Dried Pork as Influenced by Nitrate, Packaging Method and Storage

A new technique was developed to produce high quality, uniform and attractive thin sliced, cured dried pork. The effects of nitrate, packaging method and storage time on residual nitrite, TBA values, sensory properties and microbiological counts were determined. Residual nitrite decreased with increased storage time at 3 ± 1°C. The addition of nitrate plus vacuum packaging caused a greater residual nitrite level and a lower TBA value during storage. Nitrite and/or nitrate acted as an antioxidant to retard oxidative rancidity (TBA value). Dried pork manufactured by the technique described had no major rancidity problem and had an acceptable shelf life. Total aerobic plate counts, lactic acid producing microbial counts and total anaerobic counts were not affected by nitrate or packaging methods. Coliforms, molds and yeasts were not found in this dried pork.     

气调包装及天然保鲜剂对冷却鲜猪肉的保鲜效果研究

对冷却鲜猪肉分别用保鲜剂(含乳酸钠5%、异维生素C钠0.2%和乙酸0.4%的混合保鲜溶液)处理加PE塑料袋包装、PE/PA塑料袋气调包装(25% CO2、25% N2和50% O2混合气体)和保鲜剂处理加PE/PA塑料袋气调包装,与PE塑料袋包装对照,研究其在0～4℃冷却保存条件下不同处理方法的保鲜效果。每隔2d对猪肉进行感官评定、测定其TVB-N值、菌落总数,并进行球蛋白沉淀试验,以判定猪肉新鲜度的变化。结果表明:PE/PA塑料袋气调包装和保鲜剂处理均明显延长冷却鲜猪肉的保存期,可使其保存期分别达到12d和9d;两者同时应用效果更好,可使冷却鲜猪肉的保存期达到15d以上;气调包装的冷却保存猪肉颜色始终保持鲜红状态;课题组自主设计、制造的气体比例混合器,用于冷却肉的气调包装,保鲜效果优良。     

微生物和理化特性影响

本文研究不同包装方式对调理预制烤猪肉冰温（-1 ℃）贮藏中微生物和理化特性的影响。结果表明,-1 ℃冰温贮藏28 d后托盘包装样品的细菌总数（7.53 lg cfu/g）显著高于真空包装样品的细菌总数（5.54 lg cfu/g）（P<0.05）,其优势腐败菌为假单胞菌和热杀索丝菌。真空包装样品优势菌为热杀索丝菌、乳酸菌和假单胞菌。贮藏28 d后,托盘包装的样品红度（a*）值为9.88、pH为6.37、硫代巴比妥酸（TBARS）值达到了3.02 mg/kg、挥发性盐基氮（TVB-N）值为56.6 mg/100 g、感官基本不可接受,而真空包装的a*值为10.87、pH为6.13、TBARS值为1.62 mg/kg、TVB-N值为43.9 mg/100 g、感官仍有一定的可接受性。SDS?聚丙烯酰胺凝胶电泳结果表明贮藏期间真空包装样品的所有蛋白条带的强度强于托盘包装的样品,直到贮藏结束时,真空包装样品的蛋白条带仍然较粗且清晰。研究表明冰温结合真空包装可有效的延长调理预制烤猪肉的保质期。     

温度、时间和水分对配合饲料脂质酸败的影响

采用三因素二次回归正交组合设计,研究了温度（6－42℃）、时间（3－57d）和水分（9％－18％）与配合饲料（10－20kg仔猪）脂质酸败的关系。试验结果表明：脂质水解酸败随着温度升高,时间延长和水分含量升高,呈极显著线性增强（P＜0.01）。水分范围16％－18％配合饲料脂质氧化酸败最慢,随着饲料水分含量的降低（低于16％）,温度的升高（6－42℃）和时间的延长（3－57d）,脂质氧化酸败显著地增强（P＜0.05）。水分含量16％,贮藏温度低于20.6℃,贮藏时间在24d内,饲料未产生酸败味。     

基于紫外荧光成像对包装鲜猪肉存储时间预测研究

根据猪肉存储过程中脂质氧化荧光代谢产物随存储时间增加特点,开发了一套基于紫外荧光成像原理的包装鲜猪肉存储时间检测系统.选用肥瘦兼具的带皮五花肉,采集可见光彩色图像及紫外荧光图像.图像分割出肌肉区域、背膘及肉皮及荧光区域,进而提出背膘及肉皮部分中荧光区域所占图像的面积百分比作为新鲜度预测指标.研究结果显示该检测指标与存储...     

