The influence of heat-moisture treatment (HMT) and flour hydration (DY) on the restoration of dough viscoelasticity of wheat/non-wheat binary matrices was investigated by applying fundamental and ...empirical rheological procedures, and the protein structural reorganization was monitored by measuring residual protein solubility in different media, and by assessing the accessibility of thiol groups inside the protein network. Single chestnut (CN), chickpea (CP), millet (MI), and teff (T) flour samples submitted to HMT (15% moisture content, 1 h and 120 °C) were blended with wheat flour at 10% (CN, CP) and 30% (MI, T) of replacement, and binary matrices hydrated at low (L), medium (M), and high (H) DY. Structuring ability of HMT was mainly observed in cereal flour blends (T, MI), where higher elastic moduli and lower loss tangent together with solid-like elastic structure over higher shear stress were observed as compared with treated non-cereal flour blends (CN, CP). Increased flour hydration significantly weakened blends structure, inducing a stepped decrease in dynamic moduli values particularly noticed in cereal blends at highest level of flour hydration, and a shift from elastic-like to viscous-like structure at lower shear stress in non-wheat cereal matrices. The formation of a protein network with reinforced compact structure associated to the presence or formation of intramolecular (CN, CP, T) and intermolecular disulphide bonds (CN, CP, MI, T), water-soluble (CN, MI) and water-insoluble aggregates (CP, T) is feasible to achieve with proteins of non-wheat flours submitted to HMT, particularly in high DY doughs. The lower the amount of free thiols in high molecular weight proteins encompassing high degree of crosslinking, corresponded to thermally treated samples (T, MI) blended at L and M hydration levels. For thermally treated samples, the lower the amount of free thiols in high molecular weight proteins encompassing high degree of crosslinking, corresponded to T and MI binary matrices blended at L and M hydration levels. These samples exhibited a solid-like elastic structure over higher shear stress and showed increased tolerance to stress/strain before losing the structure.
The Ethiopian potato (Plectranthus edulis) is an annual tuber crop indigenous to Ethiopia. The crop is underutilized and not much studied despite its high yield of starch, which has a good potential ...to contribute to the effort in meeting the quickly growing demand for starch. In this study, the effects of the ecotype and isolation methods on the physicochemical, functional, structural, and crystalline properties of starches were evaluated. Starches were isolated from two Ethiopian potato ecotypes (Loffo and Chanqua) using distilled water (DW), 0.01% sodium metabisulphite (SMS), and 1M sodium chloride (NaCl) in the isolation media. The results showed that the lowest starch yield was obtained from Chanqua using DW (97.4%), while the maximum was from Loffo using SMS (99.3%). The L* (lightness) and whiteness values of the starches obtained from Loffo were higher than those of Chanqua starches, with NaCl and SMS extractants yielding the highest values. The bulk density, water activity (aw), pH, proximate composition (moisture content, protein, ash, fat, crude fiber, and carbohydrate contents), and techno-functional properties were established. The majority of these parameters varied depending on both the isolation method and the ecotype. The crystallinity pattern of all starches showed B-type diffraction, with differences in diffraction peak intensities between all starches. FTIR tests showed structural changes as a function of the ecotype and isolation procedure used. The Loffo ecotype exhibited considerably better results, and the SMS isolation method was found to be the most effective way to acquire the highest starch quality in most of the characteristics evaluated.
In recent years, many efforts are being made to produce tef-based food for its nutritive and health-promoting advantages. Tef grain is always whole milled because of its tiny grain size and whole ...flours contain bran (pericarp, aleurone, and germ) where major non-starch lipids could be deposited along with the lipid-degrading enzymes: lipase and lipoxygenase. As lipoxygenase shows little activity in low moisture, the inactivation of lipase is the common objective for most heat treatments to extend the shelf life of flours. In this study, tef flour lipase inactivation kinetics via hydrothermal treatments assisted using microwaves (MW) were studied. The effects of tef flour moisture level (12%, 15%, 20%, and 25%) and MW treatment time (1, 2, 4, 6, and 8 min) on flour lipase activity (LA) and free fatty acid (FFA) content were evaluated. The effects of MW treatment on flour pasting characteristics and the rheological properties of gels prepared from the treated flours were also explored. The inactivation process followed a first-order kinetic response and the apparent rate constant of thermal inactivation increased exponentially with the moisture content of the flour (
) according to the equation 0.048·exp (0.073·
) (R
= 0.97). The LA of the flours decreased up to 90% under the studied conditions. MW treatment also significantly reduced (up to 20%) the FFA level in the flours. The rheological study confirmed the presence of significant modifications induced by the treatment, as a lateral effect of the flour stabilization process.
