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).     

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.     

Quantitative characterization of food products by two-dimensional D-T2 and T1-T2 distribution functions in a static gradient

We present new NMR techniques to characterize food products that are based on the measurement of two-dimensional diffusion-T2 relaxation and T1-T2 relaxation distribution functions. These measurements can be performed in magnets of modest strength and low homogeneity and do not require pulsed gradients. As an illustration, we present measurements on a range of dairy products that include milks, yogurt, cream, and cheeses. The two-dimensional distribution functions generally exhibit two distinct components that correspond to the aqueous phase and the liquid fat content. The aqueous phase exhibits a relatively sharp peak, characterized by a large T1/T2 ratio of around 4. The diffusion coefficient and relaxation times are reduced from the values for bulk water by an amount that is sample specific. The fat signal has a similar signature in all samples. It is characterized by a wide T2 distribution and a diffusion coefficient of 10(-11) m2/s for a diffusion time of 40 ms, determined by bounded diffusion in the fat globules of 3 microm diameter.     

Fatty acid profile of Canadian dairy products with special attention to the trans-octadecenoic acid and conjugated linoleic acid isomers

Current scientific evidence indicates that consumption of industrial trans fatty acids (TFA) produced via partial hydrogenation of vegetable oils increases the risk of coronary heart disease. However, some studies have suggested that ruminant TFA, especially vaccenic acid (VA or 11t-18:1) and rumenic acid (RA or 9c,11t-18:2), which is a conjugated linoleic acid (CLA) isomer, may have potential beneficial health effects for humans. To date, no concerted effort has been made to provide detailed isomer composition of ruminant TFA and CLA of Canadian dairy products, information that is required to properly assess their nutritional impacts. To this end, we analyzed the fatty acid profile of popular brands of commercial cheese (n = 17), butter (n = 12), milk (n = 8), and cream (n = 4) sold in retail stores in Ottawa, Canada, in 2006-2007 by silver nitrate thin-layer chromatography and gas liquid chromatography. The average total TFA content of cheese, butter, milk, and cream samples were 5.6, 5.8, 5.8, and 5.5% of total fatty acids, respectively. VA was the major trans-octadecenoic acid (18:1) isomer in all the Canadian dairy samples with average levels of (as % total trans-18:1) 33.9% in cheese, 35.6% in butter, 31.0% milk, and 30.1% in cream. The different dairy products contained very similar levels of CLA, which ranged from 0.5 to 0.9% of total fat. RA was the major CLA isomer of all the dairy products, accounting for 82.4-83.2% of total CLA. There were no significant differences (P > 0.05) in the fatty acid profile between the 4 different dairy groups, which suggests lack of processing effects on the fatty acid profile of dairy fat.     

Effects of drying and pressing on the pore structure in the cellulose fibre wall studied by 1H and 2H NMR relaxation

A 1H and 2H NMR relaxation method was used to investigate the influence of drying and pressing on the pore size and pore size distribution in the cellulose fibre wall. The investigation was made in the moisture interval in which cellulose fibres normally shrink, i.e. from a moisture ratio of about 1.5 g water/g fibre to dry fibres. When the moisture content of a fibre sample was decreased by drying or pressing, the pores decreased in size and the pore size distribution became narrower. It was found that there were only small differences at a given moisture content between the pore size distributions of samples prepared by drying and by pressing. The results also indicate that the pore shrinkage in cellulose fibres during pressing or drying is a process in which the cell wall pores of a wet cellulose fibre successively shrink as the moisture content decreases. It was observed that, at low moisture contents, pressing and drying resulted in different 1H NMR spin-lattice relaxation profiles. This is discussed in terms of morphology differences in the fibre matrix. The mobility of the protons in the solid phase influences the liquid 1H NMR spin-lattice relaxation in heterogeneous systems through magnetization transfer. We have also studied the effects of hornification in recycled pulps     

Studies of <Superscript>90</Superscript>Sr presence in milk and commercial dairy products

