Using HPP (Hydrogen Peroxide Plus) to Inhibit Potato Sprouting
U. Afek,* Janeta Orenstein and E. Nuriel
Department of Postharvest Science of Fresh Produce, Gilat Experiment Station, ARO, The Volcani Center, Mobile Post Negev 2, 85-280, Israel.
Potatoes (Solanum tuberosum L.) samples ,cv. ‘Desiree’, were treated for sprout control and stored at 10 ± 1 C for 6 months. Those treated four times with HPP (hydrogen peroxide plus), applied with the “Shira Aeroponics System”, had a 0% rate of sprouting. Those treated with CIPC also had no sprouting, while the nontreated control had 84%. A single treatment with HPP or CIPC resulted, after 6 months of storage at 10 ± 1, in sprouting rates of 61 and 58%, respectively, vs. 87% in the untreated control.
ADDITIONAL KEYWORDS: Potato, Solanum tuberosum L., sprouting, storage.
HPP, Hydrogen peroxide plus
MH, Maleic hydrazide
Sprouting is a major cause of losses in stored potatoes. Not only does it reduce the number of marketable potatoes, but intense evaporation of water from sprout surfaces also reduces the weight of the remaining tubers (Afek and Warshavsky, 1998). There are two main methods of keeping potatoes sprout free during storage: storing at low temperatures (2 to 4° C) and using sprout suppressants (Khanbari and Thompson 1996; Prange, et al., 1997; Rastovski, 1987).
Low temperatures, however, cause the degradation of starch to sugar and increases the tubers sweetness (Es and Hartmans, 1987a; Morell and Rees, 1986; Rees et al., 1981; Ross and Davies, 1992). This reduces their quality, particularly when they are intended for industrial use (Rastovski, 1987). Control atmosphere (low concentration of O2 and high concentration of CO2) was also found to suppress sprouting (Prange, et al., 1997). However, a high concentration of CO2 can result in a physiological defect: black heart (Afek and Warshasky, 1998).
Many chemical compounds (e.g. ethylene, camptothecin, volatile monoterpenes, jasmonates, ethanol, nonanol, abscisic acid, indole-acetic acid, dichlorbenil dimethylnaphthalene and diisopropylnaphthalene) are known to inhibit sprouting. However, most of these substances have never been used commercially, or have been used only for a short time, (Beveridge et al., 1981; Coleman and Coleman, 1986; Es and Hartmans, 1987b; Hartmans and Es, 1979; Prange, et al., 1997; Wang et al., 1980; Wiltshire and Cobb, 1996; Lewis et al., 1997). Ozone is also has been tested as a sprout inhibitor of stored potatoes (Prange, et al., 1997).
The sprout inhibitors chloropropham (CIPC) and maleic hydrazide (MH) have also proved to be of value (Buitelaar, 1987; Es and Hartmans, 1987b; Hajslova and Davidek, 1986; Prange, et al., 1997; Yada et al., 1991). However, their application can be problematic. Due to environmental concerns, in several countries use of CIPC and other chemicals, are either restricted or may become restricted (Afek and Warshavsky, 1998; Es and Hartmans, 1987b). MH is applied as a foliar application in the field 4 to 6 weeks before harvest, but its timing is delicate: if the treatment is carried out too early, the yield will be reduced, but late treatment will have an insufficient effect on sprouting (Es and Hartmans, 1987b; Yada et al., 1991). TCNB is not effective if dormancy is broken, if the store is excessively ventilated, or if the storage temperature is kept above 10° C (Es and Hartmans, 1987b).
In recent years, several studies have found carvone to be efficacious (Oosterhaven et al., 1996; Sorce et al., 1997; Wiltshire and Cobb, 1996). It has been registered as a sprout inhibitor and is used commercially in several countries. But because it is expensive, many countries, such as Israel, do not use it.
The present study examined HPP (G.A.T.S. Biology, P.O. Box 652 Nes Ziona 74106, Israel), a new sprout inhibitor that is based on hydrogen peroxide stabilized with a mixture of substances; it was applied with a fogger (the Shira Aeroponics System).
