基于揉搓方法的板栗破壳性能的试验研究

为了研究板栗揉搓破壳机理及破壳性能，自行设计了基于揉搓破壳机理的破壳装置，对一定大小等级的板栗进行了破壳试验。通过揉搓速度和定动齿板间距对板栗破壳率和破仁率两个指标影响的单因素试验可知，板栗破壳率和破仁率均随着揉搓速度的增加而增加；齿板间距过大或过小都会使板栗的破仁率增加，齿板间距越小则板栗的破壳率越高。通过多因素正交试验和极差分析找出影响其破壳效果的主次因素分别为齿板间距和加载速度，确定了板栗破壳的最佳速度和间距分别为:20 mm/min、17.4 mm。     

仿生敲击式山核桃破壳机的设计与试验

针对目前国内山核桃破壳机实用机型少,破壳率较低,果仁损伤率较高等情况,提出了一种仿生敲击(即模仿人工加工山核桃的方式)破壳方式,研制一款仿生敲击式山核桃破壳机。根据山核桃的物料特性以及破壳时所需的各项力学特性参数,建立了破壳机构设计的数学模型。确定了敲击臂的结构尺寸,优化了凸轮结构,并最终得到了凸轮的实际轮廓曲线。该文阐述了破壳机的总体结构与性能,建立了整机的三维实体模型,并根据建模制造了样机。该样机通过现场试验,结果表明:山核桃的含水率为14.55%~16.35%,大小为直径18~22 mm(沿缝合线方向)时,破壳率为99.41%,果仁损伤率为6.25%,生产率为94.93 kg/h,满足生产要求。该研究丰富与完善了坚果类果实的破壳机理与方法,为含隔坚果类的破壳机具设计与开发提供系统的理论依据和应用基础。     

不同成熟度芡实的力学性能试验分析

随着芡实种植和消费量的增大,芡实生产的机械化要求逐渐成为芡实发展的瓶颈,其中芡实破壳机械设备的研制成为芡实产后加工过程中的一个关键问题。为给芡实破壳机械设计提供依据,对不同成熟程度芡实进行了压缩和剪切试验,分析芡实的成熟程度及受力方向对其力学性能的影响。试验结果表明,芡实在压缩和剪切试验中破裂所产生的受力载荷—变形曲线是相似的,但裂纹的产生部位和扩展方式不同;芡实破裂时的破壳力、变形量、应变能及应变能密度都随其成熟度的增加而增大;理论上垂直于芡实脐眼方向进行剪切破壳加工相对较容易。试验结果为芡实破壳机械设备的研发提供了参数依据。     

三倍体西瓜种子种壳结构及机械破壳力学特性

为实现机械破壳代替人工破壳的方式提高无子西瓜种子的发芽率。对比二倍体西瓜种子,用种壳超微结构分析方法解释了三倍体西瓜种子的发芽障碍原因;并采用3种常见的三倍体西瓜种子黑牛、蜜红和花皮,含水率分别为11.1%、11.2%和10.6%,运用常用试验方法对实现机械破壳的力学特性进行了试验研究。试验结果得出三倍体西瓜种子的加载速度对破壳力的影响;设计压缩摇杆时,其调节量标准以各品种的压缩变形量最大值为基准;加载速度宜选择80～100mm/min;最大破壳力为68.97N。研究得到的结果为开发三倍体西瓜种子破壳机械提供了基本参数和理论计算依据。     

抗结壳厌氧发酵反应器的研制与试验

以玉米秸秆为主要原料进行厌氧发酵时,发酵液上部极易形成浮渣结壳层,严重影响秸秆产气效率。为了有效抑制浮渣结壳层的产生,该研究设计了一种抗结壳厌氧发酵反应器,首先阐述破壳装置的工作原理;其次进行主要部件设计,运用Adams对破壳装置机构进行动力学仿真,并对搅拌叶片进行受力分析,依据仿真结果,确定破壳机构的传动比以及搅拌叶片安装角;进一步以DEM-CFD耦合仿真方法对斜桨式叶片仿真模型的流场和颗粒场进行了数值模拟。仿真结果表明,斜桨式叶片转动时使颗粒产生轴向流与径向流,轴向流触底延壁面上升与推进式搅拌叶片产生共同作用形成涡流,径向流增加颗粒横向移动速度,流场产生大范围横向流动打破浮渣结壳层。为了探究抗结壳反应器对浮渣结壳层的抑制作用效果,以破壳装置搅拌转速、搅拌间隔时间及单次搅拌时间为因素,浮渣层厚度为指标,进行了三因素三水平试验。试验表明,当破壳装置主轴转速为120 r/min,每次搅拌间隔时间为3 h,搅拌时间为30 min时,浮渣结壳层厚度为16.1 cm,相比对照组,浮渣结壳层厚度减小了36.1 %,该抗结壳反应器明显改善了秸秆厌氧发酵的结壳问题,可为后续抗结壳厌氧发酵反应器研制提供新思路。     

