预冷处理对冻罗非鱼片品质的影响

拟在现有冻罗非鱼片工艺中加入预冷工序。将新鲜罗非鱼片用冰水浸渍,放入不同温度(-4、-7、-18℃)条件下冻藏,定期测定pH值、色差、失水率、挥发性盐基氮(total volatile base nitrogen,TVB-N)值和质构等参数,分析预冷对冻藏品质的影响。结果显示,预冷对p H值影响最显著的温度为-7℃,10~20 d时-7℃预冷处理组罗非鱼片p H值仍在继续下降,而其对照组已开始回升。随着贮藏时间延长,罗非鱼片色差亮度L*值与红度值a*均呈现下降趋势,且贮藏温度越低,下降幅度越小,同时发现对照组L*值和a*值普遍低于预冷处理组。同时,贮藏温度越低,失水率越高,30 d罗非鱼片失水率达到最高值,-18、-7℃对照组此时失水率达7.47%、6.82%。-4℃及-7℃预冷处理对罗非鱼片TVB-N值影响较大,20 d后与对照渐趋一致;但30 d时-18℃罗非鱼片预冷处理组与对照组仍有较大差别,TVB-N值分别为8.04 mg/100 g和9.87 mg/100 g。20 d前随贮藏温度降低罗非鱼片预冷处理组与对照组的咀嚼性差异增大,之后则趋于一致。贮藏期间硬度无显著差异,弹性仅在-4℃内罗非鱼片处理组与对照组间有较明显差异,其余差异均不显著(P0.05)。内聚性的变化因无明显规律不作为评判指标。综上,预冷处理对罗非鱼冻鱼片部分冻藏品质指标有较明显的改善作用,利于保持鱼片品质,可作为生产企业的借鉴。     

茶多酚改性胶原蛋白-壳聚糖复合膜对冷藏斜带石斑鱼的保鲜效果

研究茶多酚改性后的胶原蛋白-壳聚糖复合膜对冷藏斜带石斑鱼的保鲜效果。在4℃冷藏条件下,采用空白对照、胶原蛋白-壳聚糖复合膜、茶多酚改性胶原蛋白-壳聚糖复合膜3种方式处理样品并贮藏20 d,以K值、肌动球蛋白含量、巯基(—SH)含量、Ca~(2+)-ATPase活性以及p H值、硫代巴比妥酸(thiobarbityric acid,TBA)值、挥发性盐基氮(total volatile basic nitrogen,TVB-N)值、菌落总数、感官评定值作为研究指标。结果表明:胶原蛋白-壳聚糖复合膜、茶多酚改性胶原蛋白-壳聚糖复合膜处理组斜带石斑鱼的巯基含量、肌动球蛋白含量、Ca~(2+)-ATPase活性和感官评定值均显著高于对照组(P0.05),而K值、p H值、TVB-N值、菌落总数均显著低于对照组(P0.05),且茶多酚改性胶原蛋白-壳聚糖复合膜处理组的效果优于胶原蛋白-壳聚糖复合膜处理组,其中3个处理组的TBA值的差异性不显著(P0.05)。茶多酚改性胶原蛋白-壳聚糖复合膜处理组鱼肉的肌动球蛋白变性和巯基含量降低缓慢、Ca~(2+)-ATPase活性下降受到阻碍、TVB-N值等理化指标变化以及细菌总数生长受到抑制。说明在4℃冷藏条件下,茶多酚改性胶原蛋白-壳聚糖复合膜处理组能有效延缓斜带石斑鱼的腐败变质,保鲜效果更明显。     

