Freezing-thawing

冻融
  • 文章类型: Journal Article
    在冷链物流(CCL)过程中,肉类质量(MQ)不稳定。在CCL过程中,已经开发了不同的技术来增强MQ,虽然由于复杂的环境(尤其是运输和配送),它们中的大多数不能覆盖冷链的所有环节,兼容性问题,和他们的单一效果。电场(EF)已被用作不同食品加工的新型治疗方法。EFs用于生物冷冻保存的效果和潜在优势已经在许多出版物中报道,并且已经实现了CCL中的一些商业应用。然而,关于EFs对肉类品质属性的影响及其在CCL中的应用,仍缺乏系统评价。在这次审查中,在不同的CCL环节(冷冻,解冻,和制冷过程)进行了总结。还讨论了EFs在冷冻保存肉类中的当前应用和局限性。尽管由于电穿孔和电击穿效应,高强度EF对肉类的质量属性有一些不利影响,EF在某些商业应用中已经实现的大多数CCL场景中提供了良好的适用性机会。未来的研究应该集中在肉对不同EF参数的生化反应,打破设备的限制,从而使EF技术在生产环境中更接近可用性,实现EF在CCL上的大规模经济高效应用。
    Meat quality (MQ) is unstable during cold chain logistics (CCL). Different technologies have been developed to enhance MQ during the CCL process, while most of them cannot cover all the links of the cold chain because of complex environment (especially transportation and distribution), compatibility issues, and their single effect. Electric fields (EFs) have been explored as a novel treatment for different food processing. The effects and potential advantages of EFs for biological cryopreservation have been reported in many publications and some commercial applications in CCL have been realized. However, there is still a lack of a systematic review on the effects of EFs on their quality attributes in meat and its applications in CCL. In this review, the potential mechanisms of EFs on meat physicochemical properties (heat and mass transfer and ice formation and melting) and MQ attributes during different CCL links (freezing, thawing, and refrigeration processes) were summarized. The current applications and limitations of EFs for cryopreserving meat were also discussed. Although high intensity EFs have some detrimental effects on the quality attributes in meat due to electroporation and electro-breakdown effect, EFs present good applicability opportunities in most CCL scenes that have been realized in some commercial applications. Future studies should focus on the biochemical reactions of meat to the different EFs parameters, and break the limitations on equipment, so as to make EFs techniques closer to usability in the production environment and realize cost-effective large-scale application of EFs on CCL.
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  • 文章类型: Journal Article
    茎含水量是反映植物活力并维持其内部水平衡的关键参数。鉴于对越冬期不同阶段茎部含水量特征及其影响因素的认识不足,这项研究的重点是宏碁truncumBunge,并开发了基于物联网(IoT)的生态信息监测系统。该系统包含一个专有的茎含水量传感器,允许非侵入性,在监测各种环境参数的同时,原位和实时采集茎含水量。我们详细阐明了茎含水量的变化特征及其对各种环境因素的响应。结果表明:(1)越冬期间,茎含水量在三个阶段表现出“白天上升和夜间下降”的昼夜变化,在茎含水量达到极值和每日波动范围的时刻表现出差异。茎水含量在落叶和芽破裂阶段表现出最小的波动,但在休眠阶段经历了显着的冻融交替,导致每日波动范围增加。(2)环境参数与茎含水量之间的皮尔逊相关系数随阶段动态变化。路径分析显示,在落叶阶段,茎温度和饱和蒸汽压亏缺是影响茎含水量的主要因素;在休眠期,气温和饱和蒸汽压不足直接影响茎含水量;在破芽阶段,影响茎含水量的主要参数是饱和蒸汽压亏缺和茎温度。该研究为揭示越冬期间树茎组织内的水运输模式及其环境适应机制提供了有价值的见解,协助科学制定冬季管理策略,保护树木免受严寒和冻害,同时促进下一年的健康成长。
    Stem water content serves as a pivotal parameter that reflects the plant vitality and maintains their internal water balance. Given the insufficient comprehension regarding the stem water content characteristics and its influencing factors during different stages of the overwintering period, the study focused on Acer truncatum Bunge and developed an Internet of Things (IoT)-based ecological information monitoring system. The system incorporated a proprietary stem water content sensor, allowing non-invasive, in-situ and real time acquisition of stem water content while monitoring diverse environmental parameters. We conducted a detailed elucidation of stem water content variation characteristics and their responses to diverse environmental factors. The results showed: (1) During the overwintering period, stem water content exhibited diurnal variations characterized by \" daytime ascent and nighttime