Higher Denaturation Temperature Research Articles

Impact of process conditions and type of plant protein on aggregate formation with whey protein and resulting ricotta-like gel texture

Aim of the study was to investigate the effect of process conditions and type of plant protein on protein aggregation and texture of hybrid ricotta alternatives. Four different plant proteins (soy, pea, lupin, potato) were used and first underwent a pre-treatment to increase solubility, followed by thermally-induced pre-aggregation of the hybrid systems with β-lactoglobulin-rich whey protein at varying pH and temperature. Aggregates were analysed via particle size distribution and SDS-PAGE. For production of the ricotta alternative, acidification and subsequent thermal coagulation formed the protein gel network. Texture analysis and visual evaluation of macroscopic structure was carried out.Results showed that aggregate size significantly affects gel strength. For soy-whey mixtures pH during pre-aggregation was the main factor affecting aggregate size, with a favourable diameter of 5 μm and a corresponding gel strength to whey-based ricotta of 0.9 N. Pea protein generally behaved similar to soy protein due to the similarity in protein composition and structure. In contrast, use of lupin resulted in a weaker gel, due lupin’s dense molecular structure and high denaturation temperature. Potato-whey hybrid systems formed large insoluble aggregates, which as a consequence did not contribute to gel formation. In summary, the results of the present study show that a variation of the protein type in hybrid ricotta alternatives requires process adaptations, but at the same time allows the creation of new gel structures for hybrid cheese alternatives.

Euglena gracilis Protein: Effects of Different Acidic and Alkaline Environments on Structural Characteristics and Functional Properties.

Due to the growing demand for human-edible protein sources, microalgae are recognized as an economically viable alternative source of proteins. The investigation into the structural characteristics and functional properties of microalgin is highly significant for its potential application in the food industry as an alternative source of protein. In this research, we extracted protein from Euglena gracilis by using alkaline extraction and acid precipitation and investigated its structural characteristics and functional properties in different acidic and alkaline environments. The molecular weight distribution of Euglena gracilis protein (EGP), as revealed by the size exclusion chromatography results, ranges from 152 to 5.7 kDa. EGP was found to be rich in hydrophobic amino acids and essential amino acids. Fourier infrared analysis revealed that EGP exhibited higher α-helix structure content and lower β-sheet structure content in alkaline environments compared with acidic ones. EGP exhibited higher foaming properties, emulsifying activity index, solubility, free sulfhydryl, and total sulfhydryl in pH environments far from its isoelectric point, and lower fluorescence intensity (2325 A.U.), lower surface hydrophobicity, larger average particle size (25.13 µm), higher emulsifying stability index, and water-holding capacity in pH environments near its isoelectric point. In addition, X-ray diffraction (XRD) patterns indicated that different acidic and alkaline environments lead to reductions in the crystal size and crystallinity of EGP. EGP exhibited high denaturation temperature (Td; 99.32 °C) and high enthalpy (ΔH; 146.33 J/g) at pH 11.0, as shown by the differential scanning calorimetry (DSC) results. The findings from our studies on EGP in different acidic and alkaline environments provide a data basis for its potential commercial utilization as a food ingredient in products such as emulsions, gels, and foams.

Investigation of the physicochemical and functional properties of protein concentrate and glutelin derived from an underutilized green leaf plant: Edible dock (Rumexpatientia L.×Rumextianshanicus A. Los)