The aim of this article was to present the studies of radiological level of some commercial dairy products in Mazovian, Kuyavian—Pomeranian and Lublin regions. They were carried out for 27 commercial dairy products such as two specimens of lean cottage cheese, three specimens of cottage cheese containing a limited percentage of fat, three specimens of fat cottage cheese, three specimens of milk containing 3.2% of fat, three specimens of milk containing 2.0% of fat, two specimens of sour cream containing 12% of fat, three specimens of sour cream containing 18% of fat, one specimen of 30% whipping cream, two specimens of homogenized (strawberry and vanilla) cheese, three specimens of hard rennet cheese, one specimen of powdered milk, one specimen of goat milk. For the given commercial dairy products there were calculated effective doses (μSv) obtained after consumption of 1 kg contaminated product for different age groups.     

Melting characteristics of fat present on the surface of industrial spray-dried dairy powders

The melting characteristics of the fat present on the surface (surface free-fat) of two industrial spray-dried dairy powders (cream powder and whole milk powder) were investigated in comparison with those of other milk fat fractions present in the powder, such as free-fat from the interior of the powder particle (inner free-fat) and encapsulated fat. The melting characteristics of the milk fat fractions were studied by fatty acid composition, melting profile and solid fat content profile. The results indicated that all milk fat fractions including surface free-fat contained various triglycerides with melting points ranging from -40 to +40 degrees C. However, some fractionation was observed among the different milk fat fractions. The free-fat fractions (surface free-fat and inner free-fat) had a greater proportion of high-melting triglyceride species than the encapsulated fat. Furthermore, the high-melting triglyceride species present in the free-fat fractions were slightly accumulated at the surface of powder. This phenomenon was observed in both cream powder and whole milk powder and its effect on wetting time was established. This indicates that manipulation of the surface fat content during drying operation may hold the key to functionality improvement.     

Effect of Different Drying Methods on the Nutritional Value of Hibiscus sabdariffa Calyces as Revealed by NMR Metabolomics

Red mature calyces of Hibiscus sabdariffa were collected from 16 different locations in Meghalaya, India. Samples were processed using shade drying (SD) and tray drying (TD). NMR spectroscopy was used to assess the metabolic composition of the calyces. In this study, 18 polar metabolites were assigned using 1D and 2D NMR spectra, and 10 of them were quantified. Proximate analysis showed that the TD method is more efficient at reducing moisture and maintaining the ash content of the Hibiscus biomass. NMR metabolomics indicates that the metabolite composition significantly differs between SD and TD samples and is more stable in TD plant processing. The differences in post-harvest drying has a greater impact on the metabolite composition of Hibiscus than the plant location.     

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.     

Microwave drying of granules containing a moisture-sensitive drug: a promising alternative to fluid bed and hot air oven drying

The impact of microwave drying and binders (copolyvidone and povidone) on the degradation of acetylsalicylic acid (ASA) and physical properties of granules were compared with conventional drying methods. Moist granules containing ASA were prepared using a high shear granulator and dried with hot air oven, fluid bed or microwave (static or dynamic bed) dryers. Percent ASA degradation, size and size distribution, friability and flow properties of the granules were determined. Granules dried with the dynamic bed microwave dryer showed the least amount of ASA degradation, followed by fluid bed dryer, static bed microwave oven and hot air oven. The use of microwave drying with a static granular bed adversely affected ASA degradation and drying capability. Dynamic bed microwave dryer had the highest drying capability followed by fluid bed, static bed microwave dryer and conventional hot air oven. The intensity of microwave did not affect ASA degradation, size distribution, friability and flow properties of the granules. Mixing/agitating of granules during drying affected the granular physical properties studied. Copolyvidone resulted in lower amount of granular residual moisture content and ASA degradation on storage than povidone, especially for static bed microwave drying. In conclusion, microwave drying technology has been shown to be a promising alternative for drying granules containing a moisture-sensitive drug.     