descent\" across the three stages, exhibiting differences in the moment when the stem water content reaches extremal values and daily fluctuations ranges. Stem water content exhibited minimal fluctuations during deciduous and bud-breaking stages but experienced significant freezing-thawing alternations during the dormant stage, leading to an increased daily fluctuation range. (2) The Pearson correlation coefficients between environmental parameters and stem water content varied dynamically across stages. Path analysis revealed that during the deciduous stage, stem temperature and saturation vapor pressure deficit were dominant factors influencing stem water content; during dormant stage, air temperature and saturation vapor pressure deficit directly impacted stem water content; during the bud-breaking stage, the primary parameters affecting stem water content were saturation vapor pressure deficit and stem temperature. The study provides valuable insights into unveiling the water transport patterns within tree stems tissue and their environmental adaptation mechanisms during the overwintering period, aiding in the scientific development of winter management strategies to protect trees from severe cold and freezing damage, while fostering healthy growth in the subsequent year.
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  • 文章类型: Journal Article
    人类精子冷冻保存是辅助生殖技术中的常规程序,但是由于氧化应激,它对不同的精子参数有不利影响。我们的目标是评估羟基酪醇(HT)的影响,作为一种抗氧化剂,冷冻保存后的人类精子参数。在第一阶段,采用快速冷冻法对20份正常人精液样本进行冷冻保存,分别含有0、50、100、150和200μg/mL不同浓度的HT。在第二阶段,收集20个正常精液样品,并用50和100μg/mLHT冷冻保存。HT的有益效果是通过运动能力评估(计算机辅助精子分析;CASA)来确定的。活力(曙红-苯胺黑染色),DNA完整性(精子色散测试,SCD),活性氧(DCF和DHE染色通过流式细胞术)脂质过氧化(丙二醛,冷冻保存后精子的MDA测试)和线粒体膜电位(流式细胞仪JC1染色)。解冻后,与其他组相比,50和100μg/mLHT组的精子活力有增加的趋势,但差异不显著。然而,在50和100μg/mLHT时,精子活力显着增加。我们的数据还表明,与0和50μg/mLHT相比,在100μg/mL解冻后精子DNA片段显着降低。然而,细胞内活性氧的水平,各组间脂质过氧化和线粒体膜电位无显著差异。我们的结果表明,HT可能在冻融过程中对人类精子的活力和DNA完整性具有保护作用。
    Human sperm cryopreservation is a routine procedure in assisted reproductive technology, but it has detrimental effects on different sperm parameters due to oxidative stress. Our objective was to assess the impacts of hydroxytyrosol (HT), as an antioxidant, on human sperm parameters following cryopreservation. In the first phase, 20 normal human semen samples were cryopreserved using the rapid freezing method with different concentrations of HT including 0, 50, 100, 150, and 200 μg/mL. In the second phase, 20 normal semen samples were collected and cryopreserved with 50 and 100 μg/mL HT. The beneficial effects of HT were determined by evaluation of motility (computer-assisted sperm analysis; CASA), viability (Eosin-nigrosine stain), DNA integrity (sperm chromatic dispersion test, SCD), reactive oxygen species (DCF and DHE staining by flowcytometry) lipid peroxidation (malondialdehyde, MDA test) and mitochondrial membrane potential (JC1 staining by flowcytometry) of sperm after cryopreservation. After thawing, sperm motility had an increasing trend in 50 and 100 μg/mL HT groups in comparison with other groups, althought the difference was not significant. However, sperm viability was significantly increased at 50 and 100 μg/mL HT. Our data also showed that sperm DNA fragmentation was significantly decreased after thawing at 100 μg/mL in comparison with 0 and 50 μg/mL HT. However, the level of intracellular reactive oxygen species, lipid peroxidation and mitochondrial membrane potential were not significantly different between groups. Our results showed that HT may have protective effects on the viability and DNA integrity of human sperm during the freezing-thawing process.
