Quantification of glucose,fructose and sucrose in bayberry juice by NIR and PLS

Bayberry plays an important role in the nutrition and is a very important fruit-product. It has a high economic and officinal value. In this study, glucose, fructose and sucrose in bayberry juice were detected and quantified using near-infrared (NIR) spectroscopy. The HPLC method was assumed to provide the reference value of the analyte for calibration. Partial least-squares regression (PLSR) was used to construct calibration models with different pre-processing methods. The number of PLS factors was optimised. The results show PLS models are good for predicting glucose, fructose and sucrose concentrations in bayberry juice, and their prediction accuracy can be improved by using derivative process with the exception of the glucose. The best models were mostly given by the second derivative processed spectra, especially for sucrose with the determination coefficient, R² of 0.9931. This demonstrates the potential of NIR spectroscopy to quickly detect these components simultaneously in bayberry juice with the reference method of HPLC.     

The use of malolactic Oenococcus oeni (ATCC 39401) for deacidification of media containing glucose, malic acid and citric acid

 Malolactic fermentation is widely used to reduce the acidity of grape juices in wine production. However, application of the same technology to the production of wine from berries of the northern regions is not straightforward. Unlike grapes, these berries are rich in citric and malic acid while the sugar content is low. An ideal deacidification process for the northern berries would be the microbial degradation of these acids with minimal loss of sugars. Therefore, the co-metabolism of citric acid and glucose was studied under different conditions of malic acid degradation by Oenococcus oeni. At low pH values (pH <4.5) degradation of malic acid always proceeded first to completion with practically no consumption of glucose or citric acid. After the exhaustion of malic acid the degradation of both citric acid and glucose were initiated simultaneously. Following the exhaustion of malic acid and citric acid the remaining glucose remained nonfermentable. Thus, it is concluded that, by maintaining the culture in a resting state by the control of pH, selective degradation of acids can be achieved without subsequent loss of glucose. Received: 20 January 2000     

Prediction of the amino acid composition in brown rice using different sample status by near-infrared reflectance spectroscopy

In this study, 279 samples of brown rice grains and their flour, selected from a larger original population, were scanned by NIRSystem model 5000 mono-chromator in these two kinds of sample status for near-infrared reflectance spectroscopy (NIRS) analysis. Spectral pretreatment method 2,8,8,1 combined with SNV + D scatter correction was found suitable for developing calibration equations for amino acids. Equations for total amino acid content and for all individual amino acids, excluding cystine, methionine and tyrosine, were developed with this spectral pretreatment method. These equations had low SECV (0.010–0.063%) and SEP (0.011–0.066%); with high 1 − VR (0.878–0.960), R² (0.837–0.947) and SD/SEP (2.421–4.333). The results suggest that equations for the thirteen amino acids from the two sample categories can be directly used to estimate the amino acid composition in brown rice. This indicates once more that NIRS is a powerful technology that could be very useful for the determination of amino acid content in breeding programs that involve brown rice as well as for quality control in the food industry.     

Prediction of coagulation properties, titratable acidity, and pH of bovine milk using mid-infrared spectroscopy

