Structural and functional characterization of starches from Brazilian pine seeds (Araucaria angustifolia)

Nutritional, functional and rheological properties of bunya nut flour as a versatile gluten-free option

Bunya nuts are a starch-rich food that has been consumed by Indigenous communities for thousands of years. In addition to consuming fresh nuts, they were commonly processed into flour. However, their properties as a gluten-free flour are still unknown. In this study, we investigated the nutritional, functional and rheological properties of bunya flour prepared using different methods, as well as the isolated starch, and compared to wheat, rice and chestnut flours. Overall, raw bunya nut flour showed higher fibre (8.4%d.b.), lower protein (4.7%d.b.) and higher fat content (4.4%d.b.) when compared to rice and wheat flours. Its proximate composition was similar to chestnut flour. By altering the preparation method for bunya nut flour we showed that its functional properties can be altered, for example, raw and whole bunya flours showed good foam and emulsion capacity and stability, whereas roasted bunya flour had poor emulsion activity and stability but a high water absorption capacity. Raw and fermented flours showed high peak viscosity when heated in water. Bunya flours, except for the roasted one, showed a slow rate of starch hydrolysis and high resistant starch content compared to wheat and rice flours, especially considering the role of the inner coating when not removed from the nut. Bunya nut flour is a versatile option and can overcome issues found for gluten-free flours such as poor nutritional quality and sensory properties of the resultant products.

Impact of defibrillation technique on the rheological, thermo-mechanical, and nutritional properties of nanosuspensions produced from multiple fractions of pinhão seed (Araucaria angustifolia (Bertol.) Kuntze)

This work aimed to evaluate the influence of the mechanical defibrillation technique on the pinhão nanosuspensions production obtained from the whole pinhão, its coat, and almond. The nanosuspensions were characterized concerning their composition, morphology, thermal stability, rheological behavior, compound profiling, and cytotoxicity. The results revealed a significant fiber content in pinhão coat nanosuspension (63.12 ± 0.52 %) and non-fiber carbohydrates in whole pinhão (59.00 ± 0.13 %) and almond (74.39 ± 0.23 %) nanosuspensions. The defibrillation process led to micro/nano-sized fibers in pinhão coat nanosuspensions and small-size starch granules in almond nanosuspensions. The nanosuspensions containing pinhão coat exhibited a gel-like behavior, while almond nanosuspensions displayed liquid-like characteristics. Pinhão coat nanosuspensions presented a significant content of flavonoids and phytosterols, whereas almond-based nanosuspensions contained substantial sugar amounts. No cytotoxicity was observed at the concentrations evaluated. These findings demonstrated that the defibrillation technique impacted the properties of pinhão constituents, allowing their application in new product development.

Improving the thermal stability and branching efficiency of Pyrococcus horikoshii OT3 glycogen branching enzyme

In practical applications, the gelatinisation temperature of starch is high. Most current glycogen branching enzymes (GBEs, EC 2.4.1.18) exhibit optimum activity at moderate or low temperatures and quickly lose their activity at higher temperatures, limiting the application of GBEs in starch modification. Therefore, we used the PROSS strategy combined with PDBePISA analysis of the dimer interface to further improve the heat resistance of hyperthermophilic bacteria Pyrococcus horikoshii OT3 GBE. The results showed that the melting temperature of mutant T508K increased by 3.1 °C compared to wild-type (WT), and the optimum reaction temperature increased by 10 °C for all mutants except V140I. WT almost completely lost its activity after incubation at 95 °C for 60 h, while all of the combined mutants maintained >40 % of their residual activity. Further, the content of the α-1,6 glycosidic bond of corn starch modified by H415W and V140I/H415W was approximately 2.68-fold and 1.92-fold higher than that of unmodified corn starch and corn starch modified by WT, respectively. Additionally, the glucan chains of DP < 13 were significantly increased in mutant modified corn starch. This method has potential for improving the thermal stability of GBE, which can be applied in starch branching in the food industry.

Hydrogel properties of non-conventional starches from guabiju, pinhão, and uvaia seeds

The physicochemical properties of starch vary depending on the botanical sources, thereby influencing the gelatinisation/retrogradation properties and subsequently affecting the hydrogels characteristics. This study aimed to assess the influence of botanical sources influence on starch and hydrogel properties using non-conventional starch derived from guabiju, pinhão, and uvaia seeds. Hydrogels were prepared by starch gelatinisation followed by 6 h ageing period at room temperature (20 ± 2 °C) and subjected to five freeze-thaw cycles. Pinhão starch exhibited a higher viscosity peak and breakdown, along with a lower final viscosity and setback, compared to guabiju and uvaia starches. The significantly different pasting properties influenced the porous microstructure, water absorption (p-value: 0.01), and resistance of the hydrogels (p-value: 0.01). The guabiju starch hydrogels showed a uniform pore structure without cavities, whereas pinhão and uvaia starch hydrogels exhibited agglomerated and spongy pore structures. Furthermore, the guabiju starch hydrogel demonstrated the lowest water absorption (4.56 g/g) and the highest compression resistance (1448.50 g) among all the studied starch hydrogels. In contrast, the pinhão starch hydrogel showed the highest water absorption (7.43 g/; p-value: 0.01) among all studied starch hydrogels. The hardness of uvaia starch hydrogel did not differ significantly from the guabiju and pinhão starch hydrogel. The different non-conventional starches reveal important variations in the hydrogels characteristics. This provides insights into how amylose and amylopectin interact and present alternatives for using these unique starch-based hydrogels in diverse applications.

