Physicochemical properties of esterified/crosslinked quinoa starches and their influence on bread quality.

BACKGROUND: Starch is the main component of quinoa seeds. However, quinoa starch has poor solubility in cold water and poor mechanical resistance and is easily aged, which limit its application. Therefore, modification of its structure to improve its functional properties is necessary. RESULTS: This research used acetic anhydride and sodium trimetaphosphate to modify the structure of starch molecules and investigated their influence on bread quality. The results showed that both esterification and crosslinking prevented the aggregation behavior of starch molecules. Moreover, they both decreased the gelatinization enthalpy change and relative crystallinity of the starch. Compared with native starch, modification significantly decreased the gelatinization temperature from 57.01 to 52.01 °C and the esterified starch exhibited the lowest enthalpy change with a 44.2% decrease. Modified starch increased the specific volume and decreased the hardness and chewiness of bread. Modification did not influence the moisture content in bread but impacted the water retention capacity, depending on the degree of modification. Low and medium degrees of modification improved the water retention capacity during storage. By contrast, a high degree of modification (10 g kg-1 crosslinking agent) decreased the water retention capacity. The dually modified quinoa starch (esterified and crosslinked) showed no influence on the textural properties of bread. CONCLUSION: This study demonstrated that both esterification and crosslinking significantly improved the functional properties of quinoa starch. Crosslinked or esterified quinoa starches have the potential to improve the textural properties of bakery products. © 2024 Society of Chemical Industry.

Development of pullulan-based nanocomposite films reinforced with starch nanocrystals for the preservation of fresh beef.

BACKGROUND: Incorporation of polysaccharide-based nanofillers is an effective strategy to fabricate bio-nanocomposite films with preferable mechanical, barrier, and surface hydrophobicity properties compared to pure biopolymer films. The objective of this research is to investigate the influence of starch nanocrystals obtained from native (NSNC) and waxy rice starch (WSNC) on the physical-chemical properties of pullulan-based nanocomposite films and their preservation performance on fresh beef. RESULTS: Continuous SNCs network structure was observed for pullulan-10% SNCs nanocomposite films, whereas the percolation network of SNCs was destroyed and became no longer continuous with increasing SNCs concentration up to 20% in pullulan films. Among the tested films, pullulan-10% SNCs films showed the highest TS values, lowest WVP and OTR values, due to the formation of percolating SNCs network in pullulan matrix. It is noteworthy that the WVP and OTR values of pullulan-10% WSNC films were significantly lower than that of pullulan-10% NSNC films, probably due to higher hydrophobicity and crystallinity of WSNC compared with NSNC. Beef pieces coated with pullulan-SNCs films had higher L* and a* values, lower TVB-N, TBARS, and TVC values during 7 days' storage at 4 °C compared with samples coated with pullulan films. CONCLUSION: Pullulan-SNCs nanocomposite films, especially pullulan-WSNC films, could be potentially used as a coating material for fresh beef due to their desirable oxygen and water barrier properties. © 2022 Society of Chemical Industry.

Physicochemical studies of nanocrystals of starches from two rice (Oryza sativa L.) types and their characteristics using various modern instrument techniques.

BACKGROUND: Starch nanocrystals have received considerable attention, due to their biodegradability, nontoxicity and renewable and abundant sources. The objective of this research is to compare the morphology, physicochemical characteristics and rheological properties of native (NSNC) and waxy rice starch nanocrystals (WSNC). RESULTS: Both NSNC and WSNC exhibited a platelet-like shape, and they tended to show square-like platelet morphology with increasing initial amylopectin content. Compared to native starches, three weight loss stages of NSNC and WSNC in thermogravimetric analysis curves were observed, while the thermal depolymerization of NSNC started earlier than that of WSNC. The relative crystallinity of NSNC and WSNC was 38.6% and 48.3%, respectively, which were markedly higher than that of native starches. Fourier transform infrared spectra revealed that NSNC presented the highest ratio of 1045/1014 cm-1 bands among the tested samples, which was probably due to the re-association of retrograded amylose to double-helices structure in NSNC. Moreover, the introduction of sulfur atoms on the surface of NSNC and WSNC was confirmed from the results of X-ray photoelectron spectroscopy. At 5% (w/v) and 10% (w/v) concentration levels, all SNC suspensions exhibited a shear-thinning behavior as the shear rate increased from 0.1 to 100 s-1 . CONCLUSIONS: Starch nanocrystals obtained from native and waxy rice starch can be potentially used as reinforcement in biodegradable nanocomposites for packaging, fat replacers, thickening agents and emulsion stabilizers. © 2020 Society of Chemical Industry.

