胃、肠消化后猪肝酱中铁和锌的形态分析

研究胃、肠消化对猪肝酱中Fe和Zn的形态影响。采用体外全仿生消化技术模拟猪肝酱在胃、肠中消化,利用0.45 μm微孔滤膜分离悬浮态和可溶态,通过D101大孔树脂实现无机态和有机态的分离。通过单因素试验,确定Fe最佳测定条件为乙炔流量80 L/h,燃烧器高度5 mm;Zn最佳测定条件为乙炔流量90 L/h,燃烧器高度6 mm。在此条件下,测定猪肝酱中Fe含量为112.56 μg/g,Zn含量为41.38 μg/g。胃、肠消化后除悬浮态Fe和Zn,其他各形态Fe和Zn的含量都所有增加,生物可给性变大,这表明胃、肠消化都是将一部分悬浮态Fe和Zn消化成可溶态Fe和Zn,其中以有机态Fe和Zn为主。     

Application of Electronic Nose for Measuring Total Volatile Basic Nitrogen and Total Viable Counts in Packaged Pork During Refrigerated Storage

The objective of this study was to predict the total viable counts (TVC) and total volatile basic nitrogen (TVB‐N) in pork using an electronic nose (E‐nose), and to assess the freshness of chilled pork during storage using different packaging methods, including pallet packaging (PP), vacuum packaging (VP), and modified atmosphere packaging (MAP, 40% O₂/40% CO₂/20% N₂). Principal component analysis (PCA) was used to analyze the E‐nose signals, and the results showed that the relationships between the freshness of chilled pork and E‐nose signals could be distinguished in the loadings plots, and the freshness of chilled pork could be distributed along 2 first principal components. Multiple linear regression (MLR) was used to correlate TVC and TVB‐N to E‐nose signals. High F and R² values were obtained in the MLR output of TVB‐N (F = 32.1, 21.6, and 24.2 for PP [R² = 0.93], VP [R² = 0.94], and MAP [R² = 0.95], respectively) and TVC (F = 34.2, 46.4, and 7.8 for PP [R² = 0.98], VP [R² = 0.89], and MAP [R² = 0.85], respectively). The results of this study suggest that it is possible to use the E‐nose technology to predict TVB‐N and TVC for assessing the freshness of chilled pork during storage.     

鲜猪肉水分近红外光谱在线检测方法研究

本研究目的在于应用近红外光谱技术对冷鲜猪肉深层水分含量进行在线检测方法研究。根据稳态空间分辨光谱技术设计了具有多个检测器的传感器,以750nm、805nm、850nm和970nm的LED作为光源,检测器距离为30-48mm之间,用于检测肉块样品一定深度和范围内的水分含量,从而为无损、快速地给出鲜猪肉水分含量提供一种可靠方法。实验中针对猪背最长肌进行检测,获得184个样品,其水分含量在71%-78%之间,采用多元校正预测模型计算肉块水分含量。所建模型相关系数（r）为0.783,呈显著相关,建模集标准残差（RMSEP）为0.988,验证集标准残差（RMSEP）为1.037。由此得出结论,在短波近红外范围内,利用稳态空间分辨光谱技术能够对猪肉水分含量进行在线检测。     

基于IEEE802.3af的以太网供电技术(PoE)

对基于IEEE802.3af以太网供电工业标准的以太网供电系统(PoE)的工作原理进行了详细的介绍,并简单介绍了以太网供电技术标准制定方面的一些新进展。     

酱大排杀菌条件及冷藏过程品质变化的研究

目的 研究酱大排的杀菌条件与冷藏过程中的品质变化, 解决酱大排保藏困难、容易变质的难题。方法 通过测定低温条件下的杀菌曲线及杀菌强度(F值), 研究不同杀菌条件对酱大排微生物、质构、色泽、感官的影响, 为酱大排选择最合适的低强度灭菌方案并分析了冷藏过程中的品质变化。结果 依据85、90、95、100℃下的灭菌曲线, 选择F值为5、6、8 min, 保温实验表明3种F值的产品均未胀袋, 但5 min、6 min下的菌落总数超出安全范围, 货架期较短, 选择F=8 min。对采用不同的杀菌时间温度组合进行灭菌的产品进行了色泽、质构及感官指标的分析, 发现色泽在95℃的灭菌温度下指标较好, 而质构在95~100℃的灭菌温度下均较好, 且消费者对于95℃的灭菌温度下喜好度较高, 因此确定选择95℃、23 min的灭菌条件。在4℃冷藏过程中, 相比于普通包装, 真空包装能够有效减缓品质劣化, 并且具有较高的感官评分。结论 选择F=8 min, 95℃、23 min杀菌条件结合真空包装, 可以延长酱大排的冷藏货架期并保持较好的品质。     

Extraction of Bitter Acids from Hops and Hop Products Using Pressurized Solvent Extraction (PSE)

