Dry carrots and parsnip slices can be used as food ingredients for further food preparations but also as healthy snacks, thanks to their health benefits. Pulsed electric field (PEF) resulted to be an effective pretreatment for carrots and parsnips before undergoing convective drying, because it reduced the drying time (up to 28% in parsnip and 21% in carrot slices) and, particularly at mild temperatures (50 to 60 °C), it did not affect the texture properties of both carrot and parsnip. PEF pretreatment of these roots before convective heating can be surely suggested as industrial application.
This research paper investigates the use of 5-hydroxymethylfurfural (5-HMF) as marker for the heat treatment of spreadable dairy creams (dulce de leche, DL). The proposed method applies solid-phase extraction (SPE) with final analysis by liquid chromatography coupled with high-resolution mass spectrometry (SPE-LC–MS). The method was successfully applied to analyze spreadable dairy creams prepared by hot melt extrusion using different heating temperatures from 100 to 130 °C. The concentrations of 5-HMF correlated linearly with the applied temperatures, with a signal response in the range from 0.5 to 100 μM (R2 = 0.9997). The limit of detection (LOD) was 1.54 ± 0.03 µM with a precision of 1.77%. The results were compared with the analysis of 5-HMF in spreadable dairy creams using reference methods for the determination of 5-HMF in milk products. These methods mainly employed acid digestion and derivatization as pre-processing steps and determined 5-HMF spectrophotometrically and via HPLC–UV. These resulted in higher LOD (2.99 and 2.01 μΜ) and less precision (4.44 and 2.09%) compared to the proposed method. Furthermore, the proposed pre-processing procedure was faster by omitting the acid digestion and derivatization steps and by employing SPE.
A solid‐state adaptation of the crocin bleaching assay was developed by a hot melt extrusion apparatus. Hot melt extrusion was used to prepare pellets from starch, saffron, a radical initiator (AAPH), and different concentrations of antioxidants or plant extracts. The color changes of the extruded pellets provided the antioxidant capacity of the samples by adapting a competition kinetic equation. Without radical initiators, the pellets extruded were reddish, while those with AAPH but without antioxidants were yellow. Instead, when antioxidants were present, the resulting color intensity of the pellets varied proportionally to the antioxidant concentration and type. The relative rate constant (kAH/kCrocin), indicative of antioxidant capacity, appeared to be much higher for Trolox (0.462) and ascorbate (0.276) than for olive leaf (0.019) and clove (0.023) extracts, while the latter showed higher antioxidant activity in a classical liquid assay (ORAC), highlighting the lack of correlation (R2 = 0.448) between the results from the classical ORAC assay and those of the proposed assay, likely because of the harsher processing conditions and stronger matrix interactions.
Practical applications
This study proposes a novel methodological approach to test the antioxidant activity of natural extracts in complex food formulations under harsh process conditions, like those found in hot melt extrusion. The effect of extrusion process on the remaining antioxidant activity can be tested from pellets made of starch, crocin, a radical initiator, and antioxidants. The color changes of the resulting pellets provide a practical, objective, and direct evidence of the antioxidant activity of the extracts to preserve the crocin substrate loss.
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