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  • 文章类型: Journal Article
    由各种废品制成的碱活化粘合剂可以显著减少二氧化碳的排放,提高废物回收效率,从而使它们成为普通波特兰水泥(OPC)基粘结剂的可行替代品。废料,包括粉煤灰(FA),棕榈油燃料灰(POFA),和粒状高炉矿渣(GBFS)显示出有利的效果,当应用于碱活化砂浆(AAMs)时,主要与高含量的二氧化硅有关,氧化铝,和钙。因此,包含FA的15种AAM混合物,设计了具有大量GBFS的POFA。对获得的基于GBFS/FA/POFA的AAM进行湿/干和冷冻/解冻循环。各种GBFS含量对微结构的影响,冻融循环,耐磨性,对拟议AAM的机械和耐久性特征进行了评估。结果表明,Ca的存在可以显着影响AAM的耐久性特征和长期性能。AAMs的耐磨性随CaO含量的降低而降低。此外,与通过用GBFS代替50重量%的FA制成的混合物(1.4mm)相比,70%AAMs(0.8mm)的磨损深度较低。一般来说,GBFS含量从50%增加到70%可能会在很大程度上影响侵蚀性环境暴露下的AAM特性。冻融循环过程中的膨胀和物理影响被认为破坏了C-S-H和糊状聚集体中的键,导致大裂缝的形成。据断言,由FA制成的AAM混合物,POFA和大量的GBFS可能会提供明确的机械,耐用,和环境效益,增强其在恶劣环境下的性能。
    Alkali-activated binders made from various waste products can appreciably reduce the emission of CO2 and enhance the waste recycling efficiency, thus making them viable substitutes to ordinary Portland cement (OPC)-based binders. Waste materials including fly ash (FA), palm oil fuel ash (POFA), and granulated blast furnace slag (GBFS) reveal favorable effects when applied to alkali-activated mortars (AAMs) that are mainly related to the high contents of silica, alumina, and calcium. Therefore, fifteen AAM mixes enclosing FA, POFA with high volume of GBFS were designed. The obtained GBFS/FA/POFA-based AAMs were subjected wet/dry and freeze/thaw cycles. The impact of various GBFS contents on the microstructures, freeze-thaw cycle, abrasion resistance, mechanical and durability features of the proposed AAMs were evaluated. The results showed that presence of Ca can significantly affect the AAMs durability features and long-term performance. The abrasion resistance of the AAMs was decreased with the decrease of CaO contents. Furthermore, the abrasion depth of 70% AAMs (0.8 mm) was lower in comparison to the mix made by replacing 50 wt% of FA with GBFS (1.4 mm). Generally, increase in the GBFS contents from 50 to 70% could largely impact the AAMs properties under aggressive environmental exposure. The expansion and physical impacts during the freezing-thawing cycles was argued to destroy the bonds in C-S-H and paste-aggregates, causing the formation of large cracks. It is asserted that the AAM mixes made from FA, POFA and high volume of GBFS may offer definitive mechanical, durable, and environmental benefits with their enhanced performance under aggressive environments.
