Changes in broiler breast fillet tenderness, water-holding capacity, and color attributes during long-term frozen storage

ABSTRACT:  Freezing is the most common and efficient way to maintain the quality of poultry products for long periods of time. However, tougher texture, discoloration, and drying have been reported as a result of long-term frozen storage. The impact of freezing on the tenderness, water-holding capacity, and color of broiler breast fillets was investigated for up to 8 mo. A total of 160 birds were deboned at either 2 or 6 h postmortem (PM). All deboned left fillets were frozen and stored at –18 °C for up to 8 mo, while the corresponding right fillets were assessed for texture approximately 24 h after deboning as a control measurement without any freezing treatment. Tenderness was measured by the Meullenet–Owens razor shear. Thaw loss, cooking loss, moisture content, color, and muscle shape profiles were also evaluated. No difference in tenderness was observed during the first 2 mo compared to the control (0 mo), but significantly decreased between 2 and 4 mo. The 8-mo-old fillets were the least tender, with a 31.5% increase in shear energy between 4 and 8 mo. Moisture content of cooked meat gradually decreased, showing a significant drop between 2 and 6 mo of storage, while thaw and cooking loss consistently increased over the entire storage period. The color of the frozen fillets tended to be darker, redder, and less yellow than the control, with increased storage duration. The results suggest that for optimal tenderness, frozen broiler breast fillets are best consumed within 2 mo of freezing.     

肌肽对肉鸡生长性能及胸肌肉品质的影响

在1～4组肉鸡饮水中肌肽的添加量分别为0、20、40和60 mg/L,每周测定各组肉仔鸡的周增重、料重比,并在试验结束时胸肌采样,测定胸肌肉品质指标,观察肌肽对肉鸡生长性能和胸肌肉品质的影响.结果表明:试验的前两周,肌肽大剂量组的周增重显著高于对照组(P＜0.05);4～6周龄,各剂量组的周增重均高于对照组,但差异不显著(P＞0.05);添加肌肽能明显改善饲料转化率,提高了胸肌水分含量及pH值;降低了失水率、肌纤维的直径;胸肌粗蛋白及粗脂肪的含量略微下降;中、大剂量组的胸肌色较淡而亮度增加.     

不同林分枯落物层持水特性研究

通过对赣西北大坑小流域不同林分枯落物累积量及持水量的测定,结果表明:(1)不同林分枯落物累积量差异较大,其中杉木林地的累积枯落物量最大,其次为马尾松,枫香、木等阔叶林地的累积枯落物量较小;(2)不同林分枯落物的持水量差异很大,其中杉木林为1.43~4.23 mm,马尾松为1.2~4.91 mm,枫香为1.90~3.90 mm,灌木为1.30~3.10 mm;(3)马尾松和草本枯落物的饱和持水量最大,而且在降雨初期的吸水速度也都比杉木和油茶等为快.     

两种灌草管理方式对桉树人工林土壤呼吸的影响

以福建省漳州尾巨桉(Eucalyptus urophylla×E.grandis)人工林为研究对象,研究物理去除灌草和施用除草剂2种灌草管理方式对尾巨桉人工林土壤CO2排放和凋落物分解的影响。实验时间为2012年12月至2014年11月,采用LI-COR 8100系统测定土壤呼吸,用分解袋法开展分解实验。结果表明,物理去除灌草方式下土壤温度显著升高,但土壤CO2排放降低;施用除草剂对土壤温度和土壤CO2排放无明显影响。土壤呼吸有明显的季节变化,在雨季较高,在旱季则明显降低。土壤呼吸的温度敏感系数Q10表现为去除灌草(2.49)>对照(2.38)>施用除草剂(2.15)。研究表明不同的灌草管理方式对人工林土壤碳循环影响有差异,物理去除对土壤碳排放和物质循环的效应大于施用除草剂。     

Nutritive and economic value of guinea fowl (Numida meleagris) production in developing countries

Eighty broiler guineafowls (Numida meleagris) and 80 broiler chickens (Gallus gallus domesticus) were raised from 1 day old to 12 weeks on the same starter and finisher diets. Weight gain, feed consumption, feed efficiency, cost of production, nutritive quality and mortality were compared between the two types of bird. It was found that the broiler chickens consumed nearly twice as much feed, gained more than twice as much weight and had significantly (P < 0.01)better feed efficiency than the guineafowl. It cost significantly (P < 0.01)less to produce a kilogram of flesh from the broiler chickens than from the guineafowls. However, the guineafowl carcass excelled in nutritive quality. It had significantly (P < 0.05)more protein and ash, particularly calcium and phosphorus. The fat content of the guineafowl carcass was significantly (P < 0.05)less than that of the chickens. Mortality was less for the guineafowl than for the chickens.     

Headwater reservoirs weaken terrestrial‐aquatic linkage by slowing leaf‐litter processing in downstream regulated reaches

Leaf litter breakdown is a key process, providing matter and energy to communities inhabiting many headwater streams that flow through forests. This detrital pathway is affected by many human landscape transformations; but it is little known about the impact of small headwater reservoirs on leaf litter decay in streams. Alder leaf litter breakdown rates and associated fauna were studied upstream and downstream of five small water supply reservoirs (surface‐release in rainy autumn‐winters), in the Nerbioi‐Ibaizabal drainage basin (Basque Country, Spain), to assess the effect of impoundment on headwater streams function. Breakdown rates were significantly lower below the dams, mainly associated with a reduction of the density and the biomass of shredders. Among the shredders, Nemouridae and especially Protonemura were less abundant downstream of the dam. Alterations in the physicochemical characteristics of the water due to the reservoirs were negligible throughout our study, and temperature showed only slight variations that could not explain the reduction of the rates. The effect on shredders is likely to be related to differences in the riparian environment and flow regulation by the dams. Copyright © 2010 John Wiley & Sons, Ltd.     

