Crystallization properties and polymorphism of triacylglycerols in goat's milk fat globules

The sensorial, functional, and nutritional properties of goat dairy products result from the specific fatty acid composition of goat's milk fat. However, information on the physical and thermal properties of goat's milk fat is scarce. In this study, crystallization of triacylglycerols (TG) in goat's milk fat globules was investigated using polarized light microscopy and the coupling of time-resolved synchrotron radiation X-ray diffraction (XRD) and high-sensitivity differential scanning calorimetry (DSC). The molecular organization of the solid fat phase was characterized for cooling rates between 3 and 0.1 degrees C/min. Quenching of goat's milk fat globules from 50 to -8 degrees C and 4 degrees C was also examined to identify the most unstable polymorphic forms of TG. Then, the melting behavior of fat crystals was studied on subsequent heating at 1 degrees C/min. Triple chain length (3L: 68.6-70 A) and double chain length (2L: 37-45.4 A) structures were characterized and 5 polymorphic forms, alpha, sub-alpha, beta' 1, beta' 2, and beta were identified. Polymorphic transitions were observed within goat's milk fat globules as a function of time after quenching and as a function of temperature on heating. From a technological point of view, this work will contribute to a better understanding of the rheological properties as well as on the flavor evolutions of goat's milk-based products.     

不同虫态谷蠹侵害对小麦淀粉组分及微观形态结构的影响

为了探讨不同生长发育阶段的谷蠹侵害对小麦淀粉组分及形态结构的影响。通过控制谷蠹侵害小麦的温度(30℃±1℃)、相对湿度(75%±5%)及虫口密度(1 000头/100 g),保证其完成一个生长发育周期,以谷蠹感染后的小麦为研究对象,对谷蠹不同发育阶段(卵期、幼虫期、蛹期、成虫期)侵害后小麦中粗淀粉、破损淀粉含量、还原糖含量及淀粉颗粒形貌及结构、淀粉粒度和淀粉结晶度进行测定与分析。结果表明:不同生长发育阶段的谷蠹对小麦侵害后,与谷蠹未侵害的小麦对照样相比,粗淀粉含量除在卵期略有增加外其余各期均低于对照样,在4个发育阶段谷蠹侵害后均呈现显著差异性(P0.05),还原糖含量、破损淀粉含量在各发育期均高于原始样,中位径变化则呈现波动性,且均明显低于原始样;还原糖含量从卵期到成虫期时均与原始样品差异性明显(P0.05),破损淀粉含量从卵期的2.42%上升至成虫期的5.58%,其中从卵期到幼虫期破损淀粉含量增幅最大;与原始样相比,小麦淀粉的X射线衍射曲线变化差异不明显,结晶度值各虫期间变化不显著(P0.05);淀粉的扫描电镜图显示:随着谷蠹由卵期发育至成虫期,其小麦籽粒中淀粉颗粒表面逐渐变得粗糙不完整,形状变得无规则,且小粒径颗粒增多,破损淀粉含量增加,大粒径淀粉颗粒表面出现较大凹坑和破损。因此,在实际的小麦储藏过程,应关注谷蠹在发育过程中的幼虫期对小麦品质的影响。     

Size-dependent lipid content of bovine milk fat globule and membrane phospholipids

The mammary epithelial cell produces unique structures and a range of diversely sized lipid particles from tens of micrometers to less than 1 μm. The physical, chemical, and biological properties of the differently sized milk fat globules (MFGs) and their complex membranes are not well described. Six size fractions of MFGs were obtained by gravity-based separation and analyzed, and their partial lipidome was determined. The smallest MFGs had a higher concentration of polyunsaturated fatty acids (FAs). The FAs indicative of elongase activity were highest in the smallest MFGs, whereas those FAs indicative of desaturase activity did not differ between size groups. The phosphatidylinositol concentration was highest whereas the phosphatidylserine concentration was lowest in MFGs with an average diameter of 2 μm. Phosphatidylethanolamine and cholesterol concentrations were highest whereas that of sphingomyelin was lowest in MFGs with an average diameter of 3 μm. Phosphatidylcholine concentrations did not vary between the size groups. Results suggest that the assembly of milk fat globules that differ in size is not a homogeneous nor random process and that the differences in composition may reflect discrete biosynthetic routes.     