Diafiltration affects the gelation properties of concentrated casein micelle suspensions obtained by filtration.

Using membrane filtration it is possible to selectively concentrate proteins and, in the case of microfiltration, concentrate casein micelles. During filtration, water is often added and this practice, called diafiltration, causes further release of permeable components and maintains filtration efficiency. Filtration causes changes in composition of the protein as well as the soluble phase, including soluble calcium, which is a critical factor controlling the gelation properties of the casein micelles in milk. It was hypothesized that concentrates obtained using membrane filtration with or without diafiltration would have different gelation behavior. To test this hypothesis, two concentrates of similar casein micelle volume fraction were prepared, using spiral wound polymeric microfiltration membranes with a 800 kDa molecular weight cutoff, with or without diafiltration. The concentrates showed a gelation behavior comparable to that of skim milk, with a similar gelation time and with a higher firmness, due to the higher number of protein linkages in the network. In contrast, the hydrolysis of κ-casein by chymosin and casein aggregation were inhibited in diafiltered casein micelle suspensions. When the concentrates were recombined with the original skim milk to a final concentration of 5% protein, which re-established a similar soluble phase composition, differences in gelation behavior were no longer observed: both treatments showed similar gelation time and gel firmness. These results confirmed that membrane filtration can result in concentrates with different functionality, and that ionic environmental conditions are critical to the aggregation behavior of casein micelles. This is of particular significance in industrial settings where these fractions are used as a way to standardize proteins in cheese making.

Short communication: Determination of the whey protein index in milk protein concentrates.

Milk protein concentrates are common ingredients in the dairy industry, with varying processing histories and composition. The objective of this research was to determine the feasibility of using the whey protein nitrogen (WPN) index, a well-established index for skim milk powder and nonfat dry milk, as a quality parameter for milk protein concentrates. The WPN index is a value based on the moisture-adjusted weight of skim milk powder. We hypothesized that WPN, even when standardized based on protein, may change depending on solubilization conditions of milk protein concentrates because of differences in solubilization conditions or processing history. The WPN was measured for model concentrates with different thermal history or reconstitution conditions. The WPN was not affected by an increased concentration of soluble casein in the dispersions nor after solubilization of the powder at 22 or 60°C. All reconstituted samples were standardized for protein. The WPN was also in full accordance with residual native protein measured by chromatography.

Invited review: Understanding the behavior of caseins in milk concentrates.

The colloidal properties of the casein micelles play a major role in the structural properties of milk protein concentrates. Because of their great technological importance, the structural-functional relationships of casein micelles have been studied for decades in skim milk; however, novel ingredients are now available with higher protein concentrations and varying in composition. The colloidal behavior of caseins in these systems is not fully understood. Concentrates prepared with membrane technologies, and subjected to pre- or post-modifications that affect their technological functionality, have become increasingly widespread. This has created large opportunities for innovation and generation of value-added ingredients. The manner in which caseins interact with themselves and the other components in these concentrates will affect the structure of the final matrix. During concentration by filtration, the interparticle distance between the micelles decreases considerably, increasing their spatial correlation and decreasing their diffusivity. Rearrangements occur due to changes in environmental conditions, such as ionic composition, osmotic stress, shear, pH, or heating temperature. This will have important consequences on bulk viscosity of the concentrates, as well as on the mode of formation of structures' building blocks. This paper aims at highlighting some of the important factors affecting the colloidal structure of casein micelles, their destabilization and network formation, namely, processing history, volume fraction, composition of the serum phase, and ionic equilibrium. Understanding these factors will lead to a better quality control of dairy ingredients and to the development of a new generation of ingredients with targeted functionality.

