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     

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.     

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.     

发酵乳酸度近红外光谱快速检测方法的研究

利用近红外光谱技术对发酵乳酸度进行快速分析检测。采用电位滴定仪法测定71批次含活乳酸菌发酵乳样品的酸度实测值,并同时扫描得到近红外光谱数据。以校正集均方根误差(RMSEC)、预测集均方根误差(RMSEP)、交互验证均方根误差(RMSECV)及其相关系数R_c、R_p、R_cv为评价指标建立最优的酸度定量模型。利用模型对10批次含活乳酸菌发酵乳样品的酸度进行预测。结果表明,优化后的模型,其RMSEC、RMSEP、RMSECV及其相关系数R_c、R_p、R_cv分别为3.27、4.39、4.84,0.946 2、0.922 5、0.877 8。经外部验证后,该模型酸度预测值和实测值的最大相对误差为6.76%,满足不超过10%的要求。说明模型具有良好的预测性能,可用于发酵乳中酸度的快速检测。     

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.     

烤烟中草酸、苹果酸和柠檬酸含量的分析研究

以云南、四川、河南、重庆4个烟区云烟85、K326和红大3个品种的B2L、C2L、X2L等级烟叶为材料,采用GC法测定了169个烤烟烟叶样品中草酸、苹果酸和柠檬酸的含量,并对不同产地、品种、等级和部位烤烟烟叶的多元有机酸含量进行了统计分析,结果表明:①同一地区、K326和云烟85的相同等级烤烟烟叶中草酸、苹果酸和柠檬酸含量均没有显著差异;红大和云烟85的苹果酸含量没有显著差异,而红大的草酸和柠檬酸含量均高于云烟85;②不同地区、相同品种和等级的烤烟叶中,草酸含量均没有显著性差异;苹果酸、柠檬酸含量差异显著,含量的变化趋势为:河南重庆云南和四川;③同一地区和品种、不同部位的烤烟叶中,草酸含量均为上部明显高于中部和下部,而中部和下部相当;苹果酸含量在3个部位均有较大差别,依次为:上部中部下部;柠檬酸含量下部最高,中部与上部无显著差异。     

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.     

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。     

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。     

柠檬酸处理对厚皮甜瓜黑斑病的抑制及苯丙烷代谢的作用

以\     

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。     

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。     

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).     

近红外光谱快速检测食用植物油中酸价

目的 建立基于近红外光谱快速测定食用植物油中酸价的分析方法。方法 采用冷溶剂指示剂滴定法检测371个食用植物油样品的酸价,并采集样品的近红外光谱。经过标准正态变换结合一阶导数对近红外光谱进行数据预处理,选用竞争性自适应重加权采样算法选取重要变量,建立食用植物油酸价的偏最小二乘回归模型。结果 蒙特卡洛交互验证结果显示,食用植物油酸价预测模型的验证集决定系数Q2为0.9983,交互检验的均方根误差(root mean square error of cross validation, RMSECV)为0.0461,模型预测的独立测试集的酸价与实测值相关系数为0.9834,预测效果良好。结论 本研究建立的食用植物油酸价近红外光谱快速检测方法能够满足检测要求,为评价或跟踪食用油品质提供快速无损的技术思路。