基于可见/近红外光谱的柑橘糖度在线检测分选系统的设计与试验

在6GF–4型林果无损检测与分选成套设备中,设计了基于可见/近红外光谱的柑橘糖度在线检测分选系统,系统主要包括传输装置、光谱采集装置、控制系统以及分选装置。系统在柑橘果实运动状态中采集其光谱信息,并通过所建立的果实糖度模型进行同步计算,根据所得糖度值对柑橘果实实现在线分选。在光谱采集装置中设计了双透镜式光路,可改变投射于柑橘果实上的光斑大小,通过研究比较试验参数积分时间和光斑尺寸大小,得出系统的最佳采集参数为积分时间100 ms,光斑尺寸设置为小,样本移动速率为5个/s。建立的SPXY–CARS–PLSR柑橘糖度在线检测模型校准集和预测集的决定系数分别为0.938和0.836,校准集和预测集的均方根误差分别为0.273°Brix和0.418°Brix。使用未参与建模的25个柑橘果实样本进行外部验证集的在线检测和分选,结果在1°Brix的误差范围内,检测糖度的准确率为92%;当样本分为4个等级时,系统分选正确率为92%;当样本分为3个等级时,系统分选正确率可达100%。     

近红外光谱在转基因农产品检测中的研究进展

简述了近年来近红外光谱分析技术在农产品和食品定量分析中的应用,重点介绍了近红外光谱分析在转基因植株筛选以及转基因和非转基因农产品分类和识别等方面的研究现状,比较和分析了近红外光谱与传统的转基因农产品检测方法的特点,并展望了近红外光谱分析技术在转基因农产品检测研究中的发展前景。     

二维相关光谱结合偏最小二乘法测定牛奶中的掺杂尿素

为了检验牛奶中是否掺杂尿素并将其量化测定,配置含有尿素质量浓度范围为1～20g/L之间40个牛奶样品,以掺杂物尿素浓度为外扰,分别研究了掺杂尿素牛奶的二维相关(近红外-近红外,中红外-中红外,近红外-中红外)光谱特性,在此基础上,分别选择随浓度变化大的4200～4800cm-1和1400～1704cm-1为建模区间,采用偏最小二乘方法建立定量分析模型。研究结果表明:4200～4800cm-1建模分析效果优于1400～1704cm-1建模结果,其交叉验证均方根误差为0.266g/L,对未知样品集预测相关系数达到0.999,预测均方根误差为0.219g/L,这表明所建模型具有较好的预测效果。该方法无需样品处理,成本低,为快速判别牛奶是否掺杂提供了一种新的可能的方法。     

支持向量机结合近红外光谱法测定杉木木质素的含量

采用支持向量机(SVM)结合近红外光谱(NIR)技术建立测定杉木中木质素的定量分析模型。以47个杉木样品作为实验材料,用常规方法测定了样品中木质素的含量,用近红外光谱仪采集相应的光谱,对光谱数据进行平滑、求导、小波压缩以及归一化,结合支持向量机,以径向基(RBF)作为核函数,建立了测定杉木中木质素含量的模型。校正相对误差的平方和为0.007433,预测相对误差的平方和为0.001219。结果表明,该方法测量比较准确,可以用于杉木中木质素含量的预测。     

Spectrophotometrical characteristics in the near infrared region in beech (<Emphasis Type="Italic">Fagus crenata</Emphasis>) and pine (<Emphasis Type="Italic">Pinus densiflora</Emphasis>) litters at the various decomposing stages

We examined the relationships between the absorptional characteristics in the near infrared region and the chemical changes of decomposing beech (Fagus crenata) and pine (Pinus densiflora) litters. Spectra as well as the concentrations of chemical substances approached each other and converged with decomposition, although both initial characteristics differed markedly between beech and pine. This indicated that the fundamental chemical structures were almost the same, although their organochemical composition differed. Specific absorption bands for lignin, polysaccharide, and protein were identified at 2,140 and 1,670 nm, 2,270, 1,720, 1,590, and 1,216 nm, and 2,350 nm, respectively. Absorbance at 1,670 nm, peculiar band of aromatics, showed a positive correlation with lignin concentration, which suggested the relative increment of aromatics due to condensed lignin in decomposing litters. Absorbance at 2,140 nm, characterized as the C–H bond in HRC = CHR, showed a negative correlation with lignin concentration, which suggested the decrements of some structures such as side-chains in lignin polymers unrelated to aromatics. Absorbance at 2,270, 1,720, and 1,216 nm, specified to O–H/C–O/C–H bonds in saccharide, might reflect the change of polysaccharide during decomposition because they showed a positive correlation to polysaccharide concentration. In the same way, absorbance at 2,350 nm, identified to the C–H/CH₂ bonds in protein, showed a negative correlation to nitrogen concentration in decomposing litters, which might indicate that the C–H/CH₂ bonds in protein decreased with decomposition due to microbial consumption of carbon in protein. Our findings suggested the possibility that the spectral changes indicate the litter digestibility during decomposition and that also explain the compositional change in decomposing litters.     