A comparison of the heat stability of fresh milk protein concentrates obtained by microfiltration, ultrafiltration and diafiltration.

The objective of this work was to evaluate the impact of changes during membrane filtration on the heat stability of milk protein concentrates. Dairy protein concentrates have been widely employed in high protein drinks formulations and their stability to heat treatment is critical to ensure quality of the final product. Pasteurized milk was concentrated three-fold by membrane filtration, and the ionic composition was modified by addition of water or permeate from filtration (diafiltration). Diafiltration with water did not affect the apparent diameter of the casein micelles, but had a positive effect on heat coagulation time (HCT), which was significantly longer (50 min), compared to the non diafiltered concentrates (about 30 min). UHT treatments increased the particle size of the casein micelles, as well as the turbidity of retentates. Differences between samples with and without diafiltration were confirmed throughout further analysis of the protein composition of the unsedimentable fraction, highlighting the importance of soluble protein composition on the processing functionality of milk concentrates.

Effect of lactoferrin on physicochemical properties and microstructure of pullulan-based edible films.

BACKGROUND: Pullulan is a polysaccharide polymer commonly used to produce edible films. However, pure pullulan film is usually brittle and very hydrophilic, which limit its use in both food and pharmaceutical fields. The objective of this research is to improve the structural and mechanical properties of pullulan film by incorporating globular protein lactoferrin (LF). RESULTS: The incorporation of LF increased the surface hydrophobicity and decreased the water vapor permeability (WVP) of pullulan film. The presence of low concentrations of LF (< 0.03%) has no significant influence on tensile strength (TS) and elongation at break (EAB) of pullulan film. However, further increase of LF concentration to levels > 0.03% resulted in a film-weakening effect. LF molecules aggregated with each other during the film-producing process, which presented as spherical particles from the observation of microscopy. LF aggregates dispersed homogeneously throughout the pullulan matrix and their size increased with increasing concentration. Analysis from Fourier transform infrared spectroscopy indicated that the secondary structure of LF molecules was modified during the drying process. CONCLUSIONS: It is possible to increase the hydrophobicity of pullulan film while maintaining its mechanical properties. The produced composite film can be potentially used for food and medical packaging. © 2019 Society of Chemical Industry.

Effect of chitosan on the heat stability of whey protein solution as a function of pH.

BACKGROUND: Chitosan was reported to interact with proteins through electrostatic interactions. Their interaction was influenced by pH, which was not fully characterized. Further research on the interactions between protein and chitosan at different pH and their influence on the thermal denaturation of proteins is necessary. RESULTS: In this research, the effect of chitosan on the heat stability of whey protein solution at pH 4.0-6.0 was studied. At pH 4.0, a small amount chitosan was able to prevent the heat-induced denaturation and aggregation of whey protein molecules. At higher pH values (5.5 and 6.0), whey proteins complexed with chitosan through electrostatic attraction. The formation of chitosan-whey protein complexes at pH 5.5 improved the heat stability of dispersions and no precipitation could be detected up to 20 days. The dispersion with a medium amount of chitosan (chitosan:whey protein 1:5) produced the most stable particles, which had an average radius of 135 ± 14 nm and a zeta potential value of 36 ± 1 mV. In contrast, at pH 6.0 only the dispersion with a high amount of chitosan (chitosan:whey protein 1:2) showed good shelf stability up to 20 days. CONCLUSIONS: It was possible to produce heat-stable whey protein beverages by regulating the interaction between chitosan and whey protein molecules. © 2016 Society of Chemical Industry.

Short communication: Serum composition of milk subjected to re-equilibration by dialysis at different temperatures, after pH adjustments.

The objective of this work was to investigate the properties of casein micelles after pH adjustment and their re-equilibration to the original pH and serum composition. Re-equilibration was carried out by dialyzing against skim milk at 2 different temperatures (4 or 22 °C). Turbidity, the average radius of the casein micelles, and the composition of the soluble phase were measured at different pH values, ranging between 5.5 and 8. Acidification led to the solubilization of colloidal calcium phosphate and decrease of the average radius of the micelles. With re-equilibration, casein dissociation occurred. In milk with pH values greater than 6.0, the average radius was recovered after re-equilibration. At pH values greater than neutral, an increase of the radius of casein micelles and increased dissociation of the casein were found. After re-equilibration, the radius of micelles and soluble protein in the serum decreased. The results were not affected by the temperature of re-equilibration. The changes to the calcium phosphate equilibrium and the dissociation of the micelles will have important consequences to the functionality of casein micelles.

