Microbiological quality and safety of raw and pasteurized milk marketed in and around Nairobi Region

The microbiological quality of raw and pasteurized milk marketed in Nairobi and its environs was determined. Milk samples were collected randomly at milk selling points from three market areas: rural (Kiambu/Ngong), urban (East/West of Tom Mboya street) and slum (Kibera/Mathare). Samples were analysed for titratable acidity, total viable count (TVC), Staphylococcus aureus, coliforms and Enterobacteriaceae. Titratable acidity was determined using titration method, while TVC, S. aureus and Enterobacteriaceae were determined by the spread plate methods and coliforms were determined by most probable number. Data collected were subjected to analysis of variance using Genstat statistical package. The mean acidity was 0.20% lactic acid (LA), while mean counts for TVC, S. aureus, coliforms and Enterobacteriaceae were 6.05, 3.46, 2.30, and 3.93 log10cfu/ml, respectively. The  ercentage of milk samples with acidity values greater than 0.18% LA, the upper limit set by Kenya Bureau of Standards (KEBS), was 52.8 %. Total viable count (TVC) greater than 106 cfu/ml, was detected in 95.2% and 21.4% of raw and pasteurized milk, respectively. Coliform counts greater than 4.70 and 1.0 log10cfu/ml for raw and pasteurized milk were detected in 77.8% and 4.8%, respectively of raw and pasteurized milk samples collected. Enterobacteriaceae and S. aureus were detected with mean counts ranging from 6.08-6.86 and 5.82-6.32 log10/ml, respectively. Highest mean acidity and counts were recorded from slum areas of Nairobi and there were significant differences between raw and pasteurized milk (P<0.05). The poor bacterial quality coupled with high acidity of raw milk, indicates poor hygienic practices and lack of temperature control during marketing. The incidence of high acidity and bacterial counts in pasteurized milk could indicate post process contamination and/or inappropriate storage of the milk. Most vendors of pasteurized milk were observed selling directly from the distributor crates without refrigerated storage. The rapid deterioration of raw and pasteurized milk marketed in Nairobi, at the time of this study, may be largely due to poor hygienic standards and non-adherence to temperature controls during handling, distribution and marketing. This requires urgent attention by the appropriate authorities, because the poor microbiological quality of raw milk and pasteurized milk may expose consumers to health risks associated with the consumption of contaminated milk.Key words: Marketed milk, quality, acidity, total viable count, coliforms, enterobacteriaceae, Staphylococcus aureu

Production and characterization of wine from mango fruit (Mangifera indica) varieties in Kenya

Mango is one of the most important tropical fruit. In Kenya, increased production has been observed over years paralleled by large postharvest losses which are partly attributed to poor value addition practices. This study sought to investigate the suitability of mango fruit for wine production and characterization of the wine produced. Six mature and unripe mango fruits were harvested three times from a farm in Katheka Kai Division, Machakos County of Kenya. The ripened fruits were screened for their suitability to produce wine based on juice yield, °brix (°Bx), pH, reducing sugars and titratable acidity (TTA). The wine produced was analyzed for the chemical properties whereas characterization of the major volatile compounds was determined by GC‐FID. Sensory evaluation was done using a nine point hedonic scale with a reference commercial grape wine (chardonnay). Juice recovery was dependent on variety with Kent yielding 72.8%, Apple 71.3% and Ngowe 67.6%. The extracted juice had a high sugar content ranging from 17.0 to 23.9°Bx. Apple and Ngowe variety had the most suitable properties for wine production based on sugar levels and juice yield. The ethanol content of the wines produced was between 8.9‐ 9.5 %v/v, the range acceptable for table wine. The methanol content (128‐129mg/l) was however higher than grape wine (100mg/l) although it was within the acceptable limits for wine. The sensory evaluation indicated that mango wine exhibited similar sensory characteristics with those of grape wine. This study provides evidence that mango fruits are suitable for wine processing

