Determination of the acid value of instant noodles: interlaboratory study

An interlaboratory study was performed to evaluate the method for determining the acid value of instant noodles, based on the Japanese Agricultural Standard (JAS), with extraction of lipid using petroleum ether at a volume of 100 mL to the test portion of 25 g. Thirteen laboratories participated and analyzed 5 test samples as blind duplicates. Statistical treatment revealed that the repeatability (RSDr) of acid value was <6.5%, and the reproducibility (RSDR) of acid value was <9.6%. The HorRat values (RSDR/predicted RSDR) were 1.2-1.8, where the RSDR and the predicted RSDR were obtained in terms of free fatty acids in the noodles per unit weight, using the equation [acid value = percent free fatty acids (as oleic) x 1.99] and the extracted lipid contents. This method was shown to have acceptable precision by the present study.     

Variations of moisture measurements in cheese

Data were accumulated during interlaboratory trials for cheese moisture determination from laboratories using officially recognized methods: AOAC; International Dairy Federation, and Standard Methods for the Examination of Dairy Products (SM). In one trial, ranges of means of 5 cheeses were 0.67, 0.56, and 0.19% for 5, 9, and 8 laboratories, respectively. The lower ranges for the SM method were typical of 3 other interlaboratory trials, with ranges of 0.27, 0.34, and 0.34% for 6, 7, and 5 laboratories, respectively. Within one laboratory, there were no significant differences among the 3 methods, but they all gave about 0.2% lower results than 2 other methods, one using freeze-drying, followed by drying in a vacuum, the other using cheese that was spread on sand and dried in a vacuum oven for 24 h. This finding indicated that none of the officially recognized methods removed all the moisture. Data showed that many laboratories tended to give either higher or lower results than the mean of all of them in a series of 7 interlaboratory trials. Constant results, free of biases or systematic errors, are important in application of formulas for prediction of yield of cheese for purposes of yield control, but are difficult to obtain. It is proposed that results by a laboratory in interlaboratory trials be compared with those obtained by one or more reference laboratories using a method that removes all the moisture from cheese. The difference would be applied as a constant in the predictive yield formula. That difference would likely be best as a running mean of differences in an ongoing series of trials. The reference laboratories would use frozen samples for quality control to ensure uniformity of results among trials. Mean moistures of 36.10 and 36.11% were obtained on subsamples before and after freezing for 7 months.     

固相萃取-高效液相色谱-荧光法测定方便面和烤肠中的苯并[a]芘

建立了固相萃取-高效液相色谱-荧光法检测方便面和烤肠中苯并[a]芘的方法。采用正己烷作为提取溶剂,经苯并[a]芘专用固相萃取柱HiCapt Benzo富集净化,高效液相色谱-荧光法对样品中苯并[a]芘进行分离分析。苯并[a]芘的质量浓度在0.5~20.0μg/kg范围内与色谱峰面积呈良好的线性关系,相关系数R2为0.9997。方便面和烤肠中苯并[a]芘的加标回收率分别为92.2%~98.3%和95.9%~97.9%,日内和日间相对标准偏差分别为3.34%~5.01%和2.11%~4.07%。与传统方法相比,该方法快速简单、有机溶剂消耗少,在油炸烟熏食品的苯并[a]芘分析中具有较大应用前景。     

Rapid determination of moisture and fat in meats by microwave and nuclear magnetic resonance analysis--PVM 1:2003

A peer-verified method is presented for the determination of percent moisture and fat in meat products by microwave drying and nuclear magnetic resonance (NMR) analysis. The method involves determining the moisture content of meat samples by microwave drying and using the dried sample to determine the fat content by NMR analysis. Both the submitting and peer laboratories analyzed 5 meat products by using the CEM SMART system (moisture) and the SMART Trac (fat). The samples, which represented a range of products that meat processors deal with daily in plant operations, included the following: (1) fresh ground beef, high-fat; (2) deboned chicken with skin; (3) fresh pork, low-fat; (4) all-beef hot dogs; and (5) National Institute of Standards and Technology Standard Reference Material. The results were compared with moisture and fat values derived from AOAC-approved methods, 950.46 (Forced Air Oven Drying) and 960.39 (Soxhlet Ether Extraction).     