莲子机械特性的测试研究

对莲子的机械特性进行了测试，以研究脱壳机理，为莲子脱壳机的设计提供技术数据。用压缩试验的方法求取各种工况下莲子的机械特性，分析了莲子等级和加载速率对其破壳力的影响，同时测定了不同部位、测点破壳力的差异。结果表明：莲子破壳力与等级成线性正相关关系，相关系数为0.955；加载速率与破壳力之间没有明确的关系，其应力－应变曲线的斜率随加载速率的增加而增大，而应变随之减小；莲子“赤道”与“两极”间轮廓上不同测点的破壳力差异较大，而同一部位的圆周上各点所需破壳力相差不大。该文的研究结果为莲子加工工艺的研究开发提供了理论依据。     

气调包装对松籽常温贮藏生理和品质变化的影响

以朝鲜红松带壳松籽和去壳松仁为试材,将其分别放在30 μm紫色聚氯乙烯袋、30 μm白色聚氯乙烯袋和40 μm白色聚乙烯袋中进行自发气调贮藏,研究了常温下（20～30℃）贮藏180 d期间松籽种仁的生理、品质和脂肪酸氧化变化。结果表明：与40 μm聚乙烯袋相比,30 μm紫色聚氯乙烯袋与30 μm白色聚氯乙烯袋可以形成相对低O2高CO2的贮藏条件,能有效降低带壳松籽和去壳松仁的呼吸速率和可溶性总糖的损耗,提高种仁的贮藏优品率;同时可以较好地防止总脂肪的降解,抑制酸价、过氧化值的升高和碘价的降低。综上所述,30 μm聚氯乙烯袋可以较好地保持松籽品质,相同气调包装贮藏下带壳松籽的贮藏品质优于去壳松仁。     

高压脉冲电场技术提高红松籽抗氧化肽活性

为了研究用高压脉冲电场技术(pulsed electric field,PEF)提高红松子抗氧化肽活性的效果,该文以分子量1~3k Da的红松籽多肽为试验原料,以2,2-二苯基-1-苦基肼(2,2-diphenyl-1-picrylhydrazyl,DPPH)清除率为衡量指标,借助单因素和响应面试验设计方法,优选高压脉冲电场技术处理红松籽抗氧化肽的最佳工艺参数。研究发现,当电场强度11.5 k V/cm,脉冲频率1 500 Hz,流速4.8 m L/min时,PEF处理的红松籽抗氧化肽粉的DPPH清除率为86.93%±0.31%,比未经PEF处理的DPPH清除率68.16%±0.25%,提高了18.77%;通过中红外色谱技术(mid-infrared spectroscopy,MIR)分析了最佳PEF处理的1-3 k Da红松籽抗氧化肽粉,发现其二级结构中R2C=CH2键和-CH3发生改变,研究结果为探究PEF技术提高抗氧化肽的机理提供参考。     

基于有限元分析的核桃脱壳技术研究

核桃破壳是核桃深加工的第一步,必须首先解决。经实测发现核桃形状不规则、壳仁间隙小。试验证明核桃壳完全破裂所需的变形量大于壳仁间隙,用一般的机械挤压方法破壳必将造成大量的碎仁。该文采用结构静力分析的有限单元法,通过所建核桃的几何模型和破壳的有限元模型,对核桃在几种载荷作用下的应力分布规律进行了分析,找出了核桃壳变形量不大且产生局部裂纹点多、裂纹点易扩展的最佳的施力方式。设计了导向机构。试验表明,核桃导向装置基本实现了使核桃的椭圆长轴与破壳辊轴线平行,使核桃以滚动方式挤压扩展裂纹提高了露仁率。     

