桑叶健康月饼焙烤前后品质变化的研究

以雪皮莲蓉月饼为代表,比较了桑叶粉的添加量对月饼焙烤前后的外观色泽、营养活性成分、质构和风味成分的影响。结果表明:高温焙烤能明显增加月饼饼皮的亮度、绿色和黄色,引起桑叶皮中的叶绿素损失从203.88μg/g降到101.70μg/g,但表皮的绿色进一步加深定型;桑叶粉的添加能明显增加月饼中酚类物质含量,经高温焙烤后还能保留更多的活性成分;质构分析(TPA)确定桑叶粉的添加(特别是在皮料中)有利于增加月饼的硬度、弹性、凝聚性、咀嚼性和回复性,降低其粘着性;采用固相微萃取-气相色谱-质谱(SPME-GC-MS)联用技术分析发现,焙烤导致月饼的挥发性风味物质种类逐渐增加,其中以烷烃类和呋喃类为主,而2,4-二甲基庚烷、3,6-二甲基癸烷很可能为桑叶馅月饼的特征性风味物质。     

固相微萃取与气-质联用法分析鲍鱼烘烤前后挥发性成分的变化

为揭示不同处理的鲍鱼主要特征风味成因,及时掌握鲍鱼品质变化情况。运用固相微萃取结合气-质联用技术分析解冻鲍鱼烘烤加工前后挥发性成分的变化。结果表明:加工前后鲍鱼的挥发性成分发生明显变化。主要挥发性物质有醇、醛、含氮含硫化合物、酮、烃、酸、酯、芳香族等,其中解冻鲍鱼检出39种,烘烤鲍鱼检出51种。解冻鲍鱼呈清鲜味,略带腥味,醇、醛类化合物是其主要风味物质,其中苯甲醛(20.83%)、1-辛烯-3-醇(18.35%)、甲氧基-苯基-肟(13.25%)为最主要特征风味物质。而烘烤鲍鱼风味发生明显变化,鲜鲍鱼固有的清鲜味逐渐消失,烤肉的香味显著增强,醇类,含氮含硫和酯类化合物是其主要的挥发性成分来源,其中丁二醇(42.64%)、甲基吡嗪(12.41%)为其最重要特征风味物质。     

Corneal surface wettability and tear film stability before and after scleral lens wear

PurposeThe aim of this study was to evaluate the anterior surface of scleral contact lens and ocular surface wettability before and after one-month of scleral lens wear in patients with keratoconus.MethodsForty-nine patients with keratoconus (36.26 ± 9.03 years) were recruited. The sample was divided into two groups: patients with intrastromal corneal ring (KCICRS group) and patients without ICRS (KC group). TFSQ, Schirmer I test, Ocular Surface Disease Index (OSDI questionnaire), tear break-up time (TBUT) and corneal staining were evaluated in two different visits: Baseline (before lens wear) and one-month visit (10 min after lens removal). Visual Analog Scale (VAS questionnaire) was filled in just after inserting the lenses and just before removing them. TFSQ mean and inferior were evaluated over the contact lens surface at the moment of inserting the lens (baseline visit) and after 8 h of lens wear (one-month visit).ResultsAnterior corneal surface TFSQ values increased in all groups after scleral lens wear (p < 0.05). However, there were no statistical differences found at the moment of inserting or after 8 h of lens wear on previous contact lens surface TFSQ (p > 0.05). No changes were found in tear volume for total and in KC and KCICRS groups (p > 0.05). For all groups, there was a statistical decrease of TBUT (p < 0.05). In addition, OSDI score, corneal staining and VAS score improved after scleral lens wear from baseline in total and in both KC and KCICRS groups (p < 0.05).ConclusionThe scleral contact lens surface keeps its wettability after one-month of wear. However, the wettability of the ocular surface is worse after contact lens wearing.     

