Refine
Document Type
- Conference Proceeding (7)
- Article (3)
- Working Paper (1)
Is part of the Bibliography
- yes (11)
Keywords
- antioxidant properties (1)
- apple (1)
- biofortification (1)
- phenolic compounds (1)
- selenium (1)
Institute
- Fakultät AuL (11)
Selstar® – Entwicklung und Evaluierung eines selenreichen Apfels als funktionelles Lebensmittel
(2020)
Iod ist ein essentieller Spurennährstoff in der menschlichen Ernährung. Eine ungenügende Aufnahme kann zu einer großen Anzahl von gesundheitlichen Störungen führen. Eine Möglichkeit, um dem Mangel entgegenzuwirken, ist die Anreicherung von Nahrungsmittelpflanzen mit Iod. In Untersuchungen zur Biofortifikation wurde gezeigt, dass die Stresstoleranz der Pflanze durch eine Ioddüngung erhöht werden kann. Durch eine Düngung mit Iod konnte die Aktivität von antioxidativ wirksamen Enzymen gesteigert und der Gehalt von nicht-enzymatischen Verbindungen mit antioxidativer Wirkung erhöht werden. Eine Erhöhung der Stresstoleranz könnte sich auch positiv bei einer Infektion mit Botrytis cinerea auswirken, einem weitverbreiteten pilzlichen Schaderreger im Gartenbau.
Vor diesem Hintergrund wurden im Herbst 2016 und Winter 2017 zwei Düngeversuche mit Iod bei Kopfsalat in einem Gewächshaus an der Hochschule Osnabrück durchgeführt. Dazu erfolgte eine Substratdüngung (0,00 bis 2,50 mg I (L Substrat)-1) und eine Blattdüngung (0,00 bis 1,25 kg I ha-1) mit KI. Eine Woche nach der letzten Düngung wurden die Pflanzen mit Botrytis-Sporen inokuliert. Am Ende des Versuchszeitraumes wurde bei den Kopfsalatpflanzen die Stärke des Befalls mit Botrytis cinerea bonitiert und der Iod-Gehalt in den Pflanzen sowie im Substrat analysiert. Zusätzlich wurde in einem Inkubationsversuch über drei Wochen die Festlegung von I- und IO3- in dem eingesetzten Torf-Ton-Substrat bei einer Iod-Konzentration von 2,5 mg I (L Substrat)-1 untersucht.
Die Ergebnisse der beiden Düngeversuche lassen hinsichtlich der Wirkung von Iod gegenüber einem Botrytis-Befall kein eindeutiges Urteil zu. Im ersten Düngeversuch konnte an den Pflanzen mit steigender Iod-Konzentration eine tendenzielle Zunahme des Botrytis-Befalls nach einer Substratdüngung und eine tendenzielle Abnahme nach einer Blattdüngung beobachtet werden. Ein lediglich gering ausgeprägter Botrytis-Befall konnte insbesondere bei der höchsten Iod-Konzentration nach einer Blattdüngung von 1,25 kg I ha-1 festgestellt werden. Im zweiten Düngeversuch zeigte sich bei der Befallsstärke lediglich eine tendenzielle Abnahme mit steigender Iod-Konzentration nach einer Substratdüngung. Die Iod-Gehalte im Kopfsalat waren nach einer Blattdüngung mit Werten von bis zu 3.140 µg I (100 g FM)-1 z. T. sehr hoch. Dies führte im ersten Düngeversuch zu Toxizitätsschäden an den Pflanzen. Die Ergebnisse des Inkubationsversuches zeigen zudem eine schnelle Festlegung von Iod im verwendeten Torf-Ton-Substrat bereits innerhalb einer Woche.
