Colorimetric indicator films based on carboxymethyl cellulose and anthocyanins as a visual indicator for shrimp freshness tracking.

This study aimed to evaluate the response efficiency of colorimetric indicator films based on carboxymethyl cellulose (CMC) incorporated with different anthocyanins [Karanda alone (CMC/AK), butterfly pea alone (CMC/AB), and a mixture of anthocyanins from Karanda and butterfly pea (CMC/AK75/AB25)] for tracking shrimp freshness during storage at different temperatures and times (4 °C for 8 days and 25 °C for 30 h). The mathematical models were also applied to predict their freshness and shelf life. The CMC/AK75/AB25 indicator film was the most sensitive and clearly changed color, which could be distinguished by the naked eye. Color changes indicated the shrimp deterioration processes: dark purple (fresh), purplish gray or gray (semi-fresh), and olive green or brown (spoilage). During shrimp storage at temperatures of 4 and 25 °C, the pH reached 7.52 and 8.14, TVB-N 35.98 and 72.72 mg/100 g, and TVC 5.75 and 7.88 log CFU/g, respectively, indicating shrimp had completely deteriorated. Furthermore, there was a positive correlation between the ΔE value of the indicator film and both TVB-N and TVC. These findings suggest that the CMC/AK75/AB25 indicator film could serve as a real-time visual indicator for tracking shrimp freshness and could enhance the guarantee of shrimp safety.

Smart colorimetric sensing films based on carboxymethyl cellulose incorporated with a natural pH indicator.

This study aimed to combine various natural pH indicators of anthocyanin from Karanda (CA) with anthocyanin from butterfly pea flower (BA) or curcumin (CC) to improve the sensitivity of CA. CA75/BA25 and CA25/CC75 enhanced the sensitivity of the endpoint colour change of CA. A smart colorimetric sensing film was also developed and characterised by loading different natural pH indicators on carboxymethyl cellulose (CMC) films. The addition of different natural pH indicators increased the thickness, elongation, colour (a* and b* values), and contact angle of CMC films (p < 0.05). However, the tensile strength, water vapour permeability, film solubility, light transmission, and L* value decreased when different natural pH indicators were added (p < 0.05). The indicator films demonstrated enhanced antioxidant capacity and thermal stability. The FTIR spectra showed that natural pH indicators were successfully immobilised into the CMC films. Notably, the CMC/CA75/BA25 film was the most sensitive film to changes in volatile ammonia and different pH buffer solutions. The CMC/CA75/BA25 film changed from purple to green with exposure to ammonia solution and from pink to purple to blue to green with increasing pH. Therefore, the CMC/CA75/BA25 film has potential as a colorimetric sensing film, providing a more accurate assessment result.

Physicochemical Properties of Chitosan from Green Mussel Shells (Perna viridis): A Comparative Study.

Green mussel shells (Perna viridis) are generated in huge amounts and discarded as waste materials. Such waste may be used to produce biopolymer materials such as chitosan. The physicochemical properties of chitosan prepared from different sizes of green mussel shells (small size (CHS): ≤5.00 cm in length and big size (CHB): >5.01 cm in length) were characterized and compared with commercial chitosan (CH). Furthermore, the mechanical and physicochemical properties of the blended films were also investigated. The results of the physicochemical properties showed that CHS and CHB were quite different from CH. The degree of deacetylation of CHS, CHB, and CH was found to be 32.71%, 52.56%, and 70.42%, respectively (p < 0.05). The water- and fat-binding capacities of CH were higher than those of CHS and CHB. Structural differences between CHS, CHB, and CH were studied using Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). Significant increases in thickness, water vapor permeability, and strength of the blended films were found when the extracted chitosan was added (p < 0.05). However, further study is needed to improve the chitosan extraction process, which can enhance the physicochemical properties of the obtained chitosan and be widely used in many industries.

Development of Smart Bilayer Alginate/Agar Film Containing Anthocyanin and Catechin-Lysozyme.