不同贮藏条件下熟制裸斑鱼的品质变化

为研究不同贮藏条件对工业化制作的熟制裸斑鱼贮藏期间的品质影响,选用3种贮藏方式(-120℃液氮喷淋冻结、-18℃冰箱冻结、4℃冷藏),以菌落总数、pH、硫代巴比妥酸(thiobabituric acid, TBA)、总挥发性盐基氮(total volatile basic nitrogen, TVB-N)、色泽、质构特性(硬度、弹性、咀嚼性)、气味变化为评价指标,研究贮藏16 d裸斑鱼的品质变化。结果表明:随贮藏时间的延长,菌落总数、TBA值、TVB-N值、白度均呈上升趋势,感官评分、硬度、弹性、咀嚼性均呈下降趋势,pH值呈先下降后上升的趋势。综合各指标分析得到:4℃贮藏条件下的鱼肉在第16天已失去食用价值,而-120℃液氮和-18℃储藏下的鱼肉在实验终点(16 d)并未出现腐败变质的情况。结合电子鼻气味分析,-120℃液氮,贮藏期8 d及以下的鱼肉新鲜度更加接近第0天,此时鱼肉风味尚佳。     

光照和温度对草鱼和三文鱼鱼肉贮藏品质的影响

采用4、10(无光照)、10(5 000 lx)、25℃条件,同时贮藏草鱼鱼片(除去红肉)和三文鱼鱼片,研究光照和温度对草鱼和三文鱼贮藏品质的影响。结果表明,草鱼和三文鱼贮藏过程中pH值、挥发性盐基氮(total volatile basic nitrogen,TVB-N)值、硫代巴比妥酸(thiobarbituric acid,TBA)值和色差变化差异显著(P0.05),且菌落总数(total viable count,TVC)、pH值、TVB-N值、TBA值、色差、ATP分解产物(adenosine triphosphate-related decomposition products)K值均随着贮藏时间的延长而增加。光照(5 000 lx)对于草鱼、三文鱼贮藏过程中的pH值变化、TBA值变化影响显著(P0.05),能使鱼肉中pH值增加量高于避光保存,促进光氧化,提高TBA值增加速率,而对于TVC、TVB-N值、K值、色差变化影响不显著(P0.05)。贮藏温度的差异(4、10℃)对两种鱼肉品质变化都有显著影响(P0.05)。     

不同贮藏温度下鲫鱼鱼片品质变化研究

为探究不同贮藏温度下鲫鱼鱼片保鲜效果,试验设置0℃(冰藏)、4℃(冷藏)、-3℃(微冻)和-18℃(冻藏)4组试验,以质构分析、硫代巴比妥酸(TBA)、高铁肌红蛋白、挥发性盐基氮(TVB-N)、微生物等指标变化为依据测定不同贮藏温度条件下鲫鱼鱼片的品质变化。结果表明,随着贮藏时间的延长,不同贮藏温度条件下鲫鱼鱼片的质构特性、高铁肌红蛋白、挥发性盐基氮(TVB-N)、菌落总数均出现不同程度的上升,温度越高,上升速度越快。其中,4℃(冷藏)下的鲫鱼鱼肉的贮藏货架期为9 d,0℃(冰藏)下的鲫鱼鱼肉的货架期为15 d,-3℃(微冻)和-18℃(冻藏)下鲫鱼鱼肉的货架期较长。综合各项理化指标可知鲫鱼鱼片在微冻和冰温、冻藏条件下保鲜效果明显优于冷藏。     

内源化学反应及细菌活动对冰温贮藏罗非鱼片腐败变质的贡献研究

目的 评估内源化学反应及细菌活动对冰温贮藏罗非鱼片腐败变质的贡献。方法 研究经抑菌处理及未经抑菌处理的罗非鱼片在冰温贮藏期间的菌落总数、挥发性盐基氮(total volatile basic nitrogen, TVB-N)值TVB-N 值、pH、硫代巴比妥酸(thiobarbituric acid, TBA)值TBA值及感官鲜度的变化,并采用电子鼻监测挥发性成分的变化,并对未经抑菌处理罗非鱼各指标与菌落总数间进行皮尔逊相关性分析。结果 贮藏期间经抑菌处理的样品的菌落总数始终小于5.05 log CFU/g,挥发性盐基氮(total volatile basic nitrogen, TVB-N)值小于3.0 mg/100 g,pH及电子鼻测定的各种气体成分基本未变,未发生感官腐败,虽然硫代巴比妥酸(thiobarbituric acid, TBA)值有所增加(P< 0.05),但始终低于0.05 mg MDA/100 g。而未经抑菌处理的罗非鱼片,菌落总数在21 d时达到9.18 log CFU/g,TVB-N值增至40.69 mg/100 g,pH由6.65增至7.63,电子鼻测定的氮氧化合物、硫化物及有机硫化物骤增,TBA增至0.072 mg MDA/100 g,显著高于抑菌处理的样品,感官腐败明显。结论 冰温贮藏条件下内源化学反应仅导致一定程度的脂质氧化,罗非鱼片的腐败主要由细菌活动造成。     

