Possibility of using the herbs of the labiatae (Lamiaceae) mint family in storage of ware potatoes
Mburu, Henry Kimani
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The effect of three herbs of the Labiatae (lamiaceae) mint family on potato storage was evaluated in comparative trials with the effect of tetrachlonitrobenzene (TCNB). The three herbs comprised Ocimum lamiifolium (macii), Leonotis nepetifolia (makandu) and Plectranthus (maigoya), all commonly available in potato growing areas of Kenya. The potatoes were stored in a common store with free air ventilation, and mean temperatures and relative humidities of approximately 21°C and 61% respectively. The herbs were applied as dry crushed debris, while TCNB) was applied as the usual dust formulation. Three levels of treatment were used for each herb. These were 10g/kg, 20g/kg and 30g.kg. The study was done for 94 days. Deterioration in the quality of the potatoes during storage was monitored by determining weight loss, sprouting and retention of ascorbic acid. Sprouting was measured every two to three days, while weight loss and ascorbic acid were determined every two weeks during storage. The overall best herb treatment was found to be Leonitis nepetifolia (LN). The treatment levels in each of the herbs had significant effect on the parameters monitored. In case of Leonotis nepetifolia, 10g/kg treatment retained 11.20% ascorbic acid as compared to 11.20% and 6.70% in TCNB treated and control samples respectively. LN30g/kg treated samples suffered only 15.98% weight loss as compared to 16.70% and 18.46% in TCNB treated and control samples respectively. LN10g.kg treatment suppressed sprouting by 10.71% as compared to 28.57% in TCNB treated tubers. The best herb treatment level was 10g/kg of Leonotis nepetifolia when considering all the parameters monitored together. This level had 11.20% ascorbic acid retention, 17.33% weight loss and 10.71% sprout suppression as compared to 11.20%, 16.70% and 28.57% respectively in TCNB treated tubers. 30g of Plactranthus per kg of tubers enhanced ascorbic acid retention most. Tubers in this treatment retained 21.60% of the initial ascorbic acid compared to 6.70% in the control sample and 11.2% in the TCNB treated sample. Some of the herb treatment seemed to enhance sprouting. These were specifically 10g Plectranthus and 20g Ocimum lamiifolium per kg of tubers. These had 52mm and 53mm long sprouts respectively compared to 42mm in control sample and 30mm in TCNB treated sample. LN 10g/kg was the herb treatment that suppressed sprouting most. In this treatment tubers had 11% shorter sprout than control tubers but 25% longer sprouts than TCNB treated tubers. Tubers treated with LN30g/kg and 10g Plectranthus per kg had less weight loss than even those treated with TCNB. 15.98% and 17.33% weight loss were observed in these samples respectively after 90 days of storage while 18.46% and 16.70% loss in weight were observed in control and TCNB treated tubers respectively. The study showed that the herbs of the Labiatae (lamiaceae) in particular Leonotis nepetifolia can successfully be used for storage of potatoes for short periods of up to 3 months to maintain appreciable fresh were quality.