Effects of mode and timing of calcium chloride application on tissue calcium concentration and acceptability of mango fruits

Mango (Mangifera indica L) production in Kenya directly supports approximately 200,000 farmers and many other beneficiaries. Despite this, its production suffers from post-harvest losses due to the fruits' short shelf life in ambient conditions. Calcium maintains cell integrity, strengthens the cell wall, membrane structure, and thus increases shelf life. A completely randomized block design with a split plot arrangement was used to compare the effect of spraying and immersion of ‘Van Dyke' mango fruits at maturity or 15 days later in calcium chloride at different concentrations (0.5%, 1%, 1.5%, or 0%) and times on the fruit ripening rate and organoleptic acceptance. The peel firmness (N), total soluble solids (0Brix), flesh color (Ho), beta carotene (mg/100ml), and carbon dioxide evolution (ml/kg/hr) of fruits were determined at time 0 and every two days for up to eight days in ambient conditions. Additionally, organoleptic characteristics, flesh firmness, calcium concentration (g/mg), and their correlations were determined. Fruits immersed in calcium chloride at maturity had higher retained peel firmness (10.6 N, 10.3 N), deeper flesh color (37.45, 36.78), lower total soluble solids (14, 13.8), a lower carbon dioxide evolution (30.7 ml/kg/hr), higher beta carotene and higher flesh calcium concentration than fruits exposed to other treatments. Fruits sprayed at maturity outperformed those sprayed 15 days later in the studied parameters. Flesh calcium content correlated positively with flesh firmness (r= 0.913, r= 0.852), flesh color (r= 0.828, r= 0.841), fruit aroma (r=0.8199, r=0.841), and negatively with skin shriveling (r=-0.778, r=-0.806) and fruit flavor (r=-0.811, r=-0.829). Flesh firmness correlated negatively with skin shriveling (r=-0.868, r=-0.788) and fruit flavor (r=-0.8869, r=-0.821), but positively with peel color (r=0.9115, r=0.856) and aroma (r=0.907, r=0.848). Skin shriveling was found to have a negative relationship with peel color (r=-0.944, r=-0.93) and aroma (r=-0.944, r=-0.938), but a positive relationship with fruit flavor (r=0.933, r=0.947). Peel color correlated positively with aroma (r=0.979, r=0.977) and negatively with fruit flavor (r=-0.962, r=-0.950), respectively. Despite the effectiveness of post-harvest calcium chloride immersion in extending fruit shelf life, optimal use is advised to avoid deteriorated pulp flavor and increased shriveling. More research is needed to determine how calcium chloride can be made available to the fruit while it is still attached to the tree

Aflatoxin and fumonisin mycotoxins contamination along the maize value chain in the eastern Democratic Republic of Congo

Aflatoxin and fumonisin contamination was assessed in different samples along the maize value chain in different territories of South Kivu province. Kabare and Ruzizi Plain were chosen as they represent two different agroecological areas where maize is mostly produced. Twelve districts and one town were selected across the province. The stakeholders were randomly selected, and 215 maize (139 maize grain and 76 maize flour) samples were taken for laboratory analysis. The Q + kit was used to determine the total aflatoxins and fumonisins. Three categories of maize were examined: freshly harvested dry maize, stored maize (maize stored for 3 months ±1.5 month) and market maize. Aflatoxin was found in 100% of the maize samples with the least content of 0.3 μg/kg detected in freshly harvested dry maize with mean 3.2+0.3 and levels ranging from 0.3 to 18.5 μg/kg. The average level of aflatoxin in stored grain samples was 97.9±182 μg/kg within a range of 1.16 to 841.5 μg/kg, and the mean level of aflatoxin in stored flour was 148.9±164.5 μg/kg with levels ranging from 2.05 to 905.1 μg/kg. The mean level of aflatoxin maize collected from the market was 95.1 ±164 μg/kg, with levels ranging from 1 to 823.2 μg/kg. Almost all the maize flour collected from the three areas had a high contamination level that exceeded the maximum tolerable limit of 10 μg/kg. Fumonisin was detected in all samples. However, the levels of fumonisin do not follow a specific trend with the duration of storage. The freshly harvested dry maize concentration was 2.4±5.1 μg/g, with levels ranging from 0.03 to 20.9μg/g. About 37% of freshly harvested maize samples contaminated by fumonisin exceeded the maximum tolerable limit of 4 μg/kg. There was a difference between total fumonisin in grain and flour; the average level of fumonisin in stored maize grain was 1.4±0.9 μg/g with levels ranging from 0.18- 4.7 μg/g while in flour, the level was 2.1±1.3 μg/g with levels ranging from 0.3-4.5 μg/g. Almost all the maize samples collected from the three areas had a degree of contamination that did not exceed the maximum tolerable limit of 4 μg/g. These results indicate that the two mycotoxin levels, particularly aflatoxin, were high in the different samples collected at specific nodes. Therefore, preventing mycotoxins accumulation in maize by post-harvest prevention of contamination and growth of toxigenic moulds by promoting proper grain drying and storage should be encouraged among the actors of the maize value chain.&nbsp