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  • 文章类型: Journal Article
    在研究中,褪黑激素,在Hariana公牛精液中,一种已知的抗氧化剂松果体肽被用作基于三卵黄甘油的精液补充剂中的添加剂,并评估了解冻后的精子特征。在研究中,第一组是没有褪黑激素的对照;第二组,III,IV有0.5mM,1mM,和2mM褪黑激素/80×106精子,分别为治疗组。对来自4头Hariana公牛的32个精液射精进行了冷冻处理,并评估了解冻后的精子特征。精子运动,速度,完整膜的生存能力,与所有其他组相比,IV组的总抗氧化能力显着提高(P<0.05)。与所有其他组相比,IV组的脂质过氧化和总蛋白羰基化显著降低(P<0.05)。冷冻的种群,顶体反应,Ⅳ组细胞凋亡样精子明显减少(P<0.05)。Further,第IV组74kDa蛋白的相对条带强度和对酪氨酸磷酸化蛋白显示阳性免疫反应性的精子百分比降低。孕激素受体配体结合,体外获能反应,第IV组Vanguard距离明显改善(P<0.05)。总之,发现具有2mM褪黑激素的第IV组在冻融后向Hariana公牛精子提供冷冻保护作用方面是最佳的,并且可以在精液冷冻保存期间合适地用作精液添加剂。
    In the study, melatonin, a known antioxidant pineal peptide was used as an additive in the tris-egg yolk glycerol-based semen extender in Hariana bull semen and post-thaw sperm characters were evaluated. In the study, Group I was a control without melatonin; and Group II, III, and IV were having 0.5 mM, 1 mM, and 2 mM melatonin/80 × 106 spermatozoa, respectively were treatment groups. Thirty-two semen ejaculates from 4 Hariana bulls were processed for freezing and post-thaw sperm characteristics were evaluated. Sperm motility, velocity, the viability with intact membrane, and total antioxidant capacity were markedly (P < 0.05) improved in Group IV compared to all other groups. The lipid peroxidation and total protein carbonylation were substantially (P < 0.05) decreased in Group IV compared to all other groups. The population of cryocapacitated, acrosome-reacted, and apoptotic-like spermatozoa were significantly (P < 0.05) decreased in Group IV. Further, the relative band intensity of 74 kDa protein and percent of spermatozoa showing positive immune reactivity to tyrosine-phosphorylated proteins was decreased in Group IV. The progesterone-receptor ligand binding, in vitro capacitation response, and Vanguard distance were markedly (P < 0.05) improved in Group IV. In summary- Group IV having 2 mM melatonin was found to be optimal in providing cryoprotective effects to Hariana bull spermatozoa after freezing-thawing and can be suitably used as a semen additive during semen cryopreservation.
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  • 文章类型: Journal Article
    分隔是许多细胞过程的关键,也是任何最小寿命方法的关键瓶颈。在细胞中,复杂的化学负责在正确的时间在正确的位置将生物分子聚集在一起或分开。脂质,核酸和蛋白质自组织,从而创造边界,接口和专用微环境。在巨大的单层囊泡(GUV)内利用可逆的基于RNA的液-液相分离(LLPS),我们提出了一种有效的系统,该系统能够在冻融(FT)温度循环时在GUV群体中传播基于RNA的酶促反应。我们报告说,浓缩的富含RNA的阶段的分隔可以加速这种酶促反应。在去冷凝状态下,RNA底物变得均匀分散,在冻融过程中实现囊泡之间的内容交换。这项工作探讨了脂质囊泡中的最小可逆相分离系统如何有助于在循环过程中实现时空控制,如最小细胞所需。
    Compartmentalization is key to many cellular processes and a critical bottleneck of any minimal life approach. In cells, a complex chemistry is responsible for bringing together or separating biomolecules at the right place at the right time. Lipids, nucleic acids and proteins self-organize, thereby creating boundaries, interfaces and specialized microenvironments. Exploiting reversible RNA-based liquid-liquid phase separation (LLPS) inside giant unilamellar vesicles (GUVs), we present an efficient system capable of propagating an RNA-based enzymatic reaction across a population of GUVs upon freezing-thawing (FT) temperature cycles. We report that compartmentalization in the condensed RNA-rich phase can accelerate such an enzymatic reaction. In the decondensed state, RNA substrates become homogeneously dispersed, enabling content exchange between vesicles during freeze-thawing. This work explores how a minimal reversible phase separation system in lipid vesicles could help to implement spatiotemporal control in cyclic processes, as required for minimal cells.