Chromatographic method for the determination of aflatoxin M1 in cheese, yogurt, and dairy beverages

The aim of this work was to develop and validate a method to determine aflatoxin M1 (AFM1) in cheese, yogurt, and dairy beverages. The method consisted of aqueous methanol extraction, immunoaffinity column purification and isolation, RPLC separation, and fluorescence detection. The four types of cheese samples were classified according to moisture and fat content. The mean recoveries were 71% for cheese at spiked levels from 100 to 517 ng/kg, and 76% for yogurt and dairy beverages spiked at levels from 66 to 260 ng/kg. The mean RSDs were 5.9% for cheese, and 10% for yogurt and dairy beverages. The LOD was 3 ng/kg and the LOQ was 10 ng/kg for all test commodities. To test the applicability of the developed method, a small survey of the presence of AFM1 in cheese, yogurt, and dairy beverages purchased in Ribeir?o Preto-SP, Brazil, was conducted. AFM1 was detected (> 3 ng/kg) in all samples. Twenty cheese samples (83%) were contaminated with AFM1 in the range of 13-304 ng/kg. In yogurt and dairy beverages, the contamination was lower (13-22 ng/kg) in five samples (42%). The results indicated that the method is adequate for the determination of AFM1 in these four types of cheese, as well as in yogurt and dairy beverages.     

Quantification of fatty acids as methyl esters and phospholipids in cheese samples after separation of triacylglycerides and phospholipids

Determination of the individual fatty acid composition of neutral- and phospholipids as well as the phospholipid content of dairy food and other foodstuffs are important tasks in life sciences. For these purposes, a method was developed for the separation of lipids (standards of triolein and diacylphosphatidylcholines as well as three cheese samples) by solid-phase extraction using a self-packed column filled with partly deactivated silica. Non-halogenated solvents were used for the elution of the lipid classes. Cyclohexane/ethyl acetate (1:1, v/v) served for the elution of neutral lipids, while polar lipids were eluted with three solvents (ethyl acetate/methanol, methanol, and methanol/water) into one fraction. The separated lipid fractions were transesterified and the individual fatty acids were quantified by using gas chromatography coupled to electron ionization mass spectrometry (GC/EI-MS) in the selected ion monitoring (SIM) mode. The recovery rate for standard phosphatidylcholines was ∼90% and cross-contamination from neutral lipids was negligible. The method was applied to cheese samples. Quantitative amounts of individual fatty acids in the phospholipid fraction were <0.002-0.29% of total lipids from camembert, <0.002-0.12% of total lipids from mozzarella, and <0.002-0.18% of total lipids in a goat cream cheese. Differences in the fatty acid pattern of neutral and polar lipids were detected. The quantity of the fatty acids determined in the phospholipid fraction was divided by the factor 0.7 in order to convert the fatty acid content into the phospholipid content of the cheese samples. This factor is based on the contribution of 16:0 to dipalmitoylphosphatidylcholine (DPPC). The resulting DPPC equivalents (DPPC_eq) were found to be representative for the average contribution of fatty acids to all classes of phospholipids in dairy products. Using this approach, the phospholipid content of lipids from mozzarella, camembert, and goat cream cheese was 0.60%, 1.42% and 0.79%, respectively.     

Determination of fat in dairy products using pressurized solvent extraction

Gravimetric fat data were obtained for a wide range of dairy products with fat contents ranging from 0.5 to 83% using pressurized solvent extraction at elevated temperatures and pressure (80-120 degrees C; 10.3 MPa). Extraction performance was sensitive to solvent composition, temperature, and sample matrix. By optimizing solvent mixtures, sample-solvent contact times of 8-10 min were sufficient for high recoveries from all products tested. The most successful solvents with regard to speed of extraction, selectivity, and recovery (average recovery, %) were various mixtures of hexane (or petroleum ether)-dichloromethane-methanol for dried cream (99.8%), dried whole milk (99.6%), dried buttermilk (98.2%), dried skim milk (97.0%), dried whey protein concentrate (97.5%), casein (95.0%), and caseinate (102.1%); petroleum ether-acetone-ethanol or petroleum ether-acetone-isopropanol for cheddar-type cheese (99.4%); petroleum ether-acetone for butter (99.9%); petroleum ether-acetone-isopropanol for cream (100.3%); and petroleum ether-isopropanol for liquid milks (99.0%). Relative standard deviations for repeatability were obtained for dried whole milk (0.2%), dried whey protein concentrate (0.7%), cheese (0.3%), butter (0.1%), and ultraheat treated (UHT) milk (0.7%). Solvent removal and drying of extracts with a heated block evaporator saved time compared with conventional drying ovens. Estimated savings in labor (50-75%) and solvents (80%) were substantial compared with the manual Mojonnier methods.     

