Study On The Effects Of Packing Material, Pellet Diameter And Moisture Content On Feed Quality During Storage

The paper studied effects of packing material, pellet diameter and moisture content on feed quality during storage. The study aim was to guide the feed safe storage. The main contents and results are as follows:(1) Study on the effects of packing material on feed quality during storage. The pellet feed for sturgeon brood(moisture content 10.5%, crude fat 14.1%) and three different types of packing material(OWB ordinary woven bag, OWLB ordinary woven-lining bag and LLB lamination-lining bag) were used as experimental material in the research. The feed was packed into bags mentioned above(400 g per bag) and stored under natural condition(Beijing from April to July, temperature 21~32℃, relative humidity 8%~70%) and high temperature-high humidity condition(temperature 30℃, relative humidity 80%). Analysis was conducted every 15 days during 90 days. Results showed that moisture content and water activity of the feed packed into OWB were most vulnerable to storage condition and the raising speeds and ranges under the condition of high temperature-high humidity were all biggest; OWLB and LLB could obviously inhibit hydrolytic rancidity under the condition of high temperature-high humidity and oxidative rancidity under natural condition; OWB and the condition of high temperature-high humidity would accelerate mold and the production of mycotoxins. On the basis of sensory indexes: all the three groups under the natural condition could be stored for 90 d and under the high temperature-high humidity condition the feed stored into OWB, OWLB and LLB could be stored for 15 d, 45 d and 45 d respectively. Under the two storage conditions, the quality of the feed stored into OWLB and LLB had no obvious difference. Therefore, OWLB should be chosen as packing material for its relatively low cost.(2) Study on the effects of pellet diameter on feed quality during storage. The hard pellet feed vacuum oil-coated of different pellet diameter(Φ2.5 mm, Φ3.5 mm and Φ4.5 mm) for growing swine(crude fat 5.3%) was used as the research material. After packed into polyethylene bags(1.5 kg per bag), the feed was stored under natural condition(Beijing from April to July, temperature 21~32℃, relative humidity 8%~70%) and high temperature-high humidity condition(temperature 30℃, relative humidity 80%). Analysis was conducted every 15 days during 90 days. Results showed that moisture content and water activity at the same sampling time increased significantly along with the increase of pellet diameter(P<0.05) and under the high temperature-high humidity condition, the raising ranges of moisture content and water activity of the Φ4.5 mm-feed were biggest. Under the natural condition fatty acid value increased gradually over 90 days and increased significantly with the increase of pellet diameter during 15~75 d(P<0.05). Under the high temperature-high humidity condition fatty acid value increased first and then decreased, and the increase and decrease ranges of the Φ4.5 mm-feed were largest. The bigger the pellet diameter, the earlier the fatty acid value began to decrease and the decrease of fatty acid value was associated with the activity of mold. Peroxide value, in natural condition, decreased first and then increased, while, in condition of high temperature-high humidity it decreased again at last. Under the two conditions, the biggest peroxide value always occurred in the Φ4.5 mm-feed. On the basis of sensory indexes: the feed of Φ2.5 mm and Φ3.5 mm could be stored for at least 90 d, the feed of Φ4.5 mm could be stored for 75 d, and under the high temperature-high humidity condition the feed of Φ2.5 mm, Φ3.5 mm and Φ4.5 mm could be stored for 60 d, 45 d and 30 d respectively.(3) Study on the effects of moisture content on feed quality during storage. The hard pellet feed for growing swine was used as experimental material. The feed of different moisture content(11.53%, 11.91%, 12.49%, 12.88%, 13.54% and 13.94%) was made by adding water in mixer and controlling cooling time. After packed into polyethylene bags(1.0 kg per bag), the feed was stored under natural condition(Beijing from August to October, temperature 21~30℃, relative humidity 18%~74%) and high temperature-high humidity condition(temperature 30℃, relative humidity 80%). Analysis was conducted every 15 days during 60 days. The results showed that moisture content and water activity increased during storage and the higher the initial moisture content, the bigger the increase ranges. Higher moisture content could accelerate the hydrolytic rancidity and oxidative rancidity of feed and the increase speed and range of feed with the highest initial moisture content(No.6) were biggest. The feed with higher moisture content was more prone to mildew. Mold counts of the feed with moisture content of 13.54% and 13.94% were significantly higher than other groups(P<0.05). On the basis of sensory indexes: under the high temperature-high humidity condition, the feed with moisture content of 11.53%, 11.91% and 12.49% could be stored for at least 30 d, the feed with moisture content of 12.88% could be stored for at least 15 d, and the shelf life of the feed with moisture content of 13.54% and 13.94% was shorter than 15 d. Under the natural condition, with storage pests, the shelf lives of 6 groups were between 15 d and 30 d. It is recommended that moisture content should be controlled fewer than 12.5% and storage pests should be concerned in high temperature and high humidity weather when the expected shelf life is more than 30 d in practical production.