Various modes of edible coating application vary in their coat dispersion and film formation, hence the need to determine the most effective mode of application for cassava. Edible surface coatings have been found to be effective in preserving the quality of various food products. However, there are variations in effectiveness among the different coating solutions, hence the need for optimization of the concentrations of the gums used. This study aimed at determining the most efficient coating application method on the cassava postharvest quality. Physiologically mature cassava (variety KME 1) was harvested and divided into seven portions. The various portions were coated using 1.5% xanthan gum, 1.5% xanthan/guar gum, and 2% xanthan/guar gum by both dipping and spraying method. There was no significant difference on the colour, total cyanide, ethylene production, and total phenolic content between the two application methods. The 2% xanthan/guar gum coating showed a significant difference on the dry matter content while the 1.5% xanthan gum coating had a significant difference on the respiration rate and weight loss. The 1.5 xanthan treated roots had a final dry matter content of 72.5% for the sprayed samples and 75.98% for the dipped sample while the 2% xanthan/guar gum treated roots had a final dry matter content of 64.6% and 74.1% for the dipped and sprayed root samples, respectively. The 1.5% xanthan and 2% xanthan/guar gum treated roots showed no significant difference in their action on dry matter content. The 1.5% xanthan/guar dipped and sprayed samples differed significantly on their effect on flesh firmness with final values of 35.4N and 46.1N, respectively, at 20 days after harvest. This study suggested that based on the coating solution and the parameters being observed, there generally was no varying effect of dipping and spraying methods of coating application. The choice of the efficient mode of application to use will depend on other factors such as the easiness of application.
Cassava is widely consumed in the tropical regions [
Coating of food products can be done by either dipping, spraying, brushing, extrusion, panning, or solvent casting [
The spraying technology is mostly used in food industries due to its convenience [
The effectiveness of the two modes of application differs based on the food products being coated and there is contradicting information on the most efficient between the two methods. Moreover, gums have been found to be an excellent moisture loss barrier and good in freshness preservation [
In the preliminary study, xanthan and guar gum were sourced from Sigma-Aldrich. The preliminary experiments indicated that the effectiveness of the gums sourced from Sigma-Aldrich was similar to the food grade gums sourced from a food ingredient supplier in Nairobi. Hence for the main experiment, the gums were sourced from a local food ingredient supplier. Fresh cassava root (
Completely Randomized Design was used for the experiment. The treatments included 3 different concentrations of 1.5% xanthan gum, 1.5% xanthan/guar gum, and 2% xanthan/guar gum. The different treatments were applied by both dipping and spraying method. The data was recorded at the fresh stage and at 2 day intervals for a storage duration of twenty days.
Two different coating application methods were tested to determine the most effective mode of application to be used on the cassava roots. Coating was performed on the same day that the cassava roots were harvested. The differently treated roots were then subjected to physical, physiological, and chemical analysis for the entire storage duration at two-day intervals.
The coating formulations used were 1.5% xanthan gum, 1.5% xanthan/guar gum, and 2% xanthan/guar gum. The 1.5% xanthan gum was prepared by dispensing 1.5 g of xanthan gum into 100 ml of distilled water. This was heated at 40°C on a magnetic stirrer for one hour. The 1.5% xanthan/guar gum solution was prepared by dispensing 0.75 grams of xanthan gum and 0.75 grams of guar gum into 100 ml of distilled water while the 2% xanthan guar gum solution was prepared by dispensing 1 gram of both xanthan gum and guar gum into 100 ml of distilled water and heated at 60°C on a magnetic stirrer for one hour. Coating was done on the same day that the roots were harvested. For the dipping method of application, the already cleaned roots were immersed into a bucket containing the coating solution. The roots were let to stay in the solution for three minutes after which they were removed and excess solution was left to drip off the cassava for one minute. The roots were then placed in clean plastic crates and left to dry after which they were stored for the twenty day storage duration. For the spraying technique, the solution was put in a hand held sprayer and this was then dispersed onto the cleaned roots as demonstrated by Pérez-Gallardo et al. [
A hand held penetrometer (N/g model ver 0.2, CRD-100D, Sun Scientific Co., Ltd, Japan) fitted with a probe was used to determine the firmness of flesh of the roots to a depth of 10 mm and the corresponding force required to penetrate this depth was determined according to Famiani et al
The colour of the cassava samples (3 replicates per treatment) was determined using a hunter lab colour difference meter (Minolta, Tokyo, Japan) according to Hernández-Muñoz et al. [
Cassava samples (3 replicates per treatment) were weighed while fresh and at an interval of two days for twenty days. The difference between initial and final root weight was determined for that storage period and expressed as a percentage on a fresh weight basis [
This was determined according to Ebah-Djedji et al. [
The amount of total phenolic contents was determined by the Folin-Ciocalteu method as described by Ainsworth and Gillespie [
Total HCN was analyzed using the alkaline titration method according to Famurewa and Emuekele [ TV=titre value and M=mass of sample.