基于顶空气相色谱-离子迁移谱技术分析花生烘烤后挥发性风味物质的变化

目的 建立基于顶空气相色谱-离子迁移谱（Headspace-gas chromatography-ion mobility spectrometry, HS-GC-IMS）技术分析花生烘烤后挥发性风味物质变化的方法。方法 对吉林四粒红和琼花1号两种花生品种进行去皮处理,采用HS-GC-IMS分别对其带种皮和不带种皮时烘烤的挥发性成分进行研究。结果 采用GC×IMS Library Search V2.2.1分析软件,利用内置NIST数据库和IMS数据库对样品中挥发性风味物质进行定性分析,并结合Reporter插件、Gallery Plot插件、Dynamic PCA插件采用实验室观察分析器（laboratory analytical viewer, LAV）对其建立标准曲线后进行定量分析,检出化合物共42种,主要为醛类、醇类、脂类、酮类等。带皮烘烤的花生主要挥发性成分为乙酸乙酯、异丙醇、2-甲基丁醇和正辛醛等,去皮烘烤主要挥发性成分为戊醛、2-甲基丁醛、糠醛和异戊醛等。发现经过烘烤后的林四粒红和琼花1号两种样品均有着更多的挥发性物质,吉林四粒红在烘烤后的挥发性成分比琼花1号多,尤其是去皮烘烤的样品中1-辛烯-3-醇、E-2-庚烯醛、2-庚酮、2-己烯-1-醇、戊醇、戊醛、己醇等物质的相对含量远高于琼花一号;结论 此方法结论 GC-IMS 可实现花生油挥发性风味物质的简便、快捷、灵敏、科学测定,该研究结果可为花生工业化生产提供理论指导。     

Effects of pair versus single housing on performance and behavior of dairy calves before and after weaning from milk

This experiment tested the effects of pair versus single housing on the performance and behavior of dairy calves before and after weaning. Twenty-seven Holstein calves were separated from the dam within 6 h of birth, housed in individual pens for 4 d, and then assigned to either continued individual housing (n = 9 calves) or pair housing (n = 9 pairs). Calves had ad libitum access to starter, hay, and water via buckets. Pasteurized whole milk was fed via teat twice a day for 2 h at ad libitum volumes until d 36. During the milk-feeding period, paired calves showed higher intakes of starter than did the individually housed calves (averaging 93 vs. 59 ± 11 g/d per calf). Calves were weaned from milk from d 37 to 41 by progressive dilution of milk with water, and the teat was removed on d 49. Calves in both treatments vocalized in response to teat removal but this response was less in paired calves than in individually housed calves (84 vs. 194 ± 12 calls/2-h period per calf on d 49). On d 56, calves were moved to group pens, mixed with other calves, and observed for 15 d. Starter, water, and hay were available ad libitum via automatic feeders. Compared with calves previously housed in single pens, paired calves had a shorter latency to start feeding (9.1 ± 2.6 vs. 49.5 ± 4.1 h/calf), visited the starter feeder more frequently (41.6 ± 3.0 vs. 26.4 ± 3.3 visits/d per calf), spent more time at the feeder (87.8 ± 2.5 vs. 65.3 ± 2.9 min/d per calf), and consumed more starter (3.4 vs. 2.3 ± 0.2 kg/d per calf). Weight gains at mixing were higher for paired than for individually housed calves on d 2 and 3 after mixing (0.5 vs. −2.4 ± 0.3 kg/d per calf; and 0.8 vs. −0.9 ± 0.3 kg/d per calf, respectively). The results indicate that pair housing during the milk-feeding stage reduces calf responses to weaning and improves performance after weaning when calves are housed in groups.     

不同品种鲜食型甘薯烘烤后品质的研究

为探究不同甘薯品种烘烤后的品质,以8个不同品种的甘薯为材料,测定其品种特征特性及烤制后的相关理化、感官、质构特性等指标,并对各指标进行相关性分析和主成分分析。结果表明,冀薯8号的干率最高,蛋白质含量最低;济薯26干率、总糖含量和淀粉含量均最低;冀薯7号总糖含量和淀粉含量最高;冀粉2号蛋白质含量最高;冀紫薯3号纤维素含量最高;冀元1号的纤维素含量最低。基于质构指标及主成分分析建立2个模型,得出8种甘薯质构综合得分由高到低依次为冀紫薯3号、冀粉3号、冀粉2号、烟薯25、济薯26、冀薯7号、冀元1号、冀薯8号。感官评价得出冀粉2号接受度最好,冀薯8号接受度最差。相关性分析表明营养品质、质地品质及感官品质之间具有一定的相关性。综合分析得出冀粉2号为8个甘薯品种中最优品种,其次是烟薯25、冀紫薯3号、济薯26、冀粉3号、冀薯7号、冀元1号、冀薯8号。     

Comparison of the Volatile Components of Eight Cultivars of Potato after Microwave Baking

Eight cultivars of potato were baked in a microwave oven. The flavour components of the flesh were isolated by headspace trapping onto Tenax and analysed by gas chromatography-mass spectrometry. Lipid degradation and the Maillard reaction and/or sugar degradation were the main sources of the 80 flavour components identified. It is suggested that total levels of compounds and variations among their profiles may be attributed to differences in activities of lipid enzymes and levels of flavour precursors in the range of cultivars investigated.     

