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1.
以‘秦美’猕猴桃果实为试材,于盛花期后28 d分别采用0(对照,清水)、5、10、20 mg/L 4个质量浓度的氯吡脲(1-(2-chloropyridin-4-yl)-3-phenylurea,CPPU)溶液进行蘸果处理,蘸果时间3~5 s,研究采前CPPU处理对‘秦美’猕猴桃贮藏期间果实硬度及细胞壁降解酶活力的影响。结果表明:CPPU处理加速了果实硬度、原果胶和纤维素质量分数的下降,提高了可溶性果胶质量分数及多聚半乳糖醛酸酶(polygalacturonase,PG)、果胶甲酯酶(pectin methylesterase,PME)、纤维素酶(cellulase,Cx)和β-半乳糖苷酶(β-D-galaetosidase,β-Gal)细胞壁降解活力。各处理组果实硬度与可溶性果胶质量分数和PG、Cx活力呈极显著负相关(P0.01),与原果胶、纤维素质量分数呈极显著正相关(P0.01);20 mg/L CPPU处理组果实的β-Gal活力与硬度呈显著负相关(P0.05)。CPPU处理提高了果实细胞壁降解酶的活力,促进了细胞壁的降解,加速了贮藏期间果实的软化,降低了果实的耐贮藏性。为维持猕猴桃采后果实硬度,延长贮藏期,生产中不宜使用CPPU处理,或使用的质量浓度不宜超过5 mg/L。  相似文献   
2.
《Journal of dairy science》2022,105(3):2132-2152
Bovines produce about 83% of the milk and dairy products consumed by humans worldwide, the rest represented by bubaline, caprine, ovine, camelid, and equine species, which are particularly important in areas of extensive pastoralism. Although milk is increasingly used for cheese production, the cheese-making efficiency of milk from the different species is not well known. This study compares the cheese-making ability of milk sampled from lactating females of the 6 dairy species in terms of milk composition, coagulation properties (using lactodynamography), curd-firming modeling, nutrients recovered in the curd, and cheese yield (through laboratory model-cheese production). Equine (donkey) milk had the lowest fat and protein content and did not coagulate after rennet addition. Buffalo and ewe milk yielded more fresh cheese (25.5 and 22.9%, respectively) than cow, goat, and dromedary milk (15.4, 11.9, and 13.8%, respectively). This was due to the greater fat and protein contents of the former species with respect to the latter, but also to the greater recovery of fat in the curd of bubaline (88.2%) than in the curd of camelid milk (55.0%) and consequent differences in the recoveries of milk total solids and energy in the curd; protein recovery, however, was much more similar across species (from 74.7% in dromedaries to 83.7% in bovine milk). Compared with bovine milk, the milk from the other Artiodactyla species coagulated more rapidly, reached curd firmness more quickly (especially ovine milk), had a more pronounced syneresis (especially caprine milk), had a greater potential asymptotical curd firmness (except dromedary and goat milk), and reached earlier maximum curd firmness (especially caprine and ovine milk). The maximum measured curd firmness was greater for bubaline and ovine milk, intermediate for bovine and caprine milk, and lower for camelid milk. The milk of all ruminant species can be used to make cheese, but, to improve efficiency, cheese-making procedures need to be optimized to take into account the large differences in their coagulation, curd-firming, and syneresis properties.  相似文献   
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The goal of the present study was to quantify the increase of intramammary pressure (IMP) in dry-off during an extended milking interval of 72 h. In particular, we tested the hypothesis that feed restriction (no concentrate and roughage with reduced energy) causes earlier cessation of milk secretion and a lower IMP than continued feeding of the lactational diet. In addition to repeated IMP measurements, we tested a noninvasive method that records udder firmness (UF) via external application of pressure on the udder. Two experimental groups consisted of 10 Holstein cows each, with a daily milk yield of 20 to 25 kg. The restricted group (RG) was changed to restricted feeding on the afternoon of the final milking (0 h), whereas late-lactation feeding was continued in the control group (CG). Both IMP and UF were measured before and after the final milking immediately before milking was stopped for 72 h. These measurements represented IMP and UF levels at 10 h and 0 h milking intervals, respectively. Further measurements were performed at 18, 24, 30, 36, 42, 48, and 72 h after final milking. Milk samples (2 mL) were taken through the IMP catheter at each sampling event, for analysis of somatic cell count (SCC) and serum albumin (SA). Both IMP and UF increased with time, and both parameters peaked at 30 h in CG and at 24 h in RG. The mean IMP from 18 to 72 h, compared with the 10-h IMP (normal milking interval) was higher in CG than in RG. The duration of elevated IMP and UF was prolonged in CG compared with RG (>36 h vs. 12 h). The Pearson correlation between IMP and UF was r = 0.67. Thus, the noninvasive measurement of UF is suitable to replace invasive IMP measurements. However, due to individual differences in udder shape, the correlation between UF and IMP was too low to predict exact IMP levels using UF. Both SCC (presented as logSCC) and SA increased after the final milking until the end of the experiment. The mean increase from 18 to 72 h, compared with levels immediately after final milking, was higher in CG than in RG for SCC but did not differ between treatments for SA. In conclusion, feed restriction causes a faster cessation of milk secretion and therefore limits the increase of IMP at dry-off.  相似文献   
5.