新鲜猪肉气调保鲜包装技术与设备

本文介绍鲜猪肉气调保鲜包装混合气体的组成、保持鲜肉色泽与防腐保鲜效果和GM型气体比例混合器的结构与性能。通过鲜猪肉的气调包装和真空包装保鲜效果试验得出：在0～6℃温度贮藏14天后，两种包装的保鲜和保持色泽的效果相比较，气调包装鲜猪肉的细菌总数低于真空包装，血色素的指标是真空包装的三倍。研制的GM型气体比例混合器，可使二种气体（O2与CO2或CO2与N2）或三种气体（O2、CO2、N2）任意体积比例混合，气体比例混合的精度（±1％，其标准流量在0．1MPa压力下为2．4m3／h）GM型气体比例混合器的供气量可满足热成型真空充气包装机或其他机型的气调包装操作要求。     

Discoloration of Fresh Pork as Related to Muscle and Display Conditions

Pale, soft, exudative (PSE), normal, and dark, firm, dry (DFD) pork was held 7 days at 4°C under light or dark then color was evaluated instrumentally and visually. Change in reflectance (R630-R580) was used to estimate color changes due to oxymyoglobin. PSE pork was lighter (high L*) than normal and DFD pork, but did not change over time. An increase in a* and R630-R580 occurred the first day for normal and DFD, but not for PSE samples. A subsequent increase in hue angle and decrease in R630-R580 (loss of redness) occurred in PSE and normal, but not in DFD samples. Changes in hue angle and R630-R580 were more rapid in PSE than in normal samples. Light exposure accelerated all changes except L*. Visual redness inversely correlated with L* value.     

Effects of Packaging and Processing Procedures on the Quality and Shelf Life of Fresh Pork Loins

Thirty crossbred hogs were slaughtered and the longissimus muscle from the left side was removed and divided into two equal sections within 20 min postmortem (HP) and those from the right side were removed and divided 24 hr postmortem(CP). One-half of the muscle from each side was wrapped in parchment paper (PP) and the other half was vacuum packaged (VP) and loin sections were assigned to storage intervals of 0, 7, 14, 21, or 28 days. At the end of each storage period, loins were evaluated for moisture loss, bacterial levels, off-odor, sensory properties and retail case display. VP and HP treatments had reduced moisture loss (P<0.05). Off-odor scores were higher (P<0.05) for PP wrapped loins on day 14. Few palatability differences were observed with packaging and processing treatments. Vacuum packaging had positive effects on the storage and retail display characteristics of fresh pork.     

Metmyoglobin Reducing Capacity of Fresh Normal, PSE, and DFD Pork During Retail Display

Fresh pale, soft, exudative (PSE), dark, firm, dry (DFD), and normal pork were stored under light or dark conditions at 4°C for 7 days. Sample pH, metmyoglobin reductase activity, oxygen consumption rate, and relative surface metmyoglobin and oxymyoglobin contents were determined. DFD pork had the highest metmyoglobin reductase activity and oxygen consumption rate. Enzyme activity of PSE was lower than that of normal pork, but no difference existed in oxygen consumption rate between PSE and normal samples. Metmyoglobin reductase activity dropped slowly during meat storage; oxygen consumption rate sharply decreased during the first day of storage. Both metmyoglobin reductase activity and oxygen consumption rate declined more rapidly in the light. Results can help develop guidelines for display and packaging of pork.     

鲜切草鱼片的鲜度变化及微生物生长规律研究

对鲜切草鱼片在4℃冷藏过程中的鲜度变化进行研究,并采用选择性培养基对鱼片中的微生物生长规律进行分析.实验表明4℃冷藏的鲜切草鱼片在冷藏3d内处于一级鲜度范围,冷藏8d后鱼肉严重腐败,其在4℃冷藏的贮藏期限为5～6d;在冷藏期间各种腐败微生物数量均呈现明显的上升趋势,初步确定腐败希瓦氏菌、假单胞菌和乳酸菌为鲜切鱼片中生长的优势菌群.     

Effects of pH and Time of Grinding on Lipid Oxidation of Fresh Ground Pork

Experiments detected effects of pH on lipid oxidation of fresh ground pork. Pigs received antemortem epinephrine injections or postmortem carcass electrical stimulation to manipulate ultimate postmortem pH. High-pH (>6.10) samples had lower TBA values than low-pH samples. Nonsignificant difference in TBA values between high-pH prerigor- and postrigor-ground samples indicated that, at common high pH, time of grinding had no effect on lipid oxidation. Differences in TBA values between prerigor high- and low-pH samples and postrigor high- and low-pH samples indicated that, with identical grinding treatments, inhibition of oxidation occurred at high pH. Metmyoglobin was relatively high in both low- and high-pH muscle and was not catalytically active at high pH.     

