Acetic Acid Fumigation Research Articles

Effects of acetic acid vapour on the microbial status of ‘Merchant’ and ‘Oktavia’ sweet cherries (Prunus avium L.)

Sweet cherries are highly perishable fruit, consequently postharvest treatments are indispensable if longer shelf-life is desired. The use of synthetic fungicides is getting more and more repudiated, generating the demand for new sustainable and gentle “natural” sanitation techniques such as fumigation with acetic acid (AA). Not least due to still existing technical problems and lack of knowledge of basic mechanisms of action and interactions between the various intrinsic and extrinsic factors this technique has not been introduced into practice. Therefore, the efficiency of AA fumigation at three different concentrations and two practically relevant storage temperatures was analysed on the cultivars ‘Merchant’ and ‘Oktavia’. Even low AA vapour concentrations (3 mg L−1) reduced mould counts to near the detection limit, while low temperature storage can delay (‘Merchant’) or prevent (‘Oktavia’) mould regrowth. Higher AA vapour concentrations (>3 mg L−1) sustainably reduced yeast counts during storage at 4 °C. AA vapour treatment moderately and temporarily decreased bacteria counts. Efficiency of AA fumigation varied between both ‘Merchant’ and ‘Oktavia’ cherries. AA fumigation can be, in particular, helpful against mould-caused spoilage in fruit of both cultivars. For highly efficient treatments minimum AA concentration of 6 mg L−1 is recommended.

Effects of Dry Process Technology on Quality of Different Forms “Laba” Garlic Products

This paper investigated the effects of 2 g/L acetic acid fumigation technology on the value of L*, a*, b* and the contents of blue pigment, yellow pigment and allicin of “Laba” garlic in different product forms. “Laba” garlic was prepared by three different treatments: (1) traditional dip (control sample); (2) “Laba” garlic cloves were fumigated by 2 g/L acetic acid; (3) “Laba” garlic bulbs were fumigated by 2 g/L acetic acid. During process, all the treated samples were maintained at appropriate conditions (dark, 20 °C). After 10 days of process, the value of L*, a*, b* and the contents of blue pigment, yellow pigment and allicin of “Laba” garlic in different product forms were measured. Interestingly, the results presented that the value of L*, b* and the contents of blue pigment, yellow pigment and allicin of “Laba” garlic prepared by dry process were higher than them within traditional dip samples. The technology of dry process might be a novel process method to produce “Laba” garlic in the future.

Acetic Acid Fumigation of Fruit Storage Bins to Control Diapausing Codling Moth Larvae

Fumigation with glacial acetic acid (AA) vapor successfully kills post-harvest pathogens on tree fruits and berries and reduces their spoilage in storage. In this study, we investigated whether a similar approach could be implemented to eradicate diapausing larvae of the codling moth, Cydia pomonella (L.), from fruit harvest bins they commonly infest. In 24-h tests conducted in 0.023-m3 fumigation chambers using two concentrations of vaporized AA [117,360 and 174,823 cumulative parts per million-hours (ppm-h)], mortality of diapausing larvae was 81% and 100%, respectively. A similar 24-h exposure to a 61,940 cumulative ppm-h treatment of AA caused no mortality. A 24-h fumigation of diapausing codling moth larvae placed in scaled-down plastic fruit bins treated with 55 mL of AA evaporated into a 1-m3 chamber caused 100% mortality. The same fumigation treatment of artificially infested, scaled-down wooden fruit bins caused no significant mortality of test larvae. Atmospheric concentrations of AA vapor in 1-m3 fumigation chambers containing wooden bins could not be maintained at levels necessary to cause insect death, even after multiple injections of AA. We hypothesize that either the wood or the moisture contained therein absorbs or in some other way interacts with the AA vapor. The use of AA as a fumigant targeting codling moth larvae in wooden bins is not practical or economical at this time. Fumigation of plastic fruit bins with AA would provide an economical and environmentally friendly method of killing diapausing codling moth larvae. The successful disinfestations of plastic fruit bins of codling moth would prevent these bins from being an external source of infestation, thereby decreasing overall codling moth infestation in orchards, which in turn benefits current density-dependent management practices used for the area-wide control of codling moth. chemical name: Glacial Acetic Acid (AA).

