Aims:  To evaluate the efficacy of a biodegradable silage coating for the ability to protect timothy (Phleum pratensa) type silage against spoilage and its quality under natural conditions. Methods and Results:  Triplicate mini‐silos of silage were prepared for three treatments (1: uncoated; 2: coated with biodegradable coating and 3: sealed with plastic), two types of storage (unprotected or protected from rain) and 10 sampling times (0, 7, 14, 21, 28, 35, 42, 56, 63 and 70 days postensiling). Triplicate mini‐silos were opened at each sampling time for microbiological (total aerobic bacteria, lactic acid bacteria, moulds and yeasts) and biochemical analyses [pH, dry matter (DM), water‐soluble sugars (WSC), lactic (LA), acetic, propionic and butyric acids content]. The study showed that at day 70, counts of moulds and yeasts in silages protected against rain and coated with biodegradable coating were 5·98 log CFU g−1 when compared with 5·92 and 3·62 log CFU g−1 in samples from plastic‐sealed silage and uncoated silage, respectively. The pH was low and stable pH (4·34) when compared with uncoated (7·17) and plastic sealed (8·34) silages (P  0·05). A DM, WSC and LA content of 421·7, 13·4 and 20·9 g kg−1 was, respectively, observed. For silage stored outdoors, a level of moulds and yeasts of 3·77 log CFU g−1 of silage was also observed in silages coated with biodegradable coating after 28 days of storage. A stable pH showing a mean value of 4 was also observed. The pH, DM, WSC and LA content were, respectively, 4·18, 341·1, 13·34 and 31·8 g kg−1 in these samples. After 70 days of storage, the level of moulds and yeasts on silage sealed with biodegradable coating was 7·73 log CFU g−1. A DM, WSC and LA content of 291·9, 5·56 and 10·0 g kg−1 was, respectively, observed. Conclusions:  When compared with uncoated silage, the application of biodegradable coating can preserve the quality of silage for up to a month when exposed to rain and up to 70 days when protected from rain. Significance and Impact of the Study:  Results emphasize the possibility of the use of a biodegradable coating as an alternative to plastic film for sealing horizontal bunker silos.

This experiment was performed to assess two different biodegradable coating formulations for the preservation of corn silage quality. Soy-and casein-based biodegradable coatings were evaluated for their ability to exclude oxygen and preserve corn silage. Experiments were conducted under natural conditions outdoors. The effect of the coating composition on silage quality was compared with the quality of silage covered with a plastic (0.15 mm) (positive control) and uncovered (negative control) after 4 and 8 week periods. The results showed that the two biodegradable coatings offered the same level of silage protection during the overall experiment (8 weeks). As compared with the negative control, the two formulations prevented deterioration associated with air infiltration (heating, mold growth and dry matter losses) and limited the decrease in nutritive value. Also, the pH of the coated silage was significantly lower (P ≤ 0.05) than the negative control after 4 weeks of storage. Silage coated with the biodegradable coatings was able to maintain the pH below 4.5 during the first 4 weeks of storage. The decline in lactic acid concentration seems to have been initiated by the lactate-utilizing yeasts, responsible for the increase in the silage pH. No visual growth of mold was observed in silage sealed with biodegradable coatings. This study showed that biodegradable coatings were able to protect the quality of silage during 4 weeks but the biodegradable coatings were not as good as plastic at preserving silage after 8 weeks of storage.

The effect of a hydrophobic biodegradable coating on the conservation of silage was evaluated in comparison with unsealed silage and silage covered with a polyethylene (plastic). Silage samples were subjected to biochemical analysis (pH, dry matter, water-soluble sugars, ammoniacal nitrogen, lactic acid) and microbiological analysis (total aerobes, lactic acid bacteria, moulds and yeasts) during 135 days of storage. Silage covered with the biodegradable coating had a constant pH value of 4.79 and was preserved against spoilage until day 120, whereas the pH of unsealed silage increased during the first 6 days to a value of 8.22. After 2 months of storage, silage covered with the biodegradable coating had a lower dry matter content, higher water-soluble sugar content and higher lactic acid concentration than unsealed silage. During storage the population of total aerobes was lower in silage covered with the biodegradable coating than in silage covered with plastic. Furthermore, silage covered with the biodegradable coating had a stable content of aerobic micro-organisms. The biodegradable-coated silage showed a growth of lactic acid bacteria similar to that of silage covered with plastic. Only silage covered with the biodegradable coating had a low initial content of moulds and yeasts. Air infiltration was present throughout the storage period in the plastic and biodegradable coating treatments and was linked with the degradation of silage in both cases. However, the biodegradable coating significantly (P ≤ 0.05) increased the period of silage conservation compared with that of uncoated silage.

The addition of different plasticizers, thickeners and hydrophobic compounds such as fatty acids in biodegradable coatings has been evaluated using pH values and dry matter content as criteria in silage during one month of storage at room temperature under laboratory conditions. A base coating solution was prepared with whey protein concentrate, calcium caseinate and carboxymethylcellulose. From the base coating solution, derivative coating solutions were developed to evaluate the effect of plasticizers by incorporating glycerol at different concentrations and different ratios of sorbitol and glycerol. Thickening agents were also evaluated by adding fine silage powder, coarse silage powder, hay powder, or cornstarch. Derivative coating solutions were studied to evaluate the effect of fat constituents. Canola oil, beef fat, shortening, bees wax or candellila wax were added to the base solution following various procedures. Results showed that the addition of glycerol (320 g kg −1 ) in the coating formulation resulted in a pH value of 5.21 after 31 days of storage without visible spoilage under the coating. The presence of plasticizer compounds avoids the appearance of cracking in the coating during the early stage of conservation. The pH of silage coated with formulations containing coarse or fine silage powder was preserved below 5 until day 17 as compared to the other formulations where the pH was preserved below 5 only for 10 days. The incorporation of beef fat in the coating formulation resulted in the lowest pH as compared to all the other fat compounds evaluated, showing a value of 4.61 at the end of storage. The addition of glycerol, coarse silage and beef fat in the same coating formulation recovered by a hydrophobic layer of zein stabilized the pH to 4.47 for 28 days of storage with a final dry matter content at 344.3 g kg −1 without visible spoilage under the coating during all of the storage at room temperature.