Granular architecture of lotus seed starch and its impact on physicochemical properties.

Lotus seed starch has high apparent amylose content (AAM). A representative definition of its granular architecture (e.g., lamellar structure) remained absent. This study defined the granular shape, crystalline and lamellar structures, and digestibility of twenty-two samples of lotus seed starch (LS) by comparing with those of potato and maize starches. LS granules had more elongated shape and longer repeat distance of lamellae than potato and maize starch granules. The enzymatic susceptibility of LS granules was more affected by AAM than granular architecture. Using these LSs as a model system, the relationships between lamellar structure of starch granules and properties of their gelatinized counterparts were investigated. In LSs, thinner amorphous lamella and thicker crystalline lamella were associated with higher swelling power and yield stress. The relationships were found to be connected via certain structural characteristics of amylopectin.

Impact of long-term ultrasound treatment on structural and physicochemical properties of starches differing in granule size.

Granule size is a critical parameter affecting starch processing properties. Ultrasound treatments of up to 22 h were applied on two starches differing in granule size (quinoa starch and maize starch). The two starches showed significantly different trends in both structural and physicochemical aspects affected by the ultrasound treatments. For the small granule starch (volume-weighted mean particle size of 1.79 µm), short-term ultrasonication caused an increase of swelling power. As the treatment time increased, the physicochemical properties were influenced by the degradation of amylopectin external chains. The X-ray diffraction results showed a decrease of relative crystallinity and changes of peak areas with long-term treatment. On the other hand, a balance between amylose leaching and surface damages was seen for the large granule starch (volume-weighted mean particle size of 18.3 µm). The effect of ultrasound modification on starches with different molecular and granular structures was discussed. A possible mechanism of the ultrasound effect was proposed.

Comparative study of rheological properties and Pickering emulsion stabilizing capacity of nonenyl succinic anhydride and octenyl succinic anhydride modified amaranth starches.

Functional properties and ability to stabilize Pickering emulsions of amaranth starch with the novel nonenyl succinic anhydride (NSA) modification and the widely used octenyl succinic anhydride (OSA) modification were compared. The NSA modification was more effective in altering the rheological properties of amaranth starches. NSA-modified amaranth starch showed significantly higher peak viscosity (7.13 Pa·s at DS of 0.02209) than the OSA-modified amaranth starch (6.10 Pa·s at DS of 0.03042). The gelatinization temperature, gelatinization enthalpy, and relative crystallinity of amaranth starch were more affected by the OSA than the NSA. The Pickering emulsions stabilized with NSA-modified starches had higher stability than those with the OSA-modified starches as characterized by particle size distribution, morphological, and rheological approaches. A lower degree of substitution by NSA than by OSA is needed to achieve a similar emulsification capacity. Thus, the NSA modification could be an efficient alternative to OSA modification in tailoring physicochemical and rheological functions, as well as stabilizing Pickering emulsions.

Molecular structure of lotus seed amylopectins and their beta-limit dextrins.

Investigation on amylopectin molecular structure is gaining importance for understanding starch property. Lotus seeds are a novel starch source with high apparent amylose content. Current understanding on the molecular structure of amylopectin in lotus seed starch is scarce. This study compared the molecular structure of a range of lotus seed amylopectins with those of maize and potato amylopectins. Internal structures of these amylopectins were compared via investigating the chain length distribution of their ß-limit dextrins. The average lengths and molar compositions of unit chains in lotus seed amylopectins and their ß-limit dextrins fell generally between those of maize and potato. The average chain lengths of lotus seed, maize, and potato amylopectins were 19.95 (on average), 19.11, and 21.19 glucosyl residues, respectively. Lotus seed amylopectins had higher weight proportion of clustered unsubstituted chains (44.94 % on average) than those of potato (43.99 %) and maize amylopectins (42.95 %). Results of correlation analysis indicated that apparent amylose content of LS was related to structural characteristics of its amylopectin due to the presence of long external chains. The results of this study are of fundamental importance for the utilization of lotus seed starch as a novel starch source.

Physicochemical properties of starch in sodium chloride solutions and sucrose solutions: Importance of starch structure.

The influences of sodium chloride (NaCl)/sucrose on starch properties as affected by starch structural characteristics are little understood. In this study, the effects were observed in relation to the chain length distribution (from size exclusion chromatography) and granular packing (inferred through morphological observation and determination of swelling factor and paste transmittance) of starches. Adding NaCl/sucrose dramatically delayed the gelatinization of starch that had a high ratio of short-to-long amylopectin chains and had loose granular packing. The effects of NaCl on the viscoelasticity of gelatinizing starch were related to the flexibility of amylopectin internal structure. Effects of NaCl/sucrose on starch retrogradation varied with starch structure, co-solute concentration, and analytical method. The co-solute-induced changes in retrogradation were highly associated with amylose chain length distribution. Sucrose strengthened the weak network formed by short amylose chains, while the effect was not significant on amylose chains that were capable of forming strong networks.