Functionality and characterization of modified starch films with pineapple leaf fibers

The objective of this work was to modify banana starch with pineapple leaf fibers (PALF) and its production of biodegradable films. The reaction conditions of the starch modification were a Starch/PALF mass ratio of 50, a time of 1 h and a temperature of 140 °C, to obtain a yield of 41.18 %. Characterization by FTIR and NMR confirmed that the chemical reaction was carried out. XRD and TGA analysis showed that the crystalline zones of the starch were affected during the modification and the product obtained is thermally less stable compared to unmodified starch. The modified starch showed a lower pasting profile compared to the native starch; however, the modified starch showed the ability to form a film. The starch-PALF films were obtained by the casting method and partially characterized. These films presented better mechanical properties compared to the unmodified films. Also, these films could compete with conventional non-biodegradable plastics.

Effect of high-energy mechanical milling on the physicochemical and rheological properties of chayotextle (Sechium edule Sw.) starch

This work evaluates the effect of high-energy mechanical milling time (7 levels, 20-80 min) on amylose content, crystallinity pattern, temperature and gelatinization enthalpy, morphology, and rheological properties of chayotextle (Sechium edule Sw.) starch. After 30 min of milling, granular structure was affected, and amylose values were the highest while crystallinity and gelatinization enthalpy decreased significantly. These changes allowed to obtain gels with viscoelastic properties where the elastic character (Ǵ) prevailed upon the viscous modulus (Ǵ́). Native starch showed Tan δ values of 0.6, increased significantly (0.9) after 30 min of milling due to the surge in linear chains (amylose) and loss of granular structure. Native and modified starches showed high dependence on cutting or shear speed, presenting a non-Newtonian behavior (reofluidizers). These results indicate that mechanical grinding is an alternative to obtain modified starches with applications in the food industry.

The alterations in granule, shell, blocklets, and molecular structure of pea starch induced by ultrasound

Understanding the alterations to starch multi-scale structure induced by ultrasound treatment can help in determining the effective application of ultrasound in functional-starch preparation. This study aimed to comprehensively characterize and understand the morphological, shell, lamellae, and molecular structures of pea starch granules treated by ultrasound under different temperatures. Scanning electron microscopy and X-ray diffraction analyses showed that UT (ultrasound treatment) did not change C-type of crystalline, but caused a pitted surface and endowed a looser structure and higher enzyme susceptibility as the temperature increased above 35 °C for pea starch granules. Fourier transform infrared spectroscopy and small-angle X-ray scattering analyses revealed that UT reduced the short-range ordering and increased the thickness of semi-crystalline and amorphous lamellae by inducing starch chain depolymerization, which was manifested by molecule weight and chain length distribution analysis. The sample ultrasound-treated at 45 °C had the higher proportion of B2 chains compared with the other ultrasound-treated samples because the higher ultrasonic temperature altered the disruption sites of starch chains.

Linking geographical origin with nutritional, mineral, and visual proprieties of pinhão (Araucaria angustifolia seed) from the south of Brazil

The effect of harvest location on cooked pinhão seeds (Araucaria angustifolia) was investigated with regard to its centesimal composition, minerals, and color, and later correlated with environmental and soil variables. Significant differences between cooked pinhão from various harvesting locations were seen; also, principal component analysis was performed for the minerals, protein, moisture, total starch, and color parameters. The geographic location was one of the most important factors. Caçador presented greater differences: lower values for moisture, minerals, geographic parameter, and color characteristics. However, nearby localities, such as Cruz Machado with Bituruna and Lapa with São João do Triunfo, presented similar overall values for minerals and geographic parameters. Each regional geographic location was able to present unique characteristics so that the principal component analysis categorized it in specific quadrants, which is also in agreement with the CIELAB color space. However, hierarchical tree exhibited that CAÇ was the most distinct, due to the most distant municipality, presenting a unique microbiome. The pinhão is a source of various nutrients, which contributes to healthy dietetic daily values. It provides from 20% to 30% of dietary fiber, Cu (42.2%), P (31.1%), K (23.5%), and Zn (22.1%), while also providing quantities of Mg (12.9%), Mn (12.4%), Fe (11.5%), and Ca (6.4%). Therefore, it is possible to obtain food products based on cooked pinhão that contain many nutritional components associated with human health benefits. PRACTICAL APPLICATION: The pinheiro-do-paraná is a conifer that is currently endangered. However, the commercial use of its seeds may be key to guaranteeing its preservation, in addition to strengthening the economies of households and small producers. The pinhão collected from a large area of Araucária forests, after subsequent boiling, removal of the almond, grinding, and freezing provides large amounts of carbohydrates, higher dietary fiber content, resistant starch, and large quantities of Cu, P, K, and Z, in addition to significant amounts of Mg, Mn, Fe, and Ca. All of these are desirable characteristics that increase the value of pinhão.

