Effect of Bacterial and Fungal Isolates on the Whole Grain Millet Sourdough Breads
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Journal of Life Sciences 13 (2019) 1-11 doi: 10.17265/1934-7391/2019.02.001 D DAVID PUBLISHING Effect of Bacterial and Fungal Isolates on the whole Grain Millet Sourdough Breads Tchinmegni Felenou I1*, and Tchana Kwigwa Elisee2 1. Higher Institute of Environmental Sciences (HIES), Cameroon 2. VisioTerra Scientific, France Abstract: The sourdough fermentation technique has the potential to improve the nutritional profile and safety of cereal fermented foods which forms the bulk of the diet of rural dwellers in sub-Saharan Africa. This study enumerates the bacterial and fungal isolates responsible for the fermentation of millet sourdoughs, evaluates the antimicrobial safety of the sourdough starters and the quality of bread produced thereafter. The individual flours were spontaneously fermented in the ratio 1:1 (w/v) for 48 h. At the end of the fermentation, the microbial consortium of the sourdough meals obtained were determined and also screened for antagonistic activity against selected pathogens. Chemical analysis analyses were carried out on the breads following well established procedures. Semi trained panellists were employed to access the organoleptic attributes of the product. All the sourdough starters revealed strong clearance zones against the selected food borne pathogens. The proximate compositions of the breads were improved by the sourdough fermentation process compared with the raw flour. The moisture content of flour determined ranged from 7.48 to 11.20% while the protein, fat, ash, crude fibre and carbohydrate were 9.53 to 12.4%; 2.13 to 2.78%; 0.82 to 2.87%; 2.10 to 4.67% and 71.83 to 76.33% respectively. The carbohydrate content of the breads reduced with fermentation and ranged from 63.10% to 73.33%% while the protein, ash, crude fibre and fat content ranged from 11.57 to 15.31%; 2.39 to 3.08%; 1.76 to 3.62% and 7.15 to 12.32% respectively. The highest value for calcium 48.86 mg/100 g was exhibited by pearl millet bread. Sensory evaluation showed significant difference in the bread samples. The findings have suggested that indigenous wholegrain cereals could be employed for bread production, thus reduce importation and over dependence of wheat flour and white pan bread consumption Key words: Fermentation, probiotics, pathogen, sub-Saharan, indigenous. 1. Introduction 12% [3, 4]. Present in the bran are healthy metabolites such as oligosaccharides, phytochemicals and dietary Consumers’ interest in health- promoting, nutritious, fibre [5]. Consumption of high rich fibre foods have functional and wholegrain rich foods is significantly long been proven to provide health benefits [6]. increasing, particularly against several western Utilizing the sourdough technique in the development chronic diseases such as diabetes, coeliac disease and of fibre rich functional foods such as wholegrain other cardiovascular diseases [1, 2] White pan bread sourdough bread, cake and other baked goods is an and other bakery products produced from the emerging technology in sub Saharan Africa and could endosperm flour represents 83% of the kernel, be suitable in enhancing the technological and characterized by a high soft elastic crumb structure nutritional properties of indigenous under-utilized and high volume owing to the development of gluten cereals. Sourdough fermentation is spontaneous network which entraps the gas produced from the involving the mixture of flour and water fermented fermentation by yeast and adds to the unique cellular with LAB and yeast [7]. Sourdough technique had structure. Nutritionally, white pan bread is inferior to been studied and known to distinctively improve the wholegrain which comprise germ 3% and bran dough properties of bread, flavour and taste, offer microbial safety, conveniences, enhanced nutritional Corresponding author: Tchinmegni Felenou I, Master degree in Agroforestry system, Research field(s): Food security. value through increased mineral bio-availability, 2 Effect of Bacterial and Fungal Isolates on the whole Grain Millet Sourdough Breads provide some exopolysaccharides with prebiotic from Owena market, Ilesa, Nigeria. Pearl and finger behaviour, lowers the post prandial glucose level, and millet were sorted differently to remove stones and enhance shelf life of the bread due to the lengthy debris, while acha and iburu were winnowed fermentation period of sourdough [8, 9]. The positive separately to remove extraneous materials. All effect of sourdough on the quality of bread dwells on materials were ground into fine flour using the the specific metabolic activities of LAB and yeast attrition disc mill, packaged in air tight plastic which possess the potential to produce different containers and stored in the refrigerator (4°C) until organic acids, enzymes and exopolysaccharides thereby required. All chemicals used were of analytical grade prolonging the shelf stability of the sourdough