The adverse environmental impact and health concerns associated with animal protein production have contributed to the increasing popularity of sustainable alternative proteins. Green leaf biomass represents one of the largest underutilized sources of plant-based protein globally. In this study, we extracted the protein concentrate and major protein fraction glutelin from edible dock (Rumexpatientia L.×Rumextianshanicus A. Los), a green leaf plant with promising prospects as an excellent source of food protein, to investigate their physicochemical and functional properties. Results showed that both protein concentrate (51.97 ± 3.08%, w/w) and glutelin (50.81 ± 1.30%, w/w) had similar protein contents, shared an isoelectric point of pH 3.0, and contained a well-balanced profile of amino acids. The protein concentrate had a higher denaturation temperature (104.10 °C) than glutelin (97.30 °C), but a poorer gelling ability. However, both proteins exhibited a predominant β-sheet secondary structure. The protein concentrate and glutelin exhibited distinct advantages in terms of water and oil absorption capacity, respectively. The emulsifying and foaming abilities of the two proteins exhibited a consistent trend with protein solubility, resembling U-shaped curves in a pH-dependent variation pattern. Additionally, alkaline and acidic conditions favored preferred emulsifying stability and foaming stability, respectively. The desirable properties of edible dock shed light on its immense potential as a novel alternative source of plant proteins, positioning it as a highly promising candidate for utilization as a nutritious functional ingredient within the food industry.

Dynamics and thermal stability of the bypass polymerase, DinB homolog (Dbh).

The DinB homolog polymerase (Dbh) is a member of the Y-family of translesion DNA polymerases that can synthesize using a damaged DNA template. Since Dbh comes from the thermophilic archaeon Sulfolobus acidocaldarius, it is capable of functioning over a wide range of temperatures. Existing X-ray structures were determined at temperatures where the protein is least active. Here we use NMR and circular dichroism to understand how the structure and dynamics of Dbh are affected by temperature (2°C-65°C) and metal ion binding in solution. We measured hydrogen exchange protection factors, temperature coefficients, and chemical shift perturbations with and without magnesium and manganese. We report on regions of the protein that become more dynamic as the temperature is increased toward the functional temperature. Hydrogen exchange protection factors and temperature coefficients reveal that both the thumb and finger domains are very dynamic relative to the palm and little-finger (LF) domains. These trends remain true at high temperature with dynamics increasing as temperatures increase from 35°C to 50°C. Notably, NMR spectra show that the Dbh tertiary structure cold denatures beginning at 25°C and increases in denaturation as the temperature is lowered to 5°C with little change observed by CD. Above 35°C, chemical shift perturbation analysis in the presence and absence of magnesium and manganese reveals three ion binding sites, without DNA bound. In contrast, these bound metals are not apparent in any Dbh crystal structures of the protein without DNA. Two ion binding sites are confirmed to be near the active site, as reported in other Y-family polymerases, and we report a novel ion binding site in the LF domain. Thus, the solution-state structure of the Dbh polymerase is distinct from that of the solid-state structures and shows an unusually high cold denaturation temperature.

Low-Temperature and High-Efficiency Solid-Phase Amplification Based on Formamide.

The thermal stability of DNA immobilized on a solid surface is one of the factors that affects the efficiency of solid-phase amplification (SP-PCR). Although variable temperature amplification ensures high specificity of the reaction by precisely controlling temperature changes, excessively high temperatures during denaturation can negatively affect DNA stability. Formamide (FA) enables DNA denaturation at lower temperatures, showing potential for SP-PCR. Research on FA's impacts on DNA microarrays is still limited, necessitating further optimization in exploring the characteristics of FA in SP-PCR according to particular application needs. We immobilized DNA on a chip using a crosslinker and generated DNA microarrays through bridge amplification based on FA denaturation on our automated reaction device. We optimized the denaturation and hybridization parameters of FA, achieving a maximum cluster density of 2.83 × 104 colonies/mm2. Compared to high-temperature denaturation, FA denaturation required a lower template concentration and milder reaction conditions and produced higher cluster density, demonstrating that FA effectively improves hybridization rates on surfaces. Regarding the immobilized DNA stability, the FA group exhibited a 45% loss of DNA, resulting in a 15% higher DNA retention rate compared to the high-temperature group, indicating that FA can better maintain DNA stability. Our study suggests that using FA improves the immobilized DNA stability and amplification efficiency in SP-PCR.

Monomeric Far-red and Near-infrared Fluorescent Biliproteins of Ultrahigh Brightness.