Evaluation of alternative preservation treatments (water heat treatment, ultrasounds, thermosonication and UV-C radiation) to improve safety and quality of whole tomato

Previously optimised postharvest treatments were compared to conventional chlorinated water treatment in terms of their effects on the overall quality of tomato (‘Zinac’) during storage at 10 °C. The treatments in question were water heat treatment (WHT = 40 °C, 30 min), ultrasounds (US = 45 kHz, 80 %, 30 min), thermosonication (TS =40 °C, 30 min, 45 kHz, 80 %) and ultraviolet irradiation (UV-C: 0.97 kJ m−2). The quality factors evaluated were colour, texture, sensorial analysis, mass loss, antioxidant capacity, total phenolic content, peroxidase and pectin methylesterase enzymatic activities, and microbial load reduction. The results demonstrate that all treatments tested preserve tomato quality to some extent during storage at 10 °C. WHT, TS and UV-C proved to be more efficient on minimising colour and texture changes with the additional advantage of microbial load reduction, leading to a shelf life extension when compared to control trials. However, at the end of storage, with exception of WHT samples, the antioxidant activity and phenolic content of treated samples was lower than for control samples. Moreover, sensorial results were well correlated with instrumental colour experimental data. This study presents alternative postharvest technologies that improve tomato (Zinac) quality during shelf life period and minimise the negative impact of conventional chlorinated water on human safety, health and environment.info:eu-repo/semantics/publishedVersio

On the role of ethylene, auxin and a GOLVEN-like peptide hormone in the regulation of peach ripening

BACKGROUND: In melting flesh peaches, auxin is necessary for system-2 ethylene synthesis and a cross-talk between ethylene and auxin occurs during the ripening process. To elucidate this interaction at the transition from maturation to ripening and the accompanying switch from system-1 to system-2 ethylene biosynthesis, fruits of melting flesh and stony hard genotypes, the latter unable to produce system-2 ethylene because of insufficient amount of auxin at ripening, were treated with auxin, ethylene and with 1-methylcyclopropene (1-MCP), known to block ethylene receptors. The effects of the treatments on the different genotypes were monitored by hormone quantifications and transcription profiling. RESULTS: In melting flesh fruit, 1-MCP responses differed according to the ripening stage. Unexpectedly, 1-MCP induced genes also up-regulated by ripening, ethylene and auxin, as CTG134, similar to GOLVEN (GLV) peptides, and repressed genes also down-regulated by ripening, ethylene and auxin, as CTG85, a calcineurin B-like protein. The nature and transcriptional response of CTG134 led to discover a rise in free auxin in 1-MCP treated fruit. This increase was supported by the induced transcription of CTG475, an IAA-amino acid hydrolase. A melting flesh and a stony hard genotype, differing for their ability to synthetize auxin and ethylene amounts at ripening, were used to study the fine temporal regulation and auxin responsiveness of genes involved in the process. Transcriptional waves showed a tight interdependence between auxin and ethylene actions with the former possibly enhanced by the GLV CTG134. The expression of genes involved in the regulation of ripening, among which are several transcription factors, was similar in the two genotypes or could be rescued by auxin application in the stony hard. Only GLV CTG134 expression could not be rescued by exogenous auxin. CONCLUSIONS: 1-MCP treatment of peach fruit is ineffective in delaying ripening because it stimulates an increase in free auxin. As a consequence, a burst in ethylene production speeding up ripening occurs. Based on a network of gene transcriptional regulations, a model in which appropriate level of CTG134 peptide hormone might be necessary to allow the correct balance between auxin and ethylene for peach ripening to occur is proposed. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12870-016-0730-7) contains supplementary material, which is available to authorized users

A Comparison of Modified Atmosphere Packaging Under Ambient Conditions and Low Temperature Storage on Quality of Tomato Fruit