MATERIALS AND METHODS
Plant material and storage procedure
Potato tubers (cv. ‘Desiree’) were harvested from fields in Israel’s northern Negev, cured for 12 days at 13 ± 1° C and 95% relative humidity (RH), and stored in three rooms. Each room (15 x 15 x 7 m3) contained 5 perforated ducts (70 cm in diameter) which were positioned on the floor from the plenum to the opposite wall. These ducts were covered with 750 tons of potatoes, piled 5 meters high (Brook et al., 1995). For each treatment, 5 sacks, each comprising 25 kg potatoes, were buried at random in each pile. The sacks, which had been attached to ropes to help extricate them, were removed from the piles once every five weeks, and sprout percentages were determined. This was repeated for 6 months per year over a three-year period.
Application of HPP and CIPC
On the first day after curing, the potatoes in room A received treatment with HPP (sole a.i.) for 10 h. Preliminary experiments showed that the concentration of HPP most effectively inhibited sprouting. The HPP was applied with the Shira Aeroponics System. Three fans (one m diameter) forced the combination of humidified air and HPP into the bottom of the plenum; this mist reached the perforated ducts, and was then pulled up through the potato pile to the vacuum space produced above the pile (Afek and Warshavsky, 1998).
In room B, CIPC was applied to the cured potatoes in accordance with standard commercial practices (60 g CIPC/ton of potatoes) (Afek and Warshavsky, 1998). Room C was the control: the Shira Aeroponics System produced humidified air as described in room A, but no HPP was added to the water.
After the treatments, the temperature in the storage rooms was reduced to 10 ± 1 C, and the RH adjusted to 95%; these settings were maintained for 6 months. The treatments were repeated every 5 weeks for a total of four treatments.
In addition, following the first treatment, 500 tubers were sampled from each pile, and stored under the same conditions as in the source treatments; this helped evaluate the effects of a single treatment with HPP or CIPC on sprout inhibition.
The experiment was conducted during 3 years in a randomized block design and a year was considered as one replicate. Each block comprised 15 sacks that was considered as 5 sub samples of 3 sacks for each treatment each month for a total of 90 sacks.
Data were analyzed by ANOVA procedures by means of the Statistical Analysis System (SAS) package (Cary, NC, USA).
RESULTS AND DISCUSSION
After 6 months of storage at 10 ± 1 C, during which the potatoes recieved 4 treatments with HPP or CIPC, a 0% sprouting rate was found in room A (treated with HPP) and in room B (treated with CIPC); an 84% rate was found in room C (control) (Table 1). (Sprouting was considered as less than 2 mm.) In the samples that were taken after the first treatment, the percentages of sprouting after 6 months at 10 ± 1 C were 61, 58 and 87% from rooms A, B and C, respectively (Table 2).
The trend today is to minimize the use chemicals in stored fresh produce (Crossley and Mascall, 1997), and to find alternatives to currently used potato sprout suppressants (Prange et al., 1997). Results of the present study show that HPP applied with the Shira Aeroponics System is efficacious as a sprout inhibitor (Tables 1, 2). The technology of this fogger is based on ultrasonic nebulizers; it produces very small droplets that have almost no mass, carrying the HPP as a weightless gas that covers the potatoes in the storage rooms. Microscopic examination indicated that the action of HPP in inhibition of potato sis by damaging the sprout tips.
Application of HPP by fogging with the Shira Aeroponics System technique is a method that is friendly to the environment, easy to implement and inexpensive.
Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. Series No. 442 -1998.
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Table 1. Sprouting of potato tubers (%) during 6 months of storage at 10 ± 1 C and 95% RH, following four treatments with HPP, CIPC or control.
Sprouting (%) during the storage period
|Treatment||1 month||2 months||3 months||4 months||5 months||6 months|
|HPP||0 a1||0 a||0 a||0 a||0 a||0 a|
|CIPC||0 a||0 a||0 a||0 a||0 a||0 a|
|Control||8 b||26 b||48 b||63 b||74 b||84 b|
1Different letters within a column indicate significant differences according to Fisher's protected least significant difference test
Table 2. Sprouting of potato tubers (%) during 6 months of storage at 10 ± 1 and 95% RH, following one treatment with HPP, CIPC or control.
Sprouting (%) during the storage period
|Treatment||1 month||2 months||3 months||4 months||5 months||6months|
|HPP||0 a1||9 a||22 a||37 a||50 a||61 a|
|CIPC||0 a||8 a||20 a||35 a||47 a||58 a|
|Control||14 b||37 b||52 b||65 b||73 b||87 b|
1Different letters within a column indicate significant differences according to Fisher's protected least significant difference test (P=0.05).
Note: Published with author's permission