Potassium sorbate reduces production of ethanol and 2 esters in corn silage

Abstract

The objective of this work was to evaluate the effects of biological and chemical silage additives on the production of volatile organic compounds (VOC; methanol, ethanol, 1-propanol, methyl acetate, and ethyl acetate) within corn silage. Recent work has shown that silage VOC can contribute to poor air quality and reduce feed intake. Silage additives may reduce VOC production in silage by inhibiting the activity of bacteria or yeasts that produce them. We produced corn silage in 18.9-L bucket silos using the following treatments: (1) control (distilled water); (2) Lactobacillus buchneri 40788, with 400,000 cfu/g of wet forage; (3) Lactobacillus plantarum MTD1, with 100,000 cfu/g; (4) a commercial buffered propionic acid-based preservative (68% propionic acid, containing ammonium and sodium propionate and acetic, benzoic, and sorbic acids) at a concentration of 1 g/kg of wet forage (0.1%); (5) a low dose of potassium sorbate at a concentration of 91 mg/kg of wet forage (0.0091%); (6) a high dose of potassium sorbate at a concentration of 1g/kg of wet forage (0.1%); and (7) a mixture of L. plantarum MTD1 (100,000 cfu/g) and a low dose of potassium sorbate (91 mg/kg). Volatile organic compound concentrations within silage were measured after ensiling and sample storage using a headspace gas chromatography method. The high dose of potassium sorbate was the only treatment that inhibited the production of multiple VOC. Compared with the control response, it reduced ethanol by 58%, ethyl acetate by 46%, and methyl acetate by 24%, but did not clearly affect production of methanol or 1-propanol. The effect of this additive on ethanol production was consistent with results from a small number of earlier studies. A low dose of this additive does not appear to be effective. Although it did reduce methanol production by 24%, it increased ethanol production by more than 2-fold and did not reduce the ethyl acetate concentration. All other treatments increased ethanol production at least 2-fold relative to the control, and L. buchneri addition also increased the 1-propanol concentration to approximately 1% of dry matter. No effects of any treatments on fiber fractions or protein were observed. However, L. buchneri addition resulted in slightly more ammonia compared with the control. If these results hold under different conditions, a high dose of potassium sorbate will be an effective treatment for reducing VOC production in and emission from silage. Regulations aimed at reducing VOC emission could be ineffective or even increase emission if they promote silage additives without recognition of different types of additives.

Effects of potassium sorbate and Lactobacillus plantarum MTD1 on production of ethanol and other volatile organic compounds in corn silage

“…Concentrations of methanol, 1-propanol, methyl acetate, ethyl acetate, acetaldehyde, valeraldehyde, and hexanal were measured in silage samples using a headspace gas chromatography (GC) method, following Hafner et al (2014). After opening the silos, silage samples were sealed in vacuum bags and frozen until analysis.…”

“…Weiß and Auerbach (2012) reported 45% reductions in ethyl lactate and ethyl acetate, along with a 70% reduction in ethanol, through the use of a commercial mixture of sodium benzoate and potassium sorbate (21.9% sodium benzoate, 13.2% potassium sorbate, applied at 2 g/kg (Kirsten Weiß, Humboldt Universität Berlin, Germany, personal communication)). Hafner et al (2014) found that a 1 g/kg dose of potassium sorbate reduced production of methyl acetate (by 24%) and ethyl acetate (by 46%).…”

“…Several studies have reported reductions in ethanol concentration in silage by the addition of potassium sorbate, which is commonly applied to limit growth of spoilage yeasts. Application of potassium sorbate at 0.5 g/kg or higher (fresh mass basis), alone or in combination with other chemical inhibitors, has been shown to reduce ethanol production by 58%-85% (Kleinschmit et al, 2005;Teller et al, 2012;Weiß and Auerbach, 2012;Bernardes et al, 2014;Hafner et al, 2014).…”

“…The only study to measure the effect of pure potassium sorbate on ester production was done in California, USA, and used forage with a relatively low DM content of 250 g/kg (Hafner et al, 2014). Furthermore, the response of aldehydes to potassium sorbate addition has not been evaluated.…”

“…For example, the alcohol 1-propanol is generally present at lower concentrations than ethanol, and seems to make a much smaller contribution to air quality problems (Hafner et al, 2013), despite a higher reactivity than ethanol (Carter, 2009). However, its concentration varies widely in corn silage, and it may make more of a contribution to poor air quality than ethanol in some cases (Raun and Kristensen, 2010;Hafner et al, 2013Hafner et al, , 2014.…”