Assessment of Chitosan-Rue (Ruta graveolens L.) Essential Oil-Based Coatings on Refrigerated Cape Gooseberry (Physalis peruviana L.) Quality

Abstract

Cape gooseberry (Physalis peruviana L.) is one of the main exotic fruits in demand throughout the world market. However, this fruit has problems with physical and microbial decay causing losses up to thirty percent during post-harvest stage and market storage. As an alternative for conservation, technologies based on edible coatings of biopolymers incorporating essential oils have been developed. In this paper we studied the effect of edible coatings based on chitosan (CS) and Ruta graveolens L. essential oil (RGEO) at different concentrations applied on the surface gooseberries at 18 ± 2 °C. The emulsions exhibited a reduction in the viscosity and the particle size with the increasing in the RGEO amount (from 124.7 cP to 26.0 cP for CS + RGEO 0.5% and CS + RGEO 1.5%, respectively). A lower weight loss was obtained for fruits coated with CS + RGEO 0.5% (12.7%) as compared to the uncoated (15%), while the maturity index increased in a lower amount for CS + RGEO coated than the uncoated fruits. The mesophyll growth was delayed three days after the coating applications for CS + RGEO 1.0% and 1.5%. At day twelve of the coating process, fruits with CS + RGEO 1.5% presented only 3.1 Log UFC/g of aerobic mesophylls and 2.9 Log UFC/g of molds and yeasts, while the uncoated fruits presented 4.2 Log UFC/g of aerobic mesophylls and 4.0 Log UFC/g of molds and yeasts, demonstrating a microbial barrier of the coatings incorporating RGEO in a concentration dependent manner. The CS + RGEO coating also preserve the antioxidant property of case gooseberries after twelve days of treatment under storage according to the 2,2′-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethyl-benzothiazoline-6-sulphonic acid) (ABTS) results. It was demonstrated by the ABTS method that T5 antioxidant capacity from day one to day twelve only decreases from 55% to 44%, while in the uncoated fruits (T1) the antioxidant capacity decreased from 65% to 18%. On the other hand, using the DPPH method the reduction was from 73% to 24% for the uncoated samples and 55% to 43% for T5. From the sensorial analysis, we recommend the use of CS + RGEO 0.5% that was still accepted by the panelists after the sixth day of application. These results show the potential application of these coatings as postharvest treatment under storage and low temperature conditions during twelve days of treatment for cape gooseberry fruits.

Reduction of Postharvest Quality Loss and Microbiological Decay of Tomato “Chonto” (Solanum lycopersicum L.) Using Chitosan-E Essential Oil-Based Edible Coatings under Low-Temperature Storage

“…TA is related to the organic acid contents in tomato fruits, mainly citric acid and ascorbic acid [ 26 , 35 ]. TA decreased in all coated tomatoes during the storage at low temperatures ( Table 2 ).…”

“…The present study used chitosan of medium molecular weight, taking advantage of excellent film-forming properties, superior mechanical characteristics, improved gas barrier, lesser flavor and aroma loss, and higher humidity resistance capacity than chitosan of low molecular weight [ 35 ]. On the other hand, despite the controversy that chitosan of low molecular weight presents better antimicrobial activity due to electrostatic interactions with cell membranes of the microorganisms [ 54 ], the activity of chitosan-medium molecular weight has also shown excellent antimicrobial activity due to adsorption on the cell surface for Gram-positive bacteria and fungi [ 55 ].…”

“…Moreover, essential oil addition, such as cinnamon and clove oils to the chitosan coatings, improves the antioxidant capacity of the fruits by inducing defense mechanisms to the fruits [ 60 ]. In a previous study, the preservation of the antioxidant capacity of cape gooseberries using CS + RGEO coatings was demonstrated, which also had a positive influence on the deterioration index of the fruits [ 35 ]. The preservative effect of CS + RGEO coating might be due to a free-radical scavenging ability of the essential oil [ 35 ].…”

“…In a previous study, the preservation of the antioxidant capacity of cape gooseberries using CS + RGEO coatings was demonstrated, which also had a positive influence on the deterioration index of the fruits [ 35 ]. The preservative effect of CS + RGEO coating might be due to a free-radical scavenging ability of the essential oil [ 35 ]. Additionally, some authors reported an increased stimulated activity of defense enzymes like superoxide dismutase (SOD), catalase (CAT), and peroxide dismutase (POD) in plants by the application of essentials oils [ 75 ].…”

“…The proposed study represents an excellent option to complement the antimicrobial activity of chitosan and extend the postharvest stability of tomato “chonto” under refrigeration conditions, improving the stability of tomatoes during 12 days of storage. Based on the vigorous antifungal activity of some RGEO components, the efficiency of CS + RGEO to increase the stability of fruits has been demonstrated by our group in guavas to control Colletotrichum gloesporioides fungi growth and quality aspects [ 16 ], cape gooseberries for microbial and quality assessment, and papayas [ 35 , 36 , 37 ]. This is the first time that the application of CS + RGEO coatings is reported in Tomato var.…”