Anthocyanin composition of Cabernet Sauvignon and Tempranillo grapes at different stages of ripening

Changes in anthocyanins during ripening of Cabernet Sauvignon and Tempranillo grapes were studied over a three year period. The accumulation of anthocyanins showed variations during ripening, especially during the first three weeks after veraison, and the accumulation pattern of those molecules changed only slightly from one year to another. On the other hand, the percentages of the different anthocyanins studied were different for each cultivar, and some changes were observed in both cultivars depending on the weather conditions of the growing season. In warm years the percentages of primitive anthocyanins (delphinidin 3-O-glucoside and petunidin 3-O-glucoside) were slightly lower than in a relatively cool year. Nevertheless, the anthocyanin fingerprints of Cabernet Sauvignon and Tempranillo grapes seem to be rather stable during ripening, despite the sugar content of the grapes.     

Lipase-catalyzed preparation of human milk fat substitutes from palm stearin in a solvent-free system

Human milk fat substitutes (HMFSs) were synthesized by lipozyme RM IM-catalyzed acidolysis of chemically interesterified palm stearin (mp = 58 °C) with mixed FAs from rapeseed oil, sunflower oil, palm kernel oil, stearic acid, and myristic acid in a solvent-free system. Response surface methodology (RSM) was used to model and optimize the reactions, and the factors chosen were reaction time, temperature, substrate molar ratio, and enzyme load. The optimal conditions generated from the models were as follows: reaction time, 3.4 h; temperature, 57 °C; substrate molar ratio, 14.6 mol/mol; and enzyme load, 10.7 wt % (by the weight of total substrates). Under these conditions, the contents of palmitic acid (PA) and PA at sn-2 position (sn-2 PA) were 29.7 and 62.8%, respectively, and other observed FAs were all within the range of FAs of HMF. The product was evaluated by the cited model, and a high score (85.8) was obtained, which indicated a high degree of similarity of the product to HMF.     

Analysis of the early stages of lipid oxidation in freeze-stored pork back fat and mechanically recovered poultry meat

An analytical method that can detect low levels of oxidation in food earlier than a sensory panel would be a valuable tool for food manufacturers as well as research institutes. Two model matrixes, pork back fat and mechanically recovered poultry meat (MRPM), were freeze-stored in air at -20 degrees C for 26 weeks. Peroxide value, thiobarbituric acid reactive substances, volatiles analyzed with dynamic headspace gas chromatography-mass spectrometry (GC-MS) and a gas-sensor array technique (electronic nose), chemiluminescence, and front-face fluorescence were evaluated against sensory analysis with regard to detection of early oxidation and correlation with sensory data. Fluorescence and GC-MS could detect oxidative changes in pork back fat earlier than the sensory panel and the electronic nose at the same time. The three methods were highly correlated with sensory attributes (r = 0.8-0.9). GC-MS gave the best results with regard to detection of small oxidative changes in MRPM.     

Near-infrared analysis of fat, protein, and casein in cow's milk.

Fat, crude protein, true protein, and casein were determined in cow milks by near-infrared transmission spectroscopy (NIR). Partial and overall PLS calibrations were performed on two sets of samples: partial calibration included 76 unhomogenized samples, whereas overall calibration used 96 homogenized and unhomogenized samples. Standard errors of calibration were 0.12% for fat, 0.06% for crude protein, 0.04% for true protein, and 0.05% for casein in the overall calibration. Validation of the overall calibration with an independent set of samples gave standard errors of prediction of 0. 07% for fat, 0.06% for crude protein and casein, and 0.05% for true protein. Except for fat, all of the statistical parameters were better with overall than with partial calibrations, which indicates that homogenization has an effect on NIR fat determination. Despite the relatively small number of samples included in the calibration model, NIR transmission was found to be a reliable method for the determination of fat and nitrogenous constituents in milk.     