This study investigated the potential application of mid-infrared spectroscopy (MIR 4,000-900 cm⁻¹) for the determination of milk coagulation properties (MCP), titratable acidity (TA), and pH in Brown Swiss milk samples (n = 1,064). Because MCP directly influence the efficiency of the cheese-making process, there is strong industrial interest in developing a rapid method for their assessment. Currently, the determination of MCP involves time-consuming laboratory-based measurements, and it is not feasible to carry out these measurements on the large numbers of milk samples associated with milk recording programs. Mid-infrared spectroscopy is an objective and nondestructive technique providing rapid real-time analysis of food compositional and quality parameters. Analysis of milk rennet coagulation time (RCT, min), curd firmness (a₃₀, mm), TA (SH°/50 mL; SH° = Soxhlet-Henkel degree), and pH was carried out, and MIR data were recorded over the spectral range of 4,000 to 900 cm⁻¹. Models were developed by partial least squares regression using untreated and pretreated spectra. The MCP, TA, and pH prediction models were improved by using the combined spectral ranges of 1,600 to 900 cm⁻¹, 3,040 to 1,700 cm⁻¹, and 4,000 to 3,470 cm⁻¹. The root mean square errors of cross-validation for the developed models were 2.36 min (RCT, range 24.9 min), 6.86 mm (a₃₀, range 58 mm), 0.25 SH°/50 mL (TA, range 3.58 SH°/50 mL), and 0.07 (pH, range 1.15). The most successfully predicted attributes were TA, RCT, and pH. The model for the prediction of TA provided approximate prediction (R² = 0.66), whereas the predictive models developed for RCT and pH could discriminate between high and low values (R² = 0.59 to 0.62). It was concluded that, although the models require further development to improve their accuracy before their application in industry, MIR spectroscopy has potential application for the assessment of RCT, TA, and pH during routine milk analysis in the dairy industry. The implementation of such models could be a means of improving MCP through phenotypic-based selection programs and to amend milk payment systems to incorporate MCP into their payment criteria.     

Effect of harvesting time and fruit size on titratable acidity, soluble solid and distribution of limonin in Thai tangerine juice

The effect of fruit size and harvesting of Thai tangerine fruit ( Citrus reticulata , Blanco) at different growth stages, 8–12 months after fruit set, on the distribution of limonin in whole fruit as well as in the individual fruit parts and extracted juice was investigated. The highest limonin concentration was observed in seed, followed by albedo, flavedo, segment membrane and juice sacs in decreasing order. The limonin concentration in juice as well as in whole fruit was decreased when fruit was harvested 8–12 months of fruit set. Increasing harvesting time from 8 to 12 months showed corresponding decreases in the amount of limonin in flavedo, albedo and seed. There was a decrease in titrable acidity and increase in total soluble solid and total soluble solid/titrable acidity ratio of juice with a later than normal harvesting time. However, fruit size showed no effect on limonin content and other properties of juice extracted from tangerine.     

Prediction of fatty acid content in rabbit meat and discrimination between conventional and organic production systems by NIRS methodology

To investigate the feasibility of using the NIRS methodology to analyse the fatty acid content of rabbit meat and to discriminate between conventional and organic production, the meat of a hind leg of 119 rabbits was scanned between 1100 and 2498 nm and 104 samples were sent to the laboratory for reference analysis of fatty acids by gas chromatography. A commercial spectral analysis program (WINISI-2, v. 1.04) was used to process the data and to develop chemometric models. The better calibration equation for each fatty acid, leading to a higher determination coefficient of cross-validation (r²) and low standard error of cross-validation (SECV) was retained. Prediction of linoleic, palmitic, palmitoleic and oleic acid content was excellent or good (r² between 0.90 and 0.70); prediction of arachidonic, stearic, α-linolenic and eicosatrienoic FA has r² between 0.69 and 0.50. However, miristic, vaccenic, icosaenoic and eicosadienoic FA are problematic to predict. When fatty acids were grouped, the r² of the calibration equations were: 0.85 for saturated FA, 0.83 for MUFA, 0.92 for PUFA and 0.91 for n − 6 FA, indicating excellent or good prediction. Prediction of α-linolenic FA (r² = 0.59) needs more precision. The obtained equations have been applied for predicting meat fatty acid composition of both groups of production systems, conventional and organic, for an other 52 rabbit meat samples (2 × 26). Meat of the organic source had lower (p = 0.000) monounsaturated FA (30.54% vs. 34.64%) and higher (p = 0.019) polyunsaturated FA (27.28% vs. 23.66%) than rabbit meat from the conventional system, while the saturated FA content was similar (42%) in both groups. The discriminant model correctly classified (98%) between conventional or organic produced rabbit meat.     