Effects of Dry Process Technology on Quality of “Laba” Garlic during Process

This paper investigated the effects of acetic acid and CO2 fumigation technology on the variations of crude protein, allicin and blue pigment and yellow pigment of “Laba” garlic during process. “Laba” garlic was prepared by three different treatments: (1) traditional dip (control sample); (2) 2 g/L acetic acid fumigation; (3) 5% CO2 & 2 g/L acetic acid fumigation. During process, all the treated samples were maintained at appropriate conditions (dark, 20 °C). After treated and every 3 days of the process time, the contents changing of allicin, blue pigment and yellow pigment of “Laba” garlic were measured. Interestingly, the results presented that the contents of the functional composition allicin, crude protein, blue pigment and yellow pigment of “Laba” garlic prepared by dry process were higher than them of traditional dip samples. The technology of dry process might be a novel process method to produce “Laba” garlic in the future.

Effect of acetic acid fumigation on soil-borne fungi and cucumber root rot disease under greenhouse conditions

The effect of acetic acid vapour on soil-borne fungi and root rot disease of cucumber plants under greenhouse conditions was studied. Acetic acid vapour at four concentrations was tested against linear growth and spore germination of some soil-borne fungi, in vitro. The most sensitive fungus to acetic acid vapours was Rhizoctonia solani which inhibited at 4 µl l−1, while Fusarium solani, Fusarium oxysporium f. sp. cucumerinum, Scleroitium rolfsii and Didymella melonis inhibited at 6 µl l−1. Complete inhibition of spore germination was obtained with acetic acid vapours at 4 µl l−1 with all tested fungi. Acetic acid vapours significantly reduced germination of resting stage of all tested fungi. Complete inhibition of chlamedospores of F. solani and F. oxysporum f. sp. cucumerinum was obtained with acetic acid vapour at 10 µl l−1, meanwhile, sclerotia of S. rolfsii was killed at 20 µl l−1 of acetic acid vapour. Four types of soil: sandy, loamy, clay and peat-moss were fumigated with acetic acid vapour for 60 minutes. A higher response was recorded with peat-moss and sandy soil in which soil-borne fungi were inhibited at 75 and 100 µl l−1 respectively, while in loamy and clay soil fungi were inhibited at 125 µl l−1. Peat-moss soils were artificially infested with individual cucumber root rot fungi and fumigated with acetic acid vapour for 60 minutes. A population count of pathogenic fungi and cucumber root rot disease was carried out. Results indicated that acetic acid vapour at 75 µl l−1 caused a complete reduction in the population of cucumber root rot fungi and under greenhouse conditions it reduced the cucumber root rot disease more than 93.3 and 95.4% for pre- and post-emergence respectively. It could be suggested that acetic acid vapours might be safely used for controlling cucumber root rot disease under greenhouse conditions.

Acetic Acid, Ethanol and Steam Effects on the Growth ofBotrytis cinerea in vitroand Combination of Steam and Modified Atmosphere Packaging to Control Decay in Kiwifruit

The effects of acetic acid fumigation, ethanol fumigation, and steam heat treatment on growth of Botrytis cinerea in vitro were investigated. The effect of steam heat treatments in combination with modified atmosphere packaging (MAP) on Botrytis decay development on ‘Hayward’ kiwifruit was also studied. The fungus was grown in Petri dishes on potato dextrose agar. Ethanol fumigation with 100 μl/l for 3 or 6 min, or 200 μl/l for 6 min enhanced the growth of B. cinerea. The effect of acetic acid on growth of B. cinerea was time and dosage-dependent. Fumigation with 1 μl/l for 6 min, 2 μl/l for 3 min, and 4 μl/l for 3 min promoted radial growth of the fungus when compared to the growth of the untreated control. Fumigation with 2 μl/l for 6 min delayed the growth of the fungus for the first 6 days, while fumigation with 6 μl/l for 3 min delayed the growth of the fungus after the sixth day. Fumigation with 4 or 6 μl/l acetic acid for 6 min, and 8 μl/l acetic acid for 3 or 6 min resulted in complete inhibition of fungal growth. Steam heat treatment at 45°C for 6 min, and at 48, 51, and 54°C for 3 or 6 min completely inhibited fungal growth in vitro. Furthermore, steam treatments at 47, 50, and 53°C for 3 or 6 min completely inhibited decay at the stem end of kiwifruit kept at 10°C in MAP for 12 days. However, none of the steam treatments inhibited decay in wounds on the surface of the fruit kept in MAP.

