Víctor Manuel Ocaño-Higuera

Functionalization of chitosan by a free radical reaction: Characterization, antioxidant and antibacterial potential

Chitosan was functionalized with epigallocatechin gallate (EGCG) by a free radical-induced grafting procedure, which was carried out by a redox pair (ascorbic acid/hydrogen peroxide) as the radical initiator. The successful preparation of EGCG grafted-chitosan was verified by spectroscopic (UV, FTIR and XPS) and thermal (DSC and TGA) analyses. The degree of grafting of phenolic compounds onto the chitosan was determined by the Folin-Ciocalteu procedure. Additionally, the biological activities (antioxidant and antibacterial) of pure EGCG, blank chitosan and EGCG grafted-chitosan were evaluated. The spectroscopic and thermal results indicate chitosan functionalization with EGCG; the EGCG content was 25.8mg/g of EGCG grafted-chitosan. The antibacterial activity of the EGCG grafted-chitosan was increased compared to pure EGCG or blank chitosan against S. aureus and Pseudomonas sp. (p<0.05). Additionally, EGCG grafted-chitosan showed higher antioxidant activity than blank chitosan. These results indicate that EGCG grafted-chitosan might be useful in active food packaging.

Physicochemical and Antioxidant Properties of Chitosan Films Incorporated with Cinnamon Oil

Chitosan films (CF) with cinnamon bark oil (CO) incorporated at 0% (control), 0.25%, 0.5%, and 1.0% v/v were prepared by an emulsion method. The films were characterized based on their physical properties (solubility, water vapor permeability, optical property, and microstructure) and antioxidant properties (DPPH, ABTS, and its protective effects on human erythrocytes). The results showed that the incorporation of 0.5 and 1.0% of CO into the CF significantly decreased its solubility to 22% of the control (). The water vapor permeability of the CF-CO was significantly reduced to 40% with low concentrations of CO (0.25%) incorporated into the CF. In general, the films presented a yellow coloration and an increase in transparency with the incorporation of CO into the CF. It was also observed that the incorporation of CO increased the antioxidant activity between 6.0-fold and 14.5-fold compared to the control, and the protective capacity against erythrocyte hemolysis increased by as much as 80%.

Producción y evaluación funcional de un concentrado proteico de calamar gigante (Dosidicus gigas) obtenido mediante disolución alcalina Production and functional evaluation of a protein concentrate from giant squid (Dosidicus gigas) obtained by alkaline dissolution

A protein concentrate from jumbo squid (Dosidicus gigas) was produced under alkaline conditions. Solubility, recovery of proteins, electrophoretic profile, as well as changes in the pattern of solubility of proteins recovered were determined. In the gels, its capability (functional–technological) was evaluated in terms of texture profile analysis, folding test, water holding capacity, and color attributes. The alkaline treatment promoted the autolysis of myosin heavy chain; however, the alkaline concentrate showed better gel formation ability compared with the mantle, resulting in gel strength of 11.83 ± 0.66 and 21.53 ± 2.95 N · cm at 75% and 90% compression, respectively. Nevertheless, the gels prepared from protein concentrate showed a low water holding capacity (38.1 ± 0.1%), while the folding test showed gels grade C-A and C-B for protein concentrate and mantle, respectively. Se elaboró un concentrado proteico a partir de calamar gigante (Dosidicus gigas) bajo condiciones alcalinas. Se monitoreó la solubilidad, recuperación de proteínas, el perfil electroforético, así como cambios en el patrón de solubilidad de las proteínas recuperadas. En los geles se evaluó su capacidad funcional-tecnológica en términos de su análisis del perfil de textura, prueba de doblado, capacidad de retención de agua y los atributos de color. El tratamiento alcalino promovió la autolisis de la cadena pesada de miosina; sin embargo el concentrado alcalino mostró una mejor capacidad de formación de geles en comparación con el manto, obteniéndose fuerzas de gel de 11,83 ± 0,66 y 21,53 ± 2,95 N · cm en compresiones al 75% y 90%, respectivamente. No obstante los geles elaborados a partir del concentrado proteico mostraron una pobre capacidad de retención de agua (38,1 ± 0,1%), mientras que la prueba de doblado mostró geles grado C-A y C-B para concentrado proteico y manto, respectivamente.