Improved quality and energy performance of a fixed-bed longan dryer by thermodynamic modifications

Modifications including air deflector installations in the plenum and insulation to improve performance of an industrial longan dryer were evaluated. Trials were carried out at a commercial drying facility according to industrial practices. Analyses of drying conditions, product quality and energy consumption were conducted. The study found that air velocity distribution was improved by plenum modifications and heat supply was more consistent after insulation. Modifications increased drying uniformity and insulation produced more homogenous product color. Evaluation of dryer performance showed that inverted mesh in the plenum and insulation reduced energy demand and increased efficiency by 1.51–4.27% respective of dryer modification. Cost savings of US$ 4–10 per batch were calculated with an estimated payback period of 5–12 batches. In conclusion, simple modifications of this dryer type show potential for improving product uniformity, reducing energy requirement and increasing profitability. Combination of the best modifications is recommended for further research.     

不同品种甘薯烘烤后感官、质构及香气成分的差异

选取五个品种甘薯为实验材料,研究了甘薯烘烤后理化指标、感官评分、香气成分、质构特性的差异。理化测定得出,受试品种中淀粉型甘薯蛋白质含量低于鲜食型甘薯;淀粉型甘薯总糖含量低于鲜食型甘薯;鲜食型甘薯中红瑶的总糖含量最高。感官评价得出鲜食型甘薯中红瑶、普薯32烘烤后口感较好,淀粉型甘薯中冀粉1号烘烤后口感较好;红瑶的口感最佳。质构及相关性分析得出,整体口感分别与咀嚼性、内聚性呈显著负相关（P<0.05）。红瑶的内聚性、咀嚼性数值最低,因此红瑶的口感最好。GC-MS及PLSDA分析得出,苯甲醛、苯乙醛、壬醛、橙花醇、大马士酮、芳樟醇、4-乙烯基-2-甲氧基苯酚、α-萜品烯等物质为品种间共有香气组分;芳樟醇、癸醛、2-莰烯、壬酸、糠醛五种香气成分为甘薯重要香气成分。综合得出,受试品种中最适合用于烘烤的品种为红瑶。     

生物柴油氧化前后成分分析的研究

分别以地沟油、橡胶籽油和小桐子油为原料制备生物柴油,测定了3种生物柴油的氧化稳定性,并采用傅里叶红外光谱及GC-MS分析氧化前后此3种生物柴油的成分。结果表明,地沟油生物柴油、橡胶籽油生物柴油和小桐子生物柴油的氧化诱导时间分别为1.61、0.81、1.05 h,远不能达到我国生物柴油国家标准的6 h;生物柴油主要成分是脂肪酸甲酯,氧化后脂肪酸甲酯中CC—H基团基本消失;地沟油生物柴油、橡胶籽油生物柴油和小桐子生物柴油主要由棕榈酸甲酯、亚油酸甲酯、油酸甲酯及硬脂酸甲酯组成,氧化前3种生物柴油中此4种脂肪酸甲酯总含量分别为93.07%、95.82%和97.68%,氧化后分别降为77.23%、84.51%和63.66%。氧化后生物柴油成分十分复杂,含有不同的醛、酸、酮、醇及小分子的酯等物质,且亚油酸甲酯的含量大大降低,证实了生物柴油氧化主要是含有不饱和双键或三键的脂肪酸甲酯的氧化。     

Effect of Flour Type and Baking Temperature on Cake Dynamic Height Profile Measurements During Baking

