The Effect of Hydrocolloids on Penetration Tests and Syneresis of Binary Gum Gels and Modified Corn Starch-Gum Gels.

The interactions among agar, gellan gum, gelatin, and modified waxy corn starch in the formation of mixed gels were examined in five different ratios. Binary hydrocolloid gels were prepared using three ingredients: two hydrocolloids (total hydrocolloid concentration: 0.5 wt%, ratios of mixture: 0/0.5, 0.1/0.4, 0.2/0.3, 0.3/0.2, 0.4/0.1, and 0.5/0) and water. The textural properties of the hydrocolloid gels were studied by measuring the gel strength, rigidity, breaking force, breaking point, and syneresis as functions of the mixing ratio. The higher syneresis percentage of binary modified waxy corn starch and gum gels than that of mixed gum gels after cold storage was mainly due to the retrogradation of amylopectin. Agar was shown be the most influential with regards to increasing the gel strength, breaking force, and rigidity among the three kinds of gum, while gellan gum was more effective against syneresis than agar and gelatin for storage periods of 7 and 14 days. In the mixed gels, a dramatic increase in the breaking point from 0 to 0.5% was only exhibited for gellan gum. The results provided useful information, including gel strength, rigidity, breaking force, breaking point, and syneresis, for gum and modified corn starch ingredients selected from refrigerated binary gum gels such as pudding for food product development.

Hypoglycemic peptide-enriched hydrolysates of Corbicula fluminea and Chlorella sorokiniana possess synergistic hypoglycemic activity through inhibiting α-glucosidase and dipeptidyl peptidase-4 activity.

BACKGROUND: The prevalence of diabetes mellitus worldwide has increased in recent decades. Maintaining the level of blood glucose is the most basic and important issue for diabetics. This study aimed to investigate the hypoglycemic activity of a combination of hypoglycemic peptide-enriched hydrolysates of Corbicula fluminea (ACH) and Chlorella sorokiniana (PCH). RESULTS: Combined supplementation of ACH and PCH synergistically inhibited α-glucosidase and DPP4 activities in vitro. After 4 weeks of treatment with ACH and/or PCH, the plasma glucose concentration and insulin, homeostasis model assessment-estimated insulin resistance (HOMA-IR), total cholesterol (TC) and triglyceride (TG) levels significantly decreased. The hypoglycemic peptides in ACH and PCH were purified and assayed for α-glucosidase and DPP4 activity. The hypoglycemic peptides in ACH and PCH effectively decreased α-glucosidase and DPP4 activities. In silico assays showed that these two peptide types have different docking poses, which determined their inhibitory effect against α-glucosidase and DPP4 activity. CONCLUSION: Combined treatment with hypoglycemic peptide-enriched ACH and PCH could modulate blood glucose by synergistically inhibiting α-glucosidase and DPP4 activities. © 2021 Society of Chemical Industry.

Preparation and Identification of Novel Antihypertensive Peptides from the In Vitro Gastrointestinal Digestion of Marine Cobia Skin Hydrolysates.

This research focuses on cobia skin hydrolysates and their antihypertensive effects via the inhibitory activities of angiotensin I-converting enzyme (ACE). Marine fish Cobia (Rachycentron canadum) skin was hydrolysed for 5 h using Protamex and Protease N to obtain the cobia skin protein hydrolysates PX-5 and PN-5, respectively. The soluble protein and peptide contents of the PX-5 were 612 and 270 mg/g, respectively, and for the PN-5, 531 and 400 mg/g, respectively. The IC50 of PX-5 and PN-5 on ACE was 0.221 and 0.291 mg/mL, respectively. Increasing the IC50 from 0.221 to 0.044 mg/mL by simulated gastrointestinal digestion (PX-5G) reduced the ACE-inhibitory capacity of PX-5. Using gel filtration chromatography, the PX-5G was fractioned into eight fractions. The molecular weight of the fifth fraction from PX-5G was between 630 and 450 Da, and the highest inhibitory efficiency ratio on ACE was 1552.4%/mg/mL. We identified four peptide sequences: Trp-Ala-Ala, Ala-Trp-Trp, Ile-Trp-Trp, and Trp-Leu, with IC50 values for ACE of 118.50, 9.40, 0.51, and 26.80 µM, respectively. At a dose of 600 mg PX-5 powder/kg body weight, in spontaneously hypertensive rats PX-5's antihypertensive effect significantly reduced systolic and diastolic blood pressure by 21.9 and 15.5 mm Hg, respectively, after 4 h of oral gavage.