Smart packaging can provide real-time information about changes in food quality and impart a protective effect to the food product by using active agents. This study aimed to develop a smart bilayer film (alginate/agar) with a cellulose nanosphere (CNs) from corncob. The bilayer films were prepared using 1.5% (w/w) sodium alginate with 0.25% (w/v) butterfly pea extract incorporated (indicator layer) and 2% (w/w) agar containing 0.5% (w/v) catechin−lysozyme (ratio 1:1) (active layer). The CNs were incorporated into the alginate layer at different concentrations (0, 5, 10, 20, and 30% w/w-based film) in order to improve the film's properties. The thickness of smart bilayer film dramatically increased with the increase of CNs concentration. The inclusion of CNs reduced the transparency and elongation at break of the smart bilayer film while increasing its tensile strength (p < 0.05). The integration of CNs did not significantly affect the solubility and water vapor permeability of the smart bilayer film (p > 0.05). The smart bilayer film displayed a blue film with a glossy (without CNs) or matte surface (with CNs). The developed bilayer film shows excellent pH sensitivity, changing color at a wide range of pHs, and has a good response to ammonia and acetic acid gases. The film possesses exceptional antimicrobial and antioxidant activities. The integration of CNs did not influence the antibacterial activity of the film, despite the presence of a higher level of DPPH in film containing CNs. The smart bilayer film was effectively used to monitor shrimp freshness. These findings imply that smart bilayer films with and without CNs facilitate food safety and increase food shelf life by monitoring food quality.

Extraction and Physico-Chemical Characterization of Chitosan from Mantis Shrimp (Oratosquilla nepa) Shell and the Development of Bio-Composite Film with Agarose.

Mantis shrimp (Oratosquilla nepa) exoskeleton, a leftover generated after processing, was used as a starting material for chitosan (CS) production. CS was extracted with different deacetylation times (2, 3 and 4 h), termed CS−2, CS−3 and CS−4, respectively, and their characteristics and antimicrobial and film properties with agarose (AG) were investigated. Prolonged deacetylation time increased the degree of deacetylation (DDA: 73.56 ± 0.09−75.56 ± 0.09%), while extraction yield (15.79 ± 0.19−14.13 ± 0.09%), intrinsic viscosity (η: 3.58 ± 0.09−2.97 ± 0.16 dL/g) and average molecular weight (Mν: 1.4 ± 0.05−1.12 ± 0.08 (×106 Da)) decreased (p < 0.05). FTIR spectra of extracted CS were similar to that of commercial CS. Among all the CS samples prepared, CS−3 had the best yield, DDA, Mν and antimicrobial activity. Therefore, it was chosen for the development of composite films with AG at different ratios (CS−3/AG; 100/0, 75/25, 50/50, 25/75 and 0/100). As the proportion of AG increased, the tensile strength (29.96 ± 1.80−89.70 ± 5.08 MPa) of the composite films increased, while thickness (0.056 ± 0.012−0.024 ± 0.001 mm), elongation at break (36.52 ± 1.12−25.32 ± 1.23%) and water vapor permeability (3.56 ± 0.10−1.55 ± 0.02 (×10−7 g m m−2 s−1 Pa−1)) decreased (p < 0.05). Moreover, lightness of the films increased and yellowness decreased. CS−3/AG (50/50) composite film exhibited high mechanical and barrier properties and excellent compatibility according to FTIR and SEM analyses. According to these finding, mantis shrimp exoskeleton could be used to produce CS. The developed bio-composite film based on an appropriate ratio (50/50) of CS−3 and AG has potential for being used as food packaging material.

Isolation and Characterization Cellulose Nanosphere from Different Agricultural By-Products.