Effect of ionic strength on soluble protein removal from giant squid mantle (Dosidicus gigas) and functional evaluation of protein recovery

Myofibrillar protein are the principally responsible of gelling properties in fishery resource, hence, during protein concentrate or isolated proteins preparation, sarcoplasmic protein are discarded; however, myofibrillar protein can support low levels of sarcoplasmic proteins without affecting the gelling property. Therefore, the aim of this study was to gradually remove sarcoplasmic proteins from giant squid mantle by means of different ionic strengths (I). Solutions of NaCl with different ionic strengths (I=0.0, 0.1, and 0.3) were used to obtain 3 protein concentrates. The electrophoretic profile in SDS-PAGE showed differences in protein removal with a high solubility of mantle proteins. The texture profile analysis showed that hardness increased in mantle protein washed with higher I. The total reactive sulfhydryls showed significant changes (p<0.05) detecting major formation of S-S bonds with protein removal at an I of 0.3. Differential scanning calorimetry showed a minor denaturation temperature of the actomyosin complex when protein removal was performed with an I of 0.3. The present study indicates that removal of sarcoplasmic protein as a function of I results in better quality gels.

Chemical and Functional Characterization of Sarcoplasmic Proteins from Giant Squid (Dosidicus gigas) Mantle

Modification of pH and NaCl concentration changed the physicochemical properties of sarcoplasmic proteins (SP) from jumbo squid mantle and consequently their functional properties. Better results of emulsifying activity index (EAI) and foam capacity (FC) were exhibited at pH 11 in NaCl absence due to higher solubility. But better emulsifying stability index (ESI) was obtained at pH 11 in 0.5 M NaCl, while, foaming stability (FS) was better at pH near to isoelectric point (pI). These results suggest that SP from jumbo squid may be a promising ingredient, whose functional properties can be manipulated by changing pH and NaCl concentration.

Biochemical, Physical, Chemical, and Microbiological Assessment of Blue Shrimp (Litopenaeus stylirostris) Stored in Ice

Postmortem changes in blue shrimp (Litopenaeus stylirostris) muscle were studied on the basis of biochemical, chemical, physical, and microbiological changes during an 18 day storage period at 0°C. Adenosine 5′-triphosphate (ATP) content, breakdown products, K-value, pH, trimethylamine nitrogen (TMA-N), total volatile basic nitrogen (TVB-N), water holding capacity (WHC), color, and texture (shear force) changes were examined. Also, total mesophilic and psychrophilic bacterial counts were measured. K-value increased linearly (r2 = 0.98) from an initial value of 1.37 ± 0.59 to 59.42 ± 6.05% at Day 18. Spoilage indicators TVB-N and TMA-N increased from 29.56 ± 1.33 and 0.69 ± 0.25 to 39.04 and 2.04 ± 0.59 mg of N/100 g at Day 18, respectively; meanwhile, the total viable counts of mesophilic and psychrophilic bacteria increased from 3.48 ± 0.44 and 2.61 ± 0.29 log CFU/g to 6.27 ± 0.21 and 7.14 ± 0.39 log CFU/g, respectively, which indicated spoilage at the end of the storage period. The pH, texture, WHC, and color were affected (p < 0.05) during the storage period. Overall, results indicate that blue shrimp muscle quality was maintained for 12 days of storage in ice.

Effects of pH and Sodium Chloride on the Gelling Properties of a Protein Concentrate Obtained from Jumbo Squid Mantle (Dosidicus Gigas)

Jumbo squid (Dosidicus gigas) is an underutilized fishery resource in the Gulf of California. Jumbo squid muscle could potentially be utilized to manufacture protein concentrates to be used as a base for surimi or as a food ingredient. However, the main problem is the low gelling ability of these protein concentrates compared those of with fish species. Consequently, the present study evaluated the effects of pH and the NaCl concentration on the gelling properties of protein concentrates from squid mantle. According to texture profile analysis, improved gelling properties were obtained at pH 6.0 and 1% of NaCl. During the sol-gel transition, decreased surface hydrophobicity that corresponded to an increased intensity of α-helix structures was detected. Moreover, the total sulfhydryl content decreased during gel formation. Viscoelasticity and water holding capacity analyses showed the formation of a more structured gel at pH 7.0. The higher enthalpy and denaturation temperature detected by differential scanning calorimetry at pH 7.0 and 1% NaCl showed that both variables (pH and NaCl concentration) affected the protein structure and conformation. The results demonstrated that varying pHs and NaCl concentrations improved the gelling properties of protein concentrates from squid.