不同温度贮藏对黄鳍鲷鱼肉鲜度与品质的影响

以黄鳍鲷（Acanthopagrus latus）为研究材料,通过测定鱼肉菌落总数、pH值、挥发性盐基氮（total volatile basic nitrogen,TVB-N）值、硫代巴比妥酸（2-thiobarbituric acid,TBA）值和剪切力等指标,结合感官评定,设立4℃冷藏为对照组,研究0℃和微冻（-4℃）贮藏对黄鳍鲷鱼肉鲜度和品质的影响。结果表明：在贮藏期间,各贮藏组黄鳍鲷鱼肉的菌落总数、TVB-N和TBA值均呈现上升趋势,鱼肉pH值呈先稍下降后再上升的趋势,而鱼肉剪切力和感官评分均呈逐渐下降趋势。0℃和微冻两贮藏组黄鳍鲷鱼肉各项指标的变化速率均小于4℃冷藏对照组,0℃和微冻保鲜效果明显优于4℃冷藏保鲜;0℃和微冻贮藏组,黄鳍鲷贮藏7 d后鱼肉菌落总数分别为6.88 lg（CFU/g）和5.72 lg（CFU/g）,TVB-N值分别为20.54 mg/100 g和11.40 mg/100 g,TBA值分别为0.88 mg/100 g和0.38 mg/100 g,剪切力分别为4.96 N和5.51 N,说明微冻贮藏能更好地抑制鱼肉微生物繁殖,有效地减缓鱼肉蛋白质分解和脂肪氧化,较好地保持鱼肉嫩度和品质;相比于4℃冷藏,0℃和微冻下贮藏的黄鳍鲷鱼肉货架期至少可延长2 d和8 d。     

苦荞活性肽对罗非鱼片的保鲜效果

以p H值、硫代巴比妥酸(thiobarbituric acid,TBA)、挥发性盐基氮(total volatile base nitrogen,TVB-N)、菌落总数和感官评价为指标,研究苦荞活性肽对4℃贮藏的罗非鱼片的保鲜效果。结果表明:随着贮藏时间的增加,罗非鱼片的p H值、TBA值、TVB-N值和菌落总数均呈不同程度的上升趋势,感官得分呈下降趋势。而以苦荞活性肽处理后,罗非鱼片的p H值、TBA值、TVB-N和细菌落总数较对照组低,感官得分高于对照组。其中,6mg/m L苦荞活性肽浸渍液的保鲜效果最好,可以将4℃条件下罗非鱼片的保质期由4 d延长至8 d。     

白鲢鱼片在0 ℃贮藏条件下鲜度和品质的变化

以白鲢鱼为研究对象,以菌落总数、挥发性盐基氮（total volatile basic nitrogen,TVB-N）值、pH值、色差值、三甲胺（trimethylamine,TMA）值、2-硫代巴比妥酸（2-thiobarbituric acid,TBA）值为指标,结合电子鼻、质构和感官评价,探究0 ℃条件下鲢鱼片新鲜度变化规律。结果表明,在0 ℃条件下贮藏的鲢鱼片TVB-N值、TMA值、菌落总数值均随贮藏时间的延长而呈增长趋势;pH值先降低后增高;感官评分、硬度和弹性呈降低趋势;电子鼻可以对不同贮藏时间的鲢鱼片进行有效区分;色差值和TBA值对白鲢鱼鱼片品质的判断不具有参考价值。理化指标之间具有相关性,TVB-N值和TMA值与菌落总数值呈显著正相关（RTVB-N值=0.964、RTMA值=0.951）。0 ℃贮藏条件下鲢鱼片的货架期为12 d。     

