Color Development Kinetics of Maillard Reactions

Tunable Physical Properties of Electro-Blown Spinning Dextran/Zein Nanofibers Cross-Linked by Maillard Reaction

Electrospinning biopolymer nanofibers have emerged as promising candidates for food packaging applications. In this study, dextran/zein nanofibers were fabricated using electro-blown spinning and subsequently cross-linked via the Maillard reaction (MR) at 60 °C and 50% relative humidity. Compared to traditional electrospinning, the introduction of air-blowing improved the sample preparation speed by 10 times. SEM analysis revealed that the nanofiber morphology remained stable upon MR treatment for 24 h. FTIR spectroscopy confirmed that the MR led to a deformation in the protein conformation and an increase in hydrophilicity and elasticity in the nanofibers cross-linked for 6 h. MR treatment for 18 h considerably enhanced the hydrophobicity and elastic modulus owing to covalent bond formation. Thermal analysis indicated an improved thermal stability with increasing MR duration. Mechanical property analysis revealed an increase in elastic modulus and a decrease in elongation at break for the nanofibers cross-linked for more than 6 h, indicating a trade-off between rigidity and flexibility. Notably, the water vapor permeability of the nanofibers cross-linked for 6 and 18 h was remarkably higher, which can be ascribed to the fiber morphology retention upon water evaporation. Overall, MR-cross-linked dextran/zein/xylose nanofibers showed tunable properties, making them a suitable encapsulation system for bioactive compounds.

Antioxidant Stability of Moringa Leaves Extract Powders Obtained by Cocrystallization, Vacuum Drying, and Plating

Cocrystallization, vacuum drying, and plating are three potential applications to preserve the antioxidant activity of moringa leaves. Moringa leaves extract was incorporated with sucrose at the same concentration (7 : 100, solid : solid) for all applications and stored for 30 days. This study aims to examine the effects of each application on the antioxidant stability of moringa leaves extract powders. Morphological properties by SEM showed that cocrystallized powders exhibited porous, agglomerated crystals, vacuum dried powders exhibited agglomerated crystals, and plated powders exhibited layered crystals. Based on XRD and hygroscopicity results, cocrystallization produced powders with the highest crystallinity, i.e., 69.11%, and the lowest hygroscopicity, i.e., 0.26 × 10−4 ± 0.02 × 10−4 g H2O/g solid/minute due to the slow water intake of the crystalline structure. Powders with the strongest initial antioxidant activity were obtained from cocrystallization, i.e., 3647.96 ± 20.29 ppm and followed by vacuum drying, i.e., 4378.51 ± 26.29 ppm. The least antioxidant activity was obtained from plating, i.e., 4733.46 ± 31.91 ppm. During 30 days of storage, powders obtained by cocrystallization maintained the most stable antioxidant activity (91.81–91.12%). The results indicated that the high temperature used in the process was likely to impact crystalline structure through the pore formation, which entrapped bioactive compounds and resulted in strong antioxidant activity. While, vacuum drying resulted in powders with a lower but increased antioxidant activity (84.06%–86.43%). In contrast to the other two applications, plating resulted in a decreased antioxidant activity (83.77–82.25%). This study suggests that application of cocrystallization produced moringa leaves extract powders with the strongest and most stable antioxidant activity during storage. Preserving the antioxidant stability of plant extract has been one of the major drives in the development of food encapsulation technology. Cocrystallization and vacuum drying are two relatively novel, less common techniques offering a simpler and more cost-effective method, but their effect on the antioxidant stability of moringa leaves extract has not yet been studied. This study discloses the effects of cocrystallization, vacuum drying, and plating (alternative extract incorporation method) on the antioxidant stability of moringa leaves extract powders. The results indicated that the three methods produced powders with high crystallinity and stable antioxidant stability during storage. Among the three methods, cocrystallization was the method that resulted in powders with the strongest and most stable antioxidant activity.