Low temperature and modified atmosphere packaging (MAP) were evaluated for their effectiveness in extending the postharvest storage life of tomato (Lycopersicon esculentum Mill.) fruits. Fruits were harvested at the mature-green stage of ripeness, washed, sorted and treated with a solution of sodium hypochlorite (150 ppm chlorine). The fruits were packaged in low density polyethylene bags (0.044 mm) and kept at ambient conditions of 24±2 0C and relative humidity (RH) of 65±2% or held in environmental chambers at 15 0C and RH of 65% for 4 weeks. The fruits were then transferred to ambient conditions of air, temperature and RH for a further one-week to simulate marketing conditions. Samples were evaluated initially and thereafter every week for weight loss, titratable acidity (TA), soluble solids content (SSC), pH, chlorophyll content, ascorbic acid content and visual appearance. MAP reduced weight loss better than low temperature storage. MAP was also superior in delaying ripening in the fruits for the entire four weeks as evidenced by delayed increase in SSC, chlorophyll degradation and increase in ascorbic acid content which are associated with the fruit ripening. After two weeks of storage at 15 0C most of the fruits had started shriveling, thereby leading to loss of brightness in color and there were signs of mold infection. Under MAP the carbon dioxide and ethylene concentrations in the bags increased to 9% and 31 ppm, respectively. Upon transfer of fruits to ambient conditions, fruits held under MAP ripened normally with no signs of carbon dioxide injury. At the end of five weeks, 50% of fruits held at 15 0C were spoilt while only 26% of fruits under MAP were spoilt. These results indicate that under tropical conditions the quality and storage life of tomato fruits can be extended and ripening delayed better by MAP than by low temperature storage owing to fruit susceptibility to chilling injury. Key Words: Ascorbic acid, Low temperature storage, Lycopersicon esculentum, Modified atmosphere packaging, Tomato COMPARAISON DU CONDITIONNEMENT EN ATMOSPHERE MODIFIEE SOUS CONDITIONS ENVIRONNANTES ET DE LA CONSERVATION A BASSE TEMPERATURE POUR LA QUALITE DU FRUIT DE TOMATE RESUME La conservation à basse température et le conditionnement en atmosphère modifiée (modified atmosphere packaging – MAP) ont été évalués pour leur efficacité dans le but de prolonger la durée de conservation après la récolte des fruits de tomate (Lycospersicon esculentum Mill.). Les fruits ont été récoltés à l'état de maturité vert avancé, lavés, triés et traités avec une solution d'hypochlorite de sodium (150 ppm de chlore). Les fruits ont été emballés dans des sacs en polyethylene à basse densité (0,044 mm) et conservés sous conditions environnantes à 24±2 °C avec une humidité relative (HR) de 65±2% ou maintenus dans des pièces tempérées à 158C avec HR de 65% pendant 4 semaines. Les fruits ont ensuite été transférés en conditions environnantes d'aération, de température et de HR pendant encore une semaine pour simuler les conditions de mise sur le marché. Les échantillons ont été évalués au début de l'étude et ensuite chaque semaine pour perte de poids, acidité titrable (AT), teneur en matière solide soluble (TMS), pH, teneur en chlorophylle, teneur en acide ascorbique et apparence visuelle. Le MAP avait un meilleur effet réducteur de poids que la conservation à basse température. Le MAP était aussi supérieur pour retarder la maturation des fruits, pendant toute la période de quatre semaines, ainsi que démontré par une augmentation retardée du TMS, de la dégradation du chlorophylle et de l'augmentation du contenu en acide ascorbique qui sont associés à la maturation du fruit. Après deux semaines de conservation à 158C, la plupart des fruits commençaient à se ratatiner, entraînant une perte du brilliant de la couleur, et il y avait des signes de moisissure. Dans les conditions de MAP, les concentrations de dioxyde de carbone et versène dans les sacs ont augmenté jusqu'à 9% et 31 ppm, respectivement. Lors du transfert des fruits en conditions environnantes, les fruits conservés par MAP ont mûri normalement sans montrer de signes de dommage dû au dioxyde de carbone. Après cinq semaines, 50% des fruits conservés à 15 °C étaient abimés tandis que seulement 26 % des fruits l'étaient avec le système MAP. Ces résultats indiquent que dans des conditions tropicales, la qualité et la durée de conservation des fruits de tomate peuvent être améliorées et la maturation mieux retardée en utilisant le MAP que la conservation à basse température, compte tenu de la susceptibilité des fruits aux dommages causés par le refroidissement. Mots clés: acide ascorbique; conservation à basse termpérature; Lycopersicon esculentum; conditionnement en atmosphère modifiée; tomate. AJFAND Vol.3(2) 200