Air tight containers of specific known volume fitted with self-sealing rubber septums were used. The weight of each cassava root was measured. The samples were then incubated in the air-tight plastic containers for one hour. After one hour, 1 ml of the headspace gas was drawn from each container using an air-tight syringe and injected into a gas chromatography (Shimadzu Corp., Kyoto, Japan, model GC-8A) fitted with a thermal conductivity detector and a Propak N column. The respiration rate was measured as mg CO2 per Kg per hour.
This was done according to Fugate et al. [
Comparisons among the various treatments and storage duration effects were determined by analysis of variance (ANOVA) while mean separations were performed using Tukey test at
The flesh firmness of the treated samples was determined and recorded from the first day after harvest to 20 days after harvest (DAH) as shown in Table
Changes in flesh firmness (Newtons) of cassava roots dipped and/or sprayed with different edible coating solution 20 days after harvest.
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| 61.8 ± 0.9 | 61.8 ± 0.9 | 61.8 ± 0.9 | 61.8 ± 0.9 | 61.8 ± 0.9 | 61.8 ± 0.9 | 61.8 ± 0.9 | 2.7 | 1.000 |
| 71.4 ± 4.6 | 65.7 ± 3.5 | 62.2 ± 8.2 | 66.5 ± 4.4 | 73.1 ± 8.0 | 63.8 ± 0.9 | 69.4 ± 10.0 | 19.4 | 0.871 |
| 76.8 ± 9.5 | 70.2 ± 6.0 | 64.8 ± 1.0 | 68.1 ± 2.4 | 76.2 ± 11.8 | 69.9 ± 5.0 | 81.5 ± 7.1 | 21.4 | 0.667 |
| 80.5 ± 1.2 | 78.2 ± 1.2 | 69.5 ± 1.5 | 76.9 ± 7.5 | 88.8 ± 6.8 | 75.5 ± 0.5 | 84.0 ± 6.7 | 14.1 | 0.176 |
| 90.1 ± 4.5 | 79.4 ± 2.5 | 71.2 ± 2.2 | 95.8 ± 0.4 | 89.2 ± 3.6 | 84.1 ± 1.5 | 88.0 ± 2.3 | 8.2 | <0.001 |
| 81.2 ± 9.3 | 92.5 ± 2.9 | 77.3 ± 3.4 | 55.5 ± 1.1 | 95.0 ± 1.4 | 97.2 ± 1.9 | 86.1 ± 8.8 | 14.1 | 0.176 |
| 54.8 ± 11.2 | 91.4 ± 3.8 | 95.6 ± 3.3 | 50.8 ± 5.6 | 96.0 ± 2.3 | 66.3 ± 3.5 | 61.7 ± 6.8 | 18.0 | <0.001 |
| 22.7 ± 0.9 | 58.3 ± 4.0 | 62.4 ± 2.5 | 39.6 ± 9.5 | 87.5 ± 3.3 | 53.1 ± 1.5 | 51.4 ± 6.2 | 14.7 | <0.001 |
| 15.9 ± 4.1 | 46.7 ± 4.0 | 49.3 ± 0.9 | 49.5 ± 4.4 | 78.2 ± 8.6 | 52.4 ± 0.2 | 42.6 ± 1.5 | 13.0 | <0.001 |
| 9.1 ± 0.6 | 22.5 ± 5.4 | 36.0 ± 2.3 | 44.4 ± 6.1 | 54.2 ± 4.2 | 48.7 ± 3.5 | 31.8 ± 10.3 | 16.5 | <0.001 |
| 4.0 ± 0.7 | 21.2 ± 3.3 | 29.1 ± 2.6 | 35.4 ± 2.2 | 46.1 ± 0.8 | 24.5 ± 4.3 | 24.3 ± 6.3 | 10.3 | <0.001 |
Values are means ± SE. Means with different superscript letters in a row are significantly (P≤0.05) different, n=3.
The 1.5% xanthan treated samples were both dipped and sprayed with the coating solution. The dipped sample attained a flesh firmness peak of 91.4N at 12DAH while the sprayed sample attained its firmness peak of 95.6N on the same day. From 12DAH onwards, the two samples declined in their flesh firmness Newtons as they approached 20DAH. At this point, the dipped sample had 21.2N while the sprayed sample had a slightly higher flesh firmness of 29.1N with no significant (P>0.05) differences.
In the 1.5% xanthan/guar treated cassava root, the dipped sample attained its peak of 95.8N at 8DAH while the sprayed samples attained its peak of 95.0N at 10DAH. Thereafter, there was a general decline in the flesh firmness of the treated samples as they approached 20DAH. By 20DAH, the sprayed sample had a higher flesh firmness of 46.1N while the dipped sample had 35.4N. At 20DAH, the dipped and sprayed sample showed a significant (P≤0.05) difference on the flesh firmness of the treated samples.
The 2% xanthan/guar treated roots attained firmness peak of 88.0N for sprayed samples at 8DAH while the dipped sample attained the peak of 97.2N at 10DAH. This was followed by a decline in the flesh firmness of the treated roots. The dipped sample had a final firmness of 24.5N while the sprayed sample had a firmness of 24.3N at 20DAH. Upon coating, the treated samples generally showed an increase in the flesh firmness to 10DAH followed by a decrease till 20DAH as shown in Table
At 20DAH, the control sample had a flesh firmness of 4.0N which was significantly (P>0.05) different from all the treated cassava root samples. There was generally no significant differences of the two application methods on the flesh firmness.