南极磷虾品质变化对蛋白酶酶活及可溶性蛋白质的影响

探讨南极磷虾在不同的贮藏温度、时间的条件下,蛋白酶活力及可溶性蛋白含量与品质(TVB-N、菌落总数)的关系。10℃贮藏15h,4℃贮藏36h后TVB-N和菌落总数均超出腐败范围,即使在-20℃贮藏条件下,南极磷虾也依然腐败较快。-80℃是理想的南极磷虾贮藏温度,在超低温条件下南极磷虾能够较好的保持其品质和活性。南极磷虾品质下降时(TVB-N、菌落总数对数值上升),蛋白酶活力及可溶性蛋白含量减少,且在10、4、-20℃贮藏过程中存在显著相关性。-80℃贮藏时蛋白酶活力与TVB-N、菌落总数没有显著相关性,可溶性蛋白与TVB-N、菌落总数对数值存在显著相关性。     

Comparison of Reticular and Rectal Core Body Temperatures in Lactating Dairy Cows

The Phase IV Cattle Temperature Monitoring System (CTMS; Phase IV Engineering Inc., Boulder, CO) marketed by MaGiiX (MaGiiX Inc., Post Falls, ID) uses a passive bolus equipped with a temperature sensor, a panel reader placed at a parlor entrance or exit to query the bolus, and a software package to collect, analyze, and view data. The biologically inert bolus resides in the cow's reticulum and is queried each time the cow passes the reader. Reticular temperature (RETT) and rectal temperature (RECT) were recorded simultaneously in the milking parlor exit lane in 4 consecutive milkings in each of 4 seasons, totaling 16 measurements per cow. The RETT were obtained by using the phase IV CTMS, whereas the RECT were obtained manually with a GLA M750 thermometer (GLA Agricultural Electronics, San Luis Obispo, CA). Data were edited to remove RETT likely to have been affected by a recent drinking bout. For the 2,042 observations used in analyses, means (±SD) were 39.28 (±0.41), 38.83 (±0.36), and 0.45 (±0.33) for RETT, RECT, and the difference between RETT and RECT, respectively. The RETT and RECT were strongly correlated (r = 0.645). The relationship between RETT and RECT varied by season, milking, housing system, and parity. Because dairy producers and veterinarians are accustomed to viewing rectal temperatures, equations to adjust reticular temperatures to a rectal-based scale may increase the utility of the phase IV CTMS. The resulting conversion equations were RECT = 19.23 + 0.496(RETT) for the a.m. milking and RECT = 15.88 + 0.587(RETT) for the p.m. milking.     

极端温度对三种扁谷盗属储粮害虫的致死作用

分析了42～62 ℃的极端高温、10～25 ℃的常规温度和-5～-15 ℃的极端低温对三种扁谷盗属害虫的致死作用,研究了极端低温下锈赤扁谷盗、长角扁谷盗和土耳其扁谷盗对温度的敏感差异性,评估了控温储粮技术防治扁谷盗害虫的可行性。在极端高温下, 54 ℃处理75 min、58 ℃处理60 min、62 ℃处理45 min能够完全杀灭锈赤扁谷盗成虫。在常规温度下,锈赤扁谷盗幼虫12 d死亡率低于30%,其死亡数量随时间的延长而增大。在极端低温下,长角扁谷盗对极端低温较为敏感,其次为土耳其扁谷盗、锈赤扁谷盗。极端温度防治害虫的有效性取决于有效的温度、足够的暴漏时间和处理物料的安全性。极端低温通常比极端高温需要更长的暴露时间,但长时间暴露在极端温度下被处理商品受损的风险将进一步增大。     