适宜核桃壳划口位置改善其破壳特性提高整仁率

针对目前传统单一的机械破壳方式存在的破壳率和整仁率难以平衡的问题,该文以预处理视角研究了对新疆核桃进行破壳前划口预处理的静态压力试验,试验结果表明,核桃划口预处理相比未处理核桃的破壳力和破壳形变量明显减小,整仁率明显增加;当核桃划口位置和施加载荷位置均在核桃肚部时,核桃破壳力和破壳形变量均明显减小,与未处理的核桃相比破壳力减小了139 N,减幅为38.4%;破壳形变量减小了0.37 mm,减幅为18.2%;利用三维扫描仪对研究对象进行三维建模,使其更接近物料实形,并实施模型核桃划口处理。有限元静力学分析结果表明:未划口处理的核桃,其壳体表面最大应变、应力和形变发生在加载位置;当加载力相同时,划口预处理条件下在核桃划口位置产生的应变、应力和形变量最大;当核桃划口位置和加载位置均在核桃肚部时,核桃壳表面产生的应变、应力和形变量均较大。该研究结果经验证与静态压力试验结果基本吻合。研究结果为核桃划口机和核桃破壳设备的研制提供理论支撑。     

松子的声学特性及分形判别

针对开口与未开口松子结构差异，利用声学测试系统，对开口松子与未开口松子声学特性进行测试，以区分开口与未开口松子。试验中，松子在一定高度下落，碰撞到陶瓷板，微音计接收到声音，输入计算机，利用计算机进行分析计算，得到波形图和频谱图。对开口松子与未开口松子的波形和频谱进行分析，计算其分形维。通过试验和分析计算，发现开口松子的波形分形维小于未开口松子分形维，开口松子波形分形维平均值为1.4097，而未开口松子波形分形维平均值1.6576；开口松子的频谱图分形维大于未开口松子，开口松子频谱分形维平均值为1.3497，未开口松子频谱分形维平均值为1.1846。松子波形和频谱的分形维可以作为用于判别松子是否开口的一个指标。     

Oxidative stability of tree nut oils

The oxidative stability of selected tree nut oils was examined. The oils of almond, Brazil nut, hazelnut, pecan, pine nut, pistachio, and walnut were extracted using two solvent extraction systems, namely, hexane and chloroform/methanol. The chloroform/methanol system afforded a higher oil yield for each tree nut type examined (pine nut had the highest oil content, whereas almond had the lowest). The fatty acid compositions of tree nut oils were analyzed using gas chromatography, showing that oleic acid was the predominant fatty acid in all samples except pine nut and walnut oils, which contained high amounts of linoleic acid. The tocopherol compositions were analyzed using high-performance liquid chromatography, showing that alpha- and gamma-tocopherols were the predominant tocopherol homologues present; however delta- and beta-tocopherols were also detected in some samples. The oxidative stability of nonstripped and stripped tree nut oils was examined under two conditions, namely, accelerated autoxidation and photooxidation. Progression of oxidation was monitored using tests for conjugated dienes, peroxide value, p-anisidine value, and headspace volatiles. Primary products of oxidation persisted in the earlier stages of oxidation, whereas secondary oxidation product levels increased dramatically during the later stages of oxidation. Hexanal was the major headspace aldehyde formed in all oxidized samples except walnut oil, which contained primarily propanal. Results showed that chloroform/methanol-extracted oils were more stable than hexane-extracted oils in both the accelerated autoxidation and photooxidation studies. Oils of pecan and pistachio were the most stable, whereas oils of pine nut and walnut were the least stable.     

Purification and characterization of the 7S vicilin from Korean pine (Pinus koraiensis)

Pine nuts are economically important as a source of human food. They are also of medical importance because numerous pine nut allergy cases have been recently reported. However, little is known about the proteins in pine nuts. The purpose of this study was to purify and characterize pine nut storage proteins. Reported here is the first detailed purification protocol of the 7S vicilin-type globulin from Korean pine (Pinus koraiensis) by gel filtration, anion exchange, and hydrophobic interaction chromatography. Reducing SDS-PAGE analysis indicated that purified vicilin consists of four major bands, reminiscent of post-translational protease cleavage of storage proteins during protein body packing in other species. The N-terminal ends of vicilin peptides were sequenced by Edman degradation. Circular dichroism (CD) and differential scanning calorimetry (DSC) analyses revealed that pine nut vicilin is stable up to 80 degrees C and its folding-unfolding equilibrium monitored by intrinsic fluorescence can be interpreted in terms of a two-state model.     