基于QuEChERS-HPLC法检测油炸食品中丙烯酰胺的含量

建立了基于QuEChERS(quick,easy,cheap,effective,rugged and safe)-HPLC测定油炸食品中丙烯酰胺含量的方法。 该方法的优势在于：改进的QuEChERS前处理方法中没有引入有机溶剂而直接采用纯水消除样品基底的影响。 研究中,使用纯水超声提取丙烯酰胺,丙基乙二胺(PSA)吸附剂分散净化提取液,乙腈和水(体积比1∶99)作为流动相,水系C18色谱柱分离,208 nm紫外波长条件下检测丙烯酰胺的含量。 结果表明,丙烯酰胺在0.020~0.800 μg/g浓度范围内与出峰面积呈线性关系,相关系数r=0.9994;检测限为0.005 μg/g;加标回收率为83.96%~89.43%,相对标准偏差(RSD)为2.13%~5.87%。 该方法具有操作简单、快速、可靠和灵敏度高等特点,成功应用于方便面等油炸食品中丙烯酰胺含量的测定。     

Water Status and Predictive Models of Moisture Content during Drying of Soybean Dregs Based on LF-NMR

To explore the drying characteristics of soybean dregs and a nondestructive moisture content test method, in this study, soybean dregs were dried with hot air (80 °C), the moisture content was measured using the drying method, water status was analyzed using low-field nuclear magnetic resonance (LF-NMR) and the moisture content prediction models were built and validated. The results revealed that the moisture contents of the soybean dregs were 0.57 and 0.01 g/g(w.b.), respectively, after drying for 5 and 7 h. The effective moisture diffusivity increased with the decrease in moisture content; it ranged from 5.27 × 10⁻⁹ to 6.96 × 10⁻⁸ m²·s⁻¹. Soybean dregs contained bound water (T₂₁), immobilized water (T₂₂) and free water (T₂₃ and T₂₃’). With the proceeding of drying, all of the relaxation peaks shifted left until a new peak (T₂₃’) appeared; then, the structure of soybean dregs changed, and the relaxation peaks reformed, and the peak shifted left again. The peak area may predict the moisture content of soybean dregs, and the gray values of images predict the moisture contents mainly composed of free water or immobilized water. The results may provide a reference for drying of soybean dregs and a new moisture detection method.     

石墨炉原子吸收光谱法测定红薯粉丝中的痕量铅含量

为建立对红薯粉丝中有害元素铅含量的测定方法,采用微波消解法处理红薯粉丝样品,加入2％NH4H2PO4和0．2％Mg（NO3）：混合液作为基体改进剂,用石墨炉原子吸收分光光度法测定了红薯粉丝中铅含量。结果表明,红薯粉丝样品中铅在2．0—40．0ng／mL的范围内吸光度与含量呈良好的线性关系（r=0．9956）,平均回收率为98．06％,RSD=1．67％（n=5）。可见该法简单、准确,可作为检测红薯粉丝中铅含量的方法。     

Rapid determination of moisture/solids and fat in dairy products by microwave and nuclear magnetic resonance analysis

A peer-verified method is presented for the determination of percent moisture/solids and fat in dairy products by microwave drying and nuclear magnetic resonance (NMR) analysis. The method involves determining the moisture/solids content of dairy samples by microwave drying and using the dried sample to determine the fat content by NMR analysis. Both the submitting and peer laboratories analyzed various dairy products by using a CEM SMART system (moisture) and the SMART Trac (fat). The samples included milks, creams, ice cream mix, sour cream, yogurt, cream cheese, and mozzarella, Swiss, and cheddar cheeses. These samples represented a range of products that processors deal with in daily plant operations. The results were compared with moisture/solids and fat values derived from AOAC-approved methods.     

Experimental investigation of drying of garlic clove in solar dryer using phase change material as energy storage

This investigation deals with thermodynamic analysis, which offers an alternative approach to evaluate the performance of solar dryers and thin-layer drying characteristics of garlic cloves in a developed system. The garlic cloves were dried from a moisture content of 55.5 % (w.b.) to 6.5 % (w.b.) for 8 h. The drying data obtained were fitted to five different drying kinetics models. Of these, the model suggested by Midilli et al. [28] had the best fit with the drying behavior of garlic cloves. The energy efficiency without and with recirculation of the air exiting the drying chamber during the study varied from 43.06 to 83.73 %, and 3.98 to 14.95 %, respectively, while the exergy efficiency corresponding to the energy efficiency of the drying process ranged from 5.01 to 55.30 % and 67.06 to 88.24 %, respectively.     

