Browsing by Person "Njoroge, Daniel"

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Chemical composition and consumer acceptability of oyster mushroom and sorghum-pearl millet based composite flours
(2024) Ndunge Charles, Alice; Mburu, Monica; Njoroge, Daniel; Zettel, Viktoria; Ndunge Charles, Alice; Institute of Food Bioresources Technology, Dedan Kimathi University of Technology, Nyeri, Kenya; Mburu, Monica; Institute of Food Bioresources Technology, Dedan Kimathi University of Technology, Nyeri, Kenya; Njoroge, Daniel; Institute of Food Bioresources Technology, Dedan Kimathi University of Technology, Nyeri, Kenya; Zettel, Viktoria; Department of Plant-based Foods, Institute of Food Science and Biotechnology, University of Hohenheim, Stuttgart, Germany
Due to over-reliance on starchy staple foods in Kenya Micronutrient deficiency (MD) and Protein Energy Malnutrition (PEM) are the major nutritional concerns. Despite these foods being characterized by low nutrient densities, they are still used as main food ingredient especially in making porridges. Therefore, this study intended to develop composite flour of sorghum-pearl millet blends fortified with oyster mushroom and further evaluate its chemical composition and consumer acceptability. The sorghum and pearl millet were soaked in tap water then solar dried followed by milling into flour. Oyster mushrooms were also solar dried and milled. Subsequently, oyster mushroom was substituted to sorghum-pearl millet blends at 10–50 % to achieve the composite flours. Proximate composition of the samples was determined using standard methods, Inductively Coupled Plasma Optical Emission Spectroscopy and Ultra Performance Liquid Chromatography Ultraviolet Spectroscopy/Mass Spectrometry were used for mineral and vitamin analyses, respectively. In addition, consumer acceptability test was done on thin porridges was also carried out using untrained panelists. Protein content of the composite flours increased from 11.15–19.74 %, and there were significant increases in fiber (2.68–10.66 %) and ash (1.38 % to 5–79 %). Mineral content increased with Ca, P, Na, K, Mg, Zn and Fe as high as 286.25 mg/100 g, 2088.05 mg/100 g, 167.55 mg/100 g, 1833.05 mg/100 g, 136.75 mg/100 g, 4.22 mg/100 g and 9.46 mg/100 g respectively. An improvement of B1, B2, B3, B6 and B9 vitamin contents was also observed. Sensory analysis showed relatively moderate overall acceptance of thin porridges from the composite flours, although the acceptability decreased with the increase in oyster mushroom. Specifically, composite flour with 50% oyster mushroom was rich in most nutrients but it had the lowest scores for the sensory attributes. In conclusion, addition of oyster mushroom increased the overall nutritional composition of local cereal based staple foods an indication of potential solution to PEM and MD.
Effects of Ugali maize flour fortification with chia seeds (Salvia hispanica L.) on its physico-chemical properties and consumer acceptability
(2024) Chemutai, Susan; Mburu, Monica; Njoroge, Daniel; Zettel, Viktoria
The study investigated the effect of incorporating whole chia seeds (WCS) and defatted chia seed flour (DCF) into whole maize meal for ugali preparation. Both were incorporated at substitution levels of 3%, 6%, and 9% separately, and the resulting treatments subjected to laboratory analysis. In addition, ugali samples were prepared from all the resulting flour formulations and subjected to consumer acceptability assessment. Incorporation of both DCF and WCS resulted in increased water absorption capacity (ranging from 0.78 to 0.98 g/mL), swelling index (ranging from 0.15 to 3.25 mL/g), and swelling capacity (ranging from 2.46 to 5.74 g/g). WCS decreased the bulk density and oil absorption capacity. DCF, however, resulted in an increase in bulk density and oil absorption capacity. Both DCF and WCS lowered the lightness (L*) of the products. Proximate composition ranged from 4.78 to 7.46% for crude fat, 7.22% to 9.16% for crude protein, and 1.74 to 4.27% for crude fiber. The obtained results show the potential of chia seeds as a good fortificant of maize flour since it resulted in nutritionally superior products (crude ash, crude protein, crude fat, and energy value) when compared to control. The freshly prepared ugali samples were generally acceptable to the panelists up to 9% WCS and 6% DCF substitution levels.
Novel method for the detection of adulterants in coffee and the determination of a coffee's geographical origin using near infrared spectroscopy complemented by an autoencoder
(2023) Munyendo, Leah; Njoroge, Daniel; Zhang, Yanyan; Hitzmann, Bernd
Coffee authenticity is a foundational aspect of quality when considering coffee's market value. This has become important given frequent adulteration and mislabelling for economic gains. Therefore, this research aimed to investigate the ability of a deep autoencoder neural network to detect adulterants in roasted coffee and to determine a coffee's geographical origin (roasted) using near infrared (NIR) spectroscopy. Arabica coffee was adulterated with robusta coffee or chicory at adulteration levels ranging from 2.5% to 30% in increments of 2.5% at light, medium and dark roast levels. First, the autoencoder was trained using pure arabica coffee before being used to detect the presence of adulterants in the samples. Furthermore, it was used to determine the geographical origin of coffee. All samples adulterated with chicory were detectable by the autoencoder at all roast levels. In the case of robusta‐adulterated samples, detection was possible at adulteration levels above 7.5% at medium and dark roasts. Additionally, it was possible to differentiate coffee samples from different geographical origins. PCA analysis of adulterated samples showed grouping based on the type and concentration of the adulterant. In conclusion, using an autoencoder neural network in conjunction with NIR spectroscopy could be a reliable technique to ensure coffee authenticity.
The potential of spectroscopic techniques in coffee analysis - a review
(2021) Munyendo, Leah; Njoroge, Daniel; Hitzmann, Bernd
This review provides an overview of recent studies on the potential of spectroscopy techniques (mid-infrared, near infrared, Raman, and fluorescence spectroscopy) used in coffee analysis. It specifically covers their applications in coffee roasting supervision, adulterants and defective beans detection, prediction of specialty coffee quality and coffees’ sensory attributes, discrimination of coffee based on variety, species, and geographical origin, and prediction of coffees chemical composition. These are important aspects that significantly affect the overall quality of coffee and consequently its market price and finally quality of the brew. From the reviewed literature, spectroscopic methods could be used to evaluate coffee for different parameters along the production process as evidenced by reported robust prediction models. Nevertheless, some techniques have received little attention including Raman and fluorescence spectroscopy, which should be further studied considering their great potential in providing important information. There is more focus on the use of near infrared spectroscopy; however, few multivariate analysis techniques have been explored. With the growing demand for fast, robust, and accurate analytical methods for coffee quality assessment and its authentication, there are other areas to be studied and the field of coffee spectroscopy provides a vast opportunity for scientific investigation.