glycosidic linkage breakdown. In addition to the breakdown viscosity, the stability of starch pastes is determined by their breaking point, and higher breaking point values indicate inferior stability during continuous heating and shearing procedures in comparison to native starch. Except for acetylated starch, which showed a nonsignificant rise in setback viscosity when compared with native starch, all treated starches showed a substantial increase in setback viscosity. The largest setback viscosity was found in oxidized starch, and results from a freezethaw stability experiment confirmed this. Oxidized starch had the highest syneresis, while acetylated starch had the lowest. The setback viscosity varies depending on the amount of amylose leaching, the size of the granules, and the type of swelling granules. In this study, modified starch samples had an enhanced setback viscosity due to the waxy and low amylose characteristics of the amaranth starch used. Increases in pasting temperatures of heat-moisture-treated starches indicated that amylopectin chain connections were strengthening and interactions between them expanding. Starch pastes were statistically significantly reduced in pasting temperature and peak time as a result of acetylation and oxidation processes. Because the insertion of functional groups modulated the amorphous region and decreased the intermolecular hydrogen bonds, the pasting temperature of the starch granules was lower. Modification improves the application of modified starch in products where the thickening ingredient must gelatinize quickly at low temperatures by lowering the pasting temperature and peak time. The increased efficiency of such items also decreases the energy costs involved in their processing. As a consequence, acetylated and oxidized starches are usable in formulations that require low-temperature cooking/processing to obtain pastes [22, 28].

The effect of octenyl succinylation on the functional characteristics of *Amaranthus paniculatus* starch was investigated by Bhosale and Singhal [29]. The swelling power, paste clarity, freeze-thaw stability, enhanced viscosity, and lowered gelatinization temperature of OSA-modified amaranth starch were all improved. These findings suggest that OSA-modified amaranth starch could have applications in the food business, particularly in emulsification. Pal et al. [30] investigated the qualities of hydroxypropyl derivatives derived from *A. paniculatus* starch and discovered a considerable improvement in freeze-thaw stability, suggesting that it could be used as a thickening agent in frozen foods. All starches (amaranth/quinoa) had increased pasting viscosities following modification of octenylsuccinylate (OSA), but RVA profiles were affected in different ways. In contrast to native starches, OSA starches were found to paste at a lower temperature between 73.7 and 81.4°C. Due to the fact that OSA starches have loosely packed surface areas, resulting in lower pasting

#### *Rheological Stability, Enzyme Activity, and Incorporation of Pseudocereal Powder… DOI: http://dx.doi.org/10.5772/intechopen.101890*

temperatures, the OSA group produces spatial hindrance, which is responsible for weakening internal hydrogen bonds, which increases water absorption and lowers energy expenditure for gelatinization [23]. There might be additional influences on PT change from starch compositional aspects, such as the chain length of amylopectin, granule surface, and packing arrangement within the granules. As a result of the substitution of OSA on starch granules, the pasting qualities are also compromised. Peak viscosity can be defined as the water-holding capacity of starch granules in terms of swelling and shearing ability. Starches with high peak viscosity are suited for application as food thickeners, while a low percentage of OSA starch can replace higher levels of unmodified starch. Amylose content and long-chain fraction of amylopectin have been reported as major factors influencing peak viscosity [23, 24]. Modification of quinoa starch with OSA showed that a substitution degree of 3.21% is optimal for emulsifier formation and stabilization. A higher degree of substitution (4.66%) results in the aggregation of starch granules and the decrease of starch granule stable emulsion. In addition, OSA modification is more effective than heat treatment in providing hydrophobic characteristics to quinoa. The heat treatment is only slightly better than the natural starch granules [31].

Several studies have been reported about different physical modification methods in buckwheat starches, some of these are roasting process [32], microwave and annealing treatments [33], drum-drying and ball-milling treatment [24] highpressure and high-temperature treatment [34], heat moisture treatment and annealing [24], hydrothermal processing [35], autoclaving/cooling [36], and others. The duration and quality of the gelatinization process as well as the viscosity and behavior of the gelatinization also change in nearly identical ways, including decreased or increased pasting viscosity, increased or decreased swelling power and solubility, increased retrograded starch content, increased gelatinization temperature, and slower digestion of the gelatinization [37].
