Ultrasound technology as a strategy for enhancing the content and the bioaccessibility of phenolic compounds in apple and apple-based products
- Autores: María del Carmen Naranjo Martín
- Directores de la Tesis: Pedro Elez Martínez (dir. tes.), Robert C. Soliva Fortuny (codir. tes.)
- Lectura: En la Universitat de Lleida ( España ) en 2023
- Idioma: español
- Tribunal Calificador de la Tesis: Isabel Hernando Hernando (presid.), Gemma Oms-Oliu (secret.), Begoña de Ancos (voc.)
- Programa de doctorado: Programa de Doctorado en Ciencia y Tecnología Agraria y Alimentaria por la Universidad de Lleida
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
In the recent years, innovative technologies are standing out for obtaining high quality and healthy products, in order to keep up with consumer demand. In this Doctoral thesis, the application of ultrasound (US) technology is investigated as an innovative strategy to enhance the extractability and/or trigger the phenolic compounds biosynthesis in whole apples. The objective of this Doctoral Thesis was to investigate the effects of US on the content and bioaccessibility of phenolic compounds in whole apples, as well as to study the effect of thermosonication (TS) on the content and bioaccessibility of phenolic compounds in apple juice.
Firstly, the effect of US on the individual phenolic compounds, quality attributes, as well on phenol-related enzymes in whole apples was studied at different amplitudes (100 or 25 µm), treatment times (1, 3 or 15 min) and post-treatment times (0, 24, 48, 72 h). Total phenolic compounds (TPC) were increased by US treatment while quality parameters such as soluble solids, titratable acidity, colour and firmness parameters were well-preserved. US-treated apples at 25 µm for 15 min showed an enhanced extractability of TPC (18.2 %) just after treatment, mainly for hydroxycinnamic acid and flavan-3-ol families. Furthermore, TPC were also increased in US-treated apples at 25 µm for 1 min after 48 h (11.48 % TPC) and at 100 µm for 1 min after 72 h (30.6 % TPC), highlighting the late effect of US treatment. In this line, the phenylalanine ammonia lyase (PAL) activity increased in apples treated after 48 and 72 h. Afterwards, apples were subjected to in vitro digestion to evaluate the content of phenolics in both bioaccessible and non-bioaccessible fractions, as well as the phenolic bioaccessibility. The phenolic content was higher in both bioaccessible and non-bioaccessible fraction just after applying US at 100 µm in comparison with the same conditions but after a post-treatment time of 48 h. Phenolic bioaccessibility was also higher just after US treatment than after a post-treatment of 48 h, standing the post-treatment time as a key factor. The highest phenolic bioaccessibility (1.8 %) was found just after at US treatment of 100 µm for 15 min.
Secondly, the effects of TS technology (TS at 95 ºC for 2.8 min or at 90 ºC 2.53 min) and heat (95 ºC 4.5 min or at 95 ºC 0.5 min) were investigated on individual phenolic compounds in apple juices made from US-treated apples (at 100 or 25 µm for 15 min). Juices thermosonicated at 95 ºC for 2.8 min showed the highest values for TPC (237.4 ± 54.0 mg kg-1). The phenolic profile was enhanced especially for 5-caffeoylquinic acid, epicatechin and procyanidin B2. Nevertheless, juices made from US-treated apples did not show an improvement of total or individual phenolic compounds in comparison with juices equally treated but made from untreated apples. Subsequently, these juices were subjected to an in vitro digestion to examine the phenolic content in both bioaccessible and non-bioaccessible fractions of juices, as well on the phenolic bioaccessibility. In this line, both bioaccessible and non-bioaccessible TPC fractions were raised in thermosonicated and thermally-treated juices. Nevertheless, the effect of US in apples was evident due to the highest bioaccessibility (33.1 %) observed in thermally-treated juices at 95 ºC for 0.5 min and made from US-treated apples at 100 µm.
The results obtained in this Doctoral Thesis evidence the potential of the evaluated technologies to obtain apple and apple juices with enhanced phenolic bioaccessibility. Hence, these results provide an innovative approach for developing healthier apple-derived products.