Stereospecific analysis of phospholipid classes in skeletal muscle from rats fed different fat sources

The fatty acid (FA) and dimethylacetal profiles of the sn-1 and sn-2 positions of different phospholipid (PL) classes from skeletal muscle of rats as affected by dietary FA profiles were studied. Rats were fed either a control diet, an olive oil-enriched diet, or a sunflower oil-enriched diet. The FA composition of both positions of the studied PL classes was affected by diet to different extents. The FA composition of the sn-2 position of phosphatidylserine was the most influenced by diet, while phosphatidylinositol was less affected by dietary modification. The FA profile of phosphatidylcholine reflected consumed FA better than any other studied PL. Thus, olive oil rats showed higher oleic acid (C18:1 n-9) contents in both positions of phosphatidylcholine, and sunflower oil rats had higher proportions of arachidonic acid (C20:4 n-6) in the sn-1 position of this PL class. Dimethylacetals were scarcely affected by diet, and only the dimethylacetal composition of phosphatidylethanolamine showed significant modifications.     

Physical stability of liposomes prepared from milk fat globule membrane and soya phospholipids

Previous research has shown that liposomes prepared from a milk fat globule membrane (MFGM) phospholipid fraction had a significantly higher phase transition temperature, thicker membrane, and lower membrane permeability than liposomes prepared from soya phospholipid material. Subsequent investigations into the relative stability of the two liposome dispersions have found that the MFGM phospholipid liposomes are more stable than their soya counterparts in a range of pH conditions, at a variety of storage and processing temperatures, and in the presence of mono- and divalent cations. These results illustrate some potential advantages in the use of MFGM phospholipids for the manufacture of liposomes for use in food systems.     

Headspace GC and sensory analysis characterization of the influence of different milk additives on the flavor release of coffee beverages

Previous investigations of coffee flavor have been confined to the analysis of the aroma substances. These investigations showed that about 30 volatile compounds were substantially responsible for the coffee flavor. The aim of this study was to investigate the influence of different milk additives and one coffee whitener on the release of flavor impact compounds from coffee beverages. For the investigation of these effects an external static headspace technique was developed. With this technique the most potent odorants of the coffee beverage were determined. Analyses were performed by gas chromatography/olfactometry, flame ionization detection, and mass spectrometric detection. In addition, sensory studies of the odor profiles were performed. Milk and vegetable products as additives for coffee beverages affected the release of aroma substances in the brew through their lipid, protein, and carbohydrate components. All beverages with an additive showed reduced, but typical, odor profiles for each additive.     

Dichloromethane as a solvent for lipid extraction and assessment of lipid classes and fatty acids from samples of different natures

The usefulness of the solvent mixture dichloromethane/methanol for lipid extraction and the determination of lipid classes and fatty acids in samples of different natures was conducted. Two different extraction methods were compared, one containing chloroform/methanol, another containing dichloromethane/methanol. Total lipid extraction showed some minor differences but no variation in the lipid classes. Regarding the fatty acid profile, in Echium virescens seeds, 17 major fatty acids could be identified and quantified, and all were equally extracted when either solvent system was employed. In Echium acanthocarpum hairy roots, 17 major fatty acids were quantified, showing some statistical differences for one cell line in favor of chloroform. The data obtained from the liquid nutrient medium were also comparable. The cod roe sample showed 31 major fatty acids, showing no statistical differences between the two solvent systems. Contrarily, the CH 2Cl 2 method was able to extract 31 main fatty acids found in European seabass dorsal muscle more efficiently than the CHCl 3 method. The results indicate that, for lipid extraction and fatty acid assessment, dichloromethane/methanol can readily replace the commonly employed chloroform/methanol, thus avoiding the major health, security, and regulatory problems associated with the use of chloroform.     

trans-C18:1 isomers in cheeses enriched in unsaturated fatty acids and manufactured with different milk fat globule sizes