超快速冷却结合不同包装贮藏对冷鲜猪肉品质的影响

为探究超快速冷却(冷却速度14.43℃/h)结合不同包装方式对贮藏猪肉品质的影响,对超快速冷却处理的猪背最长肌分别进行有氧托盘包装、气调包装(50%O₂+50%CO₂)、真空包装和真空收缩包装,分析猪背最长肌在(-1.0±0.5)℃贮藏过程中pH、肉色、蒸煮损失、质构特性、菌落总数、挥发性盐基氮和脂肪氧化的变化,以期明确超快速冷却结合4种包装的猪肉在贮藏期间的品质变化规律。结果表明,在贮藏30 d时,超快速冷却结合气调包装猪肉红度值a^*(3.62)高于超快速冷却结合有氧托盘包装(3.35)、真空包装(3.20)和真空收缩包装(1.66)的猪肉;超快速冷却结合真空包装和真空收缩包装的猪肉蒸煮损失分别为20.82%和21.83%,显著低于有氧托盘包装和气调包装的猪肉(P <0.05);真空收缩包装猪肉的菌落总数、挥发性盐基氮和脂肪氧化程度分别为4.92 lg(CFU/g),9.69 mg/100 g和0.77 mg MDA/kg,显著低于其它3种包装猪肉(P <0.05)。与有氧托盘包装相比,真空包装、真空收缩包...     

TBA Values, Sensory Characteristics, and Volatiles in Ground Pork During Long-term Frozen Storage: Effects of Packaging

Ground pork (30% fat) was packaged in vacuum bags (V), polyvinyl chloride film (P), Saran Wrap?(S), aluminum foil (A), or Saran?-aluminum foil combination (SA) and frozen at - 17°C for 13, 26, and 39 wk. Samples were analyzed for TBA value and pH. Volatiles were steam distilled, volatilized at 60°C, and 1 mL samples of headspace gas was analyzed using gas chromatography and mass spectrometry. Spectra for individual peaks on the total ion chromatograms were identified with spectra from known standards. Ground pork (cooked to 75°C) was evaluated by a trained sensory panel for flavor and texture. Rancid and acid odor and flavor scores and TBA values increased over time regardless of packaging treatment; however, V-packaged pork had lower scores and P-packaged had higher scores at all time periods than did that in other materials. Eighteen volatiles were identified and quantified using GC/MS; 3-hydroxy-2-butanone had the highest correlation coefficients with TBA value, odor, and flavor scores.     

Fatty Acids of Neutral and Phospholipids, Rancidity Scores and TBA Values as Influenced by Packaging and Storage

The fatty acid (FA) of neutral lipids (NL) and phospholipids (PL) and this composition's relationship to rancidity score and TBA values of cooked beef patties, during frozen storage at times up to 4½ months under vacuum and nonpackaged conditions were studied. The predominant FA in the NL was C_18:1 (46.0%), followed by C_16:0 at 29.2%. However, the PL fraction gave a more balanced distribution of FA. In the neutral lipid fractions, reduction in the C_16:1 and C_18:2 fatty acids made significant contributions to increased rancidity scores and TBA values but in the phospholipid fraction, changes in the C_18:3 and C_20:4 were of greatest importance. After 3 months of frozen storage a regression model containing the neutral lipid fatty acids C_18:1 and C_18:2 and the phospholipid fatty acids C_18:3 and C_20:4 accounted for 88% and 85% of the variation in rancidity score and TBA value.     

Effects of Drying Method, Packaging, and Storage Temperature and Time on the Quality of Dill (Anethum graveolens L.)

Sorption isotherms, color and sensory quality of the dill herb (Anethum graveolens L.) were determined over a 2-yr period in experiments investigating the effects of packaging and storage temperature and time for air-dried and freeze-dried dill. The intensity scoring of odor and taste was significantly (p < 0.01) poorer for the dried dills than for frozen dill. Drying with heated air and the subsequent deteriorative processes essentially altered the odor and taste. In the case of freeze-dried dill the storage conditions were important; when storage was at room temperature (23°C) the intensity of the odor and taste was better preserved in vacuum packages than in glass jars or paper bags.     