The change in flesh firmness of the cassava root samples is affected by the occurrence and development of the PPD. After harvesting of the cassava root crop, there is an increase in the flesh firmness of the cassava and then a later decline in the firmness. The permeabilizing of the cell membrane enhances the loss of the water and this may have led to the increase in flesh firmness [
The cassava root crop suffers cell disruption during the harvesting process and other subsequent postharvest activities such as transportation, sorting and washing. This cell disruption leads to PPD development. With the onset of PPD, there is formation of blue/black streaks on the vascular bundles of the cassava. The L
There also was a decline in the L
The 2% xanthan/guar gum treated root samples had a similar declining trend in the L
Changes in colour (L
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| 92.4 ± 0.3 | 92.4 ± 0.3 | 92.4 ± 0.3 | 92.4 ± 0.3 | 92.4 ± 0.3 | 92.4 ± 0.3 | 92.4 ± 0.3 | 0.8 | 1.000 |
| 90.4 ± 1.1 | 90.5 ± 0.7 | 89.6 ± 1.2 | 90.5 ± 0.7 | 87.6 ± 0.1 | 91.0 ± 0.2 | 90.9 ± 0.4 | 2.2 | 0.054 |
| 86.5 ± 0.9 | 89.8 ± 0.3 | 89.3 ± 0.7 | 90.5 ± 0.3 | 90.6 ± 0.3 | 89.9 ± 0.4 | 90.2 ± 0.3 | 1.5 | <0.001 |
| 86.6 ± 1.1 | 89.9 ± 0.2 | 88.7 ± 0.1 | 89.9 ± 0.2 | 89.8 ± 0.5 | 89.6 ± 0.2 | 90.1 ± 0.4 | 1.4 | 0.002 |
| 87.0 ± 1.1 | 88.9 ± 0.8 | 88.4 ± 0.6 | 88.4 ± 0.3 | 89.7 ± 0.3 | 89.2 ± 0.8 | 89.7 ± 0.2 | 1.9 | 0.122 |
| 82.2 ± 2.2 | 89.0 ± 0.4 | 87.9 ± 0.4 | 86.7 ± 0.4 | 89.6 ± 0.3 | 88.0 ± 0.7 | 88.0 ± 1.1 | 1.4 | 0.002 |
| 79.3 ± 4.2 | 88.3 ± 0.4 | 83.4 ± 4.0 | 86.8 ± 1.8 | 89.5 ± 0.3 | 84.9 ± 3.4 | 88.0 ± 1.0 | 8.1 | 0.187 |
| 77.9 ± 1.6 | 87.1 ± 0.1 | 80.8 ± 5.7 | 84.9 ± 0.7 | 88.7 ± 0.3 | 81.1 ± 1.6 | 85.7 ± 0.1 | 7.1 | 0.054 |
| 77.3 ± 1.6 | 86.0 ± 1.2 | 70.5 ± 5.1 | 83.3 ± 0.3 | 88.4 ± 0.2 | 76.2 ± 5.1 | 85.6 ± 1.7 | 8.8 | 0.006 |
| 73.6 ± 4.9 | 84.3 ± 1.0 | 70.3 ± 4.2 | 82.4 ± 1.2 | 77.9 ± 8.0 | 75.5 ± 2.5 | 85.8 ± 2.0 | 12.4 | 0.131 |
| 49.9 ± 7.0 | 79.5 ± 3.3 | 65.9 ± 5.8 | 77.1 ± 0.9 | 60.2 ± 3.4 | 67.9 ± 4.5 | 83.2 ± 3.0 | 13.3 | 0.001 |
Values are means ± SE. Means with different superscript letters in a row are significantly (P≤0.05) different, n=3.
There were generally no significant (P>0.05) differences among the treatments that were dipped and those that were sprayed with the coating solutions. This suggested that the two different coating applications had the same activity in terms of maintenance of the cassava root flesh colour.
After harvest of the cassava root crops, there is development of PPD that affected the colour of the flesh as recorded by Liu [
The weight loss of the treated root samples was determined and recorded from the first day to 20DAH. There was an increase in the percentage weight loss of the various samples till 20DAH
The 1.5% xanthan treated root samples showed an increase in weight loss to 30.0% for the dipped sample and 43.8% for the sprayed sample at 20DAH. These two samples had a significant (P≤0.05) difference on their effect on weight loss at this day.
The dipped 1.5% xanthan/guar treated roots had a percentage weight loss of 38.6% while the sprayed root had 45.6% at 20DAH. There were significant (P≤0.05) differences between the two samples at this day.
The 2% xanthan guar treated roots had no significant (P>0.05) difference at 20DAH. The dipped sample had a percentage weight loss of 37.0% while the sprayed sample had 37.7%.
At 20DAH, the control root had a 50.2% weight loss and this was the highest as compared to the lowest recorded weight loss of 30.0% which was observed in the sample treated with 1.5% xanthan gum by dipping (Table
Changes in weight loss (percentage) of cassava roots dipped and/or sprayed with different edible coating solution 20 days after harvest.