凝胶渗透色谱净化-高效液相色谱法测定油脂食品中的邻苯二甲酸酯类增塑剂

建立了油脂食品(方便面、油炸糕点、沙琪玛、食用油等)中5种主要邻苯二甲酸酯类增塑剂的凝胶渗透色谱（GPC）净化-高效液相色谱(HPLC)分析方法。食品样品用石油醚超声提取,经GPC净化后,采用反相HPLC进行分析。所用的分离柱为Labtech C18(250 mm×4.6 mm, 5 μm),以乙腈和水为流动相,梯度洗脱。方法的相关系数皆在0.997以上,目标物的检出限(信噪比为3计)为3.25～13.4 μg/L。在50 mg/L添加水平时,目标物的加标回收率为70.4%～113.6%,相对标准偏差为0.3%～5.8%(n=3)。该方法简便、快捷、实用,可用于油脂食品中邻苯二甲酸酯类增塑剂的分析测定。     

Investigation of folic acid stability in fortified instant noodles by use of capillary electrophoresis and reversed-phase high performance liquid chromatography

A single enzyme treatment with alpha-amylase, prior to the quantification of added folic acid (FA) in fortified instant fried Asian noodles with analysis performed by capillary zone electrophoresis (CZE) and reversed-phase high performance liquid chromatography (RP-HPLC) with UV detection, is described. The method was validated and optimized for capillary electrophoresis (CE) with separation achieved using a 8 mM phosphate-12 mM borate run buffer with 5% MeOH at pH 9.5. FA was well separated from matrix components with nicotinic acid (NA) employed as an internal standard. In a comparative study, separation of FA was performed using HPLC with a mobile phase consisting of 27% MeOH (v/v) in aqueous potassium phosphate buffer (3.5 mM KH(2)PO(4) and 3.2 mM K(2)HPO(4)), pH 8.5, and containing 5 mM tetrabutylammonium dihydrogen phosphate as an ion-pairing agent. For both methods, excellent results were obtained for various analytical parameters including linearity, accuracy and precision. The limit of detection was calculated to be 2.2 mg/L for CE without sample stacking and 0.10 mg/L with high performance liquid chromatography (HPLC). Sample extraction involved homogenization and enzymatic extraction with alpha-amylase. Results indicated that FA was stable during four main stages of instant fried noodle manufacturing (dough crumbs, cut sheets, steaming and frying).     

Changes in Physicochemical Properties and Volatile Compounds of Roselle (Hibiscus sabdariffa L.) Calyx during Different Drying Methods

Fresh roselle are high in moisture and deteriorate easily, which makes drying important for extending shelf-life and increasing availability. This study investigated the influence of different drying methods (oven-drying, freeze-drying, vacuum-drying, and sun-drying) on the quality of roselle calyx expressed as physicochemical properties (moisture content, water activity, soluble solids, color), volatile compounds, and microstructure. Oven-drying and freeze-drying reduced moisture content most while vacuum-drying and sun-drying were not as efficient. All drying methods except sun-drying resulted in water activities low enough to ensure safety and quality. Vacuum-drying had no impact on color of the dry calyx and only small impact on color of water extract of calyx. Drying reduced terpenes, aldehydes, and esters but increased furans. This is expected to reduce fruity, floral, spicy, and green odors and increase caramel-like aroma. Sun-drying produced more ketones, alcohols, and esters. Scanning electron microscopy revealed that freeze-drying preserved the cell structure better, and freeze-dried samples resembled fresh samples most compared to other drying techniques. The study concludes that freeze-drying should be considered as a suitable drying method, especially with respect to preservation of structure.     

Method validation by interlaboratory studies of improved hydrophilic oxygen radical absorbance capacity methods for the determination of antioxidant capacities of antioxidant solutions and food extracts

Hydrophilic oxygen radical absorbance capacity (H-ORAC) is a method for evaluating antioxidant capacities of solutions of hydrophilic compounds. In this study, we improved the original method for H-ORAC determination, and evaluated the precision of the two improved methods (methods A and B) by interlaboratory studies using 5 antioxidant solutions and 5 food extracts as test samples. An interlaboratory study of method A, in accordance with the harmonized protocol, demonstrated satisfactory performance (intermediate precision relative standard deviations (RSD(int)) ranging from 4.6 to 18.8%; the reproducibility relative standard deviations (RSD(R)) ranging from 7.0 to 21.1%, and the HorRat values ranging from 0.40 to 1.93). However, methodological problems remained, and a further improved method, method B, was thus developed. An interlaboratory study of method B by 5 participating laboratories showed better intermediate precision and reproducibility (RSD(int) and RSD(R) ranging from 1.8 to 9.4%, and from 4.4 to 13.8%, respectively), and all HorRat values for the test samples were less than 1.3, suggesting good performance for the H-ORAC measurement.     

