Multivariate Analysis Illuminates the Effects of Vacuum Drying on the Extractable and Nonextractable Polyphenols Profile of Loquat Fruit

Abstract

The current study evaluated the effects of vacuum drying on the whole polyphenol profile of loquat fruit, including extractive and nonextractive polyphenols. Absorbance analysis determined that total polyphenol content and antioxidant levels were higher in loquat fruit vacuum dried at 140 °C than in loquat fruit vacuum dried at 70 °C. The results of ultra‐HPLC–triple quadruple mass spectrum analysis showed that 15 phenolic acids and 17 flavonoids were found in dried loquat fruit. Multivariate integrative (MINT) sparse partial least square‐discriminant analysis showed that vacuum drying affects the polyphenol profile of loquat fruit. Co‐analysis of principal component analysis, partial least square‐discriminant analysis, and orthometric partial least square‐discriminant analysis revealed that vacuum drying mainly changed the content of chlorogenic acid, cryptochlorogenic acid, protocatechuic acid, phloretin, and hesperidin in loquat fruit. Chlorogenic acid (12.020 to 39.153 µg/g d.b. [dried base weight]), the main polyphenol in dried loquat fruit, was degraded to caffeic acid (0.028 to 2.365 µg/g d.b.) and protocatechuic acid (0.014 to 18.285 µg/g d.b.) during vacuum drying. Moreover, vacuum drying also induced the isomerization of chlorogenic acid into cryptochlorogenic acid (1.628 to 12.737 µg/g d.b.). These results might be used to develop dried loquat fruit with high levels of polyphenols and antioxidant activity. Practical Application Interests in polyphenols of loquat fruit had increased greatly because of their possible role in health benefits. This work provided a holistic insight in the effects of vacuum drying on polyphenols profile of loquat fruit. Current results have contributed to the development of vacuum‐drying method, which produced loquat fruit rich in polyphenols. Furthermore, it also suggested that multivariate analysis was a feasible method to reveal the important changes of polyphenols profile during food processing.

Effect of hot air drying on the polyphenol profile of Hongjv ( Citrus reticulata Blanco, CV. Hongjv) peel: A multivariate analysis

“…Moreover, the increase of some polyphenol content in the HP could be because the sample reached a high temperature at a later period in the HAD process (Chen, Yang, et al, 2011). The findings of this study concur with those of other researchers in finding that the drying process could affect non‐extractable phenolic components (Esparze‐Martínez, Miranda‐López, & Guzman‐Maldonado, 2016; Li et al, 2019; Nunes et al, 2016), particularly those which have high molecular weights than polymeric polyphenols or individual low molecular weight phenolics associated with macromolecules (Domínguez‐Rodríguez, Marina, & Plaza, 2017). It was further speculated that the bond polyphenols in HP were transformed to free polyphenol by depolymerization or dissociation when the temperature of the sample reached a high level during the later period of HAD, thereby increasing the polyphenol content.…”

“…The mobile phase was programmed as follows: 0 to 0.5 min with 20% B, 0.5 to 15 min from 20% to 90% B, 15 to 17.5 min from 90% A to 10% B, 17.5 to 18 min from 10% to 20% B, and 18 to 20 min with 20% B. UHPLC‐QqQ‐MS/MS analysis was carried out in dynamic multiple reaction monitoring (dMRM) mode and in negative ion mode (ESI ‐ ). The information regarding precursor ions and fragment ions consistent with that previously reported (Li et al, 2019).…”

“…Although the score plot of PLS‐DA is similar to that of the PCA (Figure 2a,b), the supervised analysis revealed the variables that contribute to the class separating information (Granato, Santos, Escher, Ferreira, & Maggio, 2018). Generally, the variables far away from the origin of the coordinate system in the loading plots of PLS‐DA and s‐plot of OPLS‐DA indicated that mostly responsible for the discrimination (Li et al, 2019). Accordingly, the hesperidin, quinic acid, and narirutin of HP might be mainly influenced by HAD.…”

“…The TFC was determined according to the method reported by Li et al (2019). Briefly, 10 μl of rutin standard solution or extract was mixed with 5% of NaNO 2 (10 μl).…”

“…The UHPLC‐QqQ‐MS/MS analysis of polyphenols was performed using the method previously described by our laboratory (Li et al, 2019). The polyphenol components in the extract were analyzed using an ultrahigh pressure liquid chromatography system (1290II) and triple quadruple mass spectrometry (6460‐QqQ) equipped with an electrospray ionization source (ESI) (Agilent, Santa Clara, California, USA).…”