Effect of chitosan-carvacrol edible coatings on the quality and shelf life of tilapia (Oreochromis niloticus) fillets stored in ice

Fish consumption has increased in recent years. However, fish meat is highly perishable, which demonstrates the need for technologies to preserve its quality. Edible coatings (EC) might provide an alternative to extend the shelf life of fish. The goal of this study was to evaluate the effect of EC of chitosan (C) in combination with carvacrol (CAR) on the physical and microbiological changes of tilapia fillets. Fillets were submerged for two minutes in different treatments (T1: control; T2: C 2%; T3: C 2% + 0.125% CAR; T 4: C 2% + 0.25% CAR). At the end of storage, T1 and T2 showed the lowest values of total volatile bases (TVB). The color parameters L*, a* and b* varied from each treatment. The texture decreased and the different treatments reduced the microbial population in relation to the control; T3 and T4 were the most effective. These results show that the use of C with CAR might be an alternative method to preserve the quality and safety of tilapia fillets.

Preparation and characterization of films made of poly(l-lactic acid)/poly(l-lactic acid) grafted maleic anhydride/epigallocatechin gallate blends for antibacterial food packaging

The antimicrobial activity of films made of poly(l-lactic acid)/poly(l-lactic acid) grafted maleic anhydride(copolymer)/epigallocatechin gallate(EGCG) blend was determined. The effect of epigallocatechin gallate incorporation (0.03, 0.5, 5, and 10 wt%) as a natural antibacterial was determined by direct contact, solid and liquid culture media. The film antimicrobial activity was evaluated against two bacteria (gram-negative: Pseudomonas spp.; gram-positive: Staphylococcus aureus). The copolymer was prepared and characterized by Fourier transform infrared analysis and Molau test. Furthermore, the degree of grafting was determined. The epigallocatechin gallate migration profile through the films were determined and the minimum epigallocatechin gallate concentration in films required to show antibacterial activity was evaluated. The results showed that only the films with 10 wt% epigallocatechin gallate significantly affected (p < 0.05) the cell morphology and inhibited the growth of S. aureus (56% with copolymer and 55% inhibition without copolymer) and Pseudomonas spp. (28% inhibition, with and without copolymer). Incorporating copolymer inhibited the growth of Pseudomonas spp. and induced morphological changes in S. aureus. The diffusion coefficient was dependent on the presence of copolymer, which increased the epigallocatechin gallate release rate. Incorporating epigallocatechin gallate and copolymer modified the film properties. Fourier transform infrared analysis indicated hydrogen bonds which were attributed to the interaction between copolymer and epigallocatechin gallate. The results demonstrate the potential application of poly(l-lactic acid) (biodegradable polymer) and copolymers in active packaging, as well as the importance of incorporating epigallocatechin gallate as a natural antibacterial agent.

Thermal gelation of myofibrillar proteins from aquatic organisms

ABSTRACT Gelling ability is attributed to myosin, which is the main myofibrillar protein. Therefore, its integrity is very important. However, a gel with good textural characteristics and stability depends on the inherent characteristics of its proteins, as well as on external factors (primarily temperature, pH, protein concentration and added salt). The best gels from aquatic organism proteins are obtained at a pH value of approximately 7.0. However, the concentration of salt is often variable. In contrast, when proteins are recovered using acid/alkaline dissolution, gels with good textural characteristics are obtained without salt. Hydrophobic interactions, disulfide bonds, hydrogen bonds, and electrostatic interactions are the main interactions that stabilize the protein gel. Thus, this review focuses on the study of the main factors involved in protein gelation, as well as on the extraction method effect on the gelling capacity of proteins from aquatic organisms.