Effect of hydroxypropylmethylcellulose and chitosan coatings with and without bergamot essential oil on quality and safety of cold-stored grapes

[EN] Biodegradable coatings based on hydroxypropylmethylcellulose (HPMC) or chitosan (CH) with and without bergamot essential oil were applied to table grapes, cv. Muscatel, in order to find environmentally friendly, healthy treatments with which to better preserve fresh fruit quality and safety during postharvest cold storage. Physicochemical properties (weight loss, °Brix, total phenols, antioxidant activity, colour and texture), respiration rates and microbial counts of samples were determined throughout cold storage. The coatings had a significant effect on the development of quality variables, with the additional effect of essential oil addition as a function of the polysaccharide matrix being especially notable. Although incorporation of essential oil resulted in smaller weight losses and a greater antimicrobial effect, it also led to browner samples when using CH. Chitosan coatings containing bergamot oil were more effective than pure CH and HPMC coatings at inhibiting respiration rates. All the coatings improved the mechanical resistance of the samples at the end of storage. The most recommended coating for Muscatel table grapes is CH containing bergamot oil since, despite only contributing slightly to the sample colour, this showed the highest antimicrobial activity and the greatest control of respiration rates with a reasonably good control of water loss during storage. © 2010 Elsevier B.V.The authors acknowledge the financial support provided by Ministerio de Educacion y Ciencia (Project AGL2007-65503).Sánchez González, L.; Pastor Navarro, C.; Vargas, M.; Chiralt, A.; González Martínez, MC.; Cháfer Nácher, MT. (2011). Effect of hydroxypropylmethylcellulose and chitosan coatings with and without bergamot essential oil on quality and safety of cold-stored grapes. Postharvest Biology and Technology. 60(1):57-63. https://doi.org/10.1016/j.postharvbio.2010.11.004S576360

Application and Evaluation of a Pectin-Based Edible Coating Process for Quality Change Kinetics and Shelf-Life Extension of Lime Fruit (<i>Citrus aurantifolium</i>)

Uncertain storage conditions lead to considerable quality loss in lime fruits, which affect their consumer acceptability. Studies aimed at quantifying the kinetics of quality changes under different storage conditions are valuable for minimizing the product quality loss and improving their marketability. The objective of this study was to quantify the effect of pectin-based coating on the kinetics of quality change in stored limes fruits using a pre-established coating process. Lime fruits were immersed in the coating emulsion and then surface dried, cooled, and evaluated after storage for different times at selected temperatures (10&#8722;25 &#176;C). Quality characteristics evaluated include physical (texture and color), chemical (ascorbic acid, pH, titrable acidity, total soluble solids), and physiological (respiration rate) properties. Results revealed that with the passage of time, the fruits showed progressive increase in shriveling or wilting and loss in green color, and higher temperatures accelerated these changes. The respiration rate in control samples reached 79, 35, and 7 mL CO2/(kg&#183;h) after 7 days at 25 &#176;C and 22 days at 15 and 10 &#176;C, respectively, while those of coated samples were limited to 40, 32, and 1.06 mL CO2/(kg&#183;h) after 11, 25, and 32 days at the same storage temperatures. Control fruits suffered 6%, 10%, and 24% weight loss following 8 days of storage at 10, 15, and 20 &#176;C, respectively, while the losses in coated fruits were lower (2%, 4%, and 17%, respectively). A zero-order model was found appropriate for weight loss, along with a color a value and &#916;E, while a first-order model was found to be better for firmness, brix to acidity ratio, ascorbic acid, and b and L values (R2 &gt; 0.9). The Arrhenius model was suitable for temperature sensitivity of the rate constants

Evaluation of Freeze Drying and Electrospinning Techniques for Saffron Encapsulation and Storage Stability of Encapsulated Bioactives

Saffron extract was encapsulated into a gelatin matrix by means of electrospinning and freeze drying techniques and the degradation kinetics of bioactive compounds were evaluated during their storage at 4, 24, and 35 °C as compared to non-encapsulated control. The encapsulation efficiency, thermal properties, storage stability, morphology, and diameter distribution of the encapsulated saffron extract were evaluated as output parameters. In general, both encapsulation techniques demonstrated superior retention of bioactive compounds compared to samples without encapsulation during the entire storage period. Electrospinning and freeze drying techniques were able to retain at least 96.2 and 93.7% of crocin, respectively, after 42 days of storage at 35 °C with the 15% saffron extract. The half-life (t1/2) time parameter for the control sample (with 15% saffron extract without encapsulation) was 22 days at 4 °C temperature, while that encapsulated by electrospinning was 138 days and that obtained for freeze drying was 77 days, The half-lives were longer at lower temperatures. The encapsulation efficiency of crocin, picrocrocin, and safranal associated with the electro-spun gelatin fibers were 76.3, 86.0, and 74.2%, respectively, and in comparison, the freeze drying encapsulation efficiencies were relatively lower, at 69.0, 74.7, and 65.8%, respectively. Electro-spun gelatin fibers also had higher melting and denaturation temperatures of 78.3 °C and 108.1 °C, respectively, as compared to 65.4 °C and 93.2 °C, respectively, for freeze-dried samples. Thus, from all respects, it was concluded that electrospinning was a better and more effective technique than freeze drying in terms of preserving saffron bioactive compounds

Evaluation of Freeze Drying and Electrospinning Techniques for Saffron Encapsulation and Storage Stability of Encapsulated Bioactives