The EBC method 7.7, currently used for determination of bitter acids in hop products, is a time‐consuming and laborious extraction technique. In this paper, our aim was to propose a new extraction method based on Pressurized Solvent Extraction (PSE) sometimes also called Pressurized Fluid Extraction (PFE) or Accelerated Solvent Extraction (ASE). Compared to conventional extractions, PSE offers a number of important benefits. PSE on OnePSE^® automated extractor was used for extraction of α‐ and β‐acids from hops and hop products and the parameters influencing extraction efficiency and the influence of the sample preparation method were studied. The quantitative determination of α‐ and β‐acids in the extracts was accomplished by using an HPLC apparatus equipped with diode array detector. The experimental results were compared with those obtained by the standard EBC 7.7 method and the two methods were found to be fully compatible     

猪肉脂肪氧化酶在高压结合热处理过程中失活动力学模型

为了解猪肉高压加工过程中脂肪氧化酶(lipoxygenase,LOX)活性的变化规律,以猪背最长肌为原料,经不同压力(200~700 MPa)、温度(20~60℃)结合处理后,研究LOX失活常数的变化规律,并分别用Arrhenius和Eyring方程为基础来建立LOX失活的动力学模型。结果表明,当处理温度不变时,失活常数随压力的增加而增加;同样,当处理压力不变时,失活常数随温度升高而增加。Arrhenius和Eyring方程分别适用于整个研究的温度区间和压力区间,分别以两者为基础可以建立LOX失活的动力学方程,两个方程的拟合程度均较高,决定系数分别达到0.989和0.965。因此在一定的处理温度(20~60℃)和压力(200~700 MPa)范围内,猪肉高压结合热处理过程中LOX活性的变化可以用以Arrhenius和Eyring方程为基础建立的数学模型进行预测。     

Effects of transportation time,distance, stocking density,temperature and lairage time on incidences of pale soft exudative (PSE) and the physico-chemical characteristics of pork

The study determined the effects of transportation time, distance, stocking density, temperature and lairage time on incidences of PSE and pork quality. Frequencies of PSE cases in stocking density categories within transport duration classes were determined. General linear models, regression and the principal component (PC) analysis were used to analyse the data. Highest incidences of PSE were recorded in autumn season while lowest incidences were recorded in the spring season. Transportation time and stocking density significantly affected pH_u and ultimately PSE incidences although there were no interactive effects. Highest risks of PSE occurrence were observed with more space allowance. The highest incidences of PSE were observed for animals that had travelled for two hours while the PSE cases were lower in animals that travelled for longer times. Distance travelled and transportation time had significant effects (P < 0.05) on thawing loss (TL) % of pork. No relationships were reported between the other pre-slaughter variables and pork quality attributes. With the exception of transportation time and distance travelled which had a positive relationship with TL%, variation in other pre-slaughter variables did not affect meat quality variables. The risks of PSE occurrence were dependent on stocking density and transportation time.     

Effects of onion on physicochemical properties,lipid oxidation and microbial growth of fresh pork patties

Onions with or without heating (100 °C, 30 min) were extracted with water or methanol, and antioxidant and antimicrobial activities of onion extracts were evaluated. Product characteristics of fresh pork patties containing various onion extracts were measured during refrigerated storage. Water extracts of onions showed higher extraction yield and iron chelating ability than methanol extracts (P < 0.05), whereas, the latter was more effective than the former in phenolic compounds and reducing power (P < 0.05). The addition of onion extracts [water extract from fresh onion (WEFO), methanol extract from heated onion (MEHO) and their combinations (WEFMEHO)] to pork patties decreased redness, increased yellowness, and inhibited lipid peroxidation (P < 0.05). One per cent of WEFMEHO in pork patties had antioxidant activities as effective as butylated hydroxyl toluene (BHT, 0.01%). Redness and yellowness decreased and increased with the addition of onion extract, respectively (P < 0.05).     

Effects of Eubacterium coprostanoligenes and Lactobacillus on pH, Lipid Content, and Cholesterol of Fermented Pork and Mutton Sausage-Type Mixes

Pork and mutton sausage-type mixes produced using Eubacterium coprostanoligenes with or without Lactobacillus as starter culture showed changes in pH, cholesterol and lipid content. Viability of E. coprostanoligenes was assessed by culturing samples from each treatment and analyzing for coprostanol, a cholesterol metabolite. The pH and/or cholesterol decreased (P < 0.05) in the sausage-type mixes inoculated with E. coprostanoligenes or Lactobacillus or their combinations. Variability in lipid content was observed among and within treatments. Very low (6.2 μg/g dry matter) concentrations of coprostanol were produced in sausage-mixes and cultures except when inoculated with 2.0 g of E. coprostanoligenes (from 8.2 to 130.6 μg/g dry matter).