宰后放置时间和冷冻对中式香肠品质的影响

采用均匀试验设计,以宰后放置时间和是否冷冻为考察因素,以猪肉为原料进行香肠加工,探讨宰后放置时间和是否冷冻对香肠品质的影响规律。结果表明：宰后放置时间和是否冷冻对中式香肠的感官评分没有显著影响;对pH 值、原料肉系水力、生香肠的硫代巴比妥酸反应物(TBARS)值和出品率有显著影响,且均呈非线性关系。进行优化计算得到：当所选用的原料为冷冻肉时,暂未找到共同解;当所选用的原料为未经冷冻的肉样时,宰后冷冻时间越早,出品率越大,生香肠的TBARS 值越小。因而以鲜肉为原料制作香肠,所选原料越新鲜,香肠品质越好。     

储藏方式与时间对鲜湿熟面条品质影响

探讨了鲜湿熟面条在储藏方式为常温(25℃)、冷藏(4℃)、冻藏(-18℃),储藏时间为8 d的条件下品质的变化。测定指标有酸度、TPC、白度、TPA、感官评定。试验结果表明:熟面条酸度变化与微生物繁殖呈正相关,常温储藏熟面条酸度随储藏时间延长而增大,而其他2种储藏方式基本保持不变;TPC方面,常温储藏湿面条在储藏2 d后开始发生腐败变质,而冷藏和冻藏环境仍然保持较低污染水平;白度方面,冻藏熟面条白度值明显高于其他2种方式,而冷藏和常温储藏面条经过复热后白度值增加,达到冻藏的白度水平;质构方面,冷藏使得面条硬度、弹性增大,而冻藏使面条各指标值剧烈下降,成为影响感官评定的最主要因素,同时常温与冷藏储藏面条的硬度随时间延长逐渐增大,弹性随时间延长而降低。     

Effects of Simulated Retail Display and Overnight Storage Treatments on Quality Maintenance in Fresh Broccoli

The quality of fresh broccoli during simulated retail display was evaluated using contact (ice) and air cooling separately and in combination. Chlorophyll and ascorbic acid were best maintained with air cooling, while weight was best maintained with ice cooling alone. In air-cooled display units, ice placed both on top of and beneath broccoli heads resulted in more rapid loss of chlorophyll and ascorbic acid than did bottom-icing alone. Bottom-iced broccoli in air-cooled units kept best overnight if left in place and covered with wet burlap. Removal to a 4°C walk-in cooler each night resulted in good color retention and marketability but weight loss after 4 days was significantly higher.     

Effects of Retail Style or Food Service Style Packaging Type and Storage Time on Sensory Characteristics of Bacon Manufactured from Commercially Sourced Pork Bellies

Objectives were to characterize differences in pork bellies that were stored frozen for different durations prior to processing and characterize sensory properties of the bacon derived from those bellies when stored in either retail or food service style packaging. Bellies (n = 102) were collected from 4 different time periods, fresh bellies (never frozen) and bellies frozen for 2, 5, or 7 mo, and manufactured into bacon under commercial conditions. Food service bacon was packaged in oxygen‐permeable polyvinyl lined boxes layered on wax‐covered lined paper and blast frozen (–33 °C) for 45 or 90 d after slicing. Retail bacon was vacuum‐packaged in retail packages and refrigerated (2 °C) in the dark for 60 or 120 d after slicing. At the end of respective storage times after slicing, bacon was analyzed for sensory attributes and lipid oxidation. Off‐flavor and oxidized odor of bacon increased (P < 0.01) with increasing storage time in both packaging types. Lipid oxidation increased (P < 0.01) as storage time increased from day 0 to day 45 in food service packaged bacon from frozen bellies, but was unchanged (P ≥ 0.07) with time in food service packaged bacon from fresh bellies. Lipid oxidation was also unchanged (P ≥ 0.21) over time in retail packaged bacon, with the exception of bellies frozen for 5 mo, which was increased from day 0 to day 90. Overall, off‐flavor, oxidized odor, and lipid oxidation increased as storage time after processing increased. Freezing bellies before processing may exacerbate lipid oxidation as storage time after processing was extended.     

不同贮藏温度下不同充气包装处理对鲜食枸杞贮藏品质的影响

为了研究鲜食枸杞最佳冷藏温度及充气包装条件,以新鲜、无腐烂的红枸杞为试材,采用CO₂:O₂:N₂分压比例分别为3:15:82、7:25:68、11:35:54的充气包装,在冷库中置于0、1、2℃贮藏24 d,分别对贮藏期间枸杞果实可滴定酸、还原糖、可溶性固形物、色差、腐烂率进行测定。结果表明,贮藏过程中0、1℃条件下7% CO₂+25% O₂+68% N₂气体浓度可有效维持枸杞果实中较高的还原糖、可滴定酸、可溶性固形物的含量,有效抑制果实腐烂率的下降,不同贮藏温度和不同充气包装对果实色泽没有显著影响(p>0.05)。由此表明,0、1℃条件下7% CO₂+25% O₂+68% N₂包装可有效延长鲜食枸杞贮藏期,保持果实品质。