Saffron extract was encapsulated into a gelatin matrix by means of electrospinning and freeze drying techniques and the degradation kinetics of bioactive compounds were evaluated during their storage at 4, 24, and 35 &deg;C as compared to non-encapsulated control. The encapsulation efficiency, thermal properties, storage stability, morphology, and diameter distribution of the encapsulated saffron extract were evaluated as output parameters. In general, both encapsulation techniques demonstrated superior retention of bioactive compounds compared to samples without encapsulation during the entire storage period. Electrospinning and freeze drying techniques were able to retain at least 96.2 and 93.7% of crocin, respectively, after 42 days of storage at 35 &deg;C with the 15% saffron extract. The half-life (t1/2) time parameter for the control sample (with 15% saffron extract without encapsulation) was 22 days at 4 &deg;C temperature, while that encapsulated by electrospinning was 138 days and that obtained for freeze drying was 77 days, The half-lives were longer at lower temperatures. The encapsulation efficiency of crocin, picrocrocin, and safranal associated with the electro-spun gelatin fibers were 76.3, 86.0, and 74.2%, respectively, and in comparison, the freeze drying encapsulation efficiencies were relatively lower, at 69.0, 74.7, and 65.8%, respectively. Electro-spun gelatin fibers also had higher melting and denaturation temperatures of 78.3 &deg;C and 108.1 &deg;C, respectively, as compared to 65.4 &deg;C and 93.2 &deg;C, respectively, for freeze-dried samples. Thus, from all respects, it was concluded that electrospinning was a better and more effective technique than freeze drying in terms of preserving saffron bioactive compounds

Effect of moisture content on textural attributes of dried figs

Due to their soft texture consumers prefer moist figs, which has motivated fig processors to increase the production of this product. However, as water enhances the browning reaction rate, moisture content optimisation of moist figs is very important. Processed figs must have suitable texture softness with browning kept to a minimum. The purpose of this study was to examine the effect of moisture content on the textural attributes of dried figs. Hardness, compression energy, gradient, gumminess and chewiness of fig samples decreased with moisture content exponentially, whereas the trend of springiness and cohesiveness with change of moisture content was nearly constant. Moreover, in the texture profile analysis plot of rehydrated figs, the presence of negative area is an indication of adhesiveness which was zero in control dried figs. The results of the texture profile analysis tests proved the existence of a critical moisture content of about 18.4%, above which no significant effect of moisture content on textural parameters was found. The glass-rubber transition results from differential scanning calorimeter may explain the different texture profile analysis attributes of dried figs compared with rehydrated figs

Kinetic of color and texture changes in rehydrated figs

Intermediate-moisture figs obtained by rehydration of dried figs are more suitable for direct consumption. Colour and texture are the most important quality attributes, which influence the acceptability of this product. In this research the kinetic of color and texture changes in rehydrated figs were studied as a function of time and temperature (25-90 °C). All hunter colour parameters (L*, a* and b*) were used to estimate the extent of colour change during rehydration. Results indicated that among different kinetic models, a combined kinetic model provided the best fit. Moreover, texture development kinetics over all temperature ranges were satisfactorily described by means of first-order kinetic model compared with second-order, Weibull and Peleg models. Model parameters including texture softening (k) and residual constant (A) values were calculated which also confirmed the decrease in firmness of the dried figs due to the plasticization effect of water intake. The Arrhenius model described well the temperature dependence of the reaction rate constant for colour and texture parameter

Modeling rehydration behavior of dried figs

In this research, rehydration behavior of dried figs was studied at different temperatures (25, 60, 70, 80, and 90°C). The rehydration kinetic was examined using the four most frequently used empirical models, namely, Weibull, Peleg, first-order, and exponential association models. The Weibull model gave the highest coefficient of determination (R2) and the lowest values of root mean square error (RMSE), sum of squared error (SEE), and chi-square (X2) was considered the best. In all models examined, the equilibrium moisture content showed statistically significant differences as compared to the rehydration temperature. The temperature dependence of kinetic constants was described in terms of Arrhenius relationship. The average activation energy for the four models was 24.362 kJ mol-1. During the rehydration process hardness of dried figs decreased, which was further confirmed by microscopic evaluation. Scanning electron microscopy (SEM) images of rehydrated figs indicated porous structure proposing the presence of free water

Using power ultrasound for cold gelation of kappa-carrageenan in presence of sodium ions

Usually a heating stage is required to solubilize kappa carrageenan dispersions for gel formation on cooling. This work reports cold gelation of kappa carrageenan in the presence of sodium ions using power ultrasound without using any heating stage. Carrageenan gels were prepared using ultrasound in the presence or absence of NaCl and their textural properties were compared with the gels prepared with conventional heating method. Mechanical properties of the gels strongly increased with ultrasonication time up to a certain level, and further sonication reduced mechanical characteristics. Addition of Na + ions after ultrasonication was more effective in increasing textural hardness than when Na+ is present during ultrasonication. Microscopic images demonstrated that increasing ultrasonication time up to a certain level leads to coherent gel networks and further ultrasound has a negative impact on the gel network. Solubility and intrinsic viscosity results are also presented. Moreover, Maxwell model with three elements was used to analyze stress relaxation data. Industrial relevance So far, all documented reports have indicated that to induce gelation of kappa carrageenan dispersions a preheating step is required followed by cooling. In the present work, using power ultrasound a new method for cold gelation of carrageenan dispersions is introduced. Using ultrasound, food and non-food processors can use kappa carrageenan as a viscosifying and gelling agent without using heating