Far-red and near-infrared fluorescent proteins have regions of maximum transmission in most tissues and can be widely used as fluorescent biomarkers. We report that fluorescent phycobiliproteins originating from the phycobilisome core subunit ApcF2 can covalently bind biliverdin, named BDFPs. To further improve BDFPs, we conducted a series of studies. Firstly, we mutated K53Q and T144A of BDFPs to increase their effective brightness up to 190 % in vivo. Secondly, by homochromatic tandem fusion of high-brightness BDFPs to achieve monomerization, which increases the effective brightness by up to 180 % in vivo, and can effectively improve the labeling effect. By combining the above two approaches, the brightness of the tandem BDFPs was much improved compared with that of the previously reported fluorescent proteins in a similar spectral range. The tandem BDFPs were expressed stably while maintaining fluorescence in mammalian cells and Caenorhabditis elegans. They were also photostable and resistant to high temperature, low pH, and chemical denaturation. The tandem BDFPs advantages were proved in applications as biomarkers for imaging in super-resolution microscopy.

FlashPCR: Revolutionising qPCR by Accelerating Amplification through Low ∆T Protocols.

Versatility, sensitivity, and accuracy have made the real-time polymerase chain reaction (qPCR) a crucial tool for research, as well as diagnostic applications. However, for point-of-care (PoC) use, traditional qPCR faces two main challenges: long run times mean results are not available for half an hour or more, and the requisite high-temperature denaturation requires more robust and power-demanding instrumentation. This study addresses both issues and revises primer and probe designs, modified buffers, and low ∆T protocols which, together, speed up qPCR on conventional qPCR instruments and will allow for the development of robust, point-of-care devices. Our approach, called "FlashPCR", uses a protocol involving a 15-second denaturation at 79 °C, followed by repeated cycling for 1 s at 79 °C and 71 °C, together with high Tm primers and specific but simple buffers. It also allows for efficient reverse transcription as part of a one-step RT-qPCR protocol, making it universally applicable for both rapid research and diagnostic applications.

Unveiling the contribution of Osborne protein fractions to the physicochemical and functional properties of alkaline and enzymatically extracted green lentil proteins

AbstractLentil proteins are gaining popularity as food ingredients, serving both functional and nutritional purposes. To better understand the properties of lentil proteins extracted using commercially relevant methods (alkaline and enzymatic), sequential fractionation by solubility (Osborne fractionation) was performed and the physicochemical, thermal, and functional properties of the extracts were characterized. Fractionation revealed that 43% of lentil proteins were water‐soluble (ALB, albumin‐rich), 37% salt‐soluble (GLO, globulin‐rich), 14% alkaline‐soluble (GLU, glutelin‐rich), and 3% ethanol‐soluble (PRO, prolamin‐rich). Protein extraction yields of 81% and 87% were achieved by alkaline (pH 9.0, 50 °C, 1:10 solids‐to‐liquid ratio, 60 min) and enzymatic extraction (same conditions with 0.5% (w/w) Alkaline Protease), respectively. Proteomic analysis allowed for the identification of 129 proteins among all extracts, and the ALB and GLO fractions exhibited similar protein profiles as the alkaline‐extracted proteins. The secondary structure of the protein fractions was dominated by β‐sheets (20%–35%) and unordered structures (45%–48%). Surface hydrophobicity and absolute zeta potential were negatively correlated (R2 = 0.82, p < 0.05). ALB and GLO fractions had higher denaturation temperatures than the alkaline/enzymatically‐extracted proteins, potentially due to partial denaturation. ALB and GLO fractions also had the highest solubility and emulsification capacities. Under acidic conditions, enzymatically‐extracted proteins exhibited better solubility (58 vs. 33%), emulsification (499 vs. 403 g oil/g dry sample), and similar foaming capacity (57%–69%) compared to alkaline‐extracted proteins. This study showed that alkaline and enzymatically extracted lentil proteins share physicochemical and functional characteristics with water‐ and salt‐extracted proteins, demonstrating the efficacy of these single‐stage extraction strategies in achieving high yields and desirable functionality.