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| 0 | 0 | 0 | 0 | 0 | 0 | 0 | - | - |
| 10.0 ± 0.4 | 6.0 ± 0.5 | 11.3 ± 1.5 | 9.3 ± 0.2 | 9.3 ± 0.2 | 7.3 ± 0.6 | 8.3 ± 0.2 | 2.0 | 0.001 |
| 15.9 ± 0.3 | 13.1 ± 0.3 | 16.6 ± 0.8 | 13.7 ± 0.2 | 12.8 ± 0.5 | 10.3 ± 0.3 | 11.2 ± 0.1 | 1.2 | <0.001 |
| 20.2 ± 0.2 | 11.9 ± 0.2 | 21.2 ± 0.8 | 17.1 ± 0.1 | 16.6 ± 0.2 | 13.3 ± 0.2 | 13.8 ± 0.4 | 1.2 | <0.001 |
| 25.4 ± 0.6 | 15.1 ± 0.2 | 29.2 ± 0.3 | 20.9 ± 0.4 | 21.2 ± 0.4 | 17.1 ± 0.5 | 13.1 ± 0.4 | 1.3 | <0.001 |
| 28.2 ± 0.2 | 17.0 ± 0.5 | 32.8 ± 1.4 | 23.6 ± 0.4 | 24.5 ± 0.5 | 24.4 ± 0.6 | 21.7 ± 0.8 | 1.2 | <0.001 |
| 32.6 ± 0.5 | 20.1 ± 0.2 | 37.6 ± 1.0 | 27.1 ± 0.5 | 28.9 ± 0.5 | 29.9 ± 0.4 | 24.2 ± 0.2 | 1.6 | <0.001 |
| 35.9 ± 0.2 | 23.0 ± 0.5 | 39.6 ± 0.5 | 31.0 ± 0.4 | 35.0 ± 1.0 | 31.2 ± 0.4 | 29.0 ± 0.5 | 1.6 | <0.001 |
| 39.0 ± 0.5 | 25.7 ± 0.6 | 41.2 ± 0.7 | 33.9 ± 0.4 | 41.1 ± 0.1 | 32.8 ± 1.2 | 32.9 ± 0.3 | 1.9 | <0.001 |
| 44.6 ± 1.4 | 27.6 ± 0.8 | 42.1 ± 1.2 | 35.7 ± 0.9 | 43.4 ± 1.3 | 35.7 ± 1.9 | 34.5 ± 0.8 | 3.8 | <0.001 |
| 50.0 ± 0.1 | 30.0 ± 1.7 | 43.8 ± 1.4 | 38.6 ± 1.7 | 45.6 ± 0.9 | 37.0 ± 2.2 | 37.7 ± 1.9 | 4.7 | <0.001 |
Values are means ± SE. Means with different superscript letters in a row are significantly (P≤0.05) different, n=3.
Once the cassava roots have been harvested, their weight gradually reduces due to the loss of moisture and root respiratory activities [
The dry matter of the treated roots was determined and recorded for a period of twenty days on a two-day interval. There was an increase in the dry matter content of the treated roots as they approached 20DAH.
The dipped 1.5% xanthan treated root attained a dry matter content of 76.0% while the sprayed root sample had 72.5% at 20DAH which was significantly (P≤0.05) different. The samples treated with 1.5% xanthan/guar using dipping method had a content of 72.4% while the sprayed root had 71.7%. In addition, the 2% xanthan/guar dipped root had 64.6% while the sprayed root had 74.1% at 20DAH (Table
Changes in dry matter content (percentage) of cassava roots dipped and/or sprayed with different edible coating solution 20 days after harvest.