Physicochemical properties and molecular structure of lotus seed starch.

Current understanding of physicochemical properties of lotus seed starch (LS) is scarce partly due to its largely unknown molecular structure. This study compared the physicochemical and molecular characteristics of LSs of a wide collection to those of conventional starches (potato (PS) and maize starches (MS)). Variations were found in the chemical composition, physicochemical properties, and molecular structure of LSs. Amylose content and weight-based ratio of short to long chains of amylopectin (APS:APL) were principal factors affecting the physicochemical properties of LSs from different origins. Compared with PS and MS, LSs had higher gelatinization temperatures, lower amylose leaching, and faster retrogradation. These unique properties of LSs were related to their molecular structure and chemical composition. LSs had higher amylose contents than PS and MS as evaluated by various methods. A majority of amylose chains in LS were longer than those in MS but were shorter than those in PS. The APS:APL of LSs were higher than that of MS but lower than that of PS. The results provided a structural basis for understanding the properties of LS and suggested that this unconventional starch may be complementary to conventional starches for industrial applications.

Supramolecular structure of quinoa starch affected by nonenyl succinic anhydride (NSA) substitution.

Quinoa starch granular structure as affected by nonenyl succinic anhydride (NSA) substitution was investigated by multiple approaches, including scattering, spectroscopic, and microscopic techniques. The modification had little impact on the morphology of starch granules. The NSA substitution was found mainly in the amorphous lamellae and amorphous growth rings. The NSA modification increased the thickness of the amorphous lamellae. The homogeneity of the ordered structure in the granules was improved, probably because the NSA modification reduced the amount of defects in the semi-crystalline growth ring. Compared to other chemical modifications such as acylation, succinylation was more effective in modifying the starch lamellar structure. A possible reaction pattern of NSA modification on quinoa starch is proposed, in which the NSA modification may follow the sequence of amorphous growth rings, the amorphous matrices among blocklets, amorphous and crystalline lamellae in semi-crystalline growth rings. This study provides new insights on the structural changes of starch granules induced by succinylation on the supramolecular level.

Physicochemical, rheological, and emulsification properties of nonenyl succinic anhydride (NSA) modified quinoa starch.

Nonenyl succinic anhydride (NSA) modification could be an alternative to octenyl succinic anhydride (OSA) modification of starch to obtain a range of physicochemical and rheological properties and for emulsification applications. A series of NSA-modified quinoa starches in granular form with different degrees of substitution (DS) (0.0080, 0.0175, 0.0359, and 0.0548) were prepared. The NSA modifications reduced the gelatinization temperatures and frequency dependence of storage modulus (G'), while increasing the peak viscosity, gel hardness, and G'. The NSA-modified quinoa starches with medium DS were the most effective in stabilising Pickering emulsions. The droplet size of Pickering emulsions decreased first with increasing DS before increasing at the highest DS. Modified starch with a DS of 0.0359 had the highest emulsifying capacity. Apart from the commonly used octenyl succinic anhydride (OSA) modification, the NSA-modified starches could be potential candidates as efficient Pickering emulsion stabilizers.

Solubilisation of micellar casein powders by high-power ultrasound.

High protein milk ingredients, such as micellar casein powder (MCP), exhibit poor solubility upon reconstitution in water, particularly after long-time storage. In this study, ultrasonication (20 kHz, power density of 0.75 W/ml) was used to improve the solubility of aged MCP powders. For all the MCP powders (concentration varying from 0.5 to 5%, and storage of MCP at 50 °C for up to 10 days) it was found that short time ultrasonication (2.5 min) reduced the size of the protein particles from >30 µm to ∼0.1 µm, as measured by light scattering. This resulted in an improvement of solubility (>95%) for all the MCP powders. Cryo-electron microscopy and small x-ray angle scattering showed that the MCP powders dissolved into particles with morphologies and internal structure similar to native casein micelles in bovine milk. SDS-PAGE and RP-HLPC showed that ultrasonication did not affect the molecular weight of the individual casein molecules. Compared to overhead stirring using a 4-blade stirrer, ultrasonication required less than 10 times the drawn electrical energy density to achieve a particle size 10 times smaller.

Physicochemical properties of dodecenyl succinic anhydride (DDSA) modified quinoa starch.