皮革收缩温度的检测与实现

论述了以单片机为核心的皮革收缩温度测试系统 ,水平放置被测试片、用VMIC变模式控制升温速率。实测证明 :测试结果的一致性、准确度均优于已有的测试方法。     

磨削温度研究的现状与进展

从磨削温度的理论研究和磨削温度的测量技术两个方面，概要介绍了磨削温度的研究现状。探讨了磨削温度理论研究的发展趋势，比较了目前常用的几种磨削温度测量技术的优缺点。     

精准温控贮藏对西兰花采后品质和生理变化的影响

为了探究西兰花在不同贮藏温度下的生理变化与品质差异,分别用普通冰箱[(4.0±1.0)℃]、精准温控的冰温库[(-0.5±0.3)℃]和相温库([(-0.4±0.1) ℃]3种环境贮藏采摘后的西兰花。结果表明:经过冰箱冷藏的西兰花贮藏期可达30d,30d后可溶性固形物、叶绿素、维生素C、可溶性蛋白含量下降,品质逐渐劣变;精准温控(冰温与相温)贮藏的西兰花70d后色泽饱满,营养物质含量丰富,呼吸强度与乙烯生成速率较小,且腐烂率与黄化指数处于较低水平,体现较高的超氧化物歧化酶及过氧化氢酶活性,膜质受损程度较轻、机体防御体系较强。冰温与相温贮藏60d时,西兰花维生素C质量分数分别为37.70、46.53mg·100g-1,黄酮质量分数分别为12.30、15.56mg·100g-1,过氧化氢酶活性分别为67.20、120.00U·g-1;在70d时,西兰花呼吸强度分别为463.79、416.90mg·(kg·h)-1,乙烯生成速率为83.37、63.07μL·(kg·h)-1,超氧化物歧化酶活性分别为1543.91、1588.55U·g-1。相比较冰温,相温贮藏能延缓西兰花维生素C及黄酮含量下降,抑制其呼吸强度和乙烯生成速率,使得超氧化物歧化酶和过氧化氢酶活性处于较高水平(P<0.05)。精准温控(冰温与相温)贮藏可控制西兰花的生理变化,有效延缓其采后品质下降的速率,相温贮藏优于冰温贮藏。     

Technical note: Assessment of milk temperature measured by automatic milking systems as an indicator of body temperature and fever in dairy cows

The objective of this study was to evaluate whether milk temperature (MT) measured by automatic milking system (AMS) is a reliable indicator of body temperature of dairy cows and whether cows with fever could be detected. Data loggers (Minilog 8, Vemco Ltd., Halifax, NS, Canada) measuring body temperature were inserted for 7 ± 1 d into the vaginal cavity of 31 dairy cows and programmed to take 1 reading/min. Milk temperature was recorded at each milking event by the AMS, and values from the vaginal loggers were paired with the corresponding MT. The correlation (r) between vaginal temperature (VT) and MT was 0.52. Vaginal temperature was higher (39.1 ± 0.4°C) than MT (38.6 ± 0.7°C) with a mean difference of 0.5 ± 0.6°C. The ability of MT to identify cows with fever was assessed using 2 approaches. In the first approach, VT could indicate fever at any time of the day, whereas MT could display fever only during the milking events of a given day. Different definitions of fever based on thresholds of VT and duration exceeding these thresholds were constructed. Different thresholds of MT were tested to distinguish between cows with and without fever. The combination of 39.0°C as a threshold for MT and 39.5°C for at least 2 h/d as a threshold for VT resulted in the highest combination of sensitivity (0.65) and specificity (0.65). In the second approach, we evaluated whether MT could identify cows with fever at a given milking event. A threshold of MT >38.7°C delivered the best combination of sensitivity (0.77) and specificity (0.66) when fever was defined as VT ≥39.5°C. Therefore, MT measured by AMS can be indicative of fever in dairy cows to a limited extent.     

