Browsing by Subject "Food quality"

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    Agronomic strategies to reduce potential precursors of acrylamide formation in cereals
    (2020) Stockmann, Falko; Graeff-Hönninger, Simone
    Food safety is of great importance as harmful substances formed during food processing can negatively affect human health. When the carcinogenic food ingredient acrylamide (AA) accidentally appeared in 2002, it was not expected that AA would take this much attention during the next years. Yet, after around 15 years of research, AA has finally been recognized as being harmful. In a first step, research focussed on food processing implications on AA formation. The impact of heat treatment, time of heating, baking agents, fermentation time, additives and enzymes were reported in several studies. Nevertheless, since 2011 food AA levels seem to stagnate or even increase in some years. Thus, the food industry did not show sufficient progress in reducing AA. Reducing sugars and amino acid free asparagine (Asn) are the main AA precursors. They can fluctuate in their content for instance in grain flour or potatoes shifting the focus of AA origin to the raw material. Thus, the production of raw material low in AA precursors seems important. However, lowering precursors of AA in the raw material necessitates suitable agronomic strategies to grow cereal species and cultivars low, especially in free Asn. Hence, the major goal of this thesis was to investigate the following questions concerning their impact on free Asn formation in cereals: 1. Which role does the management system plays, as organic vs. conventional farming systems highly differ in their cropping strategies? 2. What is the best nitrogen fertilization strategy when comparing organic vs. conventionally cropping systems? 3. Is there an impact of sulphur fertilization concerning sulphur amount and sulphur type? 4. Can expanding row distance and lowering seed density in low-input farming systems positively influence baking quality while keeping free Asn amounts low? 5. For organically grown cereals no level of free Asn was available. Thus, the question came up to which extent organically grown cereal species and cultivars including ancient grains like einkorn and emmer differ in free Asn. 6. Should free Asn be implemented in breeding programs if heritability is high? 7. Is there an impact of harvest timing on free Asn formation? Out of several field trials the following results were obtained: • The cropping system had a significant impact on grain yield, the level of free Asn and quality traits. Across all species, free Asn contents in flour were 26% lower under organic conditions compared to conventional farming. For wheat a maximum reduction of 50% in free Asn content was possible if organically produced. Spelt and rye were affected to a minor extend as only in single years organically grown cultivars showed up to 33% lower Asn contents. • Nitrogen (N) fertilization significantly influenced grain yield and baking quality in both cropping systems. In contrast, up to a certain amount of N free Asn was only affected to a minor extend. In particular, within the organic farming samples no significantly higher free Asn amounts were determined even if N fertilizer was raised or the N form was changed. A late N fertilization within the conventional cropping system increased crude protein content, while no clear effect was found on free Asn. Also, cultivars affected free Asn level significantly. Wheat cultivar Capo exhibited the lowest AA formation potential at a N supply of 180 kg N ha−1 while simultaneously reaching a crude protein content > 15% (conventional) and > 12% (organic). Thus, lowering free Asn by adjusting N treatments should not necessarily affect baking quality. In general, free Asn amounts in wheat varied widely both within cultivars and between cropping systems. Besides N, neither type nor amount of sulphur fertilization influenced free Asn significantly. • Extending row distance can increase quality traits protein and sedimentation value. Seed density was highly related to grain yield and test weight. Most importantly, free Asn was only minor affected by both treatments. Thus, larger row distances can be recommended to raise baking quality in organic farming systems without simultaneously affecting free Asn. Number of grains spike-1 seems to be related to free Asn (R2=0.72). This provides new insights on Asn synthesis during grain development and offers the opportunity to predict free Asn formation without expensive chemical analyzes. In contrast Asn and protein content did not show any relation while high protein contents in grain seem to lower AA amount in heated flour samples. • The impact of organically grown cereal species and cultivars in combination with marginal N supply on free Asn was clearly shown. A reduction potential of 85% was reached if rye was replaced by spelt. Surprisingly, the ancient species einkorn and emmer reached a very high free Asn content similar to rye. Heritability was high for wheat and spelt concerning locations, while regarding years, heritability was low for wheat but high for spelt and rye. For organically grown cereals, the relation between free Asn and AA formation was proven. Across species and years free Asn can serve as an indicator for AA formation (R2 of 0.69). • Harvest timing affects free Asn levels. In this context a delayed harvest can increase Asn significantly while shifting harvest 1-2 weeks earlier decreased Asn by up to 60% depending on cereal species and cropping system. After summarizing and stating the most promising steps in the frame of agronomic strategies to lower free Asn, a prediction tool for free Asn should be implemented that classifies the impact of agronomic strategies and leads to recommendations to farmers. Finally, the main riddle, that should be solved during the next studies is the question, why cereal species and cultivars differ in their Asn formation. This thesis gives some preliminary ideas but a much deeper insight is essential to establish long-term strategies to lower free Asn content.
