Drying of African leafy vegetables for their effective preservation: the difference in moisture sorption isotherms explained by their microstructure

Hag, Leonie van ‘t; Danthe, Jessica; Handschin, Stephan; Mutuli, Gibson P.; Mbuge, Duncan Onyango; Mezzenga, Raffaele

doi:10.1039/c9fo01175g

Cited by 15 publications

(9 citation statements)

References 26 publications

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“…For lower a w , the EMC is also low, compared to levels when the a w approaches one (1) [29,30]. Knowingly, the EMC decreases with increasing temperature and for the same value of relative humidity (RH) leads to the endothermic reaction [31]. It was observed for the samples CS133 and control for the temperatures of 30 to 50°C that the water content decreases when the temperature increases within the interval values of a w between 0.37 and 0.78%, of which most of the curves are found around 0.8 a w .…”

Section: Models Equationsmentioning

confidence: 99%

Sorption Isotherms and Some Functional Properties of Cowpea Varieties Flour

Amadou¹

2022

Sorption - From Fundamentals to Applications

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In sub-Sahara, preservation of processed cowpea flour remained a challenge, and there are no standard isotherm conditions for drying cowpea flour. This study aims to define the optimum isotherm conditions for cowpea flour and assess their functional properties. Adsorption isotherms of three varieties of cowpea at temperatures 30, 40, and 50°C and in each case with six different applications depending on the constant relative humidity of the medium were executed. Water and oil absorption capacities including swelling index were determined. Results show that water content at equilibrium is inversely proportional to the temperature, and at the same temperature, the water content increases when water activity augments. The adsorption isotherms are of type II according to the fitted BET and GAB models. The absorption capacities ranged from 1.06 ± 0.01, 1.08 ± 0.02, and 1.09 ± 0.01(mL/g), respectively, for CS133, CS032, and control. However, the swelling index was significantly separated (P < 0.05). The adsorption isotherm curve of the sample CS032 at 50°C shows a stronger correlation (R2 = 0.9274) than the other varieties regardless of the mathematical isotherm model used. It can be concluded that depending on some functional properties of cowpea variety flour, these varieties seemed to behave separately vis-a-vis their sorption isotherm.

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Section: Models Equationsmentioning

confidence: 99%

Sorption Isotherms and Some Functional Properties of Cowpea Varieties Flour

Amadou¹

2022

Sorption - From Fundamentals to Applications

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“…It is imperative to maintain moisture below 15% in order to prevent quality deterioration occasioned by microbial growth due to less optimal moisture content [27]. Hag et al [28] established a critical limit of ≤14% for the growth of microorganisms in dehydrated African leafy vegetables. Te utilization of artisanal traditional processing for preservation resulted in a signifcant loss (p < 0.05) of micronutrients.…”

Section: Physicochemical Qualities Of Traditionally Processedmentioning

confidence: 99%

“…Values with similar uppercase letters followed by a diferent lowercase in the superscript along the column are statistically diferent. moisture content encourage microbial spoilage of the product and thus will have a short shelf-life [28]. Te efect of photo-oxidation in the reduction of the labile micronutrients explains the loss of 66.7-80.1% in beta-carotene and 53.7-58.3% in ascorbic acid content in the sun-dried vegetables (Table 11).…”

Section: Independent Variablementioning

confidence: 99%

Comparative Characterization of Trends and Patterns of Physical and Chemical Attributes of Optimal and Traditional Processed Cowpea Leaves

Owade

Abong

Okoth

et al. 2022

Journal of Food Quality

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Seasonality in the availability of cowpea leaves has often limited their utilization and thus the promotion of preservation techniques that convert the vegetables into storable and stable forms. The recommendations for the use of highly mechanized techniques in preservation are brought into question due to limited affordability among resource-constrained households that prefer less costly approaches. Therefore, this study used statistical techniques of principal component analysis to comparatively evaluate the trends of physicochemical quality of the two diverse approaches of processing cowpea leaves. The study evaluated dehydrated cowpea leaves of different processing techniques from farmer groups and optimally processed using modern techniques for nutritional composition, phytochemical compounds, and colour changes. Sun drying techniques that excluded blanching had the least content of beta-carotene and ascorbic acid, 2.65 ± 0.95 and 21.80 ± 1.24 mg/100 g dry weight basis (dwb), respectively, accompanied by the most significant ( p < 0.001 ) deterioration of colour (7.74 ± 3.49) than techniques that included. Whereas the antinutrients declined, the difference did not significantly differ ( p > 0.05 ) based on preservation techniques. With factor analysis determining optimal nutritional quality for cowpea leaves at 8 weeks after emergence, sun drying had the highest loss of beta-carotene and ascorbic acid, 66.7–80.1% and 53.7%–58.3%, respectively ( p < 0.001 ), whereas mineral leaching, reduction of antinutrients, and colour changes were more pronounced in dehydration techniques incorporating fermentation as pretreatment. For the traditional preservation techniques, increasing retention of minerals resulted in aggravated losses of beta-carotene and ascorbic acid, whereas in the mechanized techniques, this was not the case. In concluding that the mechanized techniques have a better combination of attenuating losses of micronutrients, the study recommends that in promoting the utilization of traditional preservation techniques, low-cost processes like steam blanching can help improve the nutritional quality of the product.

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“…The drying process is used before salt is ready to pack. The drying method has been widely used in industry to improve the quality of the product [10]- [13]. In addition, salt drying is a critical method in the salt industry to improve salt quality [14].…”

Section: Introductionmentioning

confidence: 99%

Analysis and Comparison of Different Dewatering Methods On Salt Quality

et al. 2021

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The salt quality was studied by dewatering methods such as centrifugal hydro extraction, fixed bed dryer, and rotary drum dryer. The effect of different salt particle sizes was also analyzed. The centrifugal hydro extractor is found to be effective when reducing the high-water content of salt and suitable for reducing water content after the salt wash stage. Fixed bed dryers produce lower water content than rotary drum dryers. A water content lower than 1% can be achieved using fixed bed dryers. Finally, all dewatering methods such as centrifugal hydro extractors, fixed bed dryers, and rotary bed dryers are suitable for salt production methods. Reduced salt particle size from 30 to 60 mesh also improved the drying performance.

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Drying of African leafy vegetables for their effective preservation: the difference in moisture sorption isotherms explained by their microstructure

Abstract: Controlled drying preserves African leafy vegetables and fight micronutrient deficiency during droughts. The palisade parenchyma cell length determines their rehydration capacity and starch granules the texture upon cooking.

Cited by 15 publications

References 26 publications

Sorption Isotherms and Some Functional Properties of Cowpea Varieties Flour

Sorption Isotherms and Some Functional Properties of Cowpea Varieties Flour

Comparative Characterization of Trends and Patterns of Physical and Chemical Attributes of Optimal and Traditional Processed Cowpea Leaves

Analysis and Comparison of Different Dewatering Methods On Salt Quality

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