Browsing by Subject "Bioactive compounds"

Now showing 1 - 2 of 2

Highlighting outstanding beetroot varieties for the food industry - Evaluation of agronomic and compositional attributes of organically grown beetroot (Beta vulgaris L. subsp. vulgaris) varieties
(2022) Yasaminshirazi, Khadijeh; Graeff-Hönninger, Simone
The constant increase in awareness of the relationship between health and diet changed consumers’ perception of food and, accordingly, their food products’ choices. In this regard, the demand for foods, which promote mental and physical health and prevent specific diseases, has increased. Due to its high amount of bioactive compounds, which permits the reformulation of conventional products and transformation of them into functional foods, beetroot (Beta vulgaris L. subsp. vulgaris) was classified as a superfood. On account of the rising demand for organic food products, there is a necessity for varieties, which are adapted to the special requirements of organic farming. Alongside growing beetroot genotypes with desirable agronomic performances and promising contents of bioactive compounds, preserving the quality of harvested beetroots for an extended time can prolong the availability and use of this crop. Hence, affordable and easy-accessible possibilities for prolonging the shelf life of beetroot are required. This thesis aimed to disclose the genetic potential of a broad assortment of new and existing open-pollinated beetroot genotypes, which perform desirably in terms of agronomic and morphological traits (Publication I), compositional characteristics (Publication II), and quality stability (Publication III) under organic farming conditions. In this respect, in total, six genotype-screening field experiments were conducted in 2017 and 2018 at three different locations. Results of the first publication depicted a significant impact of genotype on the total and marketable yields, as well as most of the assessed morphological traits, including skin smoothness, corky surface, and beet shape uniformity. With the analysis of the contents of the total dry matter, total soluble sugar, nitrate, betalains, and total phenolic compounds in the second publication, significant differences were found between 15 studied beetroot genotypes. In addition, the outcome of the third publication demonstrated a significant effect of genotype on all measured compounds of 36 examined beetroot genotypes. Furthermore, the extent of change in the compositional quality during four months of cold storage was assessed for all studied genotypes. On account of the existing genetic variability in beetroot, it was concluded that the intended final utilization should be taken into account for the selection of suitable genotypes. In addition to the conducted assessments in Publication I – III, in the overall project framework from which this thesis was derived, the sensory characteristics of selected open-pollinated genotypes were compared with the commercially used varieties. Three sensory tests were carried out at the University of Hohenheim to determine consumers’ perception of the desired beetroot taste characteristics, including sweetness, aroma intensity, bitterness, earthy flavour, and the degree of acceptability. Generally seen, the studied open-pollinated genotypes indicated more sweetness and less bitterness compared to the F1 hybrid varieties. Furthermore, this thesis assessed the impact of nitrogen fertilisation level on selected compounds (nitrate and total soluble sugar contents) of specific genotypes (Borus, Ronjana, and Regulski Okragly) at the University of Hohenheim in 2018 and 2019. The outcomes indicated no significant influence of the N fertilisation rate on the total soluble sugar content. However, the impacts of fertilisation level and interactions between year and replication on the nitrate content were significant. Consequently, with adjusted N fertilisation, the amount of nitrate in beetroot can be directed in the desired direction based on the intended product (for example, sport drinks with high nitrate levels, and baby food with low nitrate levels). Nevertheless, in the pool of the investigated genotypes in Publication III, some genotypes possessed a comparable nitrate content with the highest values reached by using additional N-fertilisation in this experiment. To conclude, with the investigation of a broad assortment of beetroot genotypes, the findings of the present thesis revealed a high genetic variability regarding yield, morphological and compositional characteristics of beetroot, which provide new possibilities for farmers, the food industry, and consumers. To ensure the competency of the studied genotypes, further studies concerning the determination of other taste-relevant compounds like geosmin and disputable compounds such as oxalic acid are highly recommended. Moreover, to extend the use of the functional properties of fresh beetroot throughout the year, besides the selection of a suitable genotype, the external factors, such as storage conditions, should be optimized as well.
Stability of bioactive compounds and antioxidant activity in rosehip juice (Rosa spp.)
(2024) Peña, Fabiola; González, Felipe; Jiménez-Aspee, Felipe; Bustamante, Luis; Ruiz, Antonieta
Rosehip fruits, characterized by their high concentrations of bioactive compounds and antioxidant activity (AA), have been traditionally used to make jams, infusions, and juices. Thus, the objective of this research was to evaluate the stability of rosehip juice by determining the concentrations of bioactive compounds and total phenols and the AA using chromatographic and spectroscopic methods. The stability of the juice was evaluated with three treatments and different storage conditions, namely, unpasteurized–refrigerated, pasteurized–room temperature, and pasteurized–refrigerated, and measurements were taken for eight months. Individual and total phenolic compounds, evaluated by chromatographic methods, reported differences until the end of this study. The total phenolic compounds by Folin–Ciocalteu method presented an average decrease of 57% in the three treatments in relation to the initial conditions. On the other hand, the ascorbic acid content decreased considerably, disappearing at week six. Furthermore, for the unpasteurized–refrigerated and pasteurized–refrigerated samples, a correlation was found between flavonols, total phenols, ascorbic acid, and antioxidant activity determined by the TEAC method. For the pasteurized–room temperature samples, correlations were found between the levels of several flavonols, hydroxycinnamic acid, total phenols, and ascorbic acid and the antioxidant activity determined by the CUPRAC method. The stability of the compounds was mainly correlated with the storage conditions of the juice and not with pasteurization. The highest stability was observed for the unpasteurized–refrigerated and pasteurized–refrigerated samples. Although the concentrations of the compounds evaluated decreased during this study, significant levels of AA persisted, providing beneficial characteristics for consumer health.