Ultrasonic (USC) treatments have been applied to starches, flours and grains to modify their physicochemical properties and improve their industrial applicability. The extent of the modification ...caused by USC treatment depends on the treatment conditions and the natural characteristics of the treated matter. Cavitation leads to structural damage and fragmentation and partial depolymerization of starch components. The amorphous regions are more susceptible to being disrupted by ultrasonication, while the crystalline regions require extended USC exposure to be affected. The increased surface area in USC-treated samples has a higher interaction with water, resulting in modification of the swelling power, solubility, apparent viscosity, pasting properties and gel rheological and textural properties. Starch digestibility has been reported to be modified by ultrasonication to different extents depending on the power applied. The most important treatment variables leading to more pronounced modifications in USC treatments are the botanical origin of the treated matter, USC power, time, concentration and temperature. The interaction between these factors also has a significant impact on the damage caused by the treatment. The molecular rearrangement and destruction of starch structures occur simultaneously during the USC treatment and the final properties of the modified matrix will depend on the array of treatment parameters. This review summarizes the known effects of ultrasonic treatments in modifying starches, flours and grains.
Cereal β-glucan concentrates can be used in gluten-free breads to improve dough handling properties and quality of final products as well as to enhance their nutritional value; however, the presence ...of endogenous β-glucanases in rice flour, in combination with prolonged mixing, fermentation, and proofing time, can cause a substantial reduction in β-glucan molecular weight, affecting detrimentally their efficacy for bioactivity. In this study, microwave (MIWA) heating was applied to the rice flours before breadmaking at different flour water contents (13–25%) and treatment times (0-4 min) to reduce β-glucanase activity. Gluten-free breads made from the MIWA-treated rice flours were fortified with oat β-glucan concentrate to enhance their nutritional profile. The molecular weight of added β-glucan in the final products increased with increasing both flour water content and time of MIWA treatment, reflecting the magnitude of residual β-glucanase activity in the flour. Pretreatment with MIWA radiation for 4 min of the rice flour tempered at 25% moisture resulted in negligible residual β-glucanase activity and preserved to a great extent the molecular weight of β-glucans in the enriched breads. End-product quality was not affected by flour MIWA pretreatment, and even a slightly higher loaf specific volume was noted for breads made from the MIWA-treated flours (4 min MIWA at 25% moisture content) compared to that of untreated flour. These findings can contribute to the improvement of nutritional value of rice-based gluten-free breads for celiac consumers as well as of any β-glucan-containing yeast-leavened bakery product without altering its sensorial attributes. Additional studies are still required for further evaluation of the effect of more intense microwave treatment on rice flour and its application on breadmaking.
Functionality of hydrocolloids of different origin and chemical structure (sodium alginate, carrageenan, pectin, hydroxy-propyl-methylcellulose, locust bean gum, guar gum and xanthan gum) on yellow ...layer cake quality and their potential use in retarding the staling process have been studied. Hydrocolloid effects were established by measuring batter density, water losses during and after baking, and size, shape and texture of yellow layer cakes. Texture was evaluated instrumentally through a texture profile analysis (TPA) test applied on fresh and 2 days stored yellow layer cakes. A hedonic sensory test of texture, odour, flavour, appearance and overall acceptance was also carried out. Physical properties of fresh cakes and their evolution in time were notably influenced by the type of hydrocolloid involved. In general, except when pectin was used, the overall acceptability of yellow layer cakes was always improved by hydrocolloid addition. Regarding shelf-life, xanthan was able to maintain totally unaltered all texture parameters during storage.
Quinoa has recently been considered as an alternative oilseed crop due to the quality and quantity of its lipid fraction. Supercritical fluid extraction (SFE) was used as a green process to extract ...quinoa oil without solvent residues. Defatted quinoa flour is a potentially valuable raw material whose performance as food ingredient needs to be established. Structural, physicochemical, pasting, and thermal properties of quinoa (cv. Titicaca) defatted by supercritical CO
2
extraction (DQ-SCCO
2
) were characterized. In vitro starch enzymatic susceptibility was also evaluated. Full fatted quinoa (NDQ) and quinoa defatted by hexane extraction (DQ-HX) were also evaluated in parallel. DQ-SCCO
2
showed a disrupted and microporous structure due to the pressurization/depressurization of CO
2
in SFE. However, its viscometric profile was very similar to that of NDQ, while that of DQ-HX was significantly lower. This denotes a physical/thermal modification of the flour as a result of the higher temperature applied during hexane extraction, 68 °C, versus 40 °C in SFE. Defatted samples showed lower pasting temperatures (4–5 °C) and higher amylopectin retrogradation extent than NDQ. Quinoa showed a very high enzymatic susceptibility regardless its lipid content; 90% of the starch was hydrolyzed by digestive enzymes in 20 min in the three samples. However, defatted quinoa had lower slowly digestible starch content than NDQ, being the lowest value for DQ-SCCO
2
sample. The work confirms the feasibility of using DQ-SCCO
2
as a raw material in food applications, free of solvent residues, and with a technological quality superior to that obtained by extraction with organic solvents.