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| 56.1 ± 0.2 | 56.1 ± 0.2 | 56.1 ± 0.2 | 56.1 ± 0.2 | 56.1 ± 0.2 | 56.1 ± 0.2 | 56.1 ± 0.2 | 0.6 | 1.000 |
| 62.9 ± 0.9 | 57.4 ± 0.3 | 55.9 ± 2.5 | 57.7 ± 0.6 | 54.6 ± 1.9 | 53.1 ± 1.3 | 56.2 ± 1.1 | 4.3 | 0.006 |
| 64.6 ± 8.2 | 60.2 ± 1.5 | 57.9 ± 0.4 | 58.9 ± 0.5 | 55.0 ± 0.4 | 55.9 ± 1.2 | 60.5 ± 9.2 | 14.3 | 0.821 |
| 67.9 ± 0.9 | 62.7 ± 3.9 | 59.1 ± 0.6 | 61.3 ± 2.8 | 56.4 ± 0.4 | 55.9 ± 1.2 | 61.6 ± 0.4 | 5.8 | 0.095 |
| 69.5 ± 1.0 | 64.5 ± 1.6 | 59.7 ± 4.0 | 61.5 ± 4.3 | 57.7 ± 1.2 | 56.6 ± 1.6 | 61.9 ± 0.7 | 7.5 | 0.036 |
| 71.5 ± 2.4 | 66.0 ± 1.6 | 62.0 ± 0.6 | 62.1 ± 0.9 | 56.6 ± 0.5 | 58.2 ± 1.3 | 63.0 ± 2.1 | 5.8 | 0.095 |
| 73.4 ± 2.0 | 67.9 ± 5.2 | 62.8 ± 1.0 | 65.0 ± 1.4 | 58.3 ± 0.8 | 62.2 ± 0.5 | 68.8 ± 0.7 | 9.3 | 0.047 |
| 73.4 ± 1.5 | 67.4 ± 2.2 | 64.1 ± 0.9 | 67.9 ± 3.1 | 58.8 ± 0.1 | 62.6 ± 0.3 | 69.7 ± 2.9 | 5.6 | 0.001 |
| 73.4 ± 0.3 | 73.8 ± 3.3 | 70.5 ± 0.9 | 71.0 ± 1.5 | 67.2 ± 0.9 | 63.8 ± 1.3 | 70.9 ± 0.6 | 5.2 | 0.012 |
| 74.3 ± 4.8 | 74.8 ± 0.4 | 71.6 ± 0.4 | 71.3 ± 3.7 | 71.1 ± 0.7 | 63.9 ± 1.1 | 72.3 ± 0.4 | 4.9 | 0.008 |
| 77.8 ± 0.8 | 76.0 ± 0.7 | 72.5 ± 2.8 | 72.4 ± 0.7 | 71.7 ± 0.9 | 64.6 ± 1.5 | 74.1 ± 0.6 | 4.1 | <0.001 |
Values are means ± SE. Means with different superscript letters in a row are significantly (P≤0.05) different, n=3.
All the treated roots had a significant (P≤0.05) difference at 20DAH as compared to the control root that had the highest dry matter content of 77.8%. Generally, there were significant (P≤0.05) differences between the differently treated roots. The initial dry matter content of the fresh cassava root was recorded as 56.1%, similar to the range of 10%-57% reported by Ebah-Djedji et al
The total phenolic content was determined. This was recorded on the first day until 20DAH. There were no significant (P>0.05) differences amongst the various treatments.
The 1.5% xanthan dipped root sample had a decrease in its phenolic content to 8.4 mg/100g GAE while the spayed root sample had 9.1 mg/100g GAE at 20DAH. The 1.5% xanthan/guar treated root sample had 6.0 mg/100g GAE and 9.1 mg/100g GAE for the dipped and sprayed root sample respectively while the 2% xanthan/guar treated samples had 8.2 mg/100g GAE and 6.0 mg/100g GAE for the dipped and sprayed root samples, respectively. At 20DAH, the treated root samples had no significant (P>0.05) difference as compared to the control that had a total phenolic content of 7.7 mg/100g GAE. On coating using the various methods, there was a general gradual decline in the total phenolic content as it approached 20DAH (Table
Changes in total phenolic content (mg/100g GAE) of cassava roots dipped and/or sprayed with different edible coating solution 20 days after harvest.
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| 29.2 ± 2.1 | 29.2 ± 2.1 | 29.2 ± 2.1 | 29.2 ± 2.1 | 29.2 ± 2.1 | 29.2 ± 2.1 | 29.2 ± 2.1 | 6.3 | 1.000 |
| 24.3 ± 1.9 | 17.9 ± 3.5 | 27.7 ± 2.6 | 18.5 ± 3.0 | 27.7 ± 2.6 | 23.4 ± 2.0 | 21.5 ± 2.1 | 7.9 | 0.091 |
| 19.9 ± 4.6 | 16.7 ± 0.8 | 22.5 ± 1.2 | 21.6 ± 0.9 | 22.5 ± 1.2 | 20.2 ± 3.9 | 19.6 ± 1.2 | 7.4 | 0.668 |
| 17.0 ± 3.3 | 14.5 ± 1.3 | 18.1 ± 2.3 | 16.2 ± 0.6 | 18.1 ± 2.3 | 17.8 ± 0.7 | 14.5 ± 1.8 | 6.0 | 0.693 |
| 15.2 ± 1.3 | 13.6 ± 12 | 15.1 ± 1.3 | 15.2 ± 1.1 | 15.1 ± 1.3 | 14.5 ± 1.1 | 13.1 ± 2.3 | 4.3 | 0.89 |
| 14.5 ± 1.0 | 12.6 ± 0.5 | 14.8 ± 1.0 | 11.5 ± 0.3 | 14.8 ± 1.0 | 14.0 ± 1.0 | 13.1 ± 0.8 | 6.0 | 0.693 |
| 14.4 ± 2.2 | 12.5 ± 0.2 | 14.5 ± 1.4 | 11.0 ± 1.1 | 14.5 ± 1.4 | 12.6 ± 0.7 | 12.6 ± 0.3 | 3.8 | 0.359 |
| 12.8 ± 0.9 | 11.5 ± 0.6 | 12.8 ± 0.2 | 10.6 ± 2.2 | 12.8 ± 0.2 | 12.1 ± 0.8 | 12.4 ± 1.1 | 3.2 | 0.712 |
| 12.0 ± 0.9 | 9.5 ± 3.8 | 12.1 ± 1.0 | 10.5 ± 1.2 | 12.1 ± 1.0 | 11.3 ± 1.5 | 12.4 ± 1.7 | 5.6 | 0.896 |
| 8.0 ± 1.0 | 9.2 ± 0.9 | 9.4 ± 0.3 | 10.7 ± 0.5 | 9.4 ± 0.3 | 9.5 ± 0.5 | 10.3 ± 1.4 | 2.4 | 0.365 |
| 7.7 ± 2.5 | 8.4 ± 0.3 | 9.1 ± 0.5 | 6.0 ± 1.3 | 9.1 ± 0.5 | 8.2 ± 0.3 | 6.0 ± 1.2 | 3.6 | 0.361 |
Values are means ± SE. Means with different superscript letters in a row are significantly (P≤0.05) different, n=3.