Comparaison Du Conditionnement En Atmosphere Modifiee Sous Conditions Environnantes Et De La Conservation A Basse Temperature Pour La Qualite Du Fruit De Tomate

Low temperature and modified atmosphere packaging (MAP) were evaluated for their effectiveness in extending the postharvest storage life of tomato ( Lycopersicon esculentum Mill.) fruits. Fruits were harvested at the mature-green stage of ripeness, washed, sorted and treated with a solution of sodium hypochlorite (150 ppm chlorine). The fruits were packaged in low density polyethylene bags (0.044 mm) and kept at ambient conditions of 24±2 °C and relative humidity (RH) of 65±2% or held in environmental chambers at 15 °C and RH of 65% for 4 weeks. The fruits were then transferred to ambient conditions of air, temperature and RH for a further one-week to simulate marketing conditions. Samples were evaluated initially and thereafter every week for weight loss, titratable acidity (TA), soluble solids content (SSC), pH, chlorophyll content, ascorbic acid content and visual appearance. MAP reduced weight loss better than low temperature storage. MAP was also superior in delaying ripening in the fruits for the entire four weeks as evidenced by delayed increase in SSC, chlorophyll degradation and increase in ascorbic acid content which are associated with the fruit ripening. After two weeks of storage at 15 °C most of the fruits had started shriveling, thereby leading to loss of brightness in color and there were signs of mold infection. Under MAP the carbon dioxide and ethylene concentrations in the bags increased to 9% and 31 ppm, respectively. Upon transfer of fruits to ambient conditions, fruits held under MAP ripened normally with no signs of carbon dioxide injury. At the end of five weeks, 50% of fruits held at 15 °C were spoilt while only 26% of fruits under MAP were spoilt. These results indicate that under tropical conditions the quality and storage life of tomato fruits can be extended and ripening delayed better by MAP than by low temperature storage owing to fruit susceptibility to chilling injury.La conservation à basse température et le conditionnement en atmosphère modifiée (modified atmosphere packaging – MAP) ont été évalués pour leur efficacité dans le but de prolonger la durée de conservation après la récolte des fruits de tomate ( Lycopersicon esculentum Mill.). Les fruits ont été récoltés à l'état de maturité vert avancé, lavés, triés et traités avec une solution d'hypochlorite de sodium (150 ppm de chlore). Les fruits ont été emballés dans des sacs en polyethylene à basse densité (0,044 mm) et conservés sous conditions environnantes à 24±2 °C avec une humidité relative (HR) de 65±2% ou maintenus dans des pièces tempérées à 158C avec HR de 65% pendant 4 semaines. Les fruits ont ensuite été transférés en conditions environnantes d'aération, de température et de HR pendant encore une semaine pour simuler les conditions de mise sur le marché. Les échantillons ont été évalués au début de l'étude et ensuite chaque semaine pour perte de poids, acidité titrable (AT), teneur en matière solide soluble (TMS), pH, teneur en chlorophylle, teneur en acide ascorbique et apparence visuelle. Le MAP avait un meilleur effet réducteur de poids que la conservation à basse température. Le MAP était aussi supérieur pour retarder la maturation des fruits, pendant toute la période de quatre semaines, ainsi que démontré par une augmentation retardée du TMS, de la dégradation du chlorophylle et de l'augmentation du contenu en acide ascorbique qui sont associés à la maturation du fruit. Après deux semaines de conservation à 158C, la plupart des fruits commençaient à se ratatiner, entraînant une perte du brilliant de la couleur, et il y avait des signes de moisissure. Dans les conditions de MAP, les concentrations de dioxyde de carbone et versène dans les sacs ont augmenté jusqu'à 9% et 31 ppm, respectivement. Lors du transfert des fruits en conditions environnantes, les fruits conservés par MAP ont mûri normalement sans montrer de signes de dommage dû au dioxyde de carbone. Après cinq semaines, 50% des fruits conservés à 15 °C étaient abimés tandis que seulement 26 % des fruits l'étaient avec le système MAP. Ces résultats indiquent que dans des conditions tropicales, la qualité et la durée de conservation des fruits de tomate peuvent être améliorées et la maturation mieux retardée en utilisant le MAP que la conservation à basse température, compte tenu de la susceptibilité des fruits aux dommages causés par le refroidissement

