Metal-organic frameworks-based moisture responsive essential oil hydrogel beads for fresh-cut pineapple preservation.

The preservation of fresh-cut fruits and vegetables has attracted attention to the shelf-life reduction caused by high humidity. Herein, alginate/copper ions cross-linking, in-situ growth and self-assembly techniques of metal-organic frameworks (MOFs) were utilized to prepare a moisture responsive hydrogel bead (HKUST-1@ALG). As the multistage porous structure formation, tea tree essential oil (TTO) load capacity in hydrogel bead (TTO-HKUST-1@ALG) was increased from 6.1% to 21.6%. TTO-HKUST-1@ALG had excellent moisture response performance, and the release rates of TTO increased from 33.89% to 70.98% with moisture increasing from 45% to 95%. Besides, TTO-HKUST-1@ALG exhibited excellent antimicrobial, antioxidant capacity, and biocompatibility. During storage, TTO-HKUST-1@ALG effectively improved the cell membrane integrity by maintaining the balance of reactive oxygen species metabolism. The degradation of cell wall structure and tissue softening were delayed by inhibiting the cell wall-degrading enzymes activity. Briefly, TTO-HKUST-1@ALG improved the storage quality and extended shelf-life of fresh-cut pineapple, which was a promising preservative.

Characterization, Stability and Antioxidant Activity of Vanilla Nano-Emulsion and Its Complex Essential Oil.

As a natural flavoring agent, vanilla essential oil has a special aroma and flavor, but its volatility and instability limit its value. Therefore, in this study, vanilla essential oil was compounded with cinnamon essential oil to prepare nano-emulsions (composite nano-emulsions called C/VT and C/VM), and the stability of the composite essential oil emulsions was investigated. Transmission electron microscopy (TEM) images showed that the nano-emulsions were spherical in shape and some flocs were observed in C/VM and C/VT. The results showed that the average droplet sizes of C/VM and C/VT increased only by 14.99% and 15.01% after heating at 100 °C for 20 min, and the average droplet sizes were less than 120 nm after 24 days of storage at 25 °C. Possibly due to the presence of reticulated flocs, which have a hindering effect on the movement of individual droplets, the instability indices of C/VM and C/VT were reduced by 34.9% and 39.08%, respectively, in comparison to the instability indices of C/VM and C/VT. In addition, the results of antioxidant experimental studies showed that the presence of composite essential oil flocs had no significant effect on the antioxidant capacity. These results indicate that the improved stability of the composite essential oil nano-emulsions is conducive to broadening the application of vanilla essential oil emulsions.

Development, characterization and Lactobacillus plantarum encapsulating ability of novel C-phycocyanin-pectin-polyphenol based hydrogels.

In this study, it was found that the enhancement in the viability of Lactobacillus plantarum under gastrointestinal conditions by encapsulating them within novel C-Phycocyanin-pectin based hydrogels (from 5.7 to 7.1 log/CFU). The hardness, the strength and the stability of the hydrogels increased when the protein concentration was increased. In addition, the addition of resveratrol (RES), and tannic acid (TA) could improve the hardness (from 595.4 to 608.3 and 637.0 g) and WHC (from 93.9 to 94.2 and 94.8 %) of the hydrogels. The addition of gallic acid (GA) enhanced the hardness (675.0 g) of the hydrogels, but the WHC (86.2 %) was decreased. During simulated gastrointestinal conditions and refrigerated storage, the addition of TA enhanced the viable bacteria counts (from 6.8 and 8.0 to 7.5 and 8.5 log/CFU) of Lactobacillus plantarum. Furthermore, TA and GA are completely encased by the protein-pectin gel as an amorphous state, while RA is only partially encased.

Effect of sustained-release tea tree essential oil solid preservative on fresh-cut pineapple storage quality in modified atmospheres packaging.

The quality and safety of fresh-cut pineapple deteriorate during handling and storage due to physicochemical and microbial changes, so its preservation has attracted extensive attention. This study prepared sustained-release tea tree essential oil (TTO) solid preservative (SP) with an encapsulation efficiency of 71.45% and applied it on fresh-cut pineapple in modified atmospheres packaging (MAP). Results showed that TTO adsorbed on nano silicon dioxide (SiO2) was embedded in the starch-carboxymethyl cellulose network structure by extrusion. The hydrogen bond and hydrophobic interaction resulted in compact structure and good sustained-release performance of SP. The SP improved sensory quality and reduced nutrient loss and microbial spoilage of fresh-cut pineapple, which extended its shelf-life to four days. In addition, antioxidant capacity was enhanced with increasing antioxidant enzyme activity, antioxidant content, and 2,2-diphenyl-1-picrylhydrazine scavenging capacity and decreasing MDA accumulation. Therefore, sustained-release TTO solid preservative has potential for the preservation of fresh-cut pineapple.

Improving shikonin solubility and stability by encapsulation in natural surfactant-coated shikonin nanoparticles.