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    Feldstudie zur Eignung der Biophotonenmessung für die Differenzierung von ökologisch und konventionell erzeugten Hühnereiern
    (2009) Egerer, Ulrike; Grashorn, Michael
    Consumer demand for organic food is increasing. Conventional quality criteria are based on assay of individual chemical compounds, which depend much more on local conditions, climate and breed than on the production method. So alternatives need to be found to distinguish between organic and conventional food. Complementary approaches look at biological systems as a whole and focus on the inner structure of products. As shown in many studies, holistic criterions reflect differences in food quality, which are caused by the production method. F.A. POPP has rediscovered ultra weak light emissions that are presumed to originate from electromagnetic fields in living organisms. So-called 'biophotons' can be detected by highly sensitive photomultipliers as 'delayed luminescence' after illumination of the sample. Associated with living processes, the radiation reflects the state of the living tissue. In 2001 B. KÖHLER showed that egg yolks emit varying biophoton intensities depending on the husbandry system. Using standardized test conditions KÖHLER found that exposition to sunlight or to lighting that was similar to daylight, as well as feeding of green stuff, enhanced biophoton emission of yolks. The present investigation has been carried out under conditions of commercial egg production to discover whether biophoton emission is a suitable quality criterion for organic eggs. From July 2005 to November 2006, about 900 eggs have been collected in food stores and on farms. The biophoton intensity of each egg was determined and entered into a database according to its way of production (cage, deep litter, free-range, organic or from smallholders). The aim of this examination was to determine the differences in light emission of eggs originating from various production systems without standardized husbandry conditions. As a second project, a long-term observation has been conducted to see whether biophoton values of eggs remain stable over time. During the course of one year (from May 2006), biophoton emission has been measured each month. Samples have been taken from twelve hen houses with different husbandry systems: 2 houses with cage system, 4 with deep litter, 2 houses with free-range system and 4 organic farms ? adding up to more than 2,300 eggs. In addition to the measurement of biophoton emissions, conventional egg quality criteria have also been determined: egg mass, breaking strength of egg shell, albumen height, yolk color, proportion of yolk, fatty acid profile and lipid oxidation. Farmers have been interviewed about the age of their hens, flock size, lighting conditions and feed composition. Climatic conditions have been researched on the internet. It was expected that comparison of all collected data would give information on the origin and meaning of biophoton emission of egg yolks. In the present studies yolks were exposed to white light for 30 seconds. Delayed luminescence was detected for the duration of 60 seconds. The biophoton parameter used has been defined as the sum of light emission during the last 40 seconds of the measurement. Egg yolks from different animal husbandry systems differed in biophoton emissions. However, while conventionally produced egg yolks showed only minor differences, organic eggs as well as eggs from smallholders were characterized by clearly higher intensities. The long-term observation of yolks from 12 selected hen houses revealed great fluctuation of biophoton emissions over the course of the year. Nevertheless, it was remarkable that yolk samples with low contents of saturated fatty acids and high contents of polyunsaturated fatty acids showed the highest biophoton intensities. These samples originated from farms that offer both a green free range and feed including vegetables or dried grass. As KÖHLER had shown, feeding green stuff leads to higher light emissions of yolks and also influences the profile of fatty acids. Further examinations will be necessary to clarify the causality between fatty acid composition of the yolk and its biophoton emission. Another target of the described projects was to test the suitability of biophoton measurement for verifying the organic origin of eggs. In discriminant analyses egg samples of both studies were assigned to the categories 'organic' or 'conventional' according to their emission values. The hit ratio was about 70 %. This result is interesting considering the lack of techniques to distinguish between organically and conventionally produced eggs up to now. Optimization of measuring technique and procedure may improve the capability of the method. In any case, biophoton measurement could be used as a screening method. Detection of extremely low values would suggest a check of management conditions at the relevant farm, followed by comparison with standards for the respective animal husbandry system.