Effects of thermal treatment on the physicochemical and structural properties of wheat gluten proteins: insights from gluten, glutenin, and gliadin fractions

SummaryThis study examined changes in heat‐induced gluten proteins, focusing on their structure, physicochemical properties, and molecular analysis. The results demonstrated that gliadin had a high denaturation temperature (68.04 °C) and minimal aggregation during heating (25 °C–95 °C), yet it hindered thermal reaction progress of gluten effectively. Heating caused a shift from α‐helical structure to random coil and β‐turn structures, with a decrease in fluorescence intensity. High temperature reduced sulphydryl groups in gluten and glutenin, reaching 0.64 and 0.58 mmol L−1, respectively. However, the content of sulphydryl groups in gliadin remained relatively stable at around 0.37 mmol L−1. Notably, the configuration of disulphide bonds in gliadin, particularly in the g‐g‐g configuration, displayed greater stability. Microstructure analysis revealed increased compactness in all protein fractions as temperature rose. Overall, gliadin had greater thermal stability, impeding glutenin aggregation and gluten network formation. These findings provide valuable insights for cooking, processing, and storage of gluten proteins.

Effects of Wooden Breast Myopathy on Meat Quality Characteristics of Broiler Pectoralis Major Muscle and Its Changes with Intramuscular Connective Tissue.

This study aimed to investigate the effect of wooden breast (WB) myopathy on chemical composition, meat quality attributes and physiochemical characteristics of intramuscular connective tissue (IMCT) of broiler pectoralis major (PM) muscle. Thirty-six fillets were classified into varying degrees of WB condition, including normal, moderate and severe. Results show that WB myopathy altered the collagen profile in PM muscle by increasing total collagen content and decreasing collagen solubility. The composition of macromolecules in IMCT, including hydroxylysyl pyridoxine cross-linking, decorin and glycosaminoglycans, were increased with the severity of WB myopathy. Differential scanning calorimetry analysis indicated higher denaturation temperatures and lower denaturation enthalpy of IMCT for WB. Secondary structures of α-helix and β-sheet in the IMCT of WB were changed to β-turn and random coil. In addition, chemical composition and meat quality attributes showed a correlation with collagen profile and IMCT characteristics. Overall, this study emphasizes the effect of WB myopathy on IMCT and their contributions to meat quality variation.

Fermentation Characteristics, Antinutritional Factor Level and Flavor Compounds of Soybean Whey Yogurt.

Soybean whey contains high levels of off-flavors and anti-nutritional factors and is generally considered unsuitable for direct application in the food industry. In this work, to reduce beany off-flavors and anti-nutritional factors, and to improve its fermentation characteristics, soybean whey was treated with electrodialysis desalination, vacuum concentration and lactic acid bacteria (LAB) fermentation. The results showed that electrodialysis desalination increased the fermentation rate and the number of viable lactic acid bacteria of soybean whey yogurt. More than 90% of the antinutritional factor level (urease and trypsin inhibitory activity) was removed due to high-temperature denaturation inactivation and LAB degradation. Concentrated desalted soybean whey yogurt (CDSWY) possessed larger values for firmness and consistency, and a denser network microstructure compared with undesalted yogurt. Over 90% of off-flavors including hexanal, 1-octen-3-ol and 1-octen-3-one were removed after electrodialysis desalination and concentration treatment. Meanwhile, the newly generated β-damascenone through carotenoid degradation and 2,3-butanedione improved the pleasant flavor and sensory quality of CDSWY, while the salty taste of CSWY lowered its sensory quality. This study provided a theoretical basis for better utilization of soybean whey to develop a plant-based yogurt like dairy yogurt.

Characterization of Collagen from Jellyfish Aurelia aurita and Investigation of Biomaterials Potentials.