Quinoa starch granules were esterified with dodecenyl succinic anhydride (DDSA) to various degrees of substitution (DS) (0.0023-0.0095). Physicochemical properties and emulsification capacity of the modified starch were studied. Increasing DS increased the particle size, water solubility, and swelling power, while decreasing the gelatinization enthalpy change and relative crystallinity of the starch. The DDSA groups were suggested to be mostly located in the amorphous region of starch granules. With increasing DS, the viscosity and storage modulus (G') obtained from rheological analysis increased first and then decreased. The DDSA modified quinoa starch efficiently stabilized O/W Pickering emulsions and has some technical advantages compared to octenyl succinic anhydride (OSA)-modified quinoa starch. Increasing DS led to decreased droplet size of the emulsions and a higher capacity in stabilizing emulsions during storage for a period of 10 days. This study suggested the potential application of DDSA modified quinoa starch as an emulsifier in stabilizing Pickering emulsions.

Rheological properties in relation to molecular structure of quinoa starch.

Quinoa starch granules are small (~0.5 - 3µm) with potentials for some food and other applications. To better exploit it as a new starch resource, this study investigates the steady shear and dynamic oscillatory properties of 9 quinoa starches varying in composition and structure. Steady shear analysis shows that the flow curves could be well described by 4 selected mathematic models. Temperature sweep analysis reveals that the quinoa starch encounters a 4-stage process including 2 phase transitions. Structure-function relationship analysis showed that composition as well as unit and internal chain length distribution of amylopectin have significant impact on the rheological properties (e.g., G' at 90°C) of quinoa starch. The roles of some individual unit chains and super-long unit chains of amylopectin in determining the rheological properties of quinoa starch were revealed. This study may stimulate further interest in understanding the structural basis of starch rheology.

Effect of high pressure on rheological and thermal properties of quinoa and maize starches.

Quinoa starch has small granules with relatively low gelatinization temperatures and amylose content. High hydrostatic pressure (HHP) is a non-thermal technique for food processing. In this study, effects of HHP up to 600MPa on physical properties of quinoa starch were studied and compared with those of a normal maize starch. Both starches gelatinized at 500 and 600MPa. The pressure of 600MPa completely gelatinized quinoa starch as revealed by thermal analysis. Dynamic rheological analysis showed that HHP improved the gel stability of both starches during cooling. HHP had little effects on amylopectin recrystallization and gel textural properties of starch. Overall, quinoa starch was more susceptible to HHP than maize starch. The effects of HHP on some rheological properties such as frequency dependence were different between these two types of starches. The differences could be attributed to the different composition, granular and chemical structures of starch, and the presence of granule remnants.

Unit and internal chain profiles of maca amylopectin.

Unit chain length distributions of amylopectin and its φ, ß-limit dextrins, which reflect amylopectin internal structure from three maca starches, were determined by high-performance anion-exchange chromatography with pulsed amperometric detection after debranching, and the samples were compared with maize starch. The amylopectins exhibited average chain lengths ranging from 16.72 to 17.16, with ranges of total internal chain length, external chain length, and internal chain length of the maca amylopectins at 12.49 to 13.68, 11.24 to 11.89, and 4.27 to 4.48. The average chain length, external chain length, internal chain length, and total internal chain length were comparable in three maca amylopectins. Amylopectins of the three maca genotypes studied here presented no significant differences in their unit chain length profiles, but did show significant differences in their internal chain profiles. Additional genetic variations between different maca genotypes need to be studied to provide unit- and internal chain profiles of maca amylopectin.

Quinoa starch: Structure, properties, and applications.

Quinoa (Chenopodium quinoa Willd.) has gained popularity worldwide largely due to the attractive nutritional profile. It also has much potential for food security due to the great genetic diversity. Starch is the main component of quinoa grain and makes up to 70% of the dry matter. The starch plays a crucial role in functional properties of quinoa and related food products. The starch granules are rather small (∼1-3µm) with relatively low amylose contents as compared with most of the other starches. Quinoa amylopectin has significant amounts of short chains and super-long chains. These unique features have generated research interest in using the starch for food and other applications such as creating Pickering emulsions. This review summarizes the present knowledge of the isolation, composition, granular and molecular structures, physicochemical properties, modifications, and applications of quinoa starch. It becomes obvious that this starch has great potential for food and nonfood applications.

Physicochemical properties of black pepper (Piper nigrum) starch.

Black pepper (Piper nigrum) is among the most popular spices around the world. Starch is the major component of black pepper. However, little is known about functional properties of this starch. In this study, swelling, solubility, thermal properties, rheology, and enzyme susceptibility of 2 black pepper starches were studied and compared with those of maize starch. Pepper starch had lower water solubility and swelling power than maize starch. It had higher viscosity during pasting event. In dynamic oscillatory analysis, pepper starch had lower storage modulus. Thermal analysis showed that pepper starch had much higher gelatinization temperatures (e.g., conclusion temperature of 94°C) than maize starch. The susceptibility to α-amylolysis of pepper starch was not very different from that of maize starch. Overall, the differences in the physicochemical properties of the 2 pepper starches are non-significant. The relationships between structure (especially amylopectin internal molecular structure) and properties of starch components are highlighted.