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  • 文章类型: Journal Article
    聚丙烯(PP)网因其优异的生物相容性和力学性能,被广泛应用于疝修补术中。然而,腹部内脏和PP网之间的粘连仍然是一个主要问题。因此,采用聚乙烯醇(PVA)水凝胶和脂质体给药系统设计了抗粘连PP网。首先,通过冻融处理循环(FTP)在PP网表面形成PVA水凝胶涂层。随后,将冻干的PVA10-c-PP浸入装载雷帕霉素(RPM)的脂质体溶液中,直到溶胀平衡以获得抗粘连网状物RPM@LPS/PVA10-c-PP。已证明,即使在37°C或40°C的PBS溶液中浸入长达30天后,水凝胶涂层也可以稳定地固定在PP网的表面上。体外细胞测试表明,改性PP网具有优异的细胞相容性和抑制细胞粘附的潜力。此外,通过体内实验评价了RPM@LPS/PVA10-c-PP网片的抗粘连作用。在整个植入过程中,RPM@LPS/PVA10-c-PP网状物的粘附力低于原始PP网状物。在30天,RPM@LPS/PVA10-c-PP网眼的粘附评分为1.37±0.75,而原始PP为3±0.71。此外,H&E和Masson三色染色的结果证明,与天然PP相比,RPM@LPS/PVA10-c-PP网状物显示出轻微的炎症反应和明显松散的纤维组织包围PP丝。目前的发现表明,这种类型的RPM@LPS/PVA10-c-PP可能是抗粘连治疗的潜在候选者。数据可用性:数据将根据要求提供。
    Polypropylene (PP) mesh has been widely used in hernia repair as prosthesis material owing to its excellent balanced biocompatibility and mechanical properties. However, abdominal adhesion between the visceral and PP mesh is still a major problem. Therefore, anti-adhesive PP mesh was designed with poly(vinyl alcohol) (PVA) hydrogel and liposomes drug delivery system. First, PVA hydrogel coating was formed on the surface of PP mesh with freezing-thawing processing cycles (FTP). Subsequently, the lyophilized PVA10-c-PP was immersed in rapamycin (RPM)-loaded liposome solution until swelling equilibrated to obtain the anti-adhesion mesh RPM@LPS/PVA10-c-PP. It was demonstrated that the hydrogel coating can stably fix on the surface of PP mesh even after immersed in PBS solution at 37 °C or 40 °C for up to 30 days. In vitro cell tests revealed the excellent cytocompatibility and the potential to inhibit cell adhesion of the modified PP mesh. Moreover, the anti-adhesive effects of the RPM@LPS/PVA10-c-PP mesh was evaluated through in vivo experiments. The RPM@LPS/PVA10-c-PP mesh exhibited less adhesion than original PP mesh throughout the duration of implantation. At 30 days, the adhesion score of RPM@LPS/PVA10-c-PP mesh was 1.37 ± 0.75, however the original PP was 3 ± 0.71. Furthermore, the results of H&E and Masson trichrome staining proved that the RPM@LPS/PVA10-c-PP mesh showed slighter inflammation response and significant looser fibrous tissue surrounded the PP filaments as compared to the native PP. The current findings manifested that this type of RPM@LPS/PVA10-c-PP might be a potential candidate for anti-adhesion treatment. DATA AVAILABILITY: Data will be made available on request.
