Improvement of methods for the detection of Gram-negative foodborne pathogens
Margot, H.F.T. - \ 2016
Wageningen University. Promotor(en): Marcel Zwietering; Han Joosten, co-promotor(en): R. Stephan. - Wageningen : Wageningen University - ISBN 9789462578708 - 158
gram negative bacteria - pathogens - foodborne pathogens - detection - real time pcr - salmonella - escherichia coli - mung beans - gramnegatieve bacteriën - pathogenen - voedselpathogenen - detectie - real time pcr - salmonella - escherichia coli - mungbonen
Foodborne diseases are a major source of morbidity and mortality worldwide. In most cases, these diseases are caused by contaminated food products, but transmission can also subsequently occur via person to person contact. The ability to detect the pathogens is an important aspect in the verification of food safety. A major proportion of foodborne disease is caused by Gram-negative bacteria. In this thesis, the detection of Gram-negative foodborne pathogens is addressed by looking at the successive steps from enrichment to detection with Salmonella, Shiga toxin-producing E. coli and Cronobacter spp. as example pathogens. The detection of foodborne pathogens using microbiological culture media aiming at the resuscitation and growth of bacteria is still regarded as the gold standard and included in many reference methods. However, cultural methods are time and labour-intensive. Since an immediate response is required in case of contamination and during outbreaks there is a strong interest in methods that deliver information on the microbiological status of the product as quickly and reliable as possible. Rapid cultural methods and commercially available real-time PCR systems for the detection of Salmonella and STEC were compared with regards to their sensitivity and specificity. It was shown that most of the marketed systems are as reliable as the standard methods. However, false-positive results were obtained with real-time PCR systems for the detection of Salmonella. Rapid cultural methods that were based on procedures without the pre-enrichment step, reduced the time to detection but did show some ambiguous results with difficult matrices such as tea. Of the seven rapid tests for the detection of STEC, one did not detect relevant Stx subtypes.
In order to be detected, pathogens need to multiply to reach a minimum threshold level. However, because they are often sublethally injured due to hostile processing and storage conditions, they first need to be resuscitated. For most pathogens, (Salmonella, STEC and Cronobacter spp.) the first step in the detection is an enrichment including resuscitation in a non-selective medium such as BPW. Modifications to BPW were compared with respect to their ability to promote growth of unstressed and stressed Gram-negative pathogens. The aim was to develop a medium that could be used for the enrichment of pathogens in horizontal methods using only one enrichment step. The resuscitation of stressed Cronobacter cells was improved in BPW supplemented with an additional iron source and sodium pyruvate along with low levels of compounds for the inhibition of Gram-positive bacteria. However, it was observed that BPW containing these supplements allowed for less resuscitation of STEC when compared to regular BPW. Based on these results it was concluded that the application of a one-broth enrichment in food products with a high number of competing bacteria is not recommended due to the overgrowth of the target bacteria. Limitations of the current method for the detection of STEC from sprouted seeds were noticed. Therefore, the growth of stressed STEC cells from different serotypes was assessed in media used for the enrichment of Enterobacteriaceae. In addition, the growth of STEC was examined in the enrichment of sprouts using different media and incubation temperatures. It was shown that the high level of competitors was inhibiting the detection of the target pathogen and that the similarity of target and competing bacteria prevents the design of a selective enrichment procedure. In order to get a better insight in the enrichment ecology, the microbiome of mungo bean sprouts was analysed using Illumina HiSeq sequencing prior to and during the enrichment in BPW and EE-broth at different temperatures. The majority of the sprout flora was composed of bacteria belonging to the phylum Proteobacteria. Enrichment in BPW increased the proportion of Firmicutes whereas the incubation in EE-broth enriched Proteobacteria. The results point out that with the application of a selective medium like EE-broth, growth of the competitive microflora that complicates the detection of STEC is promoted. It was shown that EE-broth also resulted in good growth of STEC however, the problematic situation of low maximum population densities of the target strain in the matrix is still present. The probability of detection is not only influenced by the natural flora of a food product, but also by the physiological state of the pathogen. The influence of stress on the lag time of single cells and the resulting probability of detection were determined for Cronobacter spp. in powdered infant formula. Lag time was calculated from optical density measurement data and different scenarios were modelled. Lag time was longest after acid stress and lag time increase coincided with increased lag time variability. The probability of detection, however, depended both on the sampling plan and on the duration of the lag phase.
This thesis provides a critical evaluation of rapid methods and valuable new insights on enrichment procedures, the role of competitors in bacterial enrichment procedures and the limitations of selective agents. This information will be of great help to further improve microbiological methods and thereby contribute to more effective management of food safety.