激光诱导击穿原子光谱在土壤分析中的应用

土壤分析是土壤学研究及应用的前提和基础,传统化学土壤分析方法逐渐不能适应现代土壤学海量信息数据快速获取的需求。激光诱导击穿光谱作为一种全新的、反映土壤组成元素原子信息的光谱技术,其无需对样品进行复杂前处理,可实现原位、快速、多元素连续在线检测,每条光谱记录土壤样本独一无二的特征,可以视为土壤“指纹”,成为现代土壤分析的有效技术之一。首先介绍和分析了激光诱导击穿原子光谱的原理、光谱获取的主要影响因素、光谱数据处理的化学计量学方法等;然后阐述和梳理了基于激光诱导击穿光谱技术在土壤分析方面的应用成果和进展,包括土壤鉴定、土壤养分评估、土壤重金属测定、微观/介观尺度土壤原位表征等;最后讨论和总结了激光诱导击穿光谱技术在土壤分析中所面临的挑战及其应用展望。     

基于漫反射光谱的叶面药液浓度检测方法

应用漫反射反射光谱对叶面药液质量浓度进行了检测研究。选择350～1900nm波段,以标准偏差归一化、三点滑动平均滤波、一阶导数组合预处理,应用逐步回归分析、主成分、主成分+人工神经网络、偏最小二乘、偏最小二乘+人工神经网络回归分析建立了5种数学模型。试验结果表明这5种算法的预测均方根误差分别为0.067、0.061、0.059、0.039、0.056,偏最小二乘法建模效果优于其他模型。考虑到不同作物种类对叶面药液浓度影响,选用八角金盘、油菜、青菜3种作物叶片为对象,在偏最小二乘下建模,其预测集相关系数分别为0.994、0.974、0.929,预测均分根误差分别为0.039、0.050、0.075。表明不同种类作物对叶面药液浓度检测影响较小,漫反射光谱技术检测叶面药液浓度是可行的。     

近红外反射技术建立合肥地区精米直链淀粉含量测定模型

以合肥地区种植的203份水稻材料为检测对象,用近红外反射技术采集光谱,常规化学方法测定精米直链淀粉含量。结果表明,定标样品的直链淀粉含量分布范围为3.439%～28.046%,代表性和连续性良好。采用多种计量数学处理方法和偏最小二乘法(PLS),优化建立了精米直链淀粉含量的定量分析预测模型。定标集(C-Set)样品数132个,相关系数(Rc)0.9278,定标标准差(SEC)1.6582;验证集(V-Set)样品数67个,相关系数(Rv)0.8736,预测标准差(SEP)1.9083,并证实所建立的模型在测定精米直链淀粉含量上具有很好的准确性和实用性,对合肥地区水稻品质育种及种质资源相关研究具有实用价值。     

Detection of Frozen-Thawed Cycles for Frozen Tilapia (Oreochromis) Fillets Using Near Infrared Spectroscopy

Due to the ambient temperature fluctuation during the process of storage, transportation, and sale, frozen fillets may go through frozen-thawed cycles that result in quality changes. In order to detect the frozen-thawed cycles in frozen tilapia fillets, near infrared spectroscopy was applied. The thawing loss, cooking loss, moisture content, total volatile basic nitrogen, and texture profile of fillets in seven frozen-thawed cycles were analyzed to reflect the change of quality. A total of 60 fillets were used to collect the spectra on both dorsal and belly flesh in frozen and thawed state from the first to the seventh cycle. The results showed that there is a better discrimination among the once and the repeated frozen-thawed samples in the frozen state than the thawed state. Frozen samples were still conducive to the differentiation and had higher classification accuracy, ranging from 80% to 93.33%. Dorsal flesh was more beneficial for the differentiation than belly flesh and had the highest accuracy, ranging from 86.67% to 93.33% in the frozen state. These results showed that the nondestructive and fast detection of repeated frozen-thawed cycles in frozen tilapia fillets can be accomplished by near infrared spectroscopy, which has enormous potential for practical application.     

Assessment of plastic ingestion by pole-caught pelagic predatory fish from O'ahu,Hawai'i

1. Although the frequency of occurrence of plastic ingestion in the large-sized dolphinfish and tunas taken by the Hawai'i longline fishery is very low (frequency of occurrence < 5% of sampled individuals), the ingestion of plastic in smaller-sized specimens caught with pole-and-line gear by commercial and recreational fishers has not been investigated.
2. This study examined ingestion of >0.25 mm marine plastic debris (MPD) by four predatory fish species caught by commercial fishers around the Main Hawaiian Islands, and documented ingestion in three species: 85.7% of albacore tuna (n = 7), 40.0% of skipjack tuna (n = 10) and 12.5% of dolphinfish (n = 8).
3. Yellowfin tuna (n = 10) did not contain any MPD, probably owing to the high proportion of empty stomachs (60%).
4. For skipjack tuna, the frequency of occurrence of MPD ingestion was significantly higher for the smaller-sized specimens caught with pole-and-line (40%), compared with the larger-sized specimens caught with longlines (0%).
5. For dolphinfish, the frequency of occurrence of MPD ingestion was similar for the similar-sized specimens caught with pole-and-line and with longlines.
6. The ingested MPD items were micro–meso plastics, between 1 and 25 mm. While most ingested items were fragments, albacore also ingested line and skipjack also ingested sheets.
7. The predatory fishes ingested light MPD items that float in sea water, but there were species-specific differences in their polymer composition: albacore contained more polypropylene and polyethylene, and skipjack contained more elastomers, characterized by a high percentage of ester plasticizers.
8. Altogether, these results suggest that albacore and skipjack tunas ingest plastic of different types and polymers. Yet more research is needed to understand how differences in vertical distribution, foraging ecology and diet influence the MPD sampled by these predatory fish species.