Prediction of sweetpotato starch physiochemical quality and pasting properties using near-infrared reflectance spectroscopy

A rapid predictive method based on near-infrared reflectance (NIR) spectroscopy (NIRS) was developed to measure sweetpotato starch physiochemical quality and pasting properties. The starch samples were scanned by NIRS and analyzed for quality properties by reference methods, respectively. Results of statistical modeling indicated that NIRS was reasonably accurate in predicting amylose content (AC), amylose percent (AP), total starch content (TSC), protein content (PRC), phosphorus content (PHC), solubility (SOL), swelling power (SP), average granule diameter (AGD), big granule percent (BGP), small granule percent (SGP), crystallinity (CRY), peak viscosity (PKV), hot paste viscosity (HPV), setback (SB), and pasting temperature (P_temp) with high coefficients of determination (RSQ = 0.85–0.92) and relatively low standard errors of prediction. The results showed that NIR analysis was sufficiently accurate and effective for rapid evaluation of starch physicochemical properties in sweetpotato. The NIR-based protocol developed in this study can be used for screening large number of starch samples in food enterprises and sweetpotato breeding programs.     

柠檬酸在食品工业中的应用

柠檬酸以其独特的性质在食品加工业中广泛应用,是一种用量相当大的食品添加剂。文章概述了柠檬酸的性状及其在食品工业中的主要用途。     

巨峰浆果生长过程中的酒石酸,苹果酸变化

巨峰葡萄浆果中的主要有机酸为酒石酸、苹果酸。苹果酸含量随浆果生长呈低－高－低的变化趋势，酒石酸前期含量较高，随浆果生长不断降低。苹果酸、酒石酸在浆果生长前期存在明显的由果梗端向果顶端的递降梯度，果实发育后期这两种酸的纵向梯度不明显。     

Determination of fatty acids in broiler breast meat by near-infrared reflectance spectroscopy

The aim of this study was to develop near-infrared reflectance spectroscopy (NIRS) calibrations for determination of the fatty acids (FA) in broiler breast meat. A total of 144 breast meat samples were freeze-dried and divided into calibration set and validation set. Calibration models were developed for FA including C14:0, C16:0, C16:1n-7, C18:0, C18:1n-7, C18:1n-9, C18:2n-6, C18:3n-3, C18:3n-6, C20:0, C20:1n-9, C20:2n-6, C20:4n-6, C20:5n-3, C22:4n-6, C22:6n-3, C24:0 and C24:1n-9. Calibration models for FA groups were also developed. Calibrations based on the absolute FA content were more accurate than those based on the relative composition (%). The coefficients of determination of FA and FA groups (based on the absolute content) except C18:3n-6, C20:0, C20:2n-6 and C24:1n-9, were between 0.86 and 0.98 for calibration, and 0.83 and 0.97 for validation. The results indicate NIRS can be a feasible and rapid method for determination of FA with a mean concentration over 0.10 g/kg.     

Pectin methylesterase activity and other factors affecting pH and titratable acidity in processing tomatoes

Pectin methylesterase (PME) rapidly hydrolyzes pectin methylesters in cold break tomato juice to form methanol and to increase titratable acidity (TA). Within 30 min, the juice methanol concentration increased from 35 to over 400 μg g⁻¹ while the pH dropped from 4.45 to 4.20. On average, cold break juice pH values were 0.21 U lower and TAs 12.4 μeq g⁻¹ higher than those for hot break juices prepared from the same tomatoes. The greater TA in the cold break juices equalled the amount of methanol formed, consistent with both resulting from PME activity in the cold break juice. For 16 cultivars evaluated, there was a correlation between the methanol content of the cold break juices and the consistency of hot break juices, which could be the result of different pectin contents in the different cultivars. Differences in the citric, glutamic, and malic acid contents between these cultivars were small.     

Detection of insect fragments in wheat flour by near-infrared spectroscopy

Insect fragments in commercial wheat flour are a major concern to the milling industry because consumers expect high quality and wholesome products at the retail level. Thus, the US Food and Drug Administration (FDA) has established a defect action level of 75 insect fragments per 50 g of flour. Millers routinely test their wheat flour to comply with this federal requirement and to deliver sound flour to their consumers. The current standard flotation method for detecting fragments in flour is expensive and labor intensive. Therefore, we examined the possible use of a rapid, near-infrared spectroscopy (NIRS) method for detecting insect fragments in wheat flour. We also compared the sensitivity and accuracy of the NIRS method with that of the current standard flotation method. Fragment counts with both techniques were significantly correlated with the actual number of fragments present in flour samples. However, the flotation method was more sensitive than the NIRS method with fragment counts below the FDA defect action level. We were unable to predict whether the number of fragments in a sample exceeded the FDA action level with our NIRS instrumentation. However, we were able to predict accurately whether flour samples contained less than or more than 130 fragments. Although current NIRS instruments are unable to detect insect fragments at the FDA action level, this method should be re-examined in the future because NIRS technology is rapidly improving.     