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    The food system transformation in Vietnam : challanges for the horticultural sector posed by exports and changing consumer preferences
    (2008) Mergenthaler, Marcus; Qaim, Matin
    On the background of the food system transformation in developing countries, this cumulative dissertation answers the following research question in three articles: What are the determinants and implications of the food system transformation in the horticultural sector in Vietnam? The first article is entitled ?Quality Assurance Programs and International Market Access: Empirical Evidence from the Vietnamese Horticultural Industry?. It is based on a sample of 50 registered fruit and vegetable processing firms from allover Vietnam. With these firm survey data it is analyzed how private quality assurance programs (QAPs) in Vietnam?s horticultural sector influence the access to international markets. Results of different logistic regression models show that QAPs are critical determinants of international market access. However, the effect is market specific and depends on the type of program implemented. While international QAPs ? like HACCP, GLOBALGAP, or ISO 9000 ? notably improve access to countries of the Organization for Economic Co-operation and Development (OECD), national QAPs seem to be sufficient for exports to non-OECD countries. Domestic market sales decrease the probability of being an OECD exporter and increase the probability of being a non-OECD exporter, suggesting a certain market segmentation between high-value exports on the one hand, and domestic sales and lower-value exports on the other. Although it is argued that the food system transformation is to a large extent demand driven, most of the studies available concentrate primarily on supply side aspects. For this reason, the second article entitled ?Changing Consumer Buying Habits in Developing Countries: A Disaggregate Demand Analysis for Fruits and Vegetables in Vietnam? analyzes changing purchasing and consumption habits for fresh fruits and vegetables. The analysis is based on data from a comprehensive survey of almost 500 households in Vietnam?s two major cities, Hanoi and Ho Chi Minh City. Demand parameters are estimated with an almost ideal demand system (AIDS), disaggregating by product and process attributes that characterize modern, high-value supply chains, i.e. (i) place of purchase, particularly considering modern retailers, (ii) food safety indications, with an emphasis on formal labels, and (iii) region of production, with a focus on imports. Estimation results demonstrate that consumers? purchase decisions to buy fresh fruits and vegetables from emerging modern supply chains are heavily driven by household income (expenditures). Income elasticities range between 1.2 and 2.6. Own-price elasticities were found to be between -1.5 and -1.1 and the elasticities regarding distance to the nearest supermarket are between -0.6 and -0.3. Against the background of Vietnam?s current rapid economic development ? with incomes growing fast and supermarkets reaching higher penetration rates ? high-value agricultural products from modern supply chains will rapidly gain market shares at the expense of products from more traditional sub-sectors. In order to adapt to the new requirements in the horticultural sector, appropriate responses in supply chains are required. Such responses presuppose a good understanding of consumer preferences and valuation of new product attributes. Therefore the third article entitled ?Consumer Valuation of Food Safety and Quality Attributes in Vietnam? analyzes consumers? willingness to pay for different vegetable attributes, using contingent valuation techniques. In a mediation framework, special consideration is given to consumer perceptions. Comprehensive data from the above mentioned household survey in Hanoi and Ho Chi Minh City serve as the basis. Consumers are willing to pay an average price premium of 60% for vegetables that are free of agrochemical residues, and of 20% for a set of convenience attributes, like peeled and pre-cut vegetables. Rising income levels and media use have positive impacts on the willingness to pay. These impacts are partly mediated through different consumer perceptions. From a policy perspective, public media can and should be used to promote the spread of objective information, especially with respect to health issues. The results of the three articles have important implications for rural development strategies in poor countries, which are discussed in a concluding chapter.