Notable parts of the population in Europe suffer from allergies towards apples. To address this health problem, the analysis of the interactions of relevant allergens with other substances such as phenolic compounds is of particular importance. The aim of this study was to evaluate the correlations between the total phenolic content (TPC), polyphenol oxidase (PPO) activity, antioxidant activity (AOA), and the phenolic compound profile and the content of the allergenic protein Mal d 1 in six apple cultivars. It was found that the PPO activity and the content of individual phenolic compounds had an influence on the Mal d 1 content. With regard to the important constituents, flavan-3-ols and phenolic acids, it was found that apples with a higher content of chlorogenic acid and a low content of procyanidin trimers and/or epicatechin had a lower allergenic potential. This is probably based on the reaction of phenolic compounds (when oxidized by the endogenous PPO) with proteins, thus being able to change the conformation of the (allergenic) proteins, which further corresponds to a loss of antibody recognition. When apples were additionally biofortified with selenium, the composition of the apples, with regard to TPC, phenolic profile, AOA, and PPO, was significantly affected. Consequently, this innovative agronomic practice seems to be promising for reducing the allergenic potential of apples.
As allergy towards apples is widespread, the evaluation of various cultivation and postharvest influences on the allergenic potential is of great importance. Therefore, the analysis of the Mal d 1 content was the focus of this study, originally dealing with investigating the influence of a selenium biofortification on apple quality. The Mal d 1 content of apples was in most cases reduced when the fruits were biofortified with selenium. Apple variety and climatic conditions were identified as further influencing factors for the Mal d 1 content of the fruits. The separate analysis of the peel and the fruit flesh showed that the content of Mal d 1 in the fruit flesh was significantly lower in the biofortified samples than in the controls. In conclusion, the results indicate that the selenium biofortification of apples and biochemical mechanism behind can reduce the allergenic potential regarding the content of Mal d 1.
Iodine (I) as an essential trace element for humans is not adequately ingested in many regions of the world. For instance, in Germany about 30% of the population still does not reach the estimated iodine requirement. Obviously, current prophylaxis measures common in this country, e.g. the use of iodized salt in households and the iodine supplementation in livestock feeding, are not sufficient to completely eliminate dietary iodine deficiency. Crop plants do not need iodine for their growth. However, they are, in principle, able to absorb iodine through their roots and leaves when it is exogenously applied. Previous studies indicate that leafy vegetables are a suitable target for iodine biofortification programs. In this study we investigated the influence of different iodine fertilization approaches on iodine content, marketable quality and yield of culinary herbs.
Four different herb species, basil, chives, oregano and parsley, were cultivated in the greenhouse and grown in 13 cm plastic pots containing a peat-based growing medium. Iodine was supplied 1 - 3 weeks before harvest by a single treatment, either as a substrate drench or by using a foliar spray. Potassium iodide and potassium iodate were applied at rates between 0.1 and to 1.0 kg I/ha. To improve foliage wetting, spray solutions contained 0.02% (v/v) of the nonionic organosilicone adjuvant Break-Thru® S 240. The experiments were arranged as a randomized block design with 4 replications. At harvest the herb shoots were thoroughly flushed with tap water and excess water was removed. Afterwards the samples were dried at 60°C until weight constancy had been achieved and then finely ground at 500 µm. The iodine content was determined with a flow injection analysis system using a catalytic spectrophotometry method based on the Sandell-Kolthoff reaction.
Neither marketable quality nor herb yield was affected by any of the iodine treatments investigated in this study. The iodine content in the shoot matter increased with rising iodine supply. Foliar sprays resulted in a higher accumulation of iodine in the edible plants parts than substrate drenches. When iodine was supplied via the roots, iodide was revealed to be more efficient than iodate. In contrast, aerially fertilized iodate was absorbed at a higher rate than iodide. In the case of both tested fertilization techniques it was possible to increase the iodine content of the herbs to above 45 µg I/100 g FM. Under these preconditions the produce may be declared as “rich in iodine” according to regulation (EC) No. 1924/2006 and advertised with different health-related statements according to regulation (EU) No. 432/2012. The targeted iodine concentration level in the herbs of 100 – 200 µg I/100 g FM was obtained with a iodide substrate drench of 0.2 kg I/ha or a foliar spray of iodide and iodate at a similar or even lower iodine application rate.