EFFECT OF VARIED CALCIUM FORMULATIONS AND TIME OF APPLICATION ON POSTHARVEST QUALITY AND ORGANOLEPTIC ACCEPTABILITY OF MANGO FRUITS

Mango (Mangifera indica L.) is a highly perishable fruit with a short shelf life at ambient conditions, which may lead to post-harvest losses approximated to be 40- 45%. This reduces returns to farmers significantly. The problem is compounded by the fact that most farmers do not have access to cold storage facilities. Nutrient management has been shown to affect postharvest characteristics of fruits. Calcium particularly plays a critical role in cell membrane integrity, tissue firmness and delays lipid catabolism. Previous studies have indicated a deficiency of calcium in some mango growing regions in Kenya. A field study was carried out to determine the effect of varied calcium formulations applied at various stages of growth on mango fruits post-harvest quality and organoleptic acceptability. The study was carried out in Embu County Eastern Kenya during seasons 2017/2018 and 2018 /2019 using “Van Dyke” cultivar, aged approximately 10 years. The experiment was set up in a randomized complete block design with a split-split plot arrangement, three trees per replication, replicated thrice. Three calcium formulations: calcium chloride, calcium nitrate and Easygro™ were applied at rates of 0%,1.0%, 1.5% and 2.0% at fruit set, 30 days after fruit set and 30 days to physiological maturity. The calcium sources formed the main plots, the timing of application formed the subplots while the rates of application formed the sub-sub plots. Total soluble solids (TSS) and percentage titratable acidity (TA) were assessed at harvest and after 12 days of storage under ambient conditions (25±2ºC, 70±5% relative humidity) using standard procedures. Selected fruits’ sensory attributes were also evaluated after storage using a hedonic scale. Analysis of data was done using the 14th Edition of the Genstat software. The differences among the means of the treatments were compared using Fisher’s Protected LSD test at 5% probability level. Fruits sprayed with calcium chloride, 2.0% at fruit set had higher TSS (6.8 º brix and 6.3º brix) (10.47 º brix and 9.10 º brix), TA (1.29% and 1.27%), (0.77% and 0.675%) than other treatments at maturity and after storage in both seasons, respectively. Calcium chloride at 2.0% level of application led to a superior peel color appearance contrary to calcium nitrate and Easygro™ also applied at 2.0%, which led to an inferior peel color appearance and an inferior taste of fruits. Therefore, calcium nitrate and easy gro should be sprayed at concentration of 1.5% for good taste and peel colour appearance

EFFECT OF VARIED CALCIUM FORMULATIONS AND TIME OF APPLICATION ON POSTHARVEST QUALITY AND ORGANOLEPTIC ACCEPTABILITY OF MANGO FRUITS

Mango (Mangifera indica L.) is a highly perishable fruit with a short shelf life at ambient conditions, which may lead to post-harvest losses approximated to be 40- 45%. This reduces returns to farmers significantly. The problem is compounded by the fact that most farmers do not have access to cold storage facilities. Nutrient management has been shown to affect postharvest characteristics of fruits. Calcium particularly plays a critical role in cell membrane integrity, tissue firmness and delays lipid catabolism. Previous studies have indicated a deficiency of calcium in some mango growing regions in Kenya. A field study was carried out to determine the effect of varied calcium formulations applied at various stages of growth on mango fruits post-harvest quality and organoleptic acceptability. The study was carried out in Embu County Eastern Kenya during seasons 2017/2018 and 2018 /2019 using “Van Dyke” cultivar, aged approximately 10 years. The experiment was set up in a randomized complete block design with a split-split plot arrangement, three trees per replication, replicated thrice. Three calcium formulations: calcium chloride, calcium nitrate and Easygro™ were applied at rates of 0%,1.0%, 1.5% and 2.0% at fruit set, 30 days after fruit set and 30 days to physiological maturity. The calcium sources formed the main plots, the timing of application formed the subplots while the rates of application formed the sub-sub plots. Total soluble solids (TSS) and percentage titratable acidity (TA) were assessed at harvest and after 12 days of storage under ambient conditions (25±2ºC, 70±5% relative humidity) using standard procedures. Selected fruits’ sensory attributes were also evaluated after storage using a hedonic scale. Analysis of data was done using the 14th Edition of the Genstat software. The differences among the means of the treatments were compared using Fisher’s Protected LSD test at 5% probability level. Fruits sprayed with calcium chloride, 2.0% at fruit set had higher TSS (6.8 º brix and 6.3º brix) (10.47 º brix and 9.10 º brix), TA (1.29% and 1.27%), (0.77% and 0.675%) than other treatments at maturity and after storage in both seasons, respectively. Calcium chloride at 2.0% level of application led to a superior peel color appearance contrary to calcium nitrate and Easygro™ also applied at 2.0%, which led to an inferior peel color appearance and an inferior taste of fruits. Therefore, calcium nitrate and easy gro should be sprayed at concentration of 1.5% for good taste and peel colour appearance