bread and purchased from Sigma or BDH Company, UK. (by prolonging the period of mould attack, anti-staling 2.2 Spontaneous Fermentation of Individual Flours and prevent ropiness in the bread) [10]. Microbial safety of foods is of immense concern to public health The millet sourdoughs were prepared by mixing and of interest are Gram negative bacteria such as individual flour with tap water in the ratio 1:1 (wlv) as E.coli, Salmonellasp, Klebsiellasp, along with some previously described by Adisa and Ifesan (2016) [7]. Gram positive organisms such as Staphylococcus 2.3 Identification of Isolates aureus, Streptococcus faecalis which have been implicated in foodborne illnesses. Inactivation of Growth of Lactic acid bacteria (LAB) was α-amylase activity, production of bread with suitable estimated from each fermenting dough meal using de physical property such as extensibility, and Mann Rogosa Sharpe (MRS) agar as described by development of acid flavour as reported by Hansen et Adisa and Ifesan (2016) [7]. Pure isolates obtained al. (2002) [11] are some of the functions of sourdough were subjected to gram and spore staining. in the production of rye bread. Biochemical characterization was based on sugar The choice of fonio for this study is based upon the fermentation (glucose, fructose, lactose, sucrose and backdrop that fonio is still being under-utilized and is maltose utilization), motility, catalase production and quite rich in methionine and cysteine two important growth in 10% NaCl were done as described by amino acids lacking in other cereals. In this part of the Sneath et al. (1986) [12]. world, the majority of the populace in the rural areas Isolation and identification of fungal isolates were depend on the local grains for survival, creating a done on Malt Extract (MEA) agar and by making novel product at low cost with their indigenous grains reference to Efiuvwevwere and Uwanogho (1990) could serve for variation in their diet and at the same [13]. Pure isolates were obtained by successive time provide some health significance as most lack streaking on MEA agar after which they were stained adequate and good medical facilities. The objective of as described by FAO (1979) [14] and then subjected this work is therefore to investigate the dominating effect to carbohydrate fermentation and Cycloheximide of wholegrain millet sourdough starters on foodborne resistance test enteric organisms and wholegrain bread quality. For urea hydrolysis test, Urea broth medium was 2. Materials and Methods dispensed into tubes aseptically, in aliquots of 5 ml then autoclaved at 121°C for 20 min. A loop full of 2.1 Source of Materials cells from freshly prepared culture was suspended in The raw materials used are pearl millet (P. the sterile broth and incubated at 37°C. The tubes glaucoma), acha (D. exilis), iburu (D. iburua) and were examined half hourly for a change of colour to finger millet (E.coracana). They were all purchased red which is an indication of urease activity [15]. Effect of Bacterial and Fungal Isolates on the whole Grain Millet Sourdough Breads 3 2.4 Proximate Analyses of Flour and Bread together in a mixing bowl and the resulting dough was kneaded manually for 10 min at 30±2°C. The dough Moisture, crude fibre, total ash and crude fat was cut into shapes and placed in greased pans. It was contents were determined using the standard methods allowed to ferment for 24 h in order to allow sufficient of Association of Official Chemists [16]. The crude leavening by yeast. The oven was preheated for 1 h protein content was determined using the micro and the breads baked at 230°C for 30 min. It was Kjedahl nitrogen method. The nitrogen content was cooled at room temperature for further sensory and converted to protein using the conversion factor 6.25. proximate analysis. Carbohydrate content was determined by difference. The experiment was done in triplicate. 2.8 Physical Properties of Sourdough Breads 2.5 Screening of Sourdoughs for Antagonistic Activity This was determined according to Sanni et al. (1998) Against Selected Pathogens [19]. The loaf volume was calculated by using a slide rule to measure the height, length and breadth of the This was done using the agar well diffusion method. bread and multiplying them all. The loaf specific The test organisms were grown in nutrient broth at volume was calculated as the ratio of the loaf volume 37°C for 24 h and spread evenly by swabbing on to the weight of the bread. The crumb and crust Muellar-Hinton agar plates and 3 wells each of 6 mm colour of the bread were determined by physical diameter were bored into the plates with the aid of a observation with the eye. The elasticity of the crumb sterile cork borer. The wells were then filled with 100 µl aliquot of freshly prepared sourdough in a laminar was determined by the ability of the crumb to return airflow cabinet in order to maintain sterile condition. back to its position after it has been pressed down The inoculated plates were incubated at 37°C for 24 h within 5 min.