Utilising oleogel as a frying medium for deep fried Indian traditional product (Mathri) to reduce oil uptake

The purpose of this research was to use and analyze the influence of oleogel as a frying medium for developing low fat fried Indian traditional snack (Mathri). As consumer demand for fried foods grows, so does consumer concern about their health, as they are responsible for a variety of health disorders. Carnauba wax and soybean oil were used to produce oleogel in three different concentrations (5, 10 and 15%) which were further examined and used as frying medium. The oleogel effect on the quality attributes of snack were also investigated and compared with the soybean refined oil in this study. It was observed that Mathri fried in oleogel had better moisture retention, color, texture and a lower oil uptake than the Mathri fried in soybean oil. Moisture content in CRW samples ranged from 4 to 5%, but rose to 8.98% in the case of oil samples. Breaking strength of mathri fried in oil was 3382.1 ?g, which was more than the breaking strength of mathri fried in oleogel, which were 1974.8 ?g (5% CRW) and 1092.7 ?g (10% CRW) and 3168.1 ?g (15% CRW). Oleogel fried mathri absorbed 27.7%, 22% and 19.3% less oil than conventionally fried ones. The study shows that mathri with reduced fat and calorie content can be developed to suit the demand among health-conscious consumers for low fatty foods.     

粮食水分的测量和电子水分仪测量不确定度的评定

介绍粮食中水分的两种测量方法：烘干称重法和电测法。同一台水分仪测量不同品种的粮食可能有不同的不确定度,一台水分仪要存入多条工作曲线用以测量不同品种粮食的含水量。介绍了电子水分仪测量不确定度的评定方法。     

Characterization of biologically active compounds from different herbs: Influence of drying and extraction methods

The hot air (HA) method is the most widely implemented drying method for plants (herbs, vegetables, and fruits). This method has a few drawbacks that include long drying time, limited heat transfer, and limited thermal conductivity. This study investigated the effects of HA and infra-red (IR) heating method on biologically active compounds from different herbs (Khaffir lime, Lemongrass, Prai, Tamarind, and Turmeric). The efficiency of the drying methods was evaluated by considering (a) moisture ratio (MR), (b) specific energy consumption (SEC, MJ/kg.H₂O), (c) moisture diffusivity (D_eff), and (d) activation energy (E_a, kJ/mol). The active compounds were extracted from HA and IR dried herbs using different solvents (hexane, water, and ethanol) through Solid-Liquid Extraction (SLE) and Soxhlet Solvent Extraction (SSE) methods. The moisture removal in the IR drying process increased 10–11% for the herb samples. Specific energy consumption (SEC) increase during the IR drying process is attributed to the rapid evaporation of water at shorter time intervals than HA. Activation energy (E_a) values decreased by 1.66, 1.48, 2.24, 3.13, and 2.07 fold times for IR dried prai, turmeric, lemongrass, tamarind, and kaffir lime, respectively. The higher yields of herbal extracts and the abundance of bioactive terpene derivatives in hexane extracts were obtained from HA herbs compared to IR samples. Therefore, it is concluded that the IR method and SSE process using hexane was suitable to dry and retain the bioactive active compounds within herbs. Further, the IR method over the HA method was considered based on energy consumption, processing time, yield, and active compounds.     

Effects of Preheating Temperature,Moisture and Sodium Metabisulfite Content on Property of Maize Flour Dough

Processing temperature,maze flour particle size,and level of water and sodium metabisulfite were varied during the preparation of maize noodles.Preheated to 90-95 ℃ a mixture of maize flour or meal,water(43%-45% moisture) and salt enabled the preparation of noodles using a pasta extruder.Maize flour with smaller particle size yielded better noodles than did maize meal.The addition of sodium metabisulfite enabled the production of noodles at lower processing temperatures; however,cooking losses increased.Processing maize flour with higher water absorption yielded noodles that required longer cooking time but with decreased losses.The functionalities of starch and protein in raw ingredients and in products were determined.Starch gelatinized and retorgraded during processing maize noodles,as indicated by changes in pasting viscosity curves.Maize proteins contributed to the increased viscosity of dough above 40 ℃.The increased integrity of cooked maize noodles,however,corresponded to the increased amounts of gelatinized and retrograded starch.     