A mini-review about direct steam heating and its application in dairy and plant protein processing.

The world's requirement for plant protein consumption is increasing. However, their application in different foods is limited due to their low techno-functionality. Heating is the most widely used method to improve the functionality of proteins. Compared to indirect tubular or plate heating methods, direct steam injection heating (DSIH) can heat the sample much faster, thus modifying the structure and functionality of protein differently. It is used in the sterilization of milk to minimize the heat-induced denaturation of whey proteins and the loss of volatiles. By contrast, its application in producing plant protein ingredients is seldom. This review summarizes recent research using DSIH to process dairy- and plant-based proteins and proposes future research perspectives. DSIH is a promising technique for producing functional protein ingredients. It is of particular interest to overcome the techno-functional hurdles of plant protein blends using DSIH to improve their behavior in different food matrices.

Protection effect of gut microbiota composition and acetate absorption against hypertension-induced damages on the longevity population in Guangxi, China.

Introduction: Recent evidence supports a role for the gut microbe-metabolites in longevity. However, the phenomenon of hypertension is more common in the longevity area and whether hypertension is associated with longevity remains unclear. Here, we hypothesize that the levels of gut microbiota, SCFAs, and urine metabolites were different between hypertension elderly and hypertension longevity. Methods: We recruited 46 elderly volunteers from Donglan County, Guangxi, and 32 were selected and included in the experiment. The subjects with hypertension were divided into two groups according to age, Hypertension Elderly (HTE, aged 70.5 ± 8.59, n = 19) and Hypertension Longevity (HTL, aged 100 ± 5.72, n = 13). The gut microbiota, SCFAs, and urine metabolites were determined by three-generation 16S rRNA full-length sequencing, GC-MS, and 1H-NMR, respectively. Results: Compared with the HTL group, the HTE group had higher levels of hypertension-related genera Klebsiella and Streptococcus, while having lower levels of the SCFA-producing genera Bacteroides, Faecalibacterium, and Alistipes. Based on LEFse analysis, Klebsiella pneumoniae, Lactobacillus gasseri, Streptococcus salivarius, Ruminococcus, Actinomyces, Rikenellaceae, f_Saccharimonadaceae, Clostridium perfringens, and Bacteroids, Faecalibacterium prausnitzii, Parabacteroides, Alistipes were biomarkers that showed significant differences between the groups. In addition, the microbial pathways associated with K. pneumoniae and E. coli may promote hypertension, while A. muciniphila may play a role in reversing the development of hypertension in long-lived elderly. Metabolomics revealed that HTL contained a lower concentration of fecal acetate and propionate than HTE, while it contained a higher concentration of serum acetate and urine acetate. Furthermore, their immune cells exhibited no significant changes in SCFAs receptors. Conclusion: Although long-lived elderly have extremely high systolic blood pressure, their unique gut microbiota composition and efficient acetate absorption in the colon may offset the damages caused by hypertension and maintain healthy homeostasis.

Effect of germination time on the compositional, functional and antioxidant properties of whole wheat malt and its end-use evaluation in cookie-making.

This study investigated the effect of germination time on compositional changes and functionality of whole wheat malt flour (WMF) as well as its influence on cookie quality. The results illustrated that malting resulted in decreases of starch, protein, fat and ash, while it increased dietary fiber, carbohydrate and energy. Gel hydration, emulsifying and foaming ability, pasting viscosity decreased significantly, particularly during the first 2 days of germination. Both bound and immobilized water in WMF decreased with increasing germination time while the concentration and antioxidant capacity of extractable and hydrolyzable phenolic compounds (EPP and HPP) increased significantly in WMF and malt-based cookies. Flours changed from an integrated granular to an irregular tousy structure during germination. The incorporation of WMF induced a distorted "honey-like" comb structure to the cookies. Conclusively, controlled germination not only improves the physicochemical, functional properties of WMF but also increases nutrition value and technological performance of malt-based cookies.