Control of common bunt (Tilleta tritici and T. laevis) of wheat (Triticum aestivum cv. ‘Laura’) by fumigation with acetic acid vapour

Common bunt caused by Tilletia tritici and T. laevis remains an important disease of wheat, particularly in organic production where effective fungicides are not available. Acetic acid (AA), a potential organic seed fumigant, was evaluated for control of common bunt of wheat. The highly susceptible spring wheat cultivar Laura was inoculated with bunt spores and then fumigated with 2 and 4 g kg-1 AA vapour in 23 L chambers for 1 h at 20°C. Fumigation reduced field infection levels of common bunt in trials conducted at Lethbridge, AB during 2000, 2001, and 2003. The 4 g kg-1 rate was more effective than the 2 g kg-1 rate in reducing bunt infection, although both rates were as effective as Vitavax, the standard seed-treatment fungicide treatment. Some reduction in tiller numbers was associated with the AA treatments especially at the 4 g kg-1 rate. In vitro tests on artificial growth media showed that AA significantly decreased seed-borne mold contamination caused by several species of fungi. Acetic acid fumigation could be an important organic alternative to fungicides for control of common bunt. Key words: Covered smut, organic, seed treatment, stinking smut, vinegar

Acetic Acid Fumigation of Apple Rootstocks and Tree Fruit Scionwood to Remove External Microflora and Potential Plant Pathogens

Acetic acid (AA) fumigation of rootstocks and dormant shoots was explored as a method of eliminating plant pathogens from propagation material. Dormant shoots were tested in early winter to determine the rate of AA vapor that they could tolerate before being damaged. Apricot (Prunus armeniaca), apple (Malus ×domestica), and peach (Prunus persica) shoots collected from a single site in Dec. 1999 tolerated 30, 12, or 6 mg·L–1 AA, respectively. Vineland 3 (V3) and Malling-Merton 106 (MM.106) rootstock liners fumigated with 1 mg·L–1 AA were adequately surface-sterilized although the effect on growth was not recorded. A similar experiment with Malling 9 (M9) rootstocks showed that 12 mg·L–1 AA would eliminate most surface microorganisims from roots although it delayed shoot growth when the trees were planted. The higher 15 mg·L–1 rate delayed tree growth and appeared to kill some trees. The 12 mg·L–1 rate prevented growth of Erwinia amylovora and Pseudomonas syringae pv. syringae bacteria on shoots even when an enrichment technique was used to detect them. Finally, when 96 `Jonagold' apple shoots known to be infected by Podosphaera leucotricha were fumigated with AA in 2001, none developed powdery mildew, although 99% of the control shoots did. These promising results suggest that further research should be done toward adapting AA fumigation for use by commercial nurseries.

Use of measured concentrations of acetic acid vapour to control postharvest decay in d’Anjou pears

Decay of d’Anjou winter pears caused by Botrytis cinerea is a major problem for pear growers in North America. Acetic acid (AA) vapour could be an alternative to the use of postharvest fungicides such as thiabendazole for disease control. In fall 1998, bin lots of pears, half inoculated with B. cinerea, were fumigated with mean rates of 292 μl l−1 h AA vapour, three times over a period of 7–15 days and once with 586 μl l−1 h AA vapour. Similar trials with AA vapour rates averaging 198±39 μl l−1 h were conducted in 1999 and 2000. Treatment effectiveness was evaluated immediately after fumigation by monitoring fungal microflora on fruit surfaces and stems and after storage by recording number of decayed fruit and stems infected by species of Botrytis or Penicillium. Application of AA vapour reduced both stem and fruit surface microflora to low levels and in some cases to zero initially and after the fruit had been stored for 4 months, reduced rot by 51% on fruit inoculated with B. cinerea. Overall analysis of data from the 1998 trials showed that AA fumigation significantly reduced stem infection on fruit stored in air or controlled atmosphere storage. A trial conducted in 1999 at a commercial site established the lower rate of 198 μl l−1 h as an effective rate; fruit rot was reduced from 36 to 3% in fruit inoculated with B. cinerea and stored for 4 months. Two consecutive fumigations at 200 μl l−1 h AA vapour in 2000 on naturally contaminated fruit reduced stem infection by 43% and increased the number of mold-free fruit by 44% without any damage to the pears. The consequences of using measured amounts of AA vapour to control postharvest decay of pear are discussed.