Moisture Removal from Natural Jute Fibre by Plasma Drying Process

Low temperature plasma process is an effective alternative method compared to the conventional vacuum drying method for removing moisture. Plasma drying removes the moisture from fibres faster and to a lower level than conventional methods. It also improves the surface properties of the fibres. The jute fibre was treated with inert gas argon plasma without damaging the fibre. The OES was used to monitor the moisture desorbed from the fibre during processing. The XRD results revealed a change in the macromolecular structure as well as the crystallinity of the treated fibre. The FTIR and TGA provided the evidence of moisture removal from the fibres. It was found that the plasma treated fibres contain less than 1.8% (wt.) moisture which is a promising result when compared with conventional drying processes.The average tensile strength of the plasma treated fibres increased by 12.5% compared with those treated with the conventional vacuum dry process.     

Determination of moisture and fat in meats by microwave and nuclear magnetic resonance analysis: collaborative study

Ten laboratories participated in a collaborative study to determine the total moisture and fat in raw and processed meat products by microwave drying and nuclear magnetic resonance (NMR) spectroscopy. Meat products were prepared following the AOAC Method and analyzed using CEM Corp.'s SMART Trac Moisture and Fat Analysis system. SMART Trac provides moisture results by measuring the weight loss on drying by microwave energy. The dried sample is then analyzed by NMR spectrometry for fat content. Moisture and fat results are displayed and reported by the SMART Trac as a percentage (g/100 g). Microwave drying is an AOAC-approved reference method (Method 985.14), Moisture in Meat and Poultry Products. NMR spectrometry is a secondary technique used to determine the concentration of various constituents in biological, organic, or chemical samples. The study design was based on Youden's matched pair principle for collaborative tests. For the purposes of this study, 10 laboratories each tested 10 Youden matched pairs, for a total of 20 samples. The study samples represented a range of products processed daily in plant operations. Included were raw meat samples (beef, pork, chicken, and turkey) as well as processed meats (beef hot dog, pork sausage, and ham). The total moisture content of the undiluted samples, as received for the purposes of this study, was determined by AOAC Method 950.46 and ranged from 54.03 to 74.99%. The total fat content of the undiluted samples was determined by AOAC Method 960.39 and ranged from 1.00 to 29.79%. Statistical analysis of study results for total moisture yielded a relative standard deviation for repeatability (RSDr) range of 0.14 to 0.95% and a relative standard deviation for reproducibility (RSDR) range of 0.26 to 0.95%. Statistical analysis for total fat yielded similar RSDr and RSDR range of 0.74 to 4.08%. Results for turkey had higher RSDr and RSDR values, both at 12.6%, due to low fat content and possibly to the separation of the samples observed by some of the collaborators. Results demonstrate that microwave drying with NMR is a rapid, practical method providing results equivalent to AOAC Methods 950.46 (Forced Air Oven Drying) and 960.39 (Soxhlet Ether Extraction) in raw and processed meat products.     

Simultaneous determination of 3-monochloropropane-1,2-diol and acrylamide in food by gas chromatography-triple quadrupole mass spectrometry with coupled column separation

Both 3-monochloropropane-1,2-diol (3-MCPD) and acrylamide are contaminants found in heat-processed foods and their related products. A quantitative method was developed for the simultaneous determination of both contaminants in food by gas chromatography-triple quadrupole mass spectrometry (GC–MS/MS). The analytes were purified and extracted by the matrix solid-phase dispersion extraction (MSPDE) technique with Extrelut NT. A coupled column (a 3 m Innowax combined with a 30 m DB-5 ms) was developed to separate both compounds efficiently without derivatization. Triple quadrupole mass spectrometry in multiple reaction monitoring mode (MRM) was applied to suppress matrix interference and obtain good sensitivity in the determination of both analytes. The limit of detection (LOD) in the sample matrix was 5 μg kg⁻¹ for 3-MCPD or acrylamide. The average recoveries for 3-MCPD and acrylamide in different food matrices were 90.5–107% and 81.9–95.7%, respectively, with the intraday relative standard deviations (RSDs) of 5.6–13.5% and 5.3–13.4%, respectively. The interday RSDs were 6.1–12.6% for 3-MCPD and were 5.0–12.8% for acrylamide. Both contaminants were found in samples of bread, fried chips, fried instant noodles, soy sauce, and instant noodle flavoring. Neither 3-MCPD nor acrylamide was detected in the samples of dairy products (solid or liquid samples) and non-fried instant noodles.