Towards food autonomy: connectivity and self-help groups in Hisar, India
Singh, S. - \ 2015
Wageningen University. Promotor(en): Guido Ruivenkamp; Han Wiskerke, co-promotor(en): Joost Jongerden. - Wageningen : Wageningen University - ISBN 9789462574922 - 228
landbouw bedrijven in het klein - voedsel - autonomie - voedselproductie - voedselconsumptie - zelfhulp - samenwerking - boerenstand - plattelandsgemeenschappen - netwerken - ondernemerschap - mungbonen - landbouwontwikkeling - rurale sociologie - india - peasant farming - food - autonomy - food production - food consumption - self help - cooperation - peasantry - rural communities - networks - entrepreneurship - mung beans - agricultural development - rural sociology - india
Keywords: self-help groups, connectivity, food autonomy, peasants, micro-enterprise
Towards Food Autonomy: Connectivity and Self-help Groups in Hisar, India
Rural Sociology Group, Wageningen University, Netherlands
Abstract Food autonomy requires consideration of the various connectivity and self-help action organizing by the peasants’ communities. The socio-spatial organization of mung-bean production, household processing and consumption practices in Hisar district of Haryana-India are studied. The socio-spatial organization of food connects agriculture to its local environment, the regionally tied agriculture produce to local consumption patterns, and food production and consumption to livelihood and health, which are enabled by the abilities and practices of peasants and stimulate food autonomy. The connections are related to mung-bean food qualities at various levels of production, processing and consumption. Local mung-bean preferences of producers, processors, consumers and the market conditions are studied. It showed that local mung-bean food qualities related to suitability in the local cropping system, processing requirement (short cooking-time, better consistency and appearance) and consumption choice (easy to cook, healthy food). Mung-bean market conditions indicated that the market works against peasants (traders and urban processors are winners). However, the producers’ viewpoint on mung-bean processing at the community level is linked to the creation of new social relations in the mung-bean food network to strengthen the territorial connectivity of mung-bean for reinforcing mung-bean food autonomy. The possibilities of Self-Help Group (SHG) and SHG-based (food) Micro-Enterprise (ME) developments were discussed. In reviewing the literature on SHGs and previous empirical studies, various factors were identified that contribute to a success or failure of a functioning of SHG. These include full participation from and homogeneity among members, and clear group goals and transparency in group operations and functioning. The SHG mung-bean food-based ME initiated in Mangali village of Hisar was studied, to investigate ways in which this group functions. Results revealed three identifiable roles of the self-help peasants’ group: i) it consolidates local mung-bean food production, local resources and motivations of the peasants; ii) it develops another perspective of development based upon a more localized choice for processing, distributing, marketing and accessing local mung-bean food; and iii) it empowers local people (especially peasants and the poor rural community) and strengthens the connectivity between local mung-bean production and consumption. The need remains for technological efforts to address the specific location of peasant resources while in the SHG there is clearly a need to restore or redefine collective responsibility.
Development of iron and zinc enriched mungbean (Vigna radiata L.) cultivars with agronomic traits in consideration
Singh, R. - \ 2013
Wageningen University. Promotor(en): Richard Visser, co-promotor(en): Sjaak van Heusden. - S.l. : s.n. - ISBN 9789461736840 - 175
vigna radiata - mungbonen (green gram) - mungbonen - sporenelementen - ijzer - zink - plantenveredeling - genetische diversiteit - voeding - india - voedselsoevereiniteit - vigna radiata - green gram - mung beans - trace elements - iron - zinc - plant breeding - genetic diversity - nutrition - india - food sovereignty
Malnutrition in India, particularly among women, children and adolescents is an emergency that needs immediate attention in this fast growing and developing country. Micronutrient deficiencies are threatening public health in India more and more. Deficiencies of micronutrients drastically affect growth, metabolism and reproductive phase in humans as it does in plants and animals. Cereal and pulse based Indian diets are qualitatively deficient in micronutrients such as iron, calcium, vitamin A and zinc. This is due to a low intake of income-elastic protective foods such as pulses, vegetables, fruits, and foods of animal origin. It is presumed that if we restore the geographical connection between food production and consumption in local food networks it will help in solving this nutritional problem in India. This offers new opportunities to tailor science & technology to location specific patterns of food production and consumption, which may lead to environmentally and socially sustainable agriculture. Despite global pressure (including from science and technology) to focus agricultural cultivation on a limited number of food crops, still many so-called orphan crops like mungbean do exist and are cultivated in location-specific crop rotation systems. Particularly, the seed legumes are of major nutritional importance, especially in developing countries, because they have high protein contents of good biological value. Out of the total sales of mungbean, about half of the sales are within the village which clearly establishes the need for development of infrastructure and facilities at the village level to serve the interests of the farm households. Moreover, it is also necessary to shift the