Amylopectin molecular structure in relation to physicochemical properties of quinoa starch.

Structure-function relationships of starch components remain a subject of research interest. Quinoa starch has very small granules (∼2µm) with unique properties. In this study, nine quinoa starches varied greatly in composition, structure, and physicochemical properties were selected for the analysis of structure-function relationships. Pearson correlation analysis revealed that the properties related to gelatinization such as swelling power, water solubility index, crystallinity, pasting, and thermal properties are much affected by the amylopectin chain profile and amylose content. The parameters of gel texture and amylose leaching are much related to amylopectin internal structure. Other properties such as enzyme susceptibility and particle size distribution are also strongly correlated with starch composition and amylopectin structure. Interesting findings indicate the importance of amylopectin internal structure and individual unit chain profile in determining the physicochemical properties of starch. This work highlights some relationships among composition, amylopectin structure and physicochemical properties of quinoa starch.

Physicochemical properties of quinoa flour as affected by starch interactions.

There has been growing interest in whole grain quinoa flour for new product development due to the unique nutritional benefits. The quality of quinoa flour is much determined by the properties of its major component starch as well as non-starch components. In this study, composition and physicochemical properties of whole grain flour from 7 quinoa samples have been analyzed. Flour properties have been correlated to the flour composition and the properties of isolated quinoa starches through chemometrics. Great variations in chemical composition, swelling power, water soluble index, enzyme susceptibility, pasting, gel texture, and thermal properties of the flour have been observed. Correlation analysis showed that thermal properties and enzyme susceptibility of quinoa flour are highly influenced by the starch. Interactions of starch with non-starch components, including lipids, protein, dietary fibre, phenolics, and minerals, greatly impacted the flour properties. For example, peak gelatinization temperature of the flour is positively correlated to that of the starch (r=0.948, p<0.01) and negatively correlated to the lipid content (r=-0.951, p<0.01). Understanding the roles of starch and other components in physicochemical properties of quinoa flour provides a basis for better utilization of this specialty crop.

Molecular structure of quinoa starch.

Quinoa starch has very small granules with unique properties. However, the molecular structure of quinoa starch remains largely unknown. In this study, composition and amylopectin molecular structure of 9 quinoa starch samples were characterised by chromatographic techniques. In particular, the amylopectin internal molecular structure, represented by φ, ß-limit dextrins (LDs), was explored. Great variations in the composition and molecular structures were recorded among samples. Compared with other amylopectins, quinoa amylopectin showed a high ratio of short chain to long chains (mean:14.6) and a high percentage of fingerprint A-chains (Afp) (mean:10.4%). The average chain length, external chain length, and internal chain length of quinoa amylopectin were 16.6, 10.6, and 5.00 glucosyl residues, respectively. Pearson correlation and principal component analysis revealed some inherent correlations among structural parameters and a similarity of different samples. Overall, quinoa amylopectins are structurally similar to that from starches with A-type polymorph such as oat and amaranth starches.

Physicochemical properties of maca starch.

Maca (Lepidium meyenii Walpers) is gaining research attention due to its unique bioactive properties. Starch is a major component of maca roots, thus representing a novel starch source. In this study, the properties of three maca starches (yellow, purple and black) were compared with commercially maize, cassava, and potato starches. The starch granule sizes ranged from 9.0 to 9.6µm, and the granules were irregularly oval. All the maca starches presented B-type X-ray diffraction patterns, with the relative degree of crystallinity ranging from 22.2 to 24.3%. The apparent amylose contents ranged from 21.0 to 21.3%. The onset gelatinization temperatures ranged from 47.1 to 47.5°C as indicated by differential scanning calorimetry. Significant differences were observed in the pasting properties and textural parameters among all of the studied starches. These characteristics suggest the utility of native maca starch in products subjected to low temperatures during food processing and other industrial applications.

Morphological, Thermal, and Rheological Properties of Starches from Maize Mutants Deficient in Starch Synthase III.

Morphological, thermal, and rheological properties of starches from maize mutants deficient in starch synthase III (SSIII) with a common genetic background (W64A) were studied and compared with the wild type. SSIII deficiency reduced granule size of the starches from 16.7 to ∼11 µm (volume-weighted mean). Thermal analysis showed that SSIII deficiency decreased the enthalpy change of starch during gelatinization. Steady shear analysis showed that SSIII deficiency decreased the consistency coefficient and yield stress during steady shearing, whereas additional deficiency in granule-bound starch synthase (GBSS) increased these values. Dynamic oscillatory analysis showed that SSIII deficiency decreased G' at 90 °C during heating and increased it when the paste was cooled to 25 °C at 40 Hz during a frequency sweep. Additional GBSS deficiency further decreased the G'. Structural and compositional bases responsible for these changes in physical properties of the starches are discussed. This study highlighted the relationship between SSIII and some physicochemical properties of maize starch.