Effect of Molecular Weight and Degree of Substitution on the Physical-Chemical Properties of Methylcellulose-Starch Nanocrystal Nanocomposite Films.

This research studied the effect of molecular weight (Mw) and degree of substitution (DS) on the microstructure and physicochemical characteristics of methylcellulose (MC) films with or without SNC. The Mw and DS of three types of commercial MC (trade name of M20, A4C, and A4M, respectively) were in the range of 0.826 to 3.404 × 105 Da and 1.70 to 1.83, respectively. Mw significantly affected the viscosity of methylcellulose solutions as well as the microstructure and tensile strength of methylcellulose films, while DS had a pronounced effect on their oxygen permeability properties. The incorporation of 15% (w/w) SNC resulted in the efficient improvement of tensile strength, water, and oxygen barrier properties of films, particularly for the A4C nanocomposite films. The results from SEM and FTIR illustrated that relatively homogenous dispersion of SNC was distinguished in A4C-15% (w/w) SNC films. Furthermore, microstructures of MC-SNC nanocomposite films were strongly dependent on both Mw and DS of MC. This work offers a convenient and green method to fabricate MC-based nanocomposite films with desirable mechanical, light, oxygen, and water vapor barrier properties.

A Pilot Study of the Effect of Lactobacillus casei Obtained from Long-Lived Elderly on Blood Biochemical, Oxidative, and Inflammatory Markers, and on Gut Microbiota in Young Volunteers.

Probiotic intake has been shown to improve certain physiological health indicators. We aimed to examine effects of Lactobacillus casei LTL1879, obtained from long-lived elderly volunteers, on blood biochemical, oxidative, and inflammatory markers and gut microbiota in twenty healthy, young volunteers. Volunteers were randomly divided into equal probiotic and placebo groups and changes in blood biochemical indicators, oxidative and inflammatory markers, and gut microbiota were examined after three weeks of probiotic intervention. The probiotic group's antioxidant levels were significantly enhanced post-intervention. Total antioxidant capacity (T-AOC) levels were significantly increased (p < 0.0001), while malondialdehyde (MDA) levels decreased (p < 0.05), and total superoxide dismutase (T-SOD) levels increased, but with no significant difference. In addition, Interleukin-10 (IL-10) and tumor necrosis factor-α (TNF-α) levels were significantly up-regulated and down-regulated (p < 0.05, respectively). Escherichia coli, Enterococcus, and Bacteroides expression was significantly reduced (p < 0.05), while Clostridium leptum, Bifidobacterium, and Lactobacillus expression increased (p < 0.05). Volunteer health status was quantified using principal components and cluster analysis, indicating that the probiotic group's overall score was higher than that of the placebo group. The results of this pilot study suggest L. casei LTL 1879 can significantly improve specific immune, oxidative, and gut microbiota characteristics related to health factors.

Interfacial characteristics, colloidal properties and storage stability of dairy protein-stabilized emulsion as a function of heating and homogenization.

This research investigated the influence of processing history on physicochemical properties of dairy protein-stabilized emulsions. Emulsions were heated (UHT) either before or after a single homogenization (UHTSH, SHUHT) or homogenized both before and after heating (double homogenization, DHUHT). The results demonstrated that UHT treatment increased the protein load at the oil/water interface while homogenization prior to UHT (SHUHT) inhibited displacement of protein by surfactant molecules, and this emulsion exhibited higher interfacial protein coverage and wider size distribution compared to the emulsion produced by UHTSH. The use of the double homogenization with UHT resulted in emulsion droplets with the smallest average size and lowest concentration of unabsorbed protein. However, no difference in the protein load in a specific area was noticed between emulsions produced by DHUHT and SHUHT. When changes of surface tension at the air/water interface were measured using a drop tensiometer, SHUHT emulsion showed the fastest decrease of surface tension due to the occurrence of a lower level of surfactant displacement where more surfactant was available for fast adsorption. Emulsions prepared with DHUHT or UHTSH decreased the surface tension in a slower speed than SHUHT. During storage, partial coalescence of emulsion droplets was observed for emulsions produced with single homogenization, regardless of whether this was carried out before or after heating. Double homogenization formed more stable emulsions than single homogenization. This work clearly showed that it is possible to tailor physico-chemical functionalities of dairy protein-based emulsions by controlling the interactions between proteins or with surfactants during processing.