为了研究常温、冷链、断链3 种流通方式对桃果实品质的影响,在模拟3 种流通方式的温度环境下对桃果实进行贮藏,分析模拟流通过程中的桃果肉硬度、细胞壁果胶和糖酸含量及其组成的变化情况。结果表明,桃果实采后的贮运品质受流通温度的影响显著。模拟常温环境中流通的桃果实在4 d内即失去商品价值;恒定低温的流通条件(模拟冷链流通)可以保证桃果实在贮运期和货架期的良好品质;而模拟断链流通组的桃果实由于在贮藏过程中经历了包装、出入库等环节的温度升高,在进入货架期后果实品质快速下降,货架期第2天的果肉硬度(2.14 g/cm2)、蔗糖含量(46.48 mg/g)和苹果酸含量(3.13 mg/g)显著低于模拟冷链流通组(P<0.05)。桃果实采后冷链流通过程应尽量避免贮运环节断链造成的温度变化,研究结果可为果蔬冷链流通系统的完善提供参考。  相似文献   
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Fruits are composite materials often surrounded by a skin and sometimes containing rigid stones (pits). To understand the contribution of skin and stone to the overall texture of the fruit, model fruits were constructed from molded gelatin spheres, with rigid inclusions and a skin layer. Cross polarized light revealed the stress distribution during puncture testing and the mechanical measures of firmness, Poisson's ratio and breaking force were determined. Skin significantly raised the breaking force. Spherical stones raised the firmness—effectively reducing the deformable material in the sphere, resulting in inflated strains. Disc shaped stones compared with spherical ones, with the narrow edge normal to the force acted like an internal blade and significantly lowered the breaking force. Neither skin nor stone had any significant impact on Poisson's ratio. Three examples of real fruit (raspberries, grapes, and cherries) were tested to contextualize the findings.

Practical applications

Consumers gently squeeze fruit to gauge ripeness. Unwittingly, what we perceive while squeezing fruit is not wholly dependent on the texture of the internal flesh. In this work, we have attempted to model how the firmness and breaking force are influenced by the presence of a skin and stones of various size and shape. This has implications in both sensory and instrumental fruit testing.  相似文献   
8.
利用γ-谷维素与β-谷甾醇制备葵花油凝胶研究   总被引:1,自引:0,他引:1  
以一级压榨葵花籽油为原料,添加一定浓度的γ–谷维素与β–谷甾醇混合物制备出葵花油凝胶,探究不同制备工艺条件对葵花油凝胶硬度及微观结构的影响。在单因素试验的基础上,通过正交试验确定了6%γ–谷维素与β–谷甾醇混合物添加量葵花油凝胶的最优制备条件。试验表明,影响葵花油凝胶硬度因素的主次顺序为:冷却温度>γ–谷维素:β–谷甾醇添加比例>加热时间>加热温度;6%γ–谷维素与β–谷甾混合物醇添加量葵花油凝胶的最优制备工艺为:加热温度140℃,加热时间50 min,冷却温度5℃,γ–谷维素∶β–谷甾醇添加质量比例60∶40。在最优工艺条件下,6%γ–谷维素与β–谷甾醇添加量葵花油凝胶硬度为479.61±9.18 g。  相似文献   
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10.
The influences of vacuum impregnation (VI) on the tissue of mango cubes during atmospheric immersion in sucrose solution were investigated. Results showed that VI effectively facilitated water loss (WL) and sugar gain (SG) during the 300min immersion process, with increases of 20.59% and 31.26%, respectively. A pectin solubilization/degradation phenomenon was observed in the immersion process. The intercellular space and cross section area in the VI‐treated mango tissue increased immediately after being released to atmospheric pressure. And it was noted that after experiencing shrinkage‐relaxation period twice in the 300 min immersion process, the size of VI‐treated mango cells recovered to the original level of fresh ones. Major variations in WL, protopectin content, water soluble pectin content, firmness and microstructure of mango cubes appeared within the first 60 min. In addition, the firmness of mango cubes was positively correlated with the protopectin content (P < 0.01), but negatively correlated with WL and the water soluble pectin content (P < 0.01), indicating that WL and degradation of protopectin contributed greatly to the loss of firmness.  相似文献   
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