Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Local processing and nutritional composition of indigenous fruits : The case of monkey orange (Strychnos spp.) from Southern Africa
    Ngadze, Ruth T. ; Linnemann, Anita R. ; Nyanga, Loveness K. ; Fogliano, Vincenzo ; Verkerk, Ruud - \ 2017
    Food Reviews International 33 (2017)2. - ISSN 8755-9129 - p. 123 - 142.
    Sensory properties - Strychnos cocculoides - Strychnos innocua - Strychnos pungens - Strychnos spinose

    Monkey orange (Strychnos spp.) is a widely distributed fruit species in Southern Africa commonly consumed by the local population. It has potential to improve the nutritional status of rural populations, being a precious food source in areas with periodic shortages, since it is rich in vitamin C, zinc, and iron. To improve the availability of this food outside its production season, processing and preservation techniques used at household level need upgrading as they are unreliable and their effects on nutritional quality are unknown. Based on this review, we recommend better indigenous fruit production as a sustainable solution to malnutrition in rural areas in transition countries.

    Fermentation characteristics of yeasts isolated from traditionally fermented masau (Ziziphus mauritiana) fruits
    Nyanga, L.K. ; Nout, M.J.R. ; Smid, E.J. ; Boekhout, C. ; Zwietering, M.H. - \ 2013
    International Journal of Food Microbiology 166 (2013)3. - ISSN 0168-1605 - p. 426 - 432.
    saccharomyces-cerevisiae - volatile compounds - wine yeasts - immobilized cells - grape varieties - zimbabwe - strains - metabolism - acid - evolution
    Yeast strains were characterized to select potential starter cultures for the production of masau fermented beverages. The yeast species originally isolated from Ziziphus mauritiana (masau) fruits and their traditionally fermented fruit pulp in Zimbabwe were examined for their ability to ferment glucose and fructose using standard broth under aerated and non-aerated conditions. Most Saccharomyces cerevisiae strains were superior to other species in ethanol production. The best ethanol producing S. cerevisiae strains, and strains of the species Pichia kudriavzevii, Pichia fabianii and Saccharomycopsis fibuligera were tested for production of flavor compounds during fermentation of masau fruit juice. Significant differences in the production of ethanol and other volatile compounds during fermentation of masau juice were observed among and within the four tested species. Alcohols and esters were the major volatiles detected in the fermented juice. Trace amounts of organic acids and carbonyl compounds were detected. Ethyl hexanoate and ethyl octanoate were produced in highest amounts as compared to the other volatile compounds. S. cerevisiae strains produced higher amounts of ethanol and flavor compounds as compared to the other species, especially fatty acid ethyl esters that provide the major aroma impact of freshly fermented wines. The developed library of characteristics can help in the design of mixtures of strains to obtain a specific melange of product functionalities. Keywords: Masau juice; Fermentation; Yeast; Volatile compounds; Flavor; Wine
    Nutritive value of masau (Ziziphus mauritiana) fruits from Zambezi Valley in Zimbabwe
    Nyanga, L.K. ; Gadaga, T.H. ; Nout, M.J.R. ; Smid, E.J. ; Boekhout, T. ; Zwietering, M.H. - \ 2013
    Food Chemistry 138 (2013)1. - ISSN 0308-8146 - p. 168 - 172.
    wild plants - vitamin-c
    Ziziphus mauritiana (masau) fruits are consumed by many people in Zimbabwe. The fruits contribute significantly to people’s diet when they are in season. The objective of this study was to determine the nutritional content of the fruits and, hence, quantify their contribution to the diet. Samples of masau were collected in two seasons (August 2006 and August 2007). Both macronutrients and micronutrients were determined using standard AOAC methods of analysis. Dry matter content ranged from 21.1 ± 0.2 to 24.1 ± 0.3 g 100 g-1 of edible portion of the sweet and sour fruits, and 84.8 ± 0.2 to 87.2 ± 0.2 g 100 g-1 for the dried fruit. Crude protein per 100 g edible portion of dry weight ranged between 7.9 ± 0.0 and 8.7 ± 0.0 g, crude fat from 0.8 ± 0.0 to 1.5 ± 0.0 g, crude fibre from 4.9 ± 0.0 to 7.3 ± 0.0 g, ash