苹果汁中果酸(苹果酸)的分离(Ⅰ)--果酸在LSI-1031阴离子交换树脂上交换吸附行为的研究

研究了苹果汁中果酸在4种阴离子交换树脂上的静态吸附特性,其中LSI-1031阴离子交换树脂对果酸的交换吸附能力最强;系统测定并分析了果酸在LSI-1031阴离子交换树脂上交换吸附静态动力学、吸附等温曲线、动态动力学曲线及影响动态动力学曲线的因素,并确定了果酸交换吸附最佳工艺参数,结果表明:LSI-1031阴离子交换树脂吸附平衡时间为4h;20℃时,LSI-1031阴离子交换树脂吸附等温曲线符合Langmuir型吸附曲线;柱操作流速、果汁中果酸浓度以及温度对LSI-1031阴离子交换树脂动态动力学曲线都有影响,柱处理最佳条件为:流速3BV/h、温度50℃,并且低果酸浓度的果汁有利于提高树脂的处理量。     

Optimisation of in vitro measurement of available iron from different fortificants in citric fruit juices

The percentage of dialyzable ferrous and total iron were studied in a citric juice (pineapple and passion fruit) fortified with ferrous sulphate, micronised dispersible ferric pyrophosphate and ferrous bis-glycinate in similar concentrations (49.2 mg Fe/l). The in vitro method of Kapsokefalou and Miller (1991) [Kapsokefalou, M., & Miller, D. D. (1991). Effects of meat and selected food components on the valence of nonheme iron during in vitro digestion. Journal of Food Science, 56, 352–355.] was optimised for this matrix using 0.15 N PIPES buffer (pH 8.5) to adjust pH during pancreatic digestion. We also studied different pH values of Hepes buffer used in the measurement of iron concentrations with Ferrozine (chromogen solution). The maximum absorbances were obtained with a Hepes buffer pH value of 8.5. Ferrous sulphate was used as a reference salt due to its high bioavailability, although novel compounds, such as ferrous bis-glycinate and micronised dispersible ferric pyrophosphate, showed a high relative iron availability in this juice. Taking into account that percentage of dialysable ferrous iron is considered to be the more available fraction of total iron, the iron fortificant ferrous bis-glycinate proved to be more adequate for fortifing citric juices, giving a 10.7% of dialyzable ferrous iron. Moreover, the percentage of dialyzable total iron from ferrous bis-glycinate (31.0%) was statistically higher than those from ferrous sulphate and micronised ferric pyrophosphate (28.4% and 28.2%, respectively).     

苹果汁中果酸(苹果酸)的分离(Ⅱ)-----果酸在LSI-1031阴离子交换树脂上解吸行为的研究

研究了不同因素对果酸洗脱曲线及回收率的影响,确定了果酸洗脱回收的最佳工艺条件。结果表明:洗脱剂浓度、柱操作流速、温度及梯度洗脱对洗脱曲线及回收率有不同程度的影响,果酸洗脱回收最佳条件为:2% NaOH、2BV/h、20℃;采用梯度洗脱(2%-4%-2% NaOH),可提高果酸回收率。     

酸奶中乳酸菌数及酸度的检测与评价

酸奶中乳酸菌的含量是评价产品对于人们营养与健康作用的重要指标,而酸奶的酸度直接影响成品的质量、风味与口感。新的酸奶国家标准(GB2746-1999)中规定产品中的乳酸菌数不得低于1×106mL-1,酸度应≥70°T。本试验通过对部分市售酸奶及自制产品的检测与分析表明,酸奶成品中的乳酸菌数普遍大于1×109mL-1,个别也应大于4×108～8×108mL-1水平,而酸度均大于80°T。故笔者认为酸奶中乳酸菌数定为大于1×108mL-1及酸度大于80°T更适合产品本身的实际情况。     