Influence Of Potato Cultivar And Stage Of Maturity On Oil Content Of French Fries (Chips) Made From Eight Kenyan Potato Cultivars

French fries (chips) are increasingly becoming indispensable in menus of many restaurants and hotels in major Kenyan towns due to their relatively lower consumer prices compared to other foods. When foods are deep-oil-fried, the amount of oil absorbed by the food is important since nutritionally, the amount of oil absorbed has a marked bearing on the number of calories supplied by the food. Fried foods such as chips may contain a considerable amount of oil to such extent that their consumption is of concern to nutritionists who advocate for a decrease or an increase of fat content in the diet depending on the part of the world where they are based. Chips with lower oil content and equivalent sensory attributes are expected to be highly accepted by consumers. The influence of potato cultivar and stage of maturity on uptake of oil into chips was investigated using eight Kenyan cultivars including five varieties (Tigoni, Desiree, Dutch Robyjn, Kenya Karibu, and Kenya Sifa) and three promising potato clones coded as 393385.47, 391696.96 and 393385.39. The eight cultivars were grown under cultural standard conditions at the National Potato Research Centre, Tigoni. The crop was dehaulmed two weeks before harvesting and allowed to cure at ambient air conditions (15-19 °C/86-92 % RH) for three weeks. The potatoes were harvested at 90 or 120 days after planting. The variety of potato used had a significant effect (P≤0.05) on oil uptake, with Dutch Robyjn having the lowest oil content. The cellular structures may have affected the oil uptake into the chips by influencing solid content, moisture loss during frying or damage done to original anatomy during processing. Harvesting before maturity significantly (P≤0.05) increased oil content of chips when compared to those prepared from mature tubers. There is need for processors to wisely choose the potato cultivar in order to produce French fries with low oil content

Phytochemical studies on herbal plants commonly used for processing and preserving meat and milk

Objective: The study aims at identifying and collecting herbal plants commonly used in milk processing and preservation by the Maasai community in Kajiado district and to determine the phytochemical and mineral composition.Methodology and Results: Twenty-three herbal plants were identified; three plants were selected through community prioritization using a structured questionnaire. Analysis for phytochemical composition was done using Sofowara (1993), Trease and Evans (1989) and Harborne (1998) methods composition by AOAC method 923.03 (AOAC, 1995) and pH. Tannins, saponins, flavonoids, alkaloids, steroids, sterols, terpenoids, flavones aglycones and reducing compounds were present in all the herbal plants. The herbal plants were significantly different (P<0.05) in mineral content. The highest mineral content was calcium 90.0 mg/100 g followed by magnesium, zinc and iron.Conclusion and application of the findings: this indicates that these plants are rich in phytochemicals and minerals therefore, they can be exploited to develop nutritive food preservatives because phytochemicals have both antimicrobial and antioxidant properties. These plants can also be processed to obtain a product that will substitute the chemical preservatives in the market now that consumers are showing greater preference for products preserved with natural products.Keywords: phytochemicals, herbs, minerals, antimicrobia