Increasing the knowledge on dietary fat composition, mainly the minor components, will improve the nutritional value of foods and their labeling. In this study, we examined the trans-octadecenoic acid (C18:1) composition of Emmental cheeses enriched in unsaturated fatty acids (FA) and manufactured with milks produced by cows selected to produce small and large fat globules. The FA composition of the milks was not significantly ( P > 0.05) different from the FA composition of the corresponding Emmental cheeses. Increasing the unsaturated FA content of the cheeses using dietary manipulations lead to an increase in the trans-C18:1 and changed their isomeric profiles. In milk fat produced with the linseed-enriched diet, the trans-10 C18:1 concentration was greater than trans-11 C18:1 (vaccenic acid), which is classically the major trans-C18:1 in milk fat. The content in trans-C18:1 and more particularly in trans-10 C18:1 was negatively correlated with the size of fat globules ( r (2) = 0. 82 and 0.87, respectively) and related to milk fat depression. The trans-C18:1 content was negatively correlated with the saturated FA (slope = -0.35; r (2) = 0.81) and positively correlated with the unsaturated (slope = 0.29; r (2) = 0.85) and monounsaturated (slope = 0.32; r (2) = 0.81) FA. Focusing on the health-related considerations of fat in food products, further nutritional studies are needed to elucidate the role of trans-C18:1 isomers.     

Soil phosphorus dynamics and phytoavailability from sewage sludge at different stages in a treatment stream

The effect of different stages of sewage sludge treatment on phosphorus (P) dynamics in amended soils was determined using samples of undigested liquid (UL), anaerobically digested liquid (AD) and dewatered anaerobically digested (DC) sludge. Sludges were taken from three points in the same treatment stream and applied to a sandy loam soil in field-based mesocosms at 4, 8 and 16 t ha⁻¹ dry solids. Mesocosms were sown with perennial ryegrass (Lolium perenne cv. Melle), and the sward was harvested after 35 and 70 days to determine yield and foliar P concentration. Soils were also sampled during this period to measure P transformations and the activities of acid phosphomonoesterase and phosphodiesterase. Data show that the AD amended soils had the greatest plant-available and foliar P content up to the second harvest, but the UL amended soils had the greatest enzyme activity. Characterisation of control and 16 t ha⁻¹ soils and sludge using solution ³¹P nuclear magnetic resonance (NMR) spectroscopy after NaOH–EDTA extraction revealed that P was predominantly in the inorganic pool in all three sludge samples, with the highest proportion (of the total extracted P) as inorganic P in the anaerobically digested liquid sludge. After sludge incorporation, P was immobilised to organic species. The majority of organic P was in monoester-P forms, while the remainder of organic P (diester P and phosphonate P) was more susceptible to transformations through time and showed variation with sludge type. These results show that application of sewage sludge at rates as low as 4 t ha⁻¹ can have a significant nutritional benefit to ryegrass over an initial 35-day growth and subsequent 35-day re-growth periods. Differences in P transformation, and hence nutritional benefit, between sludge types were evident throughout the experiment. Thus, differences in sludge treatment process alter the edaphic mineralisation characteristics of biosolids derived from the same source material.     

Comparative analysis of different hemoglobins: autoxidation,reaction with peroxide,and lipid oxidation

Beef hemoglobin (Hb) had lower levels of deoxyHb and autoxidized much slower as compared to trout Hb at pH 6.3. Chicken Hb autoxidized at a rate intermediate between beef and trout Hb. In the presence of hydrogen peroxide, metHb formed rapidly from trout Hb whereas beef Hb was essentially nonreactive with hydrogen peroxide. The autoxidation rate of perch Hb was more rapid than trout Hb despite the low deoxyHb content of perch Hb. Perch Hb was a better catalyst of lipid oxidation than trout Hb when added to washed cod muscle based on formation of lipid hydroperoxides and thiobarbituric acid reactive substances. These studies indicate that autoxidation rate does not always increase with increasing deoxyHb content. The role of heme crevice volume in heme protein autoxidation is discussed. Among other factors, these studies suggest that rates of lipid oxidation in various muscle foods may depend on the relative ability of hemoglobins from different animal species to promote lipid oxidation.     