Determination of fat, protein, and total solids in ovine milk by near-infrared spectroscopy.

Analysis by near-infrared spectroscopy (NIRS) was investigated as a means of predicting quality parameters of ovine milk. Calibration equations were developed with samples of ovine milk obtained from a flock of Manchega and Lacaune dairy ewes at different stages of lactation for a wide variation in milk composition. Prediction equations for milk protein, fat, and total solids content were developed by use of reflection or transflection methods to measure absorbance values. Accuracies of measurements were compared. R2 (squared multiple correlation coefficient) values were satisfactory in most cases. The highest R2 value for milk protein content (0.92) was obtained in transflectance mode with unhomogenized milk. The highest R2 values for fat (0.99) and total solids (0.98-0.96) content were obtained in both a transflectance mode without sample conditioning and in a transflectance mode with milk homogenized at 40 degrees C. To validate the calibration, an independent set of 40 milk samples was used. The best r2 (simple correlation coefficient) values for protein, fat, and total solids were 0.92, 0.97, and 0.92, respectively. The study showed that NIRS is a potentially useful technique for evaluating the composition of unhomogenized ovine milk.     

Analysis of Mercury in Skin Lightening Cream by Microwave Plasma Atomic Emission Spectroscopy (MP-AES)

This research aimed at developing an analysis method, which was optimized and validated to determine the content of mercury in skin lightening cream discovered in the market in Bandar Lampung, Indonesia, through the use of microwave plasma atomic emission spectroscopy (MP-AES). The optimization on the analysis method was conducted on pump rate, viewing position, and reductant concentration in order to obtain the highest mercury emission intensity, while the solution stability was optimized to know the stability of mercury in the solution. The result showed that the method developed had precision with a relative standard deviation of 2.67%, recovery value of 92.78%, and linearity with an r value of 0.993, respectively. The sensitivity of the instrument detection had a limit of analysis method detection and quantification of 0.59 and 1.98 µg/L, respectively. The results of the test of the lightening cream (8 of 16 samples) positively contained mercury in the range of 422.61–44,960.79 ng/g. Therefore the method of analysis developed may be used for routine analysis of chemicals in any cosmetics products.     

A new, robust method for measuring average fibre wall pore sizes in cellulose I rich plant fibre walls

A new, robust method for measuring the average pore size of water-swollen, cellulose I rich fibres is presented. This method is based on the results of solid-state NMR, which measures the specific surface area (area/solids mass) of water-swollen samples, and of the fibre saturation point (FSP) method, which measures the pore volume (water mass/solids mass) of water-swollen samples. These results are suitable to combine since they are both recorded on water-swollen fibres in excess water, and neither requires the assumption of any particular pore geometry. The new method was used for three model samples and reasonable average pore size measurements were obtained for all of them. The structural characterization of water-swollen samples was compared with the dry structure of fibres as revealed using BET nitrogen gas adsorption after a liquid exchange procedure and careful drying. It was concluded that the structure of the water-swollen fibres sets an upper limit on what is obtainable in the dry state.     