Marine collagen sources are potent alternatives due to abundant yield, low pathogen infection risk, high biocompatibility, and any religious and ethical restrictions compared to terrestrial collagen sources. In this research, we aim to investigate the biomaterials potential of the collagen from Aurelia aurita, which is a native jellyfish species in the Marmara Sea. Spectroscopic techniques were used to investigate the structure of jellyfish collagen (JCol) from acid-soluble fraction and compared to Jellagen® from Rhizostoma pulmo. MALDI-TOF showed the main peak of Jellagen® at 276,765.161Da and jellyfish collagen at 276,761.687Da. SDS-PAGE indicated α1 and α2 bands at about 122kDa and 140kDa, respectively. In FTIR and Raman spectra, the locations of amide bands of both species were almost the same. The pI of JCol was determined as 4.46. The particle size decreased abruptly at 43oC from 890 to 290nm. Water, organic and inorganic ratios of collagen were determined at 7.14%, 63.59, and 29.27 respectively. In DSC, the denaturation temperature (Td) of JCol was found at 43.7oC and found to be higher than that of the collagens from jellyfishes that have been reported so far in the literature. Biocompatibility testing by metabolic assay revealed significantly higher fibroblast proliferation on collagen film than on the Tissue Culture Plate. To conclude, Aurelia aurita collagen would be a suitable source of collagen when biomaterials are needed to have high biocompatibility and unique macromolecular properties such as high denaturation temperatures.

Structural and molecular characterization of collagen-type I extracted from lamb feet.

This study aimed to extract collagen-I from lamb feet (LF) and examine the effects of ultrasound treatment on the structural and molecular characteristics of the collagen. Compared to ultrasonic bath treatment and conventional extraction methods, ultrasonic probe (USP) treatment significantly increased the collagen content of the extract (p<0.05). The electrophoretic profiles confirmed the presence of α- and β-chains, indicating it as type I. Furthermore, X-ray diffraction, Fourier-transform infrared spectroscopy, and circular dichroism spectra analyses revealed that the extraction method did not adversely affect the triple helix structure of the collagen. Moreover, the fibrillar structure of the collagen samples was verified through scanning electron microscopy analyses. Notably, the LF collagen exhibited a high thermal denaturation temperature owing to its elevated imino acid content. The collagen samples exhibited high solubility in acidic pH but low solubility in high salt concentrations. The present findings signified that sonication with USP can effectively enhance the yield of collagen from LF without compromising its quality. PRACTICAL APPLICATION: This study showed that ultrasonication enhanced the collagen concentration without disturbing the integrity of lamb feet collagen. We expect that lamb feet collagen can be used for industrial processes and consumer products thanks to unique product properties.

Protein concentrates from plain, aromatic and pigmented rice cultivars: Functional, thermal and morphological characterization

Protein is a vital nutrient required for growth and development of human population. It is well recognised that a significant cause of malnutrition is a lack of protein in human diet. Plant based proteins are becoming an excellent substitute for meat proteins in the development of functional foods at a fair price. When it comes to plant-based sources of high-quality protein, rice is regarded as a useful option because of its hypoallergenic properties, adequate amino acid balance, and high protein content. Therefore, protein concentrates were obtained from plain (SR-4, K-39), aromatic (Mushq Budij) and pigmented (Zhag) rice cultivars of Kashmir. Significant (p<0.05) difference was observed in protein (70.40–74.23 g/100 g) and ash (2.90–3.50 g/100 g) contents of protein concentrates isolated from different rice cultivars. Zhag protein had the lowest ‘L’ value (40.20). However, it had the highest emulsifying activity (47.29 m2/g) and emulsion stability index (13.38 min) at neutral pH. Moreover, water absorption capacity was highest for K-39 protein (1.90 g/g). Zhag protein had the highest protein solubility and foaming stability under acidic pH conditions. Zhag protein had the highest denaturation temperature (81.70 °C) and denaturation enthalpy (9.55 Jg−1). No sharp peaks were observed in the X-ray diffractogram (XRD), indicating amorphous behaviour of protein powder. Pearson's correlation revealed positive correlation between emulsifying activity indices (EAI) at pH 7 and protein solubility at pH 8 (r = 0.955, p<0.05). Surface hydrophobicity (SH) of RPCs was found to be positively correlated with EAI at pH 3 (r = 0.991, p<0.01) and foaming capacity (FC) at pH 8 (r = 0.994, p<0.01), respectively. It can be concluded from the present study that protein concentrate from pigmented rice cultivar was superior to other samples in terms of functionality and thermal attributes.