Comparison of Color Development Kinetics of Tanning Reactions of Dihydroxyacetone with Free and Protected Basic Amino Acids

Sunless tanning has become incredibly prevalent due to the increasing fashionable demand and the awareness of photodamage risks. The brown pigments are induced by dihydroxyacetone (DHA) and amino groups in the stratum corneum (SC) of skin via the Maillard reaction. While most studies concerning sunless tanning reactions have focused on free amino acids (AAs), little information is available on the impact of the side chain of AAs or proteins on this important reaction in cosmetic chemistry. To explore the reactivity and color development kinetics of different types of amino groups, three basic free AAs (Arg, His, and Lys) and three Nα-protected AAs (Boc-Arg-OH, Boc-His-OH, and Boc-Lys-OH) were used to react with DHA using a simplified model system at different reaction times, pH, and temperatures. Full factorial experiments were employed to design and analyze the effects of these three factors. The browning intensity and color characteristics were quantitatively evaluated. The factorial experiments showed that temperature had the most significant influence on the browning intensity and played a dominant role in the interactions with the reaction time and pH. It was found, for the first time, that Arg and His reacted with DHA more rapidly than Boc-Arg-OH and Boc-His-OH, while Boc-Lys-OH developed a stronger color than Lys under the same conditions, suggesting that ε-NH₂ of a lysine residue in peptides or proteins of SC may play a crucial role in the color development of DHA tanning. This study not only clearly illustrates the capability of the side chain of AAs to produce colored compounds but also provides a deeper understanding of DHA tanning.

Advances in Protein-Based Nanocarriers of Bioactive Compounds: From Microscopic Molecular Principles to Macroscopical Structural and Functional Attributes

Many proteins can be used to fabricate nanocarriers for encapsulation, protection, and controlled release of nutraceuticals. This review examined the protein-based nanocarriers from microscopic molecular characteristics to the macroscopical structural and functional attributes. Structural, physical, and chemical properties of protein-based nanocarriers were introduced in detail. The spatial size, shape, water dispersibility, colloidal stability, etc. of protein-based nanocarriers were largely determined by the molecular physicochemical principles of protein. Different preparative techniques, including antisolvent precipitation, pH-driven, electrospray, and gelation methods, among others, can be used to fabricate different protein-based nanocarriers. Various modifications based on physical, chemical, and enzymatic approaches can be used to improve the functional performance of these nanocarriers. Protein is a natural resource with a wide range of sources, including plant, animal, and microbial, which are usually used to fabricate the nanocarriers. Protein-based nanocarriers have many advantages in aid of the application of bioactive ingredients to the medical, food, and cosmetic industries.

Utilization of Sake lees as Broiler Feedstuff and its Effects on Growth Performance and Intestinal Immunity

Increasing food loss and waste (FLW) is a global problem, and efforts are being made to use waste food as potential livestock feed material. The amount of self-supplied feed is lower in Japan than in other countries, and the government recommends FLW use for animal feed. Sake (Japanese rice wine) is a traditional alcoholic beverage. During the sake manufacturing process, large amounts of squeezed solids or “lees” (sake lees) are generated. Sake lees are nutritious and functional, but are prone to spoilage. In this study, we investigated whether sake lees should be mixed with animal feed immediately or after drying. To assess the usefulness of sake lees as a poultry feed ingredient and determine the effect of sake lees on intestinal immunity, we performed a feeding trial with three treatments: a raw sake lees (RSL) diet, dried sake lees (DSL) diet, and control diet. Three-week-old broilers were fed these diets (n=8 per group) for two weeks. We then calculated feed efficiency and performed RT-qPCR to assess the effects of diet on intestinal immunity. The growth performance in the RSL diet group was equivalent to that in the control diet group. The DSL diet became difficult for broilers to eat, resulting in decreased growth performance. In the ileum of RSL-diet broilers, the mRNA expression levels of TGF-β1 and avian β-defensin (AvBD)12 were significantly increased compared to those of control diet broilers (p<0.05), and a significant correlation was observed between the two genes (p<0.05). Our results indicated that sake lees should not be dried and should be mixed immediately with feed, and this sake lees when fed to chicken activates the intestinal immunity. However, sake lees have a lower fat content than corn, and it is thus important to combine sake lees with high-energy feed.