It is significant to develop a colloidal delivery system to improve the water solubility, stability, and bioavailability of shikonin, which is a hydrophobic plant polyphenol with a variety of physiological activities. In this study, three kinds of natural surfactants (saponin, sophorolipid, and rhamnolipid) were used to prepare shikonin nanoparticles by the pH-driven method. The physicochemical and structural properties of the shikonin nanoparticles were characterized, including particle size, zeta potential, and morphology. The encapsulation efficiencies of shikonin nanoparticles coated with saponin and sophorolipid were 97.6% and 97.3%, respectively, which were much higher than that of rhamnolipid-coated shikonin nanoparticles (19.0%). Shikonin nanoparticles coated with saponin and sophorolipid showed good resistance to heat and light and maintained long-term stability during storage. Moreover, shikonin nanoparticles coated with saponin and sophorolipid improved their in vitro-bioavailability. PRACTICAL APPLICATION: These article results are of great importance for improving the stability and bioavailability of shikonin in functional foods, dietary supplements, or pharmaceutical preparations. Moreover, this study provided theoretical and practical guides for further research of shikonin nanoparticles and may promote the development of natural colloidal delivery systems.

Physicochemical, structural, and functional properties of protein fractions and protein isolate from jackfruit seeds.

The physicochemical, structural, and functional properties of albumin, globulin, glutelin, and protein isolate (JSPI) extracted from jackfruit seeds were investigated. Protein fractions and JSPI were rich in amino acids, which can be comparable to soy protein. Other essential amino acids except histidine met the FAO/WHO/UNO-recommended intake for infants and adults. Jackfruit seed proteins were mainly composed of 17-26 kDa polypeptides, ß-sheet, and random coil were the main secondary structures. Glutelin (572.55) and JSPI (246.14) have higher H0 under neutral conditions, consistent with the solubility and emulsification properties results. Albumin and globulin had good solubility and were mostly soluble under neutral or weak alkaline conditions. In general, protein fractions and JSPI exhibited good foaming and emulsification properties. Therefore, jackfruit seed proteins have the potential to be nutritious functional ingredients in the food industry. PRACTICAL APPLICATION: Jackfruit seed proteins had high essential amino acids content and good functional properties. They can be used as a new type of functional ingredients in the food industry, which can not only reduce the environment pollution of discarded seeds but also improve use of plant protein.

Molecular and Functional Properties of Protein Fractions and Isolate from Cashew Nut (Anacardium occidentale L.).

Some molecular and functional properties of albumin (83.6% protein), globulin (95.5% protein), glutelin (81.3% protein) as well as protein isolate (80.7% protein) from cashew nut were investigated. These proteins were subjected to molecular (circular dichroism, gel electrophoresis, scanning electron microscopy) and functional (solubility, emulsification, foaming, water/oil holding capacity) tests. Cashew nut proteins represent an abundant nutrient with well-balanced amino acid composition and could meet the requirements recommended by FAO/WHO. SDS-PAGE pattern indicated cashew nut proteins were mainly composed of a polypeptide with molecular weight (MW) of 53 kDa, which presented two bands with MW of 32 and 21 kDa under reducing conditions. The far-UV CD spectra indicated that cashew proteins were rich in ß-sheets. The surface hydrophobicity of the protein isolate was higher than that of the protein fractions. In pH 7.0, the solubility of protein fractions was above 70%, which was higher than protein isolate at any pH. Glutelin had the highest water/oil holding capacity and foaming properties. Protein isolate displayed better emulsifying properties than protein fractions. In summary, cashew nut kernel proteins have potential as valuable nutrition sources and could be used effectively in the food industry.

Effect of ultrasound combined with malic acid on the activity and conformation of mushroom (Agaricus bisporus) polyphenoloxidase.

Polyphenoloxidase (PPO) plays an important role in the browning of vegetables, fruits and edible fungi. The effects of ultrasound, malic acid, and their combination on the activity and conformation of mushroom (Agaricus bisporus) PPO were studied. The activity of PPO decreased gradually with the increasing of malic acid concentrations (5-60mM). Neither medium concentrations (10, 20, 30mM) malic acid nor individual ultrasound (25kHz, 55.48W/cm(2)) treatment could remarkably inactivate PPO. However, the inactivation during their combination was more significant than the sum of ultrasound inactivation and malic acid inactivation. The inactivation kinetics of PPO followed a first-order kinetics under the combination of ultrasound and malic acid. The conformation of combination treated PPO was changed, which was reflected in the decrease of α-helix, increase of ß-sheet contents and disruption of the tertiary structure. Results of molecular microstructure showed that ultrasound broke large molecular groups of PPO into small ones. Moreover, combined treatment disrupted the microstructure of PPO and molecules were connected together.

Different modes of inhibition for organic acids on polyphenoloxidase.

It is still unclear whether the inhibitory effect of organic acid on polyphenoloxidase (PPO) is due to the reversible inhibition or decrease of pH. In this study, cinnamic acid, citric acid and malic acid inhibited PPO in different modes. Results showed that the inhibition by cinnamic acid resulted from reversible inhibition, while the decrease of pH was the main cause for citric acid and malic acid. The kinetic results showed that cinnamic acid reversibly inhibited PPO in a mixed-type manner. Fluorescence emission spectra indicated that cinnamic acid might interact with PPO and quench its intrinsic fluorescence, while the decrease of the fluorescence intensity induced by citric acid or malic acid was due to the acid-pH. Cinnamic acid bound to PPO and induced the rearrangement of secondary structure. Molecular docking result revealed cinnamic acid inserted into the hydrophobic cavity of PPO by forming π-π stacking.