Hydrophobic edible composite packaging membrane based on low-methoxyl pectin/chitosan: Effects of lotus leaf cutin

Recovery and Purification of Cutin from Tomato By-Products for Application in Hydrophobic Films

Tomato pomace is a low-cost, renewable resource that has been studied for the extraction of the biopolyester cutin, which is mainly composed of long-chain hydroxy fatty acids. These are excellent building blocks to produce new hydrophobic biopolymers. In this work, the monomers of cutin were extracted and isolated from tomato pomace and utilized to produce cutin-based films. Several strategies for the depolymerization and isolation of monomeric cutin were explored. Strategies differed in the state of the raw material at the beginning of the extraction process, the existence of a tomato peel dewaxing step, the type of solvent used, the type of alkaline hydrolysis, and the isolation method of cutin monomers. These strategies enabled the production of extracts enriched in fatty acids (16-hydroxyhexadecanoic, hexadecanedioic, stearic, and linoleic, among others). Cutin and chitosan-based films were successfully cast from cutin extracts and commercial chitosan. Films were characterized regarding their thickness (0.103 ± 0.004 mm and 0.106 ± 0.005 mm), color, surface morphology, water contact angle (93.37 ± 0.31° and 95.15 ± 0.53°), and water vapor permeability ((3.84 ± 0.39) × 10^-11 mol·m/m²·s·Pa and (4.91 ± 1.33) × 10^-11 mol·m/m²·s·Pa). Cutin and chitosan-based films showed great potential to be used in food packaging and provide an application for tomato processing waste.

Intelligent pH indicator composite film based on pectin/chitosan incorporated with black rice anthocyanins for meat freshness monitoring

With the improvement of consumer awareness of food safety and the increasing concern about plastic pollution, the development of novel intelligent packaging film is imminent. This project aims to develop an environmentally friendly pH-sensitive intelligent food packaging film for meat freshness monitoring. In this study, anthocyanin-rich extract from black rice (AEBR) was added to composite film formed by the co-polymerisation of pectin and chitosan. AEBR showed strong antioxidant activity, and different colour responses to different conditions. The mechanical properties of the composite film remarkably improved when AEBR was incorporated into. Besides, the introduction of anthocyanins enables the colour of composite film to change from red to blue with the degree of meat spoilage increased which shows the indicative effect of composite films on meat putrification. Therefore, the AEBR-loaded pectin/chitosan film could be used as an indicator to monitor meat freshness in real-time.

Fabrication and Characterization of Eco-Friendly Polyelectrolyte Bilayer Films Based on Chitosan and Different Types of Edible Citrus Pectin

The eco-friendly polyelectrolyte bilayer films were prepared by layer-by-layer (LBL) casting method using chitosan (CS) and four types of edible citrus pectin as film substrates. The results showed that the polyelectrolyte bilayer films exhibited excellent comprehensive properties. Furthermore, the interaction between CS and pectin was closely related to the degree of methyl-esterification (DM), molecular weight (Mw), and zeta potential of pectin. The low DM, Mw, and high zeta potential of the low methyl-esterified pectin (LM) resulted in a denser internal structure of the bilayer film, stronger UV shielding performance, and stronger gas barrier ability. The high DM and Mw of the high methyl-esterified pectin (HM) endow the bilayer film with stronger mechanical properties, thermal stability, and antifogging property. The microstructural and spectroscopic analysis showed that there are hydrogen bonds and electrostatic interactions between the layers. Overall, the developed CS-pectin polyelectrolyte bilayer films provided potential applications for food bioactive packaging.

Pectin Films with Recovered Sunflower Waxes Produced by Electrospraying

Valorization of by-products obtained from food processing has achieved an important environmental impact. In this research, sunflower wax recovered from oil refining process was incorporated to low and high-methoxyl pectin films produced by electrospraying. Film-forming solutions and wax-added electrosprayed films were physical and structurally evaluated. The addition of sunflower wax to the film-forming solutions reduces conductivity while raising surface tension and density, whereas the type of pectin had a larger impact on viscosity, with the low-methoxyl solution having the highest value. These changes in physical solution properties influenced the film characteristics, observing thicker films with lower water vapor transmission rate (WVTR) when adding wax. Micrographs obtained by scanning electron microscopy (SEM) revealed the presence of wax particles as small spherical shapes, having a good distribution through the sectional area of films. According to X-ray diffraction (XRD), atomic force microscopy (AFM) and mechanical properties analyses, the presence of wax had an impact on the degree of crystallinity, producing a more amorphous and rougher film’s structure, without affecting the elongation percentage and the tensile stress (p>0.05). These results showed that wax addition improves the physical properties of films, while the suitability of using both pectins and the electrospraying technique was demonstrated.

Changes of Main Nutrient Components and Volatile Flavor Substances in Processing of Canned Bamboo Shoots

Canned bamboo shoots, a popular endurable storage product preserved by canning, can be used directly as a raw material for preparing dishes and processing many other downstream products. Fermentation and high temperature sterilization are decisive for product quality. During 3 days of fermentation at 25 °C, the protein and total amino acids of bamboo shoots increased remarkably and the total phenols changed a little. After steam sterilization, the total sugar decreased by 56.82%, and the protein of bamboo shoots decreased from 2.41 ± 0.04 g/100 g to 2.03 ± 0.30 g/100 g. The process significantly increased from zero the total sugar, protein and total amino acids in sterilization bamboo shoots soaking solution. GC-MS-ROAV was used for the detection of volatile flavor substances (VFCs) of bamboo shoots and soaking solution in the four processing stages. Fermented bamboo shoots after 72 h showed a strong aroma of orange oil, which was the evaluator’s preferred aroma. In the process of sterilization, Maillard reaction leads to the increase of pyrazines and furans in bamboo shoots and soaking solution, including dibenzofuran, furaneol, trimethyl-pyrazine and 2,3-dimethyl-pyrazine. Due to these volatile flavor components, the sterilized bamboo shoots spread a light caramel and cocoa flavor.

Optical pH Sensor Based on Immobilization Anthocyanin from Dioscorea alata L. onto Polyelectrolyte Complex Pectin-Chitosan Membrane for a Determination Method of Salivary pH

A simple optical pH sensor based on immobilization, Dioscorea alata L. anthocyanin methanol extract, onto a pectin–chitosan polyelectrolyte complex (pectin–chitosan PEC), has been successfully fabricated. The optical pH sensor was manufactured as a membrane made of pectin–chitosan PEC and the extracted anthocyanin. This sensor has the highest sensitivity of anthocyanin content at 0.025 mg/L in phosphate buffer and 0.0375 mg/L in citrate buffer. It also has good reproducibility with a relative standard deviation (%RSD) of 7.7%, and gives a stable response at time values greater than 5 min from exposure in a buffer solution, and the sensor can be utilized within five days from its synthesis. This optical pH sensor has been employed to determine saliva pH of people of different ages and showed no significant difference when compared to a potentiometric method.