focus of development from the urban market centres (largely developed) to the rural market centres. Linking breeding, nutrition, processing and standardisation of food products, may be designed within the experimental framework of empowering poor farmers. Hence, tailoring plant, food and social sciences to empower local mungbean production and consumption patterns has been designed as an interdisciplinary program of plant breeding, food technology, human nutrition and sociology of science and technology. Thus the ‘Tailoring Food Sciences to Endogenous Patterns of Local Food Supply for Future Nutrition’ (TELFUN) project aimed to help people in selecting their own way of local food production, processing and consumption of the best suited local food. The main objective is to strengthen “The Science in Society” approach by remodeling participatory research and development and the general aim of TELFUN was to attune disciplinary research objectives within an interdisciplinary framework to enhance food sovereignty and to improve mungbean based production and consumption pattern in selected research area (Haryana, India). As an example our research focused on further improving one of the potential nutritional crops, namely mungbean. The present work emphasizes on mungbean in general and especially on the available micronutrient variation in the mungbean germplasm. The mungbean (green gram), Vigna radiata (L.) Wilczek is native to the Indian subcontinent. They are warm season annuals, highly branched and having trifoliate leaves like the other legumes. Seeds of mungbean are small, ovoid in shape, and green in color. Mungbean seeds are high in protein (21%–28%), calcium, phosphorus and certain vitamins. Moreover they are easily digested and they replace scarce animal protein in human diets in vegetarian populations of the world. The selected area of research centres contain a high level of local biodiversity and are the locations for domestication of mungbean. This legume has co-evolved with their natural ecosystems and is well-adapted to withstand the local biotic and abiotic stresses. This will help in enabling the reconnection of the cultivation of the mungbean with their natural environments. Moreover, as domestication has taken place by local farmers during many centuries, they have accumulated local endogenous knowledge, which is very relevant for local food networks (www.telfun.info). Thus to explore the potential mungbean network, the present thesis set its objectives. They were: i) identification of the major constraints, limitations and preferences of producer’s with regard to mungbean, ii) assessing the diversity in the available germplasm and assessing the effects of different environments on selected cultivars for their mineral micronutrients and iii) to make a start to develop tools for marker assisted breeding with regard to iron and zinc.
Towards redesigning indigenous mung bean foods
Dahiya, P.K. - \ 2013
Wageningen University. Promotor(en): Tiny van Boekel, co-promotor(en): Anita Linnemann; Rob Nout. - S.l. : s.n. - ISBN 9789461735119 - 205
mungbonen - voedingswaarde - voedingsgewoonten - innovaties - productontwikkeling - nieuwe producten - india - mung beans - nutritive value - feeding habits - innovations - product development - new products - india
Redesigning traditional foods requires consideration of the various factors affecting the nutrient intake from such foods. Amongst these factors are adequate consumption, proper nutrient bioavailability and consumer satisfaction. These factors are related to traditional food quality at various levels of the food network. The physical, food processing, nutritional and anti-nutritional properties of the mung bean were reviewed. Three major factors that affect the nutritional value of grains were identified, viz. genetic makeup, agronomical practices, and agro-ecological conditions. Consumer choices for mung bean products were analyzed with respect to perception, preferences and the resulting dietary practices, to determine their impact on their nutritional potential. Food choices were influenced more by social-economic restrictions than by consumer perception and preferences. Therefore, increasing the frequency of consumption of nutrient-rich products and use of mineral enhancing accompanying foods is recommended for better nutrition. The nutritional characteristics of newly bred and established mung bean varieties in the research community were analyzed. Results showed that varieties contained 18 - 23 g protein, 4.0 - 5.6 g crude fibre and 2.5 - 4.1 g ash per 100 g dry sample. Iron, zinc, calcium, sodium and potassium ranged from 3.4 - 4.6, 1.2 - 2.3, 79 - 115, 8.1 - 13.5 and 362 - 415 mg/100 g dry weight, respectively. Phytic acid and polyphenols averaged 769 and 325 mg/100 g dry weight, respectively. Varieties differed significantly in terms of nutrient and anti-nutrient contents. Newly bred varieties were not found to be significantly more nutritive than established ones and thus breeders are recommended to focus on a combination of crop yield, nutritional value and consumer preference traits. Nutritional characteristics of the indigenous foods made with mung bean were also analyzed. Average in vitro iron, zinc and calcium accessibility of the mung bean products were 1.6, 0.9 and 41.8 mg/100 g dry weight, respectively. Phytic acid and polyphenols averaged 210 and 180 mg/100 g dry weight, respectively, and were negatively correlated with in vitro mineral accessibility. Dhals were found to be nutritionally rich in terms of mineral accessibility. Critical evaluation of all the possible factors affecting nutritional potential suggests that dhals can be used as the vehicle for increasing the mineral uptake in the malnourished population through mung bean. However, identified technological options are required to be considered while redesigning traditional mung bean products.