Functional Characteristics of Ultraviolet-Irradiated Tilapia Fish Skin Gelatin.

Studies were undertaken to investigate the effects of ultraviolet (UV) irradiation on the gel strength, color, thermal properties, protein molecular masses, and functional groups of commercially available fish gelatin samples. Commercially available tilapia skin gelatin powder was used as the raw material to investigate the functional properties of fish skin gelatin powder treated with UV irradiation for different durations (0⁻6 h). The functional properties of fish gelatin and the optimum irradiation treatment conditions were determined through gel strength testing, color characterization, differential scanning calorimetry, sodium dodecyl sulfate polyacrylamide gel electrophoresis, Fourier transform infrared (FTIR) spectroscopy, and Raman spectroscopy. UV irradiation treatment increased gel strength and thermal stability, and significantly degraded the macromolecules. FTIR and Raman spectroscopy data indicated that UV irradiation treatment did not significantly change the molecular structure of fish gelatin powder, but these methods could discriminate the molecular structure of gelatin from various sources. Irradiation for 2 h yielded the highest gel strength and melting peak temperature, and the lowest chromatic aberration.

Purification and Identification of Angiotensin I-Converting Enzyme Inhibitory Peptides and the Antihypertensive Effect of Chlorella sorokiniana Protein Hydrolysates.

Hot water was used to obtain Chlorella sorokiniana hot water extract (HWE). Subsequently, this byproduct was freeze-dried, hydrolysed at 50 °C using Protease N to obtain C. sorokiniana protein hydrolysates (PN-1), and then digested with a gastrointestinal enzyme (PN-1G). The inhibitory effects of the HWE and hydrolysates against angiotensin I-converting enzyme (ACE) were investigated. The soluble protein and peptide contents were 379.9 and 179.7 mg/g, respectively, for HWE and 574.8 and 332.8 mg/g, respectively, for PN-1. The IC50 values of the HWE, PN-1, and PN-1G on ACE were 1.070, 0.035, and 0.044 mg/mL, respectively. PN-1G was separated into seven fractions through size exclusion chromatography. The sixth fraction of the hydrolysate had a molecular weight between 270 and 340 Da, and the lowest IC50 value on ACE was 0.015 mg/mL. The amino acid sequences of the ACE-inhibitory peptides were Trp-Val, Val-Trp, Ile-Trp, and Leu-Trp, of which the IC50 values were 307.61, 0.58, 0.50, and 1.11 µΜ, respectively. Systolic blood pressure and diastolic blood pressure were reduced 20 and 21 mm Hg, respectively, in spontaneously hypertensive rats after 6 h of oral administration with a dose of 171.4 mg PN-1 powder/kg body weight.

Alkali-treated konjac glucomannan film as a novel wound dressing.

To investigate the potential medical application of konjac glucomannan (KGM), we treated KGM film with potassium hydroxide (KOH) or calcium hydroxide (Ca(OH)2), and evaluated its use as a wound dressing. The Ca(OH)2-treated KGM (Ca(OH)2-KGM) film exhibited more favorable properties of swelling, tensile strength, and elongation compared with the KOH-treated KGM (KOH-KGM) film, and also had a suitable water vapor transmission rate. Results from in vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay further indicated the biocompatibility of the Ca(OH)2-KGM film with L929 fibroblast cells and HaCaT keratinocyte cells. The Ca(OH)2-KGM film inhibited the absorption and activation of platelets, and effectively promoted wound contractility in vivo, particularly at an early healing stage. Histological examination revealed considerably collagen secretion and advanced development of granulation tissue and epithelial coverage by Days 7 and 14 postsurgery in wounds treated with Ca(OH)2-KGM film. Our study results indicate the potential use of alkali-treated KGM film as a novel wound dressing.