There was a decrease in the total phenolic content of the cassava root samples as was reported by [
The total cyanide content was analyzed and recoded for the 20 day storage duration. There was a decline of the total cyanide content from the first day to 20 DAH. The dipped 1.5% xanthan treated root attained a final cyanide content of 0.7ppm while the sprayed sample had 1.2ppm at 20 DAH. The 1.5% xanthan/guar treated roots had no significant difference on their effect on cyanide content at 20 DAH. The dipped root had 1.8ppm while the sprayed sample had 0.8ppm at 20 DAH. The dipped 2% xanthan/guar treated cassava root had a final cyanide content of 0.9ppm while the sprayed root had 1.4ppm at 20 DAH (Table
Changes in total cyanide content (ppm) of cassava roots dipped and/or sprayed with different edible coating solution 20 days after harvest.
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| 3.6 ± 0.4 | 3.6 ± 0.4 | 3.6 ± 0.4 | 3.6 ± 0.4 | 3.6 ± 0.4 | 3.6 ± 0.4 | 3.6 ± 0.4 | 1.2 | 1.000 |
| 3.4 ± 0.6 | 3.1 ± 0.3 | 2.8 ± 0.3 | 2.7 ± 0.1 | 3.2 ± 0.2 | 2.7 ± 0.2 | 2.8 ± 7.1 | 0.9 | 0.500 |
| 3.0 ± 0.5 | 3.0 ± 0.2 | 2.5 ± 3.2 | 2.1 ± 0.5 | 3.1 ± 0.5 | 2.7 ± 0.6 | 2.5 ± 4.3 | 1.3 | 0.608 |
| 3.0 ± 0.3 | 2.5 ± 0.3 | 2.5 ± 4.4 | 2.3 ± 0.2 | 2.6 ± 0.3 | 2.6 ± 0.2 | 2.4 ± 7.4 | 0.9 | 0.801 |
| 2.8 ± 0.4 | 2.3 ± 0.3 | 2.2 ± 3.1 | 1.9 ± 0.2 | 2.4 ± 0.1 | 2.5 ± 0.6 | 2.2 ± 4.1 | 1.0 | 0.650 |
| 3.0 ± 0.3 | 2.1 ± 0.1 | 2.1 ± 2.2 | 1.8 ± 0.4 | 2.2 ± 0.1 | 2.3 ± 0.4 | 2.1 ± 0.2 | 0.8 | 0.105 |
| 2.7 ± 0.1 | 2.2 ± 0.3 | 2.2 ± 4.2 | 1.7 ± 0.2 | 2.2 ± 0.5 | 2.2 ± 0.1 | 2.1 ± 0.1 | 0.8 | 0.335 |
| 2.6 ± 0.2 | 1.4 ± 0.5 | 1.7 ± 0.2 | 1.4 ± 0.1 | 1.9 ± 1.0 | 2.0 ± 0.4 | 1.7 ± 0.1 | 1.4 | 0.629 |
| 2.3 ± 0.1 | 1.4 ± 0.1 | 1.4 ± 0.3 | 1.4 ± 0.1 | 1.5 ± 0.1 | 1.7 ± 0.3 | 1.5 ± 0.1 | 0.6 | 0.070 |
| 2.0 ± 0.5 | 1.4 ± 0.4 | 1.2 ± 0.2 | 1.5 ± 0.2 | 1.5 ± 0.1 | 1.9 ± 0.1 | 1.4 ± 0.1 | 0.9 | 0.511 |
| 2.0 ± 0.2 | 0.7 ± 0.1 | 1.2 ± 0.3 | 1.8 ± 0.1 | 0.8 ± 0.1 | 0.9 ± 0.3 | 1.4 ± 0.1 | 0.6 | 0.001 |
Values are means ± SE. Means with different superscript letters in a row are significantly (P≤0.05) different, n=3.