Two 1,4-α-glucan branching enzymes successively rearrange glycosidic bonds: A novel synergistic approach for reducing starch digestibility

Enzymatically rearranging α-1,4 and α-1,6 glycosidic bonds in starch is a green approach to regulating its digestibility. A two-step modification process successively catalyzed by 1,4-α-glucan branching enzymes (GBEs) from Rhodothermus obamensi STB05 (Ro-GBE) and Geobacillus thermoglucosidans STB02 (Gt-GBE) was investigated as a strategy to reduce the digestibility of corn starch. This dual GBE modification process caused a reduction of 25.8 % in rapidly digestible starch fraction in corn starch, which were more effective than single GBE-catalyzed modification with the same duration. Structural analysis indicated that the dual GBE modified product contained higher branching density, more abundant short branches, and shorter external chains than those in single GBE-modified product. These results demonstrated that a moderate Ro-GBE treatment prior to starch gelatinization caused several suitable alterations in starch molecules, which promoted the transglycosylation efficiency of the following Gt-GBE treatment. This dual GBE-catalyzed modification process offered an efficient strategy for regulating starch digestibility.

The relationship between amylopectin fine structure and the physicochemical properties of starch during potato growth

The aim of this study was to explore the relationship between the structural and functional properties of starch isolated from Atlantic potatoes at different stages of growth without the effect of varieties and growth environment. The molecular size and chain-length distribution of amylopectin significantly varied with growth. The M_w and M_n of amylopectin ranged from 2.976 × 10⁷ to 4.512 × 10⁷ g/mol and 1.275 × 10⁷ to 2.295 × 10⁷ g/mol, respectively, suggested that the polydispersity varied with growth. The average chain length of amylopectin during potato growth showed small but significant changes and ranged from DP 23.59 to 24.73. Overall, A_fp chains, A_crystal chains, and B1 chains increased with growth, and B2 and B3 chains decreased with growth. There was wide variation in starch pasting, gelatinization, retrogradation, in vitro starch digestibility, swelling power, solubility, and gel stability properties. Specifically, potato starch harvested at the earliest time had the highest resistant starch content. The variation trend of swelling power and solubility was similar, reached highest value at 42 days, were 20.38 g/g and 8.83%, respectively. Correlation analysis revealed that the physicochemical properties were significantly affected by amylopectin fine structure. The results of this study enhance our understanding of the structure-function relationship of potato starch.

Hydrothermal–Microwave Processing for Starch Extraction from Mexican Avocado Seeds: Operational Conditions and Characterization

Avocado seeds are an agroindustrial residue widely produced in Mexico that are causing various environmental problems due to their accumulation. The evaluation of avocado residues to recover biopolymers by microwave-assisted extraction (MAE) and the characterization of avocado starch properties were studied in the present work. A central-composite design was used to optimize the MAE process. Moreover, a comparison was performed between MAE non-isothermal mode (NO–ISO) and conventional extraction. Starch optimization by MAE was obtained at 161.09 °C for 56.23 min with an extraction yield of 49.52% ± 0.69%, while with NO–ISO at 161 °C was obtained 45.75% ± 2.18%. Conventional extraction was 39.04% ± 2.22%. Compared with conventional starch, MAE starch showed similar proprieties and molecular spectra. In contrast, MAE starch showed high solubility, low water absorption capacity, a non-granular structure with small particle size (<2 µm) and polydispersity of fragments at different sizes of polymers. Therefore, MAE is a viable technology to extract the starch, and avocado seed can be considered an excellent starch source for the development of novel functional foods, contributing to promoting sustainability across the food chain.

Molecular structure of starch isolated from jackfruit and its relationship with physicochemical properties

The molecular structure of starches isolated from five jackfruits (M2, M3, M4, M8 and X1) and its relationship with physicochemical properties were investigated. Although they had uniform amylose (AM) content, the five jackfruit starches displayed different physicochemical properties, including their pasting, thermal, crystal and texture properties. Furthermore, differences in the molecular structure (i.e., average weight-average molar mass (Mw) of amylose and amylopectin (AP) as well as the same AP fine structure) were also found in the five jackfruit starches. The results indicated that jackfruit starch with a larger Mw of amylose and proportions of DP 25–36, DP ≥ 37 and chain length had a lower peak viscosity, breakdown, final viscosity, setback and adhesiveness, but a higher pasting and gelatinization temperature, gelatinization temperature range, gelatinization enthalpy and relative crystallinity. Xiangyinsuo 1 hao (X1) starch, which originated from Xinglong in Hainan province, China, had special physicochemical properties, which were ascribed to its lower amylopectin Mw, smaller particle size, and perfect amylopectin structure. The results showed that the most important intrinsic factors that could determine the physicochemical properties of starch were its molecular structure, including the Mw of amylose and AP as well as a fine AP structure.