Characterization of pine nuts in the U.S. market, including those associated with "pine mouth", by GC-FID

Taste disturbances following consumption of pine nuts, referred to as "pine mouth", have been reported by consumers in the United States and Europe. Nuts of Pinus armandii have been associated with pine mouth, and a diagnostic index (DI) measuring the content of Δ5-unsaturated fatty acids relative to that of their fatty acid precursors has been proposed for identifying nuts from this species. A 100 m SLB-IL 111 GC column was used to improve fatty acid separations, and 45 pine nut samples were analyzed, including pine mouth-associated samples. This study examined the use of a DI for the identification of mixtures of pine nut species and showed the limitation of morphological characteristics for species identification. DI values for many commercial samples did not match those of known reference species, indicating that the majority of pine nuts collected in the U.S. market, including those associated with pine mouth, are mixtures of nuts from different Pinus species.     

Use of the chloroplast gene ycf1 for the genetic differentiation of pine nuts obtained from consumers experiencing dysgeusia

Pine nuts are a part of traditional cooking in many parts of the world and have seen a significant increase in availability/use in the United States over the past 10 years. The U.S. Food and Drug Administration (US FDA) field offices received 411 complaints from U.S. consumers over the past three years regarding taste disturbances following the consumption of pine nuts. Using analysis of fatty acids by gas chromatography with flame ionization detection, previous reports have implicated nuts from Pinus armandii (Armand Pine) as the causative species for similar taste disturbances. This method was found to provide insufficient species resolution to link FDA consumer complaint samples to a single species of pine, particularly when samples contained species mixtures of pine nuts. Here we describe a DNA based method for differentiating pine nut samples using the ycf1 chloroplast gene. Although the exact cause of pine nut associated dysgeusia is still not known, we found that 15 of 15 samples from consumer complaints contained at least some Pinus armandii, confirming the apparent association of this species with taste disturbances.     

Effects of heat and ultraviolet radiation on the oxidative stability of pine nut oil supplemented with carnosic acid

The effects of carnosic acid (CA) of different concentrations (0.05, 0.1, and 0.2 mg/g) and two common antioxidants (butylated hydroxytoluene and α-tocopherol) on oxidative stability in pine nut oil at different accelerated conditions (heating and ultraviolet radiation) were compared. The investigation focused on the increase in peroxide and conjugated diene values, as well as free fatty acid and thiobarbituric acid-reactive substances. The changes in trans fatty acid and aldehyde compound contents were investigated by Fourier transform infrared spectroscopy, while the changes in pinolenic acid content were monitored by gas chromatography-mass spectrometry. The results show that CA was more effective in restraining pine nut oil oxidation under heating, UV-A and UV-B radiation, in which a dose-response relationship was observed. The antioxidant activity of CA was stronger than that of α-tocopherol and butylated hydroxytoluene. Pine nut oil supplemented with 0.2 mg/g CA exhibited favorable antioxidant effects and is preferable for effectively avoiding oxidation.     