Effects of wet-pressing-induced fiber hornification on enzymatic saccharification of lignocelluloses

This article reports the effect of wet-pressing-induced fiber hornification on enzymatic saccharification of lignocelluloses. A wet cellulosic substrate of bleached kraft eucalyptus pulp and two wet sulfite-pretreated lignocellulosic substrates of aspen and lodgepole pine were pressed to various moisture (solids) contents by variation of pressing pressure and pressing duration. Wet pressing reduced substrate moisture content and produced irreversible reduction in fiber pore volume—fiber hornification—as reflected in reduced water retention values (WRVs), an easily measurable parameter, of the pressed substrates. Wet pressing resulted in a reduction in substrate enzymatic digestibility (SED) by approximately 20% for the two sulfite-pretreated substrates when moisture content was reduced from approximately 75% to 35%. The reduction in SED for the cellulosic substrate was less than 10% when its moisture content was reduced from approximately 65% to 35%. The results indicated that reduction in SED is negligible when samples were pressed to solids content of 40% but observable when pressed to solids content of 50%. It was also found that WRV can correlate to SED of hornified substrates resulting from the same never-dried or pressed sample independent of the hornification process (e.g., pressing or drying). This correlation can be fitted using a Boltzmann function. Cellulase adsorption measurements indicated that wet-pressing-induced fiber hornification reduced cellulose accessibility to cellulase. The results obtained in this study provide guidelines to high-solids enzymatic saccharification of pretreated biomass.     

Development and Physicochemical Properties of Low Saturation Alternative Fat for Whipping Cream

We developed an alternative whipping cream fat using shea butter but with low saturation. Enriched stearic-oleic-stearic (SOS) solid fat was obtained from shea butter via solvent fractionation. Acyl migration reactant, which mainly contains asymmetric SSO triacylglycerol (TAG), was prepared through enzymatic acyl migration to obtain the creaming quality derived from the β’-crystal form. Through enzymatic acyl migration, we obtained a 3.4-fold higher content of saturated-saturated-unsaturated (SSU) TAG than saturated-unsaturated-saturated (SUS) TAG. The acyl migration reactant was refined to obtain refined acyl migration reactant (RAMR). An alternative fat product was prepared by blending RAMR and hydrogenated palm kernel oil (HPKO) at a ratio of 4:6 (w/w). The melting points, solid fat index (SFI), and melting curves of the alternative products were similar to those of commercial whipping cream fat. The alternative fat had a content of total unsaturated fatty acids 20% higher than that of HPKO. The atherogenic index (AI) of alternative fat was 3.61, much lower than those of whipping cream fat (14.59) and HPKO (1220.3), because of its low atherogenic fatty acid content and high total unsaturated fatty acids. The polymorphic crystal form determined by X-ray diffraction spectroscopy showed that the β’-crystal form was predominant. Therefore, the alternative fat is comparable with whipping cream that requires creaming quality, and has a reduced saturated fat content.     

Determination of crude fat in meat by supercritical fluid extraction: direct method: PVM 3:2000

Meat samples are prepared by passing meat through a food chopper, bowl cutter, or food processor, subsampling the meat, and mixing the meat with granular diatomaceous earth. No drying step is necessary. Supercritical CO2 is then used to extract crude fat (which is defined as the components of meat that are extractable with petroleum ether, without digestion of the sample). Extracted material is deposited on glass wool contained in collection vials. After removal of any residual moisture from the extracts, percent crude fat is determined by weight gain of the collection vial. This method has been peer-verified by 3 laboratories, for a wide variety of raw and processed meat products containing 6-28% crude fat. Samples were prepared at the submitting laboratory. Ground samples were split into 4 portions, packed in Whirlpack bags, and immediately frozen. Frozen samples were sent by overnight room temperature, and percent fat was determined (in triplicate), without further processing of the samples. Analysis of the samples was completed within 1 week of sample prepara. tion. On the basis of this study, it can be estimated that all repeatability and reproducibility values are <3.0. Mean accuracy of the direct gravimetric supercritical fluid extraction method for meat samples ranged from +0.22 to -1.41 when the method was compared with AOAC Method 960.39. Interferences are unlikely but would include any nonfat substance that is added to (processed) meat, is soluble in nonpolar solvents, and is present in a quantity that would alter results. This method is expected to perform equally well for all meats with fat content within the stated range of applicability.