Cellulose nanospheres (CN) have been considered a leading type of nanomaterial that can be applied as a strengthening material in the production of nanocomposites. This work aimed to isolate and characterize the properties of CN from different agricultural by-products. CNs were successfully isolated from rice straw, corncob, Phulae pineapple leaf and peel using acid hydrolysis (60% H2SO4) combined with homogenization-sonication (homogenized at 12,000 rpm for 6 min and ultrasonicated for 10 min). The results showed that the CN from rice straw (RS-CN) and corncob (CC-CN) exhibited high yields (22.27 and 22.36%) (p < 0.05). All hydrolyzed CNs exhibited a spherical shape with a diameter range of 2 to 127 nm. After acid hydrolysis, Fourier transform infrared (FTIR) results showed no impurities. X-ray diffraction (XRD) showed that the structure of cellulose was changed from cellulose-I to cellulose-II. However, cellulose-I remained in pineapple peel cellulose nanosphere (PP-CN). The crystalline index (CI) ranged from 43.98 to 73.58%, with the highest CI obtained in the CC-CN. The CN from all sources presented excellent thermal stability (above 300 °C). The functional properties, including water absorption Index (WAI), water solubility index (WSI) and swelling capacity were investigated. PP-CN showed the highest WAI and swelling capacity, while the PL-CN had the highest WSI (p < 0.05). Among all samples, CC-CN showed the highest extraction yield, small particle size, high CI, and desirable functional properties to be used as a material for bio-nanocomposites film.

Green Tea Extract Enrichment: Mechanical and Physicochemical Properties Improvement of Rice Starch-Pectin Composite Film.

The effects of green tea extract (GTE) at varying concentrations (0.000, 0.125, 0.250, 0.500, and 1.000%, w/v) on the properties of rice-starch-pectin (RS-P) blend films were investigated. The results showed that GTE addition enhanced (p < 0.05) the antioxidation properties (i.e., total phenolic content, DPPH radical scavenging activity, and ferric reducing antioxidant power) and thickness of the RS-P composite film. The darker appearance of the RS-T-GTE blend films was obtained in correspondence to the lower L* values. However, the a* and b* values were higher toward red and yellow as GTE increased. Though GTE did not significantly alter the film solubility, the moisture content and the water vapor permeability (WVP) of the resulting films were reduced. In addition, the GTE enrichment diminished the light transmission in the UV-Visible region (200−800 nm) and the transparency of the developed films. The inclusion of GTE also significantly (p < 0.05) lowered the tensile strength (TS) and elongation at break (EAB) of the developed film. The FT-IR spectra revealed the interactions between RS-P films and GTE with no changes in functional groups. The antimicrobial activity against Staphylococcus aureus (TISTR 764) was observed in the RS-P biocomposite film with 1% (w/v) GTE. These results suggested that the RS-P-GTE composite film has considerable potential for application as active food packaging.

Development of Intelligent Gelatin Films Incorporated with Sappan (Caesalpinia sappan L.) Heartwood Extract.

This study aimed to develop intelligent gelatin films incorporated with sappan (Caesalpinia sappan L.) heartwood extracts (SE) and characterize their properties. The intelligent gelatin film was prepared through a casting method from gelatin (3%, w/v), glycerol (25% w/w, based on gelatin weight), and SE at various concentrations (0, 0.25, 0.50, 0.75, and 1.00%, w/v). The thickness of the developed films ranged from 43 to 63 µm. The lightness and transparency of the films decreased with the increasing concentration of SE (p < 0.05). All concentrations of gelatin films incorporated with SE exhibited great pH sensitivity, as indicated by changes in film color at different pH levels (pH 1−12). Significant decreases in tensile strength were observed at 1.00% SE film (p < 0.05). The addition of SE reduced gelatin films' solubility and water vapor permeability (p < 0.05). The chemical and physical interactions between gelatin and SE affected the absorption peaks in FTIR spectra. SE was affected by increased total phenolic content (TPC) and antioxidant activity of the gelatin film, and the 1.00% SE film showed the highest TPC (15.60 mg GAE/g db.) and antioxidant activity (DPPH: 782.71 µM Trolox/g db. and FRAP: 329.84 mM/g db.). The gelatin films combined with SE could inhibit S. aureus and E. coli, while the inhibition zone was not observed for E. coli; it only affected the film surface area. The result suggested that gelatin films incorporated with SE can be used as an intelligent film for pH indicators and prolong the shelf life of food due to their antioxidant and antimicrobial activities.