Update on the healthful lipid constituents of commercially important tree nuts

Uncharacteristic of most whole foods, the major component of tree nuts is lipid; surprisingly, information on the lipid constituents in tree nuts has been sporadic and, for the most part, not well reported. Most published papers focus on only one nut type, or those that report a cultivar lack a quality control program, thus making data comparisons difficult. The present study was designed to quantify the healthful lipid constituents of 10 different types of commercially important tree nuts (i.e., almonds, black walnuts, Brazil nuts, cashews, English walnuts, hazelnuts, macadamias, pecans, pine nuts, and pistachios) according to standardized, validated methods. The total lipid content of each nut type ranged from 44.4 ± 1.9% for cashews to 77.1 ± 1.7% for macadamias. As expected, the major fatty acids present in the tree nuts were unsaturated: oleic (18:1 ω9) and linoleic (18:2 ω6) acids. A majority of the lipid extracts contained <10% saturated fatty acids with the exceptions of Brazil nuts (24.5%), cashews (20.9%), macadamias (17.1%), and pistachios (13.3%). The total tocopherol (T) content ranged from 1.60 ± 1.27 mg/100 g nutmeat in macadamias to 32.99 ± 0.78 in black walnuts. The predominant T isomers in the nut types were α- and γ-T. Tocotrienols were also detected, but only in 6 of the 10 nut types (i.e., Brazil nut, cashews, English walnuts, macadamias, pine nuts, and pistachios). In most cases, total phytosterol contents were greater in the present study than reported in peer-reviewed journal papers and the USDA National Nutrient Database for Standard Reference, which is attributed to total lipid extraction and the inclusion of steryl glucosides in the analysis; the levels were highest for pistachios (301.8 ± 15.4 mg/100 g nutmeat) and pine nuts (271.7 ± 9.1 mg/100 g nutmeat). Minor sterols were also quantified and identified using GC-FID and GC-MS techniques.     

Speciation of arsenic in different types of nuts by ion chromatography-inductively coupled plasma mass spectrometry

In this work the quantitative determination and analytical speciation of arsenic were undertaken in different types of nuts, randomly purchased from local markets. The hardness of the whole nuts and high lipid content made the preparation of this material difficult for analysis. The lack of sample homogeneity caused irreproducible results. To improve the precision of analysis, arsenic was determined separately in nut oil and in the defatted sample. The lipids were extracted from the ground sample with the two portions of a mixture of chloroform and methanol (2:1). The defatted material was dried and ground again, yielding a fine powder. The nut oil was obtained by combining the two organic extracts and by evaporating the solvents. The two nut fractions were microwave digested, and total arsenic was determined by inductively coupled plasma mass spectrometry (ICP-MS). The results obtained for oils from different types of nuts showed element concentration in the range 2.9-16.9 ng g(-)(1). Lower levels of arsenic were found in defatted material (<0.1 ng g(-)(1) with the exception of Brazil nuts purchased with and without shells, 3.0 and 2.8 ng g(-)(1) respectively). For speciation analysis of arsenic in nut oils, elemental species were extracted from 2 g of oil with 12 mL of chloroform/methanol (2:1) and 8 mL of deionized water. The aqueous layer, containing polar arsenic species, was evaporated and the residue dissolved and analyzed by ion chromatography-ICP-MS. The anion exchange chromatography enabled separation of As(III), dimethylarsinic acid (DMAs(V)), monomethylarsonic acid (MMAs(V)), and As(V) within 8 min. Several types of nuts were analyzed, including walnuts, Brazil nuts, almonds, cashews, pine nuts, peanuts, pistachio nuts, and sunflower seeds. The recovery for the speciation procedure was in the range 72.7-90.6%. The primary species found in the oil extracts were As(III) and As(V). The arsenic concentration levels in these two species were 0.7-12.7 and 0.5-4.3 ng g(-)(1), respectively. The contribution of As in DMAs(V) ranged from 0.1 +/- 0.1 ng g(-)(1) in walnuts to 1.3 +/- 0.3 ng g(-)(1) in pine nuts. MMAs(V) was not detected in almonds, peanuts, pine nuts, sunflower seeds, or walnuts, and the highest concentration was found in pistachio nuts (0.5 +/- 0.2 ng g(-)(1)).     

Nuclear magnetic resonance spectroscopy and chemometrics to identify pine nuts that cause taste disturbance

Nontargeted 400 MHz (13)C and (1)H nuclear magnetic resonance (NMR) spectroscopy was used in the context of food surveillance to reveal Pinus species whose nuts cause taste disturbance following their consumption, the so-called pine nut syndrome (PNS). Using principal component analysis, three groups of pine nuts were distinguished. PNS-causing products were found in only one of the groups, which however also included some normal products. Sensory analysis was still required to confirm PNS, but NMR allowed the sorting of 53% of 57 samples, which belong to the two groups not containing PNS species. Furthermore, soft independent modeling of class analogy was able to classify the samples between the three groups. NMR spectroscopy was judged as suitable for the screening of pine nuts for PNS. This process may be advantageous as a means of importation control that will allow the identification of samples suitable for direct clearance and those that require further sensory analysis.