between 3.0 ± 0.0 and 4.3 ± 0.0 g and carbohydrate between 79.5 ± 0.0 and 83.2 ± 0.0 g. The fruits were rich in vitamin C (15.0 ± 0.0–43.8 ± 0.02 mg 100 g-1) and the energy values ranged between 1516.0 ± 1.73 and 1575.0 ± 2.3 kJ 100 g-1. Furthermore, the fruits contained (mg 100 g-1 of dry weight) potassium from 1865.0 ± 1.3 to 2441.0 ± 1.1, calcium from 160.0 ± 0.3 to 254.0 ± 0.1, sodium between 185.0 ± 0.1 and 223.0 ± 0.2, magnesium between 83.0 ± 0.0 and 150.0 ± 0.13 and phosphorous from 87.0 ± 0.1 to 148.0 ± 0.5. Manganese and copper contents ranged between 0.7 ± 0.03 and 1.6 ± 0.03, while iron and zinc ranged between 2.1 ± 0.43 and 4.3 ± 0.1, and 0.6 ± 0.0–0.9 ± 0.0 mg 100 g-1 of dry weight, respectively. The masau fruit is therefore a good potential source of carbohydrates, proteins and micronutrients, such as calcium, potassium, sodium, phosphorous, copper, iron, Vitamin C and zinc
    Genotypic and phenotypic characteristics of yeasts isolated from masau (Ziziphus mauritiana) fruits and their traditionally fermented fruit pulp
    Nyanga, L.K. ; Nout, M.J.R. ; Smid, E.J. ; Boekhout, T. ; Zwietering, M.H. - \ 2012
    In: 23rd International ICFMH Symposium FoodMicro 2012, Istanbul, Abstract Book. - Istanbul : Istanbul Technical University, Chemical and Metallurgical Engineering Faculty - ISBN 9789755614236 - p. 128 - 128.
    Yeasts preservation: alternatives for lyophilisation
    Nyanga, L.K. ; Nout, M.J.R. ; Smid, E.J. ; Boekhout, T. ; Zwietering, M.H. - \ 2012
    World Journal of Microbiology and Biotechnology 28 (2012)11. - ISSN 0959-3993 - p. 3239 - 3244.
    ziziphus-mauritiana - starter cultures - trehalose - viability - fermentation - survival - efficacy - zimbabwe - storage - fruits
    The aim of the study was to compare the effect of two low-cost, low technology traditional methods for drying starter cultures with standard lyophilisation. Lyophilised yeast cultures and yeast cultures preserved in dry rice cakes and dry plant fibre strands were examined for viable cell counts during 6 months storage at 4 and 25 °C. None of the yeast cultures showed a significant loss in viable cell count during 6 months of storage at 4 °C upon lyophilisation and preservation in dry rice cakes. During storage at 25 °C in the dark, yeast cultures preserved in dry rice cakes, and lyophilised cultures of Saccharomyces cerevisiae and Issatchenkia orientalis showed no significant loss of viable cells up to 4 months of storage. Yeast cultures preserved in dry plant fibre strands had the greatest loss of viable count during the 6 months of storage at 25 °C. Preservation of yeasts cultures in dry rice cakes provided better survival during storage at 4 °C than lyophilisation. The current study demonstrated that traditional methods can be useful and effective for starter culture preservation in small-scale, low-tech applications.
    Ziziphus mauritiana (masau) fruits fermentation in Zimbabwe: from black-box to starter culture development
    Nyanga, L.K. - \ 2012
    Wageningen University. Promotor(en): Marcel Zwietering, co-promotor(en): Rob Nout; T. Boekhout. - S.l. : s.n. - ISBN 9789461733757 - 114
    ziziphus mauritiana - fermentatieproducten - alcoholische dranken - frisdranken - ziziphus mauritiana - fermentation products - alcoholic beverages - soft drinks

    This thesis reports on studies of microbiological and biochemical properties of masau (Ziziphus mauritiana) fruit fermentation and the development of starter cultures for the production of masau beverages.

    A survey to document the traditional processing techniques was conducted using a questionnaire and focus group discussions in each of the three districts, i.e., Mudzi, Mt Darwin and Muzarabani in Zimbabwe. The survey results showed that the masau fruit is usually gathered by women and children, and eaten raw or processed into products such as porridge, traditional cakes, mahewu (non-alcoholic fermented beverage), jam, which are sold at local markets. It is also naturally fermented under uncontrolled conditions and distilled into kachasu. The nutritional composition of the masau fruit was analysed. The fruits are good sources of nutrients such as carbohydrates, protein, and essential micronutrients such as calcium, potassium, phosphorus, copper, iron, zinc and vitamin C.

