Petra Terpinc

Due to the presence of diverse phenolic classes in wild strawberry (Fragaria vesca L.) leaves, there is an ever-growing effort to find new, efficient methods for their recovery and detailed characterization. Microwave-assisted extraction (MAE) and accelerated solvent extraction (ASE) were evaluated to understand the impact of the extraction temperature, extraction time, and solvent-to-sample ratio (SSR) on the quantitative and qualitative properties of the obtained extracts. The highest total phenolic content (8027 mg GA/100 g DW), as well as the highest DPPH^• antiradical activity (903 μmol TE/g DW), was obtained with ASE at 150 °C with a static time of 5 min and an SSR of 40:1, while the highest ABTS^•+ antiradical activity (681 μmol TE/g DW) and FRAP (2389 μmol TE/g DW) were obtained with MAE after 5 min at 80 °C and an SSR of 40:1. A total of 54 different phenolics were identified by UPLC/MS-MS, some for the first time. The MAE extract had a higher content of phenolic acids (40%; esp. p-hydroxybenzoic acid, gallic acid) and myricetin, while the ASE extract was richer in proanthocyanidins (88%; esp. procyanidin B1, procyanidin trimer), flavonols (29%; esp. quercetin, quercetin-3-glucuronide, rutin), flavan-3-ols (50%; esp. epicatechin), and flavones (39%; esp. luteolin). The results indicated that for optimal extraction conditions, the target phenolics and the desired antioxidant properties of the obtained extracts should be considered.

Wild strawberry (Fragaria vesca L.) leaves possess diverse antioxidant properties, mainly due to the different classes of phenolics. In this study, microwave-assisted extraction (MAE) and accelerated solvent extraction (ASE) of wild strawberry phenolics were carried out to understand the impact of extraction temperature, extraction time and solvent-to-sample ratio (SSR) on the quantitative and qualitative properties of the obtained extracts. The highest total phenolic content (8027 mg GA/100 g DW), as well the highest DPPH• antiradical activity (903 mol TE/g DW) was obtained with ASE at 150 °C, static time 5 min and SSR of 40:1; while the highest ABTS•+ antiradical activity (681 mol TE/g DW,) and FRAP (2389 mol TE/g DW) was obtained with MAE after 5 min at 80 °C and a SSR of 40:1. The correlation analysis showed that phenolics largely contributed to the antioxidant properties of the studied MAE extracts, while correlation was not found in ASE extracts. A total of 54 different phenolics were identified by UPLC/MS-MS in MAE and ASE extracts obtained at optimal extraction conditions. MAE extract was shown to have a higher content of phenolic acids (40%), but lower content of proanthocyanidins (88%), flavonols (29%), flavan-3-ols (50%) and flavones (39%) than ASE extract.

This research aimed to study the dynamic changes in phenolic antioxidants between the germ and the rest of the germinated seed of wheat and spelt and to evaluate the whole grain flour from germinated seeds as a functional supplement. Longer germination resulted in higher TPC, DPPH, and ABTS values when considering the entire germinated seed, while the optimal germination time was not consistent when considering the germ and the remaining germinated seed separately. While in the germinated seed (without germ) the majority of TPC was determined to be bound phenolics (up to 92%), the extractable form dominated in the germ (up to 69%). The most abundant phenolic antioxidants in germinated wheat and spelt seeds, trans-ferulic acid, cis-ferulic acid, and p-coumaric acid, increased significantly with germination. Only breads with 5% germinated spelt or wheat flour were suitable for the production of a food product, showing higher extractable TPC, antioxidant activity, individual phenolic acids, and improved specific volume, and were preferred because of their appearance, aroma, and color. The PCA biplot showed that the addition of 15% and 30% germinated flours had the greatest positive impact on phenolic properties, while breads with the addition of 5% germinated flour had the greatest positive impact on specific volume and color.

In the present study, the partial substitution of common white wheat flour for a bread recipe with variously bioprocessed wholegrain spelt was investigated. The addition of 1% and pasteurised 5% “germinated + enzymatic treated” spelt flour to wheat flour significantly improved the specific volume of the bread, but their texture profile analysis and sensory evaluation were not satisfactory. A higher percentage of added bioprocessed spelt flour darkened the colour of the bread. Breads with the addition of more than 5% of bioprocessed spelt flour were unacceptable in terms of quality and sensory parameters. The highest extractable and bound individual phenolics were found in breads with 5% “germinated + fermented” spelt flour (GFB5) and 5% pasteurised “germinated + enzymatic treated” spelt flour (GEB5P). A strong positive correlation was determined between trans-ferulic acid and TPC and DPPH^• radical scavenging activity. The GEB5P bread showed the highest increase in extractable and bound trans-ferulic acid content, by 320% and 137%, respectively, compared to the control bread. Principal component analysis showed differences between the control bread and enriched breads in terms of their quality, sensory and nutritional properties. Breads with 2.5% and 5% “germinated + fermented” spelt flour had the most acceptable rheological, technological and sensory characteristics, in addition to a substantial improvement in their antioxidant content.