Fumigation with acetic acid vapor to control decay of stored apples

Introduction. Apples are potentially subject to blue mold decay caused by Penicil- lium expansum if stored at 1 °C for three or more months or if wounded during handling. Results from trials with apples contaminated with conidia of P. expansum and fumigated in small cham- bers with acetic acid (AA) vapor indicated that fruit could be sterilized to reduce decay without effect on fruit quality. The objective of this study was to determine if larger quantities of apples treated with AA vapor would have less decay after storage and/or wounding. It was also impor- tant to determine if fumigation would affect apple quality and aroma. Materials and methods. Apple cultivars were harvested at commercial maturity for use in AA fumigation trials. Apples arti- ficially or naturally contaminated with conidia of P. expansum were fumigated with AA vapor in a 1 m3 gas tight chamber at 10 °C for 1 h to 24 h or dipped in 450 μg thiabendazole 〈 L -1 solu- tion. Fruit fumigated in standard wooden or plastic apple boxes, or small wooden bins were either wounded and evaluated for decay after a week at 20 °C or stored at 1 °C for three or more months and evaluated for decay. Then apple quality was assessed. Results. Apples naturally contaminated with Penicillium spp. that had been stored at 1 °C in air storage and treated with AA vapour had 50% less decay than the control fruit. In another experiment, AA fumigation was as effective as thiabendazole in reducing decay. AA fumigation reduced decay of fruit coming out of storage for apples stored for 3 months, and a second AA fumigation reduced infection of wounds on these same apples. AA fumigation before storage did not affect apple quality or vinegar aroma. Discussion. AA fumigation showed great potential for reducing decay in stored apples. It could be used as an organic alternative to synthetic fungicides for control of blue mold decay.

Fumigation of Fruit with Acetic Acid to Prevent Postharvest Decay

Acetic acid (AA) as a vapor at low concentrations was effective in preventing fruit decay by postharvest fungi. Fumigation with 2.7 or 5.4 mg AA/liter in air at 2 and 20C reduced germination of Botrytis cinerea Pers. and Penicillium expansum Link conidia to zero after they had been dried on 0.5-cm square pieces of dialysis tubing. Decay of `Golden Delicious', `Red Delicious', and `Spartan' apples (Malus domestica Borkh.) inoculated with 20 μl drops of conidia of B. cinerea (1.0 × 105 conidia/ml) or P. expansum (1.0 × 106 conidia/ml) was prevented by fumigating with 2.0 and 2.7 mg AA/liter, respectively. Tomatoes (Lycopersicon esculentum Mill.), grapes (Vitis vinifera L.), and kiwifruit [Actinidia deliciosa (A. Chev.) C.F. Liang et R. Ferguson var. deliciosa] inoculated with B. cinerea or navel oranges (Citrus sinensis L.) inoculated with P. italicum Wehmer did not decay when fumigated with 2.0 mg AA/liter at 5C. AA fumigation at low temperatures (1 and 5C) with 2.0 or 4.0 mg AA/liter prevented decay of `Spartan' and `Red Delicious' apples and `Anjou' pears (Pyrus communis L.) inoculated with B. cinerea and P. expansum, respectively. `Spartan' apples immersed in a suspension of P. expansum conidia (1.4 × 105 conidia/ml) and fumigated with 2.7 mg AA/liter at 5C had an average of 0.7 lesions per fruit compared to 6.1 for nontreated fruit. Increasing the relative humidity from 17% to 98% increased the effectiveness of AA fumigation at 5 and 20C. At the concentrations used in our trials, AA had no apparent phytotoxic effects on the fruit. The potential for commercial fumigation with AA to control postharvest decay of fruit and vegetables appears promising.