A dynamic height profile method using digital imaging of cakes at 2 min intervals during baking was used to analyze changes in volume during baking for cakes made with three different flour types (plain flour, heat-treated cake flour, and strong white flour) and baked at three different temperatures (175°C, 190°C, and 205°C). The cakes made from the different flours showed, with some exceptions, a similar trend in the shape and development of the top contour during baking. In the first 4–6 min of baking, there was relatively little expansion followed by a period of rapid expansion to the maximum volume and a period of contraction up to the end of baking. For the three flour types, volume peaked at 16–17 min for the medium and high baking temperatures and at 20 min for the low baking temperature. Cakes made from heat-treated cake flour and strong white flour baked at low and high temperatures produced cakes where the center of the cake was lower than the surrounding pins resulting in a final undesirable dimpled cake contour. A higher baking temperature caused the cake to rise more rapidly. Baking at high temperature produced cakes which shrank the most (P < 0.001) during cooling. Among all combinations of flour type and different temperature treatments, cake made from heat-treated cake flour baked at the middle temperature produced the best final cake in terms of a final dome-shape contour, an appreciable volume during baking, less volume shrinkage during baking, and maximum cross-sectional area of the half cake after 1 h cooling.     

Presence of an older weaned companion influences feeding behavior and improves performance of dairy calves before and after weaning from milk

In commercial dairy production, calves are typically separated from the dam at a young age. This practice may interfere with developmental processes mediated by social interactions that occur between the calf, her dam, and older social partners. The aim of this study was to test the prediction that calves housed with an older weaned companion would show earlier intake of solid feed before weaning and higher growth rates during and after weaning compared with calves housed with calves of their own age. Forty-five dairy calves were separated from their dams and housed individually for approximately 7 d. Afterward, calves were assigned to pens composed of groups of either 3 young calves or 2 young calves and an older weaned calf. Group pens were equipped with automatic milk, water, starter, hay feeders, and scales. Weaning was by gradual reduction of milk volume over 5 d, from d 36 to d 40. During the preweaning period (d 1 to d 35), the number (8.8 vs. 5.1 ± 0.5 visits/d per calf) and duration (13.2 vs. 8.2 ± 1.1 min/d per calf) of visits to the hay feeder was higher for calves housed with an older companion, and calves in this treatment consumed more hay (57.9 vs. 25.6 ± 4.7 g/d) than did calves housed in groups of similar age. Starter intake did not differ between treatments before weaning, but the number of visits (15.2 vs. 9.4 ± 0.6 visits/d) and the time spent at the starter feeder (6.5 vs. 3.4 ± 0.5 min/d) were higher for calves housed with an older weaned companion. During the weaning period (d 36 to d 40), calves housed with an older companion spent more time at the starter feeder (22.1 vs. 12.9 ± 1.9 min/d) and made fewer unrewarded visits to the milk feeder (17.0 vs. 26.1 ± 1.9 visits/d) than did calves housed in groups of similar age. During the postweaning period (d 41 to d 55), calves housed with an older weaned companion spent less time at the hay feeder (32.5 vs. 58.5 ± 5 .5 min/d) and more time at the starter feeder (41.4 vs. 28.2 ± 3.7 min/d), and consumed more starter (1.8 vs. 1.3 ± 0.1 kg/d). Calves housed with an older weaned companion gained more weight during the preweaning (0.89 vs. 0.76 ± 0.03 kg/d) and postweaning (1.4 vs. 1.1 ± 0.05 kg/d) periods. We conclude that housing young calves with an older weaned companion stimulates feeding behavior and growth before and after weaning from milk.     

精炼前后葡萄籽油的品质变化

研究了精炼前后葡萄籽油的品质变化。采用GC-MS分析方法测定葡萄籽油精炼前后脂肪酸组成、甾醇组成及含量变化,并利用高效液相色谱法测定葡萄籽油精炼前后维生素组成及含量变化,同时利用国家标准方法测定葡萄籽油精炼前后矿物质元素含量变化。结果表明:葡萄籽毛油经过精炼后,感官品质与理化品质都得到很大提升;精炼对油中脂肪酸、矿物质元素影响不大;精炼后甾醇含量明显减少,维生素E、K损失严重。     

Evaluation of several modifications of an ecometric technique for assessment of media performance