Extraction and characterization of type I collagen from scales of Mexican Biajaiba fish

Abstract Type I collagen is a high-value polymer found naturally in animal species and with many applications in the biomedical field. Collagen is frequently obtained from bovine tendons, but this source presents the risk of disease transmission, thus marine collagen is becoming an alternative source of this valuable material. In the present work, we report the successful extraction and characterization of the natural collagen found in the scales of Biajaiba, a highly consumed fish native to the Gulf of Mexico. We obtained acid- and pepsin-soluble type I collagens with high denaturation temperatures, high hydroxyproline contents, and yields in the ranges reported for other fish scales. Our work proposes a useful alternative for transforming the huge quantities of discarded fish scales in our country to extract a high-value product for biomedical applications.

Protein isolate from basil seeds (Ocimum basilicum L.): Physicochemical and functional characterisation

Protein was isolated by isoelectric precipitation from basil seeds (after mucilage and oil extraction) and investigated for its physicochemical and functional properties. The protein content of basil seed protein isolate (BPI) was 89.08%. High performance liquid chromatography (HPLC) showed presence of essential amino acids. Glutamic acid (17.40%), threonine (13.65%), and arginine (11.32%) were abundant. Sodium dodecyl sulphate polyacrylamide gel (SDS-PAGE) analysis showed molecular weights in the range of 11.5 to 77.6 kDa. Differential scanning calorimetry (DSC) of basil seed protein isolate revealed a high denaturation temperature (95.34 °C). The Fourier transform infrared spectroscopy (FTIR) indicated presence of amide I, II, and III groups. Characteristic peaks for β- sheet conformation were also observed. Results showed that BPI had high emulsifying ability index (298.4 m2/g) at pH 10. Solubility was lowest at pH 9 (10.69%). Functional properties such as protein solubility, foaming, and emulsification properties were high at pH 10. An increasing trend was observed from pH 2 to 5. High bulk density (0.799 g/ mL) and low water absorption capacity (0.51 g/ g) was observed.

Physicochemical and functional properties of Pleurotus eryngii proteins with different molecular weight

Pleurotus eryngii, rich in polysaccharides and proteins, is precious commercial edible fungus with favorable nutrition. In this study, four kinds of Pleurotus eryngii proteins (PEPs) with different molecular weight (PEP: control, PEP-I: >100 kDa, PEP-II: 50–100 kDa, PEP-III: 10–50 kDa) were prepared by alkaline-solution and ultrafiltration method. The results revealed that PEP-I (82.5 °C) and PEP-III (81.9 °C) with high denaturation temperature. Glu, Asp, Leu, and Lys were the most enriched amino acids in PEPs. The SDS-PAGE results revealed that a low molecular weight fraction of 17 kDa was clearly obtained in the PEP-III. The secondary structure of PEPs was mainly β-turn and β-sheet, and account for 79.8–90.3% of the total content. Moreover, PEP-II and PEP-III had better solubility and emulsification compared to PEP-I and PEP. Finally, the antioxidant capacity of PEPs, especially PEP-II and PEP-III, shown significantly ·OH scavenging capacity and Fe2+ chelating force. The key findings suggested in this paper refer to the exploration of functional properties and antioxidant activity of Pleurotus eryngii protein. The PEP-III with low molecular weight is potentially advantageous as a protein alternative resource application in the food industry.

PH and ultrasound driven structure-function relationships of soy protein hydrolysate

The structural, thermodynamic and functional properties of soy protein hydrolysate (SPH) modified by treatment at different pH values (3, 5, and 9 and pH 7 as control) followed by ultrasound treatment (240 W, 30 min) were investigated. The treatment of SPH at alkaline pH combined with ultrasound treatment resulted in a reduction in the particle size and turbidity, enhancement in the surface negative charge and disulfide bond (SS) content, and exposure of more surface sulfhydryl (SH) groups, resulting in increased surface hydrophobicity and fluorescence intensity compared to those of the samples treated at pH 3–7. In addition, the alkaline-treated samples were more structurally stable than those treated at other pH values, having higher denaturation temperatures and enthalpies; moreover, these samples had higher solubility and emulsifying and foaming capacities. In addition, ultrasound-assisted pH treatment altered the secondary and tertiary structures of SPH by altering the covalent and non-covalent interactions, although there was no effect on the molecular weight distribution of proteins. In conclusion, ultrasound-assisted pH treatment is an effective method to improve physicochemical properties of SPH for applications in the food industry.