The aim of the study was to determine whether the partial replacement of wheat flour with bioprocessed spelt flour contributes to a higher bioaccessibility of the antioxidants in bread. The results showed that the type and amount of bioprocessed spelt flour in a bread recipe has a major impact on the extractable and bound TPC, the content of individual phenolics, their antioxidant activity, and their bioaccessibility as determined by in vitro digestion. Extractable p-coumaric and trans-ferulic acids in breads decreased after digestion, while extractable cis-ferulic and p-hydroxybenzoic acids increased. The bioaccessibility of TPC in the control bread (100% wheat flour), and in bread enriched with 5% “germinated + fermented” spelt flour (GFB5), did not differ. However, the digested GFB5 bread contained 5.2-times more extractable, and 1.3-times more bound, trans-ferulic acid than the digested control bread. trans-Ferulic acid showed the lowest bioaccessibility, up to 2.8%. In GFB2.5 and GFB5 breads, the bioaccessibility of p-coumaric, trans-ferulic, and cis-ferulic acids was higher than in other digested breads. PCA visualized the difference between the undigested and digested breads. The incorporation of germinated and fermented, or germinated and enzymatic, treated spelt flour in a white bread recipe could be an attractive way of providing consumers with nutritionally interesting foods.

The goal of this research was to evaluate the impact of different bioprocessing techniques on improved bioaccessibility of phenolics from spelt seeds. Despite the negative influence of gastrointestinal digestion, fermentation of germinated seeds significantly increased the bioaccessibility of total phenolics and their antioxidant activity compared to digested raw seeds. Enzymatic treated fermented seeds showed the highest relative bioaccessibility of p-coumaric and trans-ferulic acids, while their absolute contents were significantly higher in “germinated + fermented” seeds. Our research suggests that pretreatment of spelt seeds with hydrolytic enzymes improves access of fermenting microorganisms to structural elements, resulting in an increased content of extractable and bound trans-ferulic acid. Significantly higher biostability of phenolics was observed in raw seeds. Some major quality changes in the composition of extracts were observed under simulated in vitro digestion, since antioxidants of the same extract showed a different relative decrease in DPPH^• and ABTS^•+ scavenging activities compared to the raw seeds or their corresponding undigested counterparts. It is therefore important to increase the content of extractable antioxidants in seeds by bioprocessing, since they are strongly diminished during digestion.

A solid-phase extraction (SPE) technique was developed and optimised for isolation and concentration of extractable and bound phenolic acids from germinated spelt seeds, for analysis by liquid chromatography–mass spectrometry. Samples initially underwent solvent extraction under different conditions to maximise the yield of phenolic antioxidants. Optimal extraction conditions for extractable phenolics were absolute methanol as solvent, sample-to-methanol ratio 1:9, and reconstitution in non-acidified water. The bound phenolics were extracted from sample pellets using hydrolysis with 2 M NaOH, acidification of the hydrolysate with formic acid, and simultaneous isolation and purification using Strata X polymeric RP tubes. Compared to liquid-liquid extraction, this direct SPE protocol has significant advantages in terms of higher extraction efficiencies of total and individual phenolics and their antioxidant activities. These data suggest that direct SPE represents a rapid and reliable method for quantitative analysis of both the extractable and the commonly overlooked bound phenolics in Triticum spelta seeds.

Since they are eaten regularly, cereals based food make a significant contribution to the daily energy intake, meanwhile in whole-grain form they contribute to higher micronutrients intake that refined cereal products. The bound phenolic compounds, which are accumulated in cereal bran, play a key role in the duodenum, where they are transformed to the absorbable metabolites by microbial fermentation. In part two, an analysis of phenolic compounds is presented, with emphasis on the hydrolysis and extraction procedure for bound phenolic compounds, their quantification and identification. Due to poor bioavailability of non-extractable phenolic compounds, which critically limits the exploitation of their wide potential, the article also discusses techniques and new strategies that enable the release of phenolic compounds from insoluble bound forms during food processing. Two current approaches, germination and fermentation, are presented in more details. With transformation of bound phenolic compounds to more easily accessible free phenolic compounds, we also benefit from their antioxidant and antimicrobial efficacy in addition to a favorable anti-cancer effect on the colon. The awareness of consumers and their demand for healthier foods led to the exploration and incorporation of natural ingredients in the production of value added products. The extraction of ferulic acid from whole grain cereal products and its incorporation in functional food products is definitely an important area of future research.