Application of Acidulants to Control Salmonella spp. in Rendered Animal Fats and Oils with Different Levels of Unsaturation

Salmonella-contaminated pet foods could potentially become a source of human salmonellosis. This study evaluated the survival of Salmonella without and with the addition of acidulants in different fat types (chicken fat (CF), canola oil (CO), Menhaden fish oil (FO), lard (La), and tallow (Ta)) commonly used to coat dry pet food kibbles. The minimum inhibitory concentration (MIC) of individual acidulants and the combination were determined using the broth microdilution method. Autoclave-sterilized rendered fats were treated with pre-determined concentrations of antimicrobial acidulants (0.5% sodium bisulfate (SBS), 0.5% phosphoric acid (PA), 0.25% lactic acid (LA), etc.) and incubated overnight at 45 °C. The treated fats were inoculated with approximately eight logs of a Salmonella cocktail. Microbiological analyses were conducted separately for the fat-phase and water-phase at predetermined time intervals (0, 2, 6, 12, and 24 h) by plating them onto TSA plates. After incubating at 37 °C for 24 h, the plate count results were expressed as log CFU/mL. The MIC of SBS was 0.3125%, and of PA and LA were both 0.1953% against cocktail Salmonella serotypes. We observed a possible synergistic effect when SBS and organic acid were combined. All the acidulant tested at targeted concentrations individually as well as in combination with organic acids were highly effective against Salmonella spp. (non-detectable within 2 h) across different fat types. A potent anti-bactericidal effect leading to non-detectable Salmonella immediately (<1 h) at 45 °C was observed in the aqueous phase of the fish oil system, even without the addition of acidulants. These findings are significant for the dry pet food industries, where potential post-processing contamination of Salmonella could be controlled by treating fats and oils with acidulants.

Beyond the Recycle of Raw Chicken Fat

The wasted raw fat of chicken was extracted and recrystallized with slowly stir at various cooling temperature to get a clear out-looking and liquid chicken oil. The recovery percentage of liquid chicken oil is about 100, 87, 78, 49 and 0% at 25, 21, 17, 13 and 9°C. The chicken liquid oil has a new composition of fatty acids than the original oil (p < 0.05) and has a safety range in acid value and peroxide value. The fatty acid ratio of the liquid chicken oil obtained at 13°C to be 1:1.6:0.9 (SFA: MUFA: PUFA) is believed to be good dietary oil. The concept of ideal fatty acid ratio comes from Hayes' report (1:1.5:1, SFA: MUFA: PUFA) which is also found to mimic to human lipid fatty acid ratio. Statistically evaluation on Hayes' basis, it showed that the liquid chicken oil scored even better than the extra virgin olive oil. In conclusion, this study not only first open a new gate for the recycle of global raw chicken fat to a dietary oil but also give an evidence that the chicken oil seems more compatible to human lipid on the hypothetic basis of biocompatibility.

Evaluation of anaerobic co-digestion of dairy manure with food wastes via bio-methane potential assay and CSTR reactor

The introduction of food wastes into anaerobic digestion (AD) brings a promising scenario of increasing feedstock availability and overall energy production from AD. This study evaluated the biodegradability and methane potential from co-digestion of two typical food wastes, kitchen waste and chicken fat, with dairy manure. For single substrate, the bio-methane potential assays showed that kitchen waste had the highest methane yield of 352 L-CH4 kg(-1)-VS added, 92% more than dairy manure alone. Chicken fat at the same Volatile Solid (VS) level (2 g L(-1)) inhibited bio-methane production. Addition of kitchen waste and chicken fat to a VS percentage of up to 40% improved overall methane yield by 44% and 34%, respectively. Synergistic effect was observed when either combining two or three substrates as AD feedstock, possibly as a result of increased biodegradability of organic materials in chicken fat and kitchen waste compared with dairy manure. Addition of chicken fat improved methane yield more than kitchen waste. However, addition of chicken fat VS over 0.8 g L(-1) should be cautiously done because it may cause reactor failure due to decrease in pH. The maximum methane yield was 425 L-CH4 kg(-1)-VS, achieved at a VS ratio of 2:2:1 for kitchen waste, chicken fat, and dairy manure. Results from batch AD experiment demonstrated that supplementing dairy manure to chicken fat and/or kitchen waste improved alkalinity of substrate due to the inclusion of more titratable bases in dairy manure, and therefore stabilized the methanogenesis and substantially improved biogas yield. A mixture of substrates of kitchen waste, chicken fat, and dairy manure at a ratio of 1:1:3 was fed to a continuously stirred tank reactor operated at organic loading rates of 3.28, 6.55, and 2.18 g-COD L(-1)-day (hydraulic retention time of 20, 10, and 30 days, respectively) under mesophilic condition, and methane production rate reached 0.65, 0.95, and 0.34 L-CH4 L(-1)-reactor-day.