Recovery of Listeria monocytogenes 101M, Jonesia denitrificans, salmonellae, and Pediococcus sp. NRRL B-2354 across nine media was evaluated with three modified versions of an ecometric method. Two approaches involved the use of broth cultures (10(8) to 10(9) CFU/ml) of individual strains and either large (10-microl) or small (1-microl) presterilized plastic loops. The third approach involved precultured slants and the inoculation of media with presterilized plastic inoculating needles (10(4) CFU per needle). Absolute growth indices (AGIs) were compared. No significant differences (P < 0.05) between methods were found when tryptic soy agar supplemented with 0.6% yeast extract (TSAYE) was used for the recovery of L. monocytogenes, J. denitrificans, Pediococcus sp. NRRL B-2354, and Salmonella spp. However, the small loop-broth technique recovered significantly fewer Salmonella enterica Typhimurium DT104 and Salmonella Senftenberg 775W cells than the other two techniques did. The performance of each individual bacterial strain on each of nine media was assayed. The recovery of L. monocytogenes was excellent (AGI > 4.8) with TSAYE, PALCAM, modified Oxford medium (MOX), and Baird-Parker agar and slight with modified PRAB (AGI = 0.4) and deMan Rogosa Sharpe (MRS) agar (< 0.1), and the organism was not recovered with the remaining media (modified lysine iron agar [MLIA], xylose lysine desoxycholate [XLD] agar, and xylose lysine tergitol 4 [XLT4] agar). The recovery of J. denitrificans with TSAYE and MOX was excellent, significantly better than that achieved with PALCAM (AGI = 3.0), but the organism was not recovered with Baird-Parker agar or with the other media tested. The recovery of Pediococcus sp. NRRL B-2354 was excellent with TSAYE and modified PRAB medium > Baird-Parker agar > acidified MRS agar, but the organism was not recovered with any of the other media tested. The best recovery of S. enterica Typhimurium DT104 was achieved with TSAYE > MLIA > or = XLD agar > or = XLT4 agar > Baird-Parker > PALCAM, MOX, acidified MRS agar, modified PRAB, and MRS agar. The best recovery of Salmonella Senftenberg 775W was achieved with TSAYE, MLIA, and XLD agar > XLT4 agar, but the organism was not recovered with the other media evaluated.     

北极熊毛纤维清洗前后的密度

北极熊毛纤维具有独特的中空膜结构,和其他的蛋白质纤维一样,北极熊毛纤维表面也含有各种不同种类的油脂。在毛发的热传递过程中,密度是一个很重要的参数。因此,在测量北极熊毛纤维的密度时有必要考虑油脂因素。文章对北极熊毛纤维清洗前后的密度进行了测量和对比,虽然测得的清洗前后北极熊毛纤维的密度差异不大,但是对于生活在-50℃的极地环境中的北极熊来说,毛纤维密度的微小变化也会极大地影响其热传递过程。     

Microbiological conditions of moisture-enhanced pork before and after cooking

Substantial numbers of aerobic bacteria but few coliforms or Listeria spp. and no Escherichia coli were recovered from both swab samples and brines circulated in cleaned equipment used for injecting pork loins. After meat was processed for 30 or 60 min, the numbers of aerobic bacteria in brines had increased by >1 log unit, to about 4.5 log cfu ml⁻¹, but coliforms were <2 and E. coli and Listeria spp. were <1 log cfu ml⁻¹. The numbers of bacteria on the surfaces of pork loins before and after injection of the meat were similar. No bacteria were recovered from the deep tissues of the uninjected meat, but aerobic bacteria were recovered at log-mean numbers of 2.1 log cfu g⁻¹ and coliforms at log-total numbers of 1.2 log cfu 25 g⁻¹ from 25 samples of deep tissues of injected meat. Aerobic bacteria were recovered at log total numbers of 1.0 log cfu 25 g⁻¹ from 25 samples of injected pork cooked to a central temperature of 61 °C, but no bacteria were recovered from the deep tissues of meat cooked to 70 °C. The findings suggest that moisture-enhanced pork cooked to a medium rare condition can be microbiologically safe.     

烘焙纸的特性及研究进展

介绍了烘焙纸的主要用途,其可用作烧烤及烤箱垫纸、蒸笼垫纸、食品包装、蛋糕杯;并简单介绍了烘焙纸的市场概况,分析了烘焙纸的剥离性、防油性、耐温性、成型度、安全性等主要特性,总结了国内外烘焙纸的生产工艺、研究进展;最后对我国烘焙纸的发展进行了展望。     

淀粉酶和蛋白酶及其在焙烤食品中作用

本文对淀粉酶和蛋白酶的作用机理及其在焙烤食品中作用进行详细论述,介绍淀粉酶和蛋白酶的添加量和添加方法,α－淀粉酶测定方法,同时讨论了在实际应用中应该注意的一些问题。