Cruciferin improves stress resistance and simulated gastrointestinal survival of probiotic Limosilactobacillus reuteri in the model encapsulation system

Encapsulation is a viable strategy to improve the stability and survival of probiotics during processing, storage, and consumption. Cruciferin, a major canola protein with high denaturation temperature and resistance to gastric degradation, has potential for encapsulation and protection of probiotics against harsh conditions in processing and gastrointestinal tract. Cruciferin/alginate capsules were fabricated to encapsulate probiotics, and were characterized using confocal and scanning electron microscopy (SEM). The bacterial viability was studied during storage, processing, and gastro-intestinal transit. Limosilactobacillus reuteri TMW 1.656 was encapsulated in spherical cruciferin/alginate capsules (2.2 ± 0.1 mm) prepared using an extrusion method. SEM images of the capsules showed that the bacteria were entrapped within the porous structure which was formed by the complexation of cruciferin and alginate. The confocal microscopy images confirmed that cruciferin and alginate were homogeneously distributed throughout the capsules. The shelf life of the bacteria in the presence of cruciferin and alginate increased up to 8 weeks at 4 °C, while unencapsulated (free) bacteria lost their viability after 2 weeks storage. The heat resistance of encapsulated bacteria exposed to 65 °C and 70 °C was improved by up to ∼ 4 and 2 log cycles, respectively, compared to unencapsulated bacteria. Encapsulation also protected L. reuteri against gastric low pH and enzymes; the viability was 3 logs higher when compared to unencapsulated bacteria. The capsules were degraded in simulated intestinal fluid, leading to the release of the encapsulated bacteria, whereas the wall materials increased the resistance of released bacteria to bile salts. Comparison between the viability of unencapsulated bacteria in presence of cruciferin/alginate mixtures and bacteria encapsulated in the capsules revealed that capsule formation provided physical barriers to the harsh conditions and played a key role in the protection of bacteria. This study showed that cruciferin/alginate capsules are capable to improve stability and shelf life of Limosilactobacillus reuteri.

Comparison of physicochemical and in vitro hypoglycemic activity of bamboo shoot dietary fibers from different regions of Yunnan.

In this study, the physicochemical properties, thermal characteristics, and in vitro hypoglycemic activity of dietary fibers extracted from four bamboo shoots were characterized and compared. The results showed that Dendrocalamus brandisii Munro (C-BSDF) had the highest dietary fiber content (6.1%) and the smallest particle size (222.21 μm). SEM observations found that C-BSDF exhibited a loose and porous microstructure, while FTIR and XRD confirmed that C-BSDF had a higher degree of decomposition of insoluble dietary fiber components and the highest crystallinity, resulting in a better microstructure. Furthermore, C-BSDF exhibited excellent physiochemical properties with the highest water hold capacity, water swelling capacity, and preferable oil holding capacity. Thermal analysis showed that C-BSDF had the lowest mass loss (64.25%) and the highest denaturation temperature (114.03°C). The hypoglycemic activity of dietary fibers from bamboo shoots were examined in vitro and followed this order of activity: C-BSDF>D-BSDF>A-BSDF>B-BSDF. The inhibition ratios of GAC, GDRI and α-amylase activity of C-BSDF were 21.57 mmol/g, 24.1, and 23.34%, respectively. In short, C-BSDF display excellent physicochemical and functional properties due to its high soluble dietary fiber content, small particle size with a high specific surface area, and loose microstructure. Thus, D. brandisii Munro can be considered a promising new source of dietary fiber for hypoglycemic health products.