Isoprenoid, lipid, and protein contents in intact plastids isolated from mesocarp cells of traditional and high-pigment tomato cultivars at different ripening stages

This study reports quali-quantitative analyses on isoprenoids, phospholipids, neutral lipids, phytosterols, and proteins in purified plastids isolated from fresh fruits of traditional (Donald and Incas) and high-pigment (Kalvert and HLY-18) tomato cultivars at four ripening stages. In all of the investigated cultivars, lycopene, β-catotene, lutein, and total carotenoids varied significantly during ripening. Chromoplasts of red-ripe tomato fruits of high-pigment cultivars accumulated twice as much as lycopene (307.6 and 319.2 μg/mg of plastid proteins in Kalvert and HLY-18, respectively) than ordinary cultivars (178.6 and 151.7 μg/mg of plastid proteins in Donald and Incas, respectively); differences in chlorophyll and α-tocopherol contents were also evidenced. Phospholipids and phytosterols increased during ripening, whereas triglycerides showed a general decrease. Regardless of the stage of ripening, palmitic acid was the major fatty acid in all cultivars (ranging from 35 to 52% of the total fatty acids), followed by stearic, oleic, linoleic, linolenic, and myristic acids, but their relative percentage was affected by ripening. Most of the bands detected on the SDS-PAGEs of plastid proteins were constantly present during chloroplast-to-chromoplast conversion, some others disappeared, and only one, with a molecular weight of ~41.6 kDa, was found to increase in intensity.     

Primary and secondary metabolite composition of kernels from three cultivars of Portuguese chestnut (Castanea sativa Mill.) at different stages of industrial transformation

Chestnut (Castanea sativa) is an important basic food in rural diets and a major starch crop used in a similar way to potatoes. Chestnuts are a fundamental economic resource in the "chestnut regions" not only for the fruit but also for the chestnut wood. Chestnuts have become increasingly important with respect to human health, for example, as an alternative gluten-free flour source. Chestnuts are also a rich source of other beneficial compounds, but there have been few studies on the composition during processing. In this study, we analyzed the chemical composition of three Portuguese cultivars at different stages of industrial processing. The chestnut cultivars were Longal, Judia, and Martaínha. All three cultivars had high moisture contents but were low in ash, crude fat, and crude protein contents, with high starch and low fiber contents. The free amino acid contents, including various essential amino acids, varied depending on the cultivar. All three cultivars also had a significant content of polyphenolics with gallic acid; ellagic acid was predominant among hydrolyzable and condensed tannins. Many of these compounds are known to exert significant positive effects on human health. The one-way analysis of variance for fresh chestnut shows significant differences among the three cultivars for most of the studied parameters. The same statistical analysis applied to each one of the two cultivars (Judia and Longal) sampled for the four processing steps analyzed indicates a significant effect of this factor in practically all of the constituents. On the other hand, the two-way analysis of variance shows that, besides the residual, the processing step and the interaction cultivar x processing step were the factors that more contributed for the total variation observed in the constituents analyzed, while the contribution of cultivar was much less significant.     

Foliar analysis of sulphur in different soybean cultivar stages and its relation to yield

Abstract

Six soybean cultivars (maturity group V) were sown in a Typic Argiudoll. Experimental plots were arranged in a randomized block design with three replications. Sampling dates were at different stages: V, R2, R4, and R55. All the varieties showed that the greatest sulfur (S) concentrations were in stage V and the lowest in stage R55. No significant differences were found between the means of the S concentrations during the V, R4, and R55 stages. In the R2 stage, there was a poor correlation with the weight of 1,000 seeds.     

Obtention and characterization of phenolic extracts from different cocoa sources

The aim of this study was to evaluate several cocoa sources to obtain a rich phenol extract for use as an ingredient in the food industry. Two types of phenolic extracts, complete and purified, from different cocoa sources (beans, nibs, liquor, and cocoa powder) were investigated. UPLC-MS/MS was used to identify and quantify the phenolic composition of the extracts, and the Folin-Ciocalteu and vanillin assays were used to determine the total phenolic and flavan-3-ol contents, respectively. The DPPH and ORAC assays were used to measure their antioxidant activity. The results of the analysis of the composition of the extracts revealed that the major fraction was procyanidins, followed by flavones and phenolic acids. From the obtained results, the nib could be considered the most interesting source for obtaining a rich phenolic cocoa extract because of its rich phenolic profile content and high antioxidant activity in comparison with the other cocoa sources.