Enhancing the UV-Light Barrier, Thermal Stability, Tensile Strength, and Antimicrobial Properties of Rice Starch-Gelatin Composite Films through the Incorporation of Zinc Oxide Nanoparticles.

The effects of zinc oxide nanoparticles (ZnONPs) on the properties of rice starch−gelatin (RS−G) films were investigated. ZnONPs were synthesized by a green method utilizing Asiatic pennywort (Centella asiatica L.) extract. The ZnONPs were rod-shaped, with sizes ranging from 100−300 nm. An increase in the concentration of ZnONPs significantly (p < 0.05) increased the thickness (0.050−0.070 mm), tensile strength (3.49−4.63 MPa), water vapor permeability (5.52−7.45 × 10−11 g m/m2 s Pa), and thermal stability of the RS−G−ZnONPs nanocomposite films. On the other hand, elongation at break (92.20−37.68%) and film solubility (67.84−30.36%) were significantly lower (p < 0.05) than that of the control RS−G film (0% ZnONPs). Moreover, the addition of ZnONPs strongly affected the film appearance, color, transmission, and transparency. The ZnONPs had a profound effect on the UV-light barrier improvement of the RS−G film. The crystalline structure of the ZnONPs was observed in the fabricated nanocomposite films using X-ray diffraction analysis. Furthermore, the RS−G−ZnONPs nanocomposite films exhibited strong antimicrobial activity against all tested bacterial strains (Staphylococcus aureus TISTR 746, Bacillus cereus TISTR 687, Escherichia coli TISTR 527, Salmonella Typhimurium TISTR 1470) and antifungal activity toward Aspergillus niger. According to these findings, RS−G−ZnONPs nanocomposite film possesses a potential application as an active packaging: antimicrobial or UV protective.

Mechanical and Physicochemical Properties of Composite Biopolymer Films Based on Carboxymethyl Cellulose from Young Palmyra Palm Fruit Husk and Rice Flour.

Carboxymethyl cellulose from young Palmyra palm fruit husk (CMCy) film has low water barrier properties, which can limit its application. Thus, the combination of CMCy with other polysaccharides, such as rice flour (RF), may solve this problem. The aim of this study is to prepare the CMCy/RF composite films in different proportions (CMCy100, CMCy75/RF25, CMCy50/RF50, CMCy25/RF75, and RF100) and investigate their mechanical and physicochemical properties. The film strength (33.36−12.99 MPa) and flexibility (9.81−3.95%) of the CMCy/RF composite films decreased significantly (p < 0.05) with an increase in the RF proportion. Blending the RF with CMCy could improve the water vapor permeability (9.25−6.18 × 10−8 g m m−2 s−1 Pa−1) and film solubility (82.70−21.64%) of the CMCy/RF composite films. Furthermore, an increased lightness with a coincidental decreased yellowness of the CMCy/RF composite films was pronounced when the RF proportion increased (p < 0.05). However, the addition of RF in different proportions did not influence the film thickness and transparency. Based on SEM micrographs, all film samples had a relatively coarser surface. FTIR spectra showed that some interactions between CMCy and RF blended films had occurred. According to these findings, the CMCy50/RF50 composite film was found to be the best formulation because it has good mechanical and physicochemical properties.

Properties of fish myofibrillar protein film: effect of glycerol-sorbitol combinations.