Prediction of lamb meat fatty acid composition using near-infrared reflectance spectroscopy (NIRS)

The aim of this study was to assess the feasibility of near-infrared reflectance spectroscopy (NIRS) for predicting lamb meat fatty acid composition. We compared ground vs. intact non-ground meat samples to determine whether grinding and homogenisation of meat samples improved the performance of the predictions. We used 76 male lambs, of which 32 were pasture-fed and 44 stall-fed with concentrate and hay. The reflectance spectrum of Longissimus lumborum muscle was measured at wavelengths between 400 and 2500 nm. Predictions were better with ground than with intact muscle samples. NIRS accurately predicts several individual fatty acids (FA) (16:0, 18:0, 16:1 Δ9 cis, 17:1 Δ9 cis, 18:1 Δ9 cis, 18:1 Δ11 cis and 16:1 Δ9 trans) and several FA groups (total linear saturated FA, total branched saturated FA, total saturated FA, total cis monounsaturated FA (MUFA), total trans MUFA, total MUFA and total polyunsaturated PUFA). These results show the potential of NIRS as a rapid, and convenient tool to predict the major FA in lamb meat.     

Detecting bunch withering disorder in date fruit by near infrared spectroscopy

This study introduces the application of near infrared spectroscopy (NIRs) to detect bunch withering disorder in date fruit (cv. Mazafati). The samples included intact as well as infected date fruits at different stages of ripening. Chemometric evaluation of the data was performed by soft independent modeling of class analogy (SIMCA), partial least squares discriminant analysis (PLS-DA), and principal components analysis combined with artificial neural networks (PCA–ANN). The PLS-DA algorithm was able to provide models with the best classification performance, followed by SIMCA and then PCA–ANN. The maturity stage of samples influenced the performance of the classification methods. The classification accuracy for the late harvested samples was better than those harvested at normal time and the combined data set in all classification analyses. The total accuracies of 82%, 93% and 86%, respectively for normal, late and combined data sets demonstrate that NIRs with PLS-DA has a strong potential to detect the bunch withering disorder in date fruit.     

Non-destructive and rapid analysis of chemical compositions in Thai steamed pork sausages by near-infrared spectroscopy

The objective of the present study was to evaluate the ability of near-infrared (NIR) spectroscopy to predict chemical compositions of Thai steamed pork sausages in relation to different types of sample presentation forms of NIR measurements (with and without plastic casing). NIR spectra of sausages were scanned to predict the chemical compositions, protein, fat, ash and carbohydrate non-destructively. NIR spectrum features of the sausage samples were strongly influenced by physical properties of the samples, such as the presence of plastic casing and inhomogeneous physical structure inside the samples, yielding significant baseline fluctuations. Thus, regression models were developed using partial least squares (PLS) regressions with two pretreatment methods, namely multiplicative scatter correction (MSC) and second derivative, which overcame the baseline problems. The prediction results suggest that the contents for the protein, fat and moisture can be estimated well with the proper selection of the pretreatment method.     

无效变量消除法在油菜籽芥酸近红外无损速测中的应用

探索改善油菜籽芥酸近红外预测模型准确度与精密度的方法,利用无效变量消除法（UVE）,对135个油菜籽样品近红外光谱信号进行筛选,并利用筛选后的光谱对油菜籽芥酸含量进行偏最小二乘法交叉验证。结果表明,UVE法筛选变量后建立的芥酸校正模型对未知样品预测结果的准确度和速度显著优于全波长参与建立的芥酸校正模型。散射校正加一阶导数对光谱预处理,UVE法筛选变量,偏最小二乘法交叉验证建立的校正模型效果最好,其预测值与标准值的相关系数R达到0.92,交叉验证预测均方差为2.2。因此,用UVE进行波长选择后建立的近红外模型,能准确快速地对油菜籽芥酸含量进行定量分析。