Optimisation of the broiler production supply chain

In this paper, we propose a mixed integer programming (MIP) model for the Chicken Flock Sizing, Allocation and Scheduling Problem (CFSASP), which is an important planning problem in the broiler production supply chain. To solve the CFSASP efficiently, two variants of rolling horizon heuristics (RHHs) have been developed and applied on the case of a Norwegian broiler production company. Computational results show that the RHHs successfully obtain high-quality solutions within a reasonable time. The value of optimisation is verified through comparison with the case company's plans, where the solutions from optimisation outperforms the current solutions. Sensitivity analyses are also conducted to provide managerial insights regarding certain strategic decisions, such as how many and which days to use for hatching of chickens. Due to the promising results, the case company is now implementing an optimisation-based decision support system based on the MIP model and solution methods shown in this paper.     

Broiler chicken litter application timing effect on Coastal bermudagrass in southeastern U.S.

Presently, more than 85% of the broiler chicken (Gallus gallus domesticus) litter (BCL) is being applied to pasture lands year-round. This practice results in nutrient losses and potentially unfavorable environmental impacts particularly during the wet winter months. A field plot experiment was initiated in 2001 on a Ruston silt loam in Mize, MS to identify the proper BCL application timing that enhances BCL nutrient uptake by crops while minimizing undesirable nutrient buildup in soil. Seven treatments (BCL application timings) were employed on previously established “Coastal” hybrid bermudagrass [Cynodon dactylon (L.) Pers.] plots. For each treatment, the quantity of broiler chicken litter (a mixture of chicken manure plus bedding materials) needed for each plot was calculated based on the BCL total N content to provide 400 kg N ha⁻¹ for top bermudagrass yield (18 Mg ha⁻¹) and applied either as a single, two-way split, or three-way split at different dates as follow: May; May/June; April/May/June; May/June/July; June/July/August; July/August/September; and August/September/October. Bermudagrass was harvested 5 times each year for dry matter (DM) and nutrient uptake determination. Significant differences in DM yield were observed in each year among application timings. The greatest DM yield was 18.6 Mg ha⁻¹ for the single application in May and lowest at 15.0 Mg ha⁻¹ for Aug/Sep/Oct application dates in 2001 and followed by the same trend in 2002. The N and P uptake by bermudagrass ranged from 270 to 381, and 53 to 63 kg ha⁻¹ respectively, in 2001. Similar trend, but lower values for nutrient uptake were observed in 2002. Significant differences were observed among BCL application timings in regard to soil residual of total carbon (TC), total nitogen (TN), Mehlich 3 extracted P (M3-P), NO₃–N, Cu, and Fe elements at the end of the study. In general, summer and early fall BCL applications resulted in greater buildup of most of these elements. Based on the results of this study, there is a wide window (May–July) for BCL application timing on bermudagrass considering the criteria of producing high yield and low soil residual nutrient. However, the best BCL application timing should be in spring (late April–June) when minimum temperatures exceed those required (24–27°C) for bermudagrass growth.     

The impact of historic land use and modern forestry on nutrient relations of Central European forest ecosystems

In the past forests in Central Europe were not only sources of timber and fuelwood but also sources of nutrients to sustain the human population. The use of forests as pastures is still common in some areas while other formerly widespread practices such as litter raking or pollarding have been abandoned. Harvesting of wood, a material of extremely low mineral nutrient content and of wide C/N-ratio depletes nutrients and acid neutralizing capacity at only moderates rates, harvesting of other biomass fractions has a much more severe impact on forest ecosystems. Soil acidification from intensive biomass harvesting of historic land use equaled or exceeded present soil acidification due to the deposition of air pollutants. As a result of historic land use the majority of Central European forest ecosystems was severely depleted of nutrients and acid neutralizing capacity when modern long-rotation forestry became the dominant form of forest land use. At present high deposition rates of acidifying air pollutants prevent the recovery of forest ecosystems in Central Europe. It has to be noted that ecosystem degradation due to excessive biomass harvesting led to systems which were depleted both in nitrogen and acid neutralizing capacity, while high nitrogen deposition rates from Central European air pollution cause a novel combination of progressive soil acidification and concurrent nitrogen saturation. This combination has a high potential for aggravating mineral nutrient deficiencies and nutritional disorders in forest ecosystems.     

3种草本凋落物混用强化修复石油污染土壤的效果

为明确凋落物混用对修复油污土壤效果的影响,以含石油质量分数15 g/kg的污染土壤为研究对象,分别加入质量分数2%的单种凋落物(胡枝子、铁杆蒿、黄蒿的凋落物)及3种凋落物的混合物(质量比为1∶1∶1),在室温(20~25 ℃)、恒湿(饱和水质量分数50%)的条件下进行150 d的修复模拟实验。基于单种凋落物的处理结果及其在混合物中所占比例,计算混合物处理后污染物降解率以及土壤生化指标的理论预测值,并与实测值进行比较,以研究凋落物混用对土壤石油污染修复效果的影响。结果表明：凋落物混用强化了凋落物对土壤石油污染物的降解效果,使石油降解率比对应预测值提高了12.16%,其中饱和烃、芳香烃和非烃物质的降解率比对应预测值分别提高了14.43%、9.24%和10.52%;凋落物混用强化了凋落物对土壤漆酶和过氧化氢酶活性的刺激作用,但同时削弱了其对木质素过氧化物酶、蔗糖酶和多酚氧化酶活性的刺激作用,对土壤硝态氮的补充效果以及对土壤的酸化效应。