UV-C and hyperoxia abiotic stresses to improve healthiness of carrots: study of combined effects

Abstract

Phenolic compounds are phytochemicals with high health-promoting properties. Carrot is a vegetable highly worldwide consumed although its phenolic content is low compared to other plant products. The aim of this work was to evaluate changes in phenolic compounds in carrots caused by abiotic stresses. The phenylalanine ammonia-lyase (PAL) activity, phenolic compounds and total antioxidant capacity (TAC) changes during storage up to 72 h at 15°C after wounding (shredding), 9 kJ UV-C m -2 pretreatment and hyperoxia (80 kPa) conditions of carrots were studied. Shredding and hyperoxia storage induced the highest phenolic compounds and TAC enhancements. Accumulation of phenolic compounds in shredded carrots could be structured in the following phases: 1st phase (\24 h): unchanged phenolic compounds levels with minimum PAL activity; 2nd phase (24-48 h): moderate phenolic increases (&600-700 mg CAE kg -1 accumulated in 24 h) concurring with the greatest increase of PAL activity; 3nd phase (48-72 h): high phenolic increases (&1600-2700 mg CAE kg -1 , accumulated in 24 h) while a moderate increment of PAL activity was registered. Although UV-C pretreatment of shreds reduced phenolic accumulation, 600 % increments were still registered in those samples stored under hyperoxia conditions for 72 h. However, the contents of chlorogenic acid at 72 h were 1.4-fold higher in irradiated shreds under hyperoxia compared to the same samples under air conditions.

Combined application of wounding stress and extrusion as an innovative tool to obtain carrot powders with modified functional properties

“…Regarding a-value (redness), non-extruded CC showed the highest value (20.60) and was significantly higher when compared with non-extruded WSC (13.76). Reduction of redness intensity in carrots due to wounding stress can be related to a white color formation during storage as a result of cell-wall constituents biosynthesis in its surface (Cisneros-Zevallos, Saltveit, & Krochta, 1995) and has been used as a quality index (whitening index-WI) in wounded carrots (Formica-Oliveira et al, 2016). This is consistent with the positive linear correlation between lightness values and the increment of insoluble lignin in WSC (Table 2) (r = 0.658; α = 0.1).…”

Effect of abiotic stresses on bioactive contents of vegetables and high-pressure technology in related functional beverages

“…These phenolic compounds accounted 69.6, 11.0, 9.8 and 9.5 % of the sum of individual phenolic compounds, respectively. Similar initial TPC of carrot has been previously reported being hydroxycinnamic acids and their derivatives the major phenolic compounds found (Alegria et al, 2016;Formica-Oliveira et al, 2016a;Jacobo-Velázquez et al, 2011). The 3-CQA content of samples was proportionally much lower than TPC, although 3-CQA was the main phenolic compound.…”

“…The 3-CQA content of samples was proportionally much lower than TPC, although 3-CQA was the main phenolic compound. Similar observation could be also deduced from similar studies with shredded carrots (Alegria et al, 2016;Formica-Oliveira et al, 2016a;Heredia and Cisneros-Zevallos, 2009;Jacobo-Velázquez et al, 2011). Latter finding can be explained since other antioxidant compounds of carrots may react with the Folin-Ciocalteu reagent overestimating the TPC.…”

“…Phenolic levels of all samples progressively increased throughout storage. Such increase of these phytochemicals is a response to the applied postharvest abiotic stresses like wounding and radiation (Avena-Bustillos et al, 2012;Cisneros-Zevallos, 2003;Formica-Oliveira et al, 2016a). This phenolic biosynthesis has been reported to be a consequence of PAL activation after such abiotic stresses, as previously discussed, being proposed ATP and reactive oxygen species as signalling molecules (Jacobo-Velázquez et al, 2011).…”

“…• UV-C: 4.0 kJ m -2 UV-C (159 s). The UV-C dose was selected based on our previous studies in order to achieve a proper microbial reduction while keeping quality and safety of the product (Formica-Oliveira et al, 2016a;Martínez-Hernández et al, 2015a).…”