Anchote (Coccinia abyssinica (Lam.) Cogn) is a potentially important source of starch and an underutilized root and tuber crop indigenous to Ethiopia. In this study, the physicochemical, ...morphological, thermal, and rheological properties of native starches isolated from four cultivars of anchote tubers were studied and compared to potato and cassava starches, which were considered as references. The amylose content of anchote starches varied from 15.8–22.3%. The anchote cultivars showed different granule sizes, but all revealed a B-type crystalline structure, identical to potato starch. The phosphorus content of anchote starches ranged from 82–93 mg/100 g and was much higher than that of potato and cassava (60.3 and 5.8 mg/100 g, respectively). This characteristic could govern several functional properties of anchote starches, making them suitable for applications in different types of noodles, glucose syrups, and viscous products. The gelatinization temperature and enthalpy of anchote starches, which ranged from 60.97 °C to 69.33 °C and 16.87 to 18.38 J/g, respectively, were considerably different compared to potato and cassava starches. Significant variations were also observed among the pasting properties of starches from anchote cultivars. They showed a higher stability to heating and shearing, having higher TV (2046 to 2280 mPa·s) and lower BV (248 to 487 mPa·s) values, and a higher final viscosity (3409 to 3686 mPa·s) than potato and cassava, which are important characteristics in food processing and when high gel viscosity is required after cooling. Anchote starch gels exhibited rheological characteristics of true gels, showing much lower (tan δ)1 values and significantly higher viscoelastic moduli than those found in cassava and potato gels. The present study revealed significant differences among the physicochemical properties of anchote starches, depending on the cultivar, and demonstrated their promising potential in food product development and other industrial applications.
The pasting and rheological properties of starch gels from different botanical origins have been widely used to evaluate the application of these starches in pharmaceutical and food products. ...However, the ways in which these properties are modified by starch concentration and their dependence on amylose content and thermal and hydration properties have not been adequately established so far. An exhaustive study of the pasting and rheological properties of starch gels (maize and rice (normal and waxy in both cases), wheat, potato, and tapioca) at concentrations of 6.4, 7.8, 9.2, 10.6, and 11.9 g/100 g was performed. The results were evaluated in terms of a potential equation fit between each parameter and each gel concentration. The parameters determined for the gels at the studied concentrations were correlated with the hydration properties and thermal properties by applying principal component analysis (PCA). Wheat starch, followed by normal maize and normal rice starches, presented a greater capacity to modulate their gels' pasting and viscoelastic properties via their concentration in water. On the contrary, the characteristics of waxy rice and maize, potato, and tapioca starches were barely modified by concentration in pasting assays, but the gels of potato and tapioca showed noticeable changes in their viscoelastic properties as functions of concentration. In the PCA plot, the non-waxy cereal samples (wheat, normal maize, and normal rice) were located close to each other. Wheat starch gels were the most dispersed on the graph, which is consistent with the high dependence on the concentration of the gel shown in most of the studied parameters. The waxy starches had close positions not too distant from those of the tapioca and potato samples and with little influence from amylose concentration. The potato and tapioca samples were close to the vectors of the crossover point in rheology and peak viscosity in their pasting properties. The knowledge gained from this work allows a better understanding of the effects of starch concentration on food formulations.
Cajanus Cajans and Dolichos lab‐lab legume starches from Argentine cultivars were investigated under a technological and nutritional point of view. Their physico‐chemical, structural, thermal and the ...rheological properties of their gels were evaluated. Rice (RS) and potato (PS) starches were included as references. In vitro digestibility from Englyst method was also evaluated. Legume starches had the highest amylose content and the most stable chemical structure. Their rapidly digestible starch and starch digestibility rate index were very low, similar to PS, and fivefold lower than RS. They had a much higher slowly digestible starch content than PS. Legume starches showed the highest gel stability versus heating and stirring and an intermedium pasting temperature between RS and PS. They formed viscoelastic gels at 6% concentration with stronger elastic‐like behaviour and higher yield stress than references. Our results indicate these legumes represent an efficient starch source to provide tailor‐made properties to food/industrial applications.
Characterization of Pigeon Pea and Dolichos Bean legume starches.
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