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  • 文章类型: Journal Article
    未经授权:睾丸组织的冷冻保存为保护濒危物种提供了新的可能性,遗传上有价值的个体,甚至是意外死亡的青春期前个体的生育潜力。然而,这项技术的使用仍然是一个挑战。在这项研究中,研究了睾丸组织的缓慢冷冻和玻璃化保存方法,以找出哪种冷冻保存方法可以更好地保存多种野生物种的睾丸生殖细胞的活力和DNA完整性。
    UNASSIGNED:睾丸是从18只偶蹄动物(野猪,鹿,矮人山羊,麦尔·瞪羚,欧洲Mouflon,非洲森林水牛,马来亚塔米尔,DorcasGazelle,伊比利亚ibex,gnu,红河猪),5只灵长类动物(疣猴,卷尾猴,mandrill),8个食肉动物(灰狼,波斯豹,宾图龙,欧洲水貂,美国黑熊,suricata),和2只啮齿动物(巴塔哥尼亚马拉)。睾丸属于成年人,被切成小块,并通过针头浸入式玻璃化或使用被动冷却装置进行不受控制的缓慢冷冻进行冷冻保存。升温或解冻后,睾丸组织被酶消化,两种生殖细胞类型根据其形态进行分化:圆形细胞(精原细胞,精母细胞,和早期精子)和细长细胞(细长精子和精子)。通过SYBR-14/碘化丙啶评估细胞活力,同时通过荧光显微镜的TUNEL测定进行DNA片段化。
    UNASSIGNED:我们的初步结果表明,与玻璃化相比,我们不受控制的缓慢冷冻方法更好地保留了细长细胞的活力和DNA完整性。在所有物种中都观察到这种趋势,在偶蹄动物中很重要,食肉动物,和灵长类动物。同样,通过不受控制的缓慢冷冻,灵长类动物中圆形细胞的活力和DNA完整性也得到了更好的维持,在食肉动物中,通过针浸玻璃化在这种类型的细胞中显示出更好的结果。在偶蹄动物和啮齿动物中,两种技术都以类似的方式保留了圆形细胞的活力,尽管在偶蹄动物中进行针浸玻璃化后,这些细胞的DNA完整性更高。
    未经批准:总而言之,每种冷冻保存方法的有效性受到物种和细胞类型之间的系统发育多样性的影响。
    UNASSIGNED: Cryopreservation of testicular tissues offers new possibilities to protect endangered species, genetically valuable individuals or even the fertility potential of prepubertal individuals who have died unexpectedly. However, the use of this technique still remains a challenge. In this study, slow freezing and vitrification of testicular tissue was investigated to find out which cryopreservation method could better preserve the viability and DNA integrity of testicular germ cells in diverse wild species.
    UNASSIGNED: Testes were obtained post-mortem from 18 artiodactyls (wild boar, roe deer, dwarf goat, mhor gazelle, European mouflon, African forest buffalo, Malayan tapir, dorcas gazelle, Iberian ibex, gnu, red river hog), 5 primates (colobus monkey, capuchin monkey, mandrill), 8 carnivores (gray wolf, Persian leopard, binturong, European mink, American black bear, suricata), and 2 rodents (Patagonian mara). The testicles belonged to adult individuals and were cut into small pieces and cryopreserved by needle immersed vitrification or uncontrolled slow freezing using a passive cooling device. After warming or thawing, testicular tissues were enzymatically digested and two germ cell types were differentiated based on their morphology: rounded cells (spermatogonia, spermatocytes, and early spermatids) and elongated cells (elongated spermatids and spermatozoa). Cell viability was assessed by SYBR-14/propidium iodide while DNA fragmentation by TUNEL assay with fluorescence microscope.
    UNASSIGNED: Our preliminary results revealed that our uncontrolled slow freezing method better preserved the viability and DNA integrity of elongated cells than vitrification. Such trend was observed in all species, being significant in artiodactyls, carnivores, and primates. Similarly, the viability and DNA integrity of rounded cells was also better maintained in primates by uncontrolled slow freezing, while in carnivores, vitrification by needle immersion showed better results in this type of cells. In artiodactyls and rodents both techniques preserved the viability of rounded cells in a similar manner, although the DNA integrity of these cells was greater after needle immersed vitrification in artiodactyls.
    UNASSIGNED: In conclusion, the effectiveness of each cryopreservation method is affected by the phylogenetic diversity between species and cell type.