The effects of glycerol-sorbitol combinations (G/S) at different ratios (0: 2, 0.5: 1.5, 1: 1, 1.5: 0.5, and 2: 0, w/w) on the properties of fish myofibrillar protein (FMP) films were evaluated and then compared to those of synthetic wrap film (polyvinyl chloride; PVC). The thickness of FMP films plasticized with G/S at various ratios was in the range of 0.012 to 0.013 mm and transparency values were 3.81-3.86. Significant increases in elongation at break (65.81-116.53%), oxygen permeability (12.83-36.11 cm3/m2/day), and water vapour permeability (0.27-1.43 × 10-10 g/m/s/Pa) were observed when the proportion of glycerol increased (P < 0.05). No significant difference was observed in a* and b* values, compared to the PVC film. However, tensile strength values (12.56-3.52 MPa) decreased when the proportion of glycerol increased (P < 0.05). A change in the amount of sorbitol influenced the thermal properties of FMP films. According to their properties, up to 50% of glycerol could be substituted for sorbitol in order to enhance the strength, barrier, and thermal properties of the FMP films.

Effects of plasticizers on the properties of fish myofibrillar protein film.

This study investigated the effects of various plasticizer types [glycerol (GLY), sorbitol (SOR), and polyethylene glycol (PEG)] on the properties of fish myofibrillar protein (FMP) film. FMP films plasticized with GLY showed the greatest elongation at break (116.53%). It also showed the greatest water vapor permeability (1.43 × 10-10 g m-1 s-1 Pa-1). The film plasticized with SOR exhibited the highest tensile strength (12.56 MPa) and film solubility (62.59%). PEG plasticized film showed to have yellowish colour as indicated by the high b* value and low light transmission at 280 nm. Furthermore, FMP films containing PEG and SOR possessed lower moisture content than films with GLY. FT-IR and electrophoretic properties were not affected by any types of plasticizer. The appearance of the FMP film was similar to that of the PVC film. It was concluded that plasticizers had major effects on FMP films. They not only plasticize the protein film, but also affected other major film properties.

Characterization of fish myofibrillar protein film incorporated with catechin-Kradon extract.

This study investigates the properties of films made from fish myofibrillar protein (FMP) incorporated with combinations of catechin-Kradon extract (C/K) (20%, w/w) at different ratios. The experimental films were compared to a polyvinyl chloride (PVC). The thickness and the transparency of the films were in the range of 0.014-0.015mm and 3.65-3.77, respectively. Significant decreases were observed in elongation at break (35-122%), water vapor permeability (0.54-1.26×10-10gm-1s-1Pa-1) properties, and a gradual decrease in L* value was pronounced when the proportions of catechins were increased (P<0.05). FMP films incorporated with C/K demonstrated to have very good barrier properties to UV light and also enhanced the thermal stability of the developed FMP films. All film samples had a smooth surface; however coarser surfaces were observed when the amounts of catechins were increased. Furthermore, the developed FMP films showed high antioxidant capability. However, no significant antimicrobial activity was observed in this film. It is determined that FMP films enriched with C/K can be used for food packaging, with particular potential for active packaging. However, as compared with the PVC, the FMP films need further development, especially in terms of their mechanical and water barrier properties.

Effect of protein concentrations on the properties of fish myofibrillar protein based film compared with PVC film.

The effect of protein concentrations on the properties of fish myofibrillar protein film (FMP) were investigated and compared with commercial wrap film (polyvinyl chloride; PVC). FMP (2 %, w/v) showed the highest mechanical properties [tensile strength: 4.38 MPa and elongation at break: 133.05 %], and water vapor permeability [2.81 × 10(-10) g m(-1) s(-1) Pa(-1)]. FMP contained high molecular weight cross-links, resulting in complex film network, as indicated by lower film solubility (19-22 %) and protein solubility (0.6-1.3 %). FMP showed excellent barrier properties to UV light at the wavelength of 200-280 nm. FMP had the thickness [0.007-0.032 mm], color attributes and transparency similar to PVC film [thickness: 0.010 mm]. Therefore, protein concentration majority influenced the properties of develop FMP. The protein content of 1 % (w/v) had potential to be developed the biodegradable film with comparable properties to the commercial wrap film.