The respiration rate of both the dip and spray treated sample was analyzed. Upon coating, the treated samples obtained two different peaks. The first peak occurred at the 2DAH while the second peak occurred at different days based on the treatment. The 1.5% xanthan treated root showed its first peak of 2.5 mg CO2/kg/h and 3.2 mg CO2/kg/h for the dipped and sprayed samples, respectively. The second peak was observed at 14DAH for the dipped sample and 12DAH for the sprayed sample at a respiration rate of 6.6 mg CO2/kg/h and 7.7 mg CO2/kg/h, respectively. The two samples had significant (P≤0.05) differences at 20DAH. The 1.5 xanthan/guar treated sample had their first peaks of 3.6 mg CO2/kg/h for the dipped sample while the sprayed sample had a respiration rate of 3.5 mg CO2/kg/h at 4DAH and 2DAH, respectively. The second peak was observed at 12DAH for sprayed sample while the dipped sample had its peak at 16DAH. The respiration rate for the samples was 5.7 mg CO2/kg/h for the sprayed sample while the dipped sample had 8.0 mg CO2/kg/h. The two samples had no significant (P>0.05) differences at 20DAH.
The 2% xanthan/guar treated roots attained their first peak at 2DAH for both the dipped and the sprayed roots. The dipped root had a respiration rate of 3.1 mg CO2/kg/h while the sprayed sample had a rate of 2.8 ml CO2/kg/h at the same day. The second peak of 6.5 mg CO2/kg/h was attained at the 12DAH for both the dipped and sprayed roots. The second peak was followed by a decline in the respiration rate towards zero as it approached 20DAH (Table
Changes in total respiration rate (mg CO2/kg/h) of cassava roots dipped and/or sprayed with different edible coating solution 20 days after harvest.
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| 1.1 ± 0.1 | 0.7 ± 0.0 | 1.1 ± 0.0 | 1.1 ± 0.0 | 1.0 ± 0.0 | 0.9 ± 0.0 | 1.1 ± 0.1 | 0.1 | <0.001 |
| 5.7 ± 0.0 | 2.5 ± 0.0 | 3.2 ± 0.1 | 2.5 ± 0.1 | 3.5 ± 0.2 | 3.1 ± 0.0 | 2.8 ± 0.1 | 0.2 | <0.001 |
| 2.6 ± 0.0 | 3.9 ± 0.2 | 5.2 ± 1.6 | 3.6 ± 0.1 | 1.1 ± 0.1 | 2.9 ± 0.0 | 2.1 ± 0.0 | 1.8 | 0.006 |
| 3.4 ± 0.1 | 1.3 ± 1.1 | 3.5 ± 0.3 | 2.3 ± 0.1 | 1.9 ± 0.1 | 3.2 ± 0.3 | 2.9 ± 0.0 | 1.4 | <0.001 |
| 6.2 ± 0.1 | 3.09 ± 0.06 | 5.38 ± 0.04 | 4.47 ± 0.08 | 2.57 ± 0.23 | 3.43 ± 0.22 | 4.43 ± 0.03 | 0.40 | <0.001 |
| 3.04 ± 0.10 | 4.6 ± 0.2 | 6.7 ± 0.2 | 5.9 ± 0.0 | 3.6 ± 1.1 | 4.3 ± 1.1 | 4.2 ± 0.1 | 1.4 | <0.001 |
| 3.1 ± 0.1 | 5.1 ± 0.0 | 7.7 ± 0.2 | 6.1 ± 0.1 | 5.7 ± 0.3 | 6.5 ± 0.1 | 12.7 ± 5.3 | 6.1 | 0.1 |
| 3.5 ± 0.1 | 6.6 ± 0.1 | 7.1 ± 0.2 | 7.5 ± 0.1 | 4.0 ± 1.2 | 5.7 ± 0.2 | 6.1 ± 0.2 | 1.5 | <0.001 |
| 3.5 ± 0.1 | 5.5 ± 0.0 | 7.3 ± 0.0 | 8.0 ± 0.1 | 3.1 ± 1.2 | 5.0 ± 0.0 | 5.4 ± 0.2 | 1.4 | <0.001 |
| 4.0 ± 0.3 | 3.8 ± 1.5 | 6.0 ± 0.6 | 6.5 ± 0.1 | 4.9 ± 0.3 | 4.6 ± 0.2 | 4.5 ± 0.9 | 2.1 | 0.002 |
| 3.7 ± 0.1 | 0.5 ± 0.1 | 3.8 ± 0.5 | 3.6 ± 0.4 | 3.2 ± 0.2 | 3.7 ± 0.3 | 3.4 ± 0.2 | 0.9 | <0.001 |
Values are means ± SE. Means with different superscript letters in a row are significantly (P≤0.05) different, n=3.
The two peaks formed during the respiration process of the cassava root crop is due to wounding and biochemical changes for the 1st and 2nd peak respectively [
The ethylene production rate was determined from the first day to 20DAH. There were no significant differences between the differently coated roots. Upon coating, there was formation of one peak which was dependent on the efficiency of the coating solutions to reduce gaseous exchange between the cassava and the environment, which was followed by a decline.