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  • 文章类型: Journal Article
    本研究旨在评估磁共振成像(MRI)和计算机视觉技术对新鲜(原始F)(n=12)和冻融(FT)(n=12)牛肉进行分类并预测理化,通过优化图像分析(算法)和数据分析(回归)的方法,测试不同的算法-回归组合。分类和预测结果的准确性尤其取决于算法。发现了不同的最佳组合进行分类(分形与CForest,RF或SVM)以及原始FT(Fractal-CForest或Fractal-RF)和煮熟的FT样品(Classic-RF)的质量参数预测。因此,MRI的计算分析,特别是分析图像的算法,可以设置为目标(分类或预测)和样品类型(生的或熟的)的函数,而分析的特征是不相关的。这项研究首先显示了MRI对牛肉进行分类的能力(生F与原始FT),并以无损的方式确定质量特性。
    This study aims to evaluate the capability of Magnetic Resonance Imaging (MRI) and computer vision techniques to classify fresh (raw F) (n = 12) and frozen-thawed (FT) (n = 12) beef and predict physico-chemical, texture and sensory characteristics by optimization the methodology for image analysis (algorithm) and data analysis (regressor), testing different algorithm-regressor combinations. The accuracy of the classification and prediction results especially depend on the algorithm. Different optimum combinations were found for classification (Fractal with CForest, RF or SVM) and prediction of quality parameters of raw FT (Fractal-CForest or Fractal-RF) and cooked FT samples (Classic-RF). Thus, the computational analysis of MRI, especially the algorithm to analyze the image, may be set as a function of the aim (classification or prediction) and of the type of sample (raw or cooked), while the analysed characteristic is not relevant. This study firstly showed the capability of MRI to classify beef (raw F vs. raw FT) and to determine quality characteristics in a non-destructive way.
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  • 文章类型: Journal Article
    冷冻已广泛用于食品的长期保存。然而,冻融(FT)处理通常会影响魔芋等食物凝胶的质地和结构。对于FT处理后的质地控制,澄清食品凝胶在FT过程中的结构变化是很重要的。在这项研究中,我们使用同步同步加速器小角X射线/广角X射线散射(SAXS/WAXS)技术研究了FT过程中魔芋葡甘露聚糖(GM)凝胶的聚集结构。FT处理导致更多的GM结晶,因此,压缩应力的大幅增加。原位SAXS/WAXS测量揭示了以下发现:在冻结时,水分子从GM的聚集阶段出来,在解冻后,他们回到聚合阶段,但是聚集的结构没有恢复到冷冻之前的结构;凝胶网络由于冷冻过程中冰晶的生长而增强了不均匀性。此外,我们研究了添加剂如聚乙烯醇(PVA)和抗冻糖蛋白(AFGP)对冻融GM凝胶的机械和结构性能的影响。虽然PVA和AFGP的加入抑制了GM的结晶,它不能防止冰晶的生长和凝胶网络不均匀性的增加。因此,与未经FT处理的GM凝胶相比,含有PVA或AFGP的冻融GM凝胶的压缩应力明显更高,尽管它们低于冻融的转基因凝胶。这项研究的结果可能不仅有助于控制冻融食品的质地,而且有助于改善生物材料的机械性能。
    Freezing has been widely used for long-term food preservation. However, freezing-thawing (FT) treatment usually influences the texture and structure of food gels such as konjac. For their texture control after FT treatment, it is important to clarify the structural change of food gels during the FT process. In this study, we investigated the aggregated structures of konjac glucomannan (GM) gels during the FT process using simultaneous synchrotron small-angle X-ray/wide-angle X-ray scattering (SAXS/WAXS) techniques. The FT treatment resulted in more crystallization of GM, and consequently, a large increase in compressive stress. In-situ SAXS/WAXS measurements revealed the following findings: on freezing, water molecules came out of the aggregated phase of GM and after the thawing, they came back into the aggregated phase, but the aggregated structure did not return to the one before the freezing; the gel network enhanced the inhomogeneity due to the growth of ice crystals during freezing. Furthermore, we examined the influence of additives such as polyvinyl (alcohol) (PVA) and antifreeze glycoprotein (AFGP) on the mechanical and structural properties of freeze-thawed GM gels. Although the addition of PVA and AFGP suppressed the crystallization of GM, it could not prevent the growth of ice crystals and the increase in the inhomogeneity of the gel network. As a result, the compressive stresses for freeze-thawed GM gels containing PVA or AFGP were significantly higher compared with those of GM gels without FT treatments, although they were lower than those of freeze-thawed GM gels. The findings of this study may be useful for not only the texture control of freeze-thawed foods but also the improvement of the mechanical performance of the biomaterials.
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