Effects of pH-modification on the rennet coagulation of concentrated casein micelles suspensions.

The aggregation of a mixed suspension of native and pre-acidified casein micelles was observed using rheology. Pre-acidified micelles were prepared by addition of glucono-delta-lactone, once pH of 6 or 5.5 was reached, the suspension was concentrated and added to untreated skim milk. Gelation was followed by addition of chymosin, for mixes before or after re-equilibration to the original milk pH. When pre-concentrated micelles were acidified, an earlier gelation point was shown, as well as a higher elastic modulus, compared to control suspensions. When skim milk containing pre-acidified micelles was re-equilibrated to the original pH no gelation was observed after addition of chymosin, in spite of very similar levels of diffusible calcium and phosphate concentration to those of the original milk. It was concluded that it may be possible to fine tune the rheological properties of the final chymosin induced gel network, by pretreating only a portion of the casein micelles, and modifying their colloidal calcium phosphate and the ratio of soluble to micellar casein.

Acid and rennet-induced coagulation behavior of casein micelles with modified structure.

This review summarizes the effects of heating, acidification, high pressure treatment and enzymatic modification on coagulation (acid or rennet) behavior of casein micelles. Heating improves acid coagulation of casein micelles while it impairs rennet coagulation. Acidification results in the dissociation of colloidal calcium phosphate (CCP) and facilitates rennet-induced casein aggregation. Partial-rennet treatment of casein micelles improves acid gelation and leads to the formation of acid gels with higher elastic modulus and strength. Transglutaminase (TG) treatment increases casein micelle integrity and forms acid gels with homogeneous network and increased water holding capacity (WHC). TG treatment before renneting prohibits rennet coagulation while TG treatment following renneting produces gels with improved elastic modulus and WHC. The disintegration of casein micelles during high pressure treatment favors rennet coagulation while whey protein denaturation hinders coagulation. In contrast, high pressure treatment favors acid gelation, resulting in the formation of gels with increased rigidity and strength.

Characterization of the Structural and Colloidal Properties of α-Lactalbumin/Chitosan Complexes as a Function of Heating.

This research investigated the interaction between α-lactalbumin (α-la) and chitosan at different temperatures. Chitosan was added to α-la solution (5 g L-1) to achieve different α-la/chitosan ratios (8:1, 5:1, and 2:1), which were then subjected to different heating temperatures (20, 70, and 90 °C). The results indicated that a low amount of chitosan (8:1) precipitated α-la molecules. Increasing chitosan to a ratio of 5:1 resulted in exposure of the internal structure of α-la, and those formed complexes had high turbidity and average size, which were decreased by an increasing temperature. A further increase of chitosan to a ratio of 2:1 protected the internal structure of α-la molecules. All samples exhibited a similar adsorption behavior at the air/water interface, but the presence of chitosan significantly increased film elasticity. The produced complexes can be regarded as functional ingredients, which can be used as an emulsifying agent and a delivery material to control the release of bioactive compounds.

Interaction between lactoferrin and whey proteins and its influence on the heat-induced gelation of whey proteins.

In this paper, the influence of lactoferrin (LF) on the structural development of whey protein isolate (WPI) gels during heating was investigated. The results demonstrated that the presence of sufficient LF could improve the strength and elasticity of WPI gels. When 30% LF was added, the elastic modulus of WPI gels increased from 254 ±â€¯31 and 413 ±â€¯58 Pa to 3222 ±â€¯105 and 2730 ±â€¯131 Pa at pH 6.7 and 5.8, respectively. The addition of LF improved the water holding capacity (WHC) of WPI gels at pH 6.7, while no improvement was observed at pH 5.8. LF interacted with whey proteins differently at pH 6.7 and 5.8 during heating. The LF/whey proteins complexes formed at pH 6.7 had smaller sizes and narrower size distributions than those formed at pH 5.8.