The dipped 1.5% xanthan treated root attained a peak of 2.2 nl C2H4/g/h on 12DAH while the sprayed sample had 4.9 nl C2H4/g/h at 14DAH. The 1.5% xanthan/guar dipped sample had a peak of 2.2 nl C2H4/g/h at 14DAH while the sprayed sample had 2.8 nl C2H4/g/h on the same day. The sprayed 2% xanthan/guar treated root had its peak of 6.1 nl C2H4/g/h at 16DAH while the dipped sample did not attain a peak during the 20 day storage duration. At 20DAH, there was no significant difference in the various treated roots as the ethylene production rate range was very small-0.2 to 0.6 nl C2H4/g/h (Table
Changes in total ethylene production rate (nl C2H4/g/h) of cassava roots dipped and/or sprayed with different edible coating solution 20 days after harvest.
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| 0.5 ± 0.0 | 0.04 ± 0.0 | 0.1 ± 0.0 | 0.1 ± 0.1 | 0.1 ± 0.0 | 0.2 ± 0.2 | 0.02 ± 0.0 | 0.2 | 0.605 |
| 2.1 ± 0.0 | 0.3 ± 0.0 | 0.3 ± 0.0 | 0.4 ± 0.1 | 0.6 ± 0.1 | 1.2 ± 1.2 | 0.3 ± 0.0 | 0.2 | 0.019 |
| 0.3 ± 0.0 | 0.01 ± 0.0 | 0.4 ± 0.0 | 0.6 ± 0.0 | 0.03 ± 0.0 | 0.1 ± 0.0 | 0.02 ± 0.0 | 0.04 | <0.001 |
| 0.1 ± 0.1 | 0.1 ± 0.0 | 0.3 ± 0.0 | 0.02 ± 0.0 | 0.3 ± 0.0 | 0.1 ± 0.1 | 0.1 ± 0.0 | 0.1 | <0.001 |
| 0.01 ± 0.0 | 0.03 ± 0.0 | 1.0 ± 0.1 | 0.4 ± 0.3 | 1.5 ± 0.1 | 1.6 ± 0.1 | 0.7 ± 0.1 | 0.4 | <0.001 |
| 0.4 ± 0.0 | 0.9 ± 0.3 | 1.9 ± 0.9 | 1.0 ± 0.3 | 1.2 ± 0.7 | 0.1 ± 0.0 | 1.0 ± 0.8 | 1.6 | 0.287 |
| 0.02 ± 0.1 | 2.2 ± 0.1 | 0.3 ± 0.0 | 0.9 ± 0.5 | 0.7 ± 0.1 | 0.6 ± 0.0 | 1.1 ± 0.5 | 0.8 | 0.004 |
| 0.2 ± 0.0 | 0.9 ± 0.2 | 2.9 ± 0.5 | 2.2 ± 0.2 | 2.8 ± 0.2 | 0.5 ± 0.1 | 1.3 ± 0.0 | 0.6 | <0.001 |
| 12.4 ± 4.0 | 0.8 ± 0.2 | 4.9 ± 1.1 | 1.6 ± 0.3 | 0.7 ± 0.1 | 0.7 ± 0.1 | 6.1 ± 0.8 | 4.9 | 0.001 |
| 0.2 ± 0.1 | 0.3 ± 0.0 | 0.1 ± 0.0 | 0.1 ± 0.0 | 0.1 ± 0.0 | 0.2 ± 0.0 | 0.6 ± 0.1 | 0.1 | <0.001 |
| 0.6 ± 0.0 | 0.3 ± 0.0 | 1.0 ± 0.0 | 0.2 ± 0.1 | 0.8 ± 0.4 | 0.3 ± 0.0 | 1.5 ± 0.2 | 0.6 | 0.003 |
Values are means ± SE. Means with different superscript letters in a row are significantly (P≤0.05) different, n=3.
Ethylene is one of the gases that affect various biochemical processes in various products. From the time of harvest, there was a slight increase in the ethylene production leading to formation of a peak and this might be attributed to the ethylene produced due to wounding [
The thickness of the coating solution is crucial to the activity of the coat hence it should be well adjusted to suit its purpose. A very thick film may lead to anaerobic respiration hence the production of CO2, and off-flavors. The thickness of the coating directly correlates to the concentration, draining time and viscosity of the coating solution [
All the coating solutions improved the postharvest life of cassava with respect to the control which was not coated. The application of edible coatings on the cassava root, extended the postharvest shelf life of the cassava with minimal alterations to its quality. The 1.5% xanthan/guar gum treated roots showed the best quality and had the longest shelf life extension of up to 20 days when stored at 25°C. Generally, no significant (P≤0.05) difference was recorded between the two different coating applications of dipping and spraying on the cassava root samples. No difference was noted on the colour changes, total cyanide content, total phenolic content, and firmness for all the treatments. However, the 1.5% differently coated xanthan roots had a significant difference on respiration rate and weight loss, while the 1.5% xanthan/guar gum coated roots had different effects on the ethylene production rate. The dipped and sprayed 2% xanthan/guar gum treated roots showed a significant difference in their effect on the dry matter content.
The data used to support the findings of this study are available from the corresponding author upon request.
This paper is part of a thesis under
The authors declare no conflicts of interest concerning the publication of this research article.
This research work was supported by the Bureau of Food Security-USAID under the terms of award number AID-BFS-IO-1200004 through the World Vegetable Center AVRDC, Arusha, and the German Academic Exchange Service-DAAD under personal reference number (91602039, 2015).