    In order to enable the selection of starter cultures for the production of masau wine and distillate, yeasts, yeast-like fungi, and lactic acid bacteria present on the unripe, ripe and dried fruits, and in the fermented masau fruits were isolated and identified using physiological and molecular methods. The predominant species were identified as Saccharomyces cerevisiae, Pichia kudriavzevii, P. fabianii, Aureobasidium pullulans, Lactobacillus agilisand L. plantarum. The yeast species were then characterised with respect to ethanol and flavour compounds production. Significant differences in the production of ethanol and other volatile compounds were observed during fermentation of masau juice among and within the tested Saccharomyces, Pichia and Saccharomycopsis species. Alcohols and esters were the major volatiles detected in the fermented juice. Ethyl hexanoate and ethyl octanoate were produced in highest amounts as compared to the other flavour compounds.

    Two traditional low-tech methods for preserving starter cultures, i.e., stabilisation of yeast cultures in dried plant fibre strands, and in rice cakes, were compared with standard lyophilisation. Viable cell counts made during six months storage at 4 °C and 25 °C of lyophilised yeasts, and yeast cultures preserved in dry rice cakes and dry plant fibre strands showed that the rice cake method performed significantly better than lyophilisation.

    The developed library of fermentation characteristics of yeasts can help in the design of mixtures of strains to obtain a specific melange of masau product functionalities. The defined starter cultures could be preserved using the traditional approaches, which are suitable for small-scale, low-tech applications.

    Traditional processing of masau fruits (Ziziphus mauritiana) in Zimbabwe
    Nyanga, L.K. ; Nout, M.J.R. ; Gadaga, T.H. ; Boekhout, T. ; Zwietering, M.H. - \ 2008
    Ecology of Food and Nutrition 47 (2008)1. - ISSN 0367-0244 - p. 95 - 107.
    organic-acid - beverages
    A survey of the traditional processing techniques of masau was conducted using a questionnaire and two focus group discussions in Mudzi, Mt. Darwin, and Muzarabani districts in Zimbabwe. Masau fruits form part of the family diet and generate additional income by selling at local markets. Surplus fruits are sun dried and can be transformed into various products such as porridge, traditional cakes, mahewu, and also fermented to produce a spirit called Kachasu. The ethanol content of the fermented fruit pulp ranged from 2.1 - 3.7 mL 100mL(-1), whereas the traditionally made distillate contained 23.8 - 45.6 mL 100 mL(-1).
    Yeasts and lactic acid bacteria microbiota from masau (Ziziphus mauritiana) fruits and their fermented fruit pulp in Zimbabwe
    Nyanga, L.K. ; Nout, M.J.R. ; Gadaga, T.H. ; Theelen, R.M.C. ; Boekhout, T. ; Zwietering, M.H. - \ 2007
    International Journal of Food Microbiology 120 (2007)1-2. - ISSN 0168-1605 - p. 159 - 166.
    aureobasidium-pullulans - ribosomal dna - identification - foods - microorganisms - beverages - enumeration - flora
    Masau are Zimbabwean wild fruits, which are usually eaten raw and/ or processed into products such as porridge, traditional cakes, mahewu and jam. Yeasts, yeast-like fungi, and lactic acid bacteria present on the unripe, ripe and dried fruits, and in the fermented masau fruits collected from Muzarabani district in Zimbabwe were isolated and identified using physiological and molecular methods. The predominant species were identified as Saccharomyces cerevisiae, Issatchenkia orientalis, Pichia fabianii and Aureobasidium pullulans. A. pullulans was the dominant species on the unripe fruits but was not isolated from the fermented fruit pulp. S. cerevisiae and I. orientalis were predominant in the fermented fruit pulp but were not detected in the unripe fruits. S. cerevisiae, I. orientalis, P. fabianii and S. fibuligera are fermentative yeasts and these might be used in the future development of starter cultures to produce better quality fermented products from masau fruit. Lactic acid bacteria were preliminary identified and the predominant strains found were Lactobacillus agilis and L. plantarum. Other species identified included L. bifermentans, L. minor, L. divergens, L. confusus, L. hilgardii, L. fructosus, L. fermentum and Streptococcus spp. Some of the strains of LAB could also potentially be used in a mixed-starter culture with yeasts and might contribute positively in the production of fermented masau fruit products.
    Isolation and identification of yeasts from Masau (Ziziphus mauritiana) fruits and their fermented products in Zimbabwe
    Nyanga, L.K. ; Nout, M.J.R. ; Gadaga, T.H. ; Boekhout, T. ; Zwietering, M.H. - \ 2006
    In: Food safety and food biotechnology: diversity and global impact. - Food Micro 2006 - p. 250 - 250.
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