基于AD590的发酵罐多点温度测量系统

为开发啤酒、制药等行业所需的端面测温传感器,利用自制的能测量多点温度的传感器,采用集成温度传感器AD590作为测温元件,依据其温度特性并通过其接口电路和集成温度传感器矩阵网络以及单片机微功耗技术,系统研究发酵罐内的温度分布,设计了一种新型的温度测量系统.该系统只需将传感器信号引入,无需再作其它调整就可完成高精度的多点温度测量.     

R404A/R23复叠式超低温制冷系统试验

依托自建的R404A/R23复叠式超低温制冷试验台,采用控制单一变量的方法,研究蒸发温度与冷凝温度对复叠式制冷循环中压缩机压缩比、排气温度、吸气压力、制冷剂流量和制冷系数的影响。结果表明:当蒸发温度从-50℃降至-55℃时,系统制冷系数下降最快,达到2.1%;当冷凝温度从28℃升至30℃时,系统制冷系数下降最快为1.7%,且蒸发温度下降1℃比冷凝温度上升1℃对系统性能系数影响更大。另外,当蒸发温度为-55℃,冷凝温度为36℃时,压缩机排气温度达到最高90℃,此时,系统性能系数最低为1.5,所以,有效控制压缩机排气温度对系统安全和高效运行至关重要。     

Impact of intake water temperatures on reticular temperatures of lactating dairy cows

Automatic temperature recording may allow early detection of disease, estrus, heat stress, and the onset of calving. The phase IV Cattle Temperature Monitoring System (MaGiiX Inc., Post Falls, ID) utilizes a passive bolus equipped with a temperature sensor, a stationary panel reader to query the bolus, and software to collect, analyze, and display data. One potential limitation to collection of reticular temperatures is the effect of water temperature and consumption on recorded temperatures. Two replicated 3 × 3 Latin square experiments were conducted at the Purdue Dairy Research and Education Center to assess the impact of water intake on reticular temperatures using the Cattle Temperature Monitoring System. Nine high-producing, mid-lactation, second-parity cows with low somatic cell counts were selected. Before administering a water treatment, access to feed and water was restricted for at least 2 h. Baseline reticular temperatures were established from measurements before water intake. In experiment 1, treatments were 25.2 kg of hot water (34.3°C ± 1.0), warm water (18.2°C ± 0.4), or cold water (7.6°C ± 0.4). In experiment 2, treatments were 18.9 kg of body-temperature water (38.9°C ± 0.2), cold water (5.1°C ± 0.4), or control (no water). Following water intake, reticular temperatures were collected for 3 h. In experiment 1, an initial dramatic decrease in reticular temperature was observed followed by a gradual increase toward baseline. Least squares means for maximum drop in temperature were 8.5 ± 0.5, 6.9 ± 0.5, and 2.2 ± 0.5°C for cold, warm, and hot water treatments, respectively. Yet at 3 h, reticular temperatures did not return to the baseline. In experiment 2, control cows remained within the baseline confidence interval through the observation period, and cows receiving body temperature water experienced an initial decrease in temperature (0.4 ± 0.2°C) with a return to within the baseline confidence interval within 15 min. Cows receiving cold water did not return to within the baseline confidence interval after a large decrease of 9.2 ± 0.2°C during the 3-h observational period. Moreover, a regression analysis of continued ascent in temperatures predicted that temperatures would return to baseline within 3.5 h. These results demonstrate that, when cows consume large quantities of cold water, the effect of water intake is sizable and sustained. The value of reticular temperatures for daily monitoring in a production setting hinges largely on the implications of this impact.     

典型食品物料的共晶、共熔温度研究

实验研究和分析结果表明一些典型食品物料的共晶温度比共熔温度低;共晶曲线比共熔曲线的斜率变化大;物料晶核形成阶段的电阻变化率小于物料大冰晶成长阶段的电阻变化率,进而又小于物料共晶阶段的电阻变化率。从理论上初步探讨了汤料的共晶、共熔温度与物料的物性、胶体结构及盐度有关。因此通过改变物料的胶体结构和盐度可降低被冻结物料的熔点,进而降低冻结能量的消耗。