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High hydrostatic pressure (HHP) processing has been proposed as an innovative tool to induce the secondary metabolism of fresh produce, inducing the accumulation of health-promoting compounds. In the present study, the effect of HHP applied to whole carrots only for the time needed to reach 60 or 100 MPa (come-up time, CUT) on the content of free and bound phenolics immediately after processing and during storage (3 d at 15°C) was evaluated. In addition, variables such as the phenylalanine ammonia-lyase (PAL) activity as well as the respiration rate and volatile organic compounds (VOCs) production (related with ethylene) were determined during storage. As an immediate response to HHP, samples treated at 100 MPa showed increases in the content of free [5-O-caffeoylquinic acid (63.9%) and 3,4-di-O-feruloylquinic acid (228.6%)] and bound [p-coumaric acid (82.6%)] phenolics. Furthermore at 1 day, samples treated at 60 MPa showed accumulation of free phenolics [4,5-di-O-caffeoylquinic acid (60.2%), and isocoumarin (98.9%)], whereas samples treated at 100 MPa showed increases of 5-O-caffeoylquinic acid (291.2%) and 3,4-di-O-feruloylquinic acid (466.1%). At 2 days of storage, whole carrots treated at 60 MPa showed accumulation of bound phenolics [rutin (85.5%) and p-coumaric acid (214.7%)], whereas at 3 days 100 MPa samples showed higher quercetin (371.2%). During storage, samples treated at 60 and 100 MPa showed higher respiration rate, and ethylene production, respectively. The main physiological changes induced by HHP in carrots are summarized in a physiological model. HHP-treated carrots could be used as fresh food or as raw material to produce functional food and beverages.

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Wounding stress (by shredding) was applied to carrots prior to dehydration and milling to obtain a carrot powder with higher fiber and phenolic compounds as compared with control carrot powder (CCP). FCP showed higher water and oil absorption capacity than CCP. FCP addition to sausage formulations at 4% didn't affect purge loss, and resulted in sausages with higher phenolic compounds and dietary fiber. Furthermore, FCP formulations presented adequate sensory acceptability and its carotenoid and phenolic content remained stable during storage. FCP could be used as an ingredient in sausage formulation to increase the content of nutraceuticals without affecting its shelf-life.

The present study evaluated the effects of ultraviolet B (UVB) radiation and wounding stress, applied alone or combined, on the biosynthesis of phenolic compounds and ascorbic acid in the peel and pulp of red prickly pear (Opuntia ficus-indica cv. Rojo Vigor). Whole and wounded-fruit samples were treated with UVB radiation (6.4 W·m−2) for 0 and 15 min, and stored for 24 h at 16 °C. Phytochemical analyses were performed separately in the peel and pulp. The highest phenolic accumulation occurred after storage of the whole tissue treated with UVB, where the main phenolic compounds accumulated in the peel and pulp were quercetin, sinapic acid, kaempferol, rosmarinic acid, and sinapoyl malate, showing increases of 709.8%, 570.2%, 442.8%, 439.9%, and 186.2%, respectively, as compared with the control before storage. Phenylalanine ammonia-lyase (PAL) activity was increased after storage of the whole and wounded tissue treated with UVB light, and this increase in PAL activity was associated to phenolic accumulation. On the other hand, l-galactono-γ-lactone dehydrogenase (GalLDH) activity and ascorbic acid biosynthesis was enhanced due to UVB radiation, and the effect was increased when UVB was applied in the wounded tissue showing 125.1% and 94.1% higher vitamin C content after storage when compared with the control. Respiration rate was increased due to wounding stress, whereas ethylene production was increased by wounding and UVB radiation in prickly pears. Results allowed the generation of a physiological model explaining the UVB and wound-induced accumulation of phenolic compounds and ascorbic acid in prickly pears, where wounding facilitates UVB to access the underlying tissue and enhances an apparent synergistic response.