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Summary: The aim of this study was to investigate the mechanisms behind protein–protein interactions in a co‐precipitate of whey protein isolate (WPI) and pea protein isolate (PPI). A co‐precipitate and blend, consisting of 80% WPI and 20% PPI, were compared. Covalent disulphide interactions were studied by blocking of free thiols with N‐Ethylmaleimide (NEM), while electrostatic interactions were studied in systems with 0.5 m NaCl and hydrophobic interactions with 0.2% SDS. Protein solubility, stability and secondary, tertiary and quaternary protein structures were analysed. Co‐precipitation did not introduce different protein–protein interactions than the direct blending of proteins. SDS affected solubility (P < 0.05), secondary and tertiary structure. However, the effects of NEM and NaCl were significant greater (P < 0.05) on the same parameters and thermal stability, especially when combined (P < 0.01). Thus, the protein–protein interactions in a whey–pea co‐precipitate and protein blend consisted of disulphide bonds and electrostatic interactions. [ABSTRACT FROM AUTHOR]

Summary: The aim was to optimise the yield of co‐precipitation of whey protein isolate (WPI) and pea protein isolate (PPI) and compare co‐precipitates and protein blends with respect to solubility. The yield of co‐precipitates was tested with different protein ratios of WPI and PPI in combination with different temperatures and acid precipitation (pH 4.6). The highest precipitation yield was obtained at protein ratios WPI < PPI, high temperature and alkaline protein solvation. The solubility was measured by an instability index and absorption spectroscopy of re‐suspended precipitated proteins at pH 3, 7 and 11.5. Co‐precipitates had significantly lower solubility than protein blends. Protein ratios WPI > PPI, low precipitation temperature and high pH showed the highest solubility. Differences in protein composition between co‐precipitates and protein blends were observed with SDS‐PAGE and matrix‐assisted laser desorption ionisation time‐of‐flight, and indicated different protein–protein interaction in samples, which needs further investigations. [ABSTRACT FROM AUTHOR]

Summary: Norbixin, a carotenoid extracted from the seeds of the annatto (Bixa orellana) plant, can be used in aqueous food applications, where other carotenoids are too hydrophobic to solubilise in a water environment. The aim of this work was to investigate the effect of pH, antioxidants and transition metal ions with and without hydrogen peroxide (H2O2) on the stability of norbixin in aqueous solutions as well as determining the interaction between these factors and light. The stability of norbixin in buffered aqueous solution stored in light or in the dark was evaluated using absorbance spectrophotometry. Light, reduced pH and metal ions both with and without H2O2 increased the bleaching of norbixin, whereas chelators and the natural antioxidants, ascorbic acid and tocopherol, reduced the bleaching of norbixin. Light significantly increased the loss of norbixin alone and in combination with the other factors. [ABSTRACT FROM AUTHOR]

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This study demonstrates a link between the fat crystal network, fracturing behavior, and sound emission upon breakage. SOS, PSO, PPO, and POP rich fats were characterized by SAXS/WAXS and confocal laser scanning microscopy. Simultaneous texture and acoustic analysis was conducted by the use of a texture analyzer connected with an acoustic envelope detector and augmented by a broad band microphone combined with a digital sampling oscilloscope. Results shows a high correlation between negative values of the 2nd derivative of force curves, providing a measure of the energy release, and the sound intensity ( r = 0.89, p < 0.05). No relation between acoustic properties and polymorphic behavior, crystal size, or crystal morphology was found. All fats crystallized into a β′ form within 1 day of storage. Subsequently, only the PPO and POP rich fats transformed into the β form (2-4 wk). Evaluation of the relative strength of intra- and interparticle links within the fat crystal network, indicate an important role of inter-particle links for the sound intensity, whereas intra-particle links were of less importance. It is hypothesized that strong interparticle links provide a strong rigid structure resulting in build-up of energy during compression and a fast energy release upon breakage accompanied by sound emission. Practical applications: Results from this study provide important knowledge on acoustic properties of fat which can contribute to ensuring a suitable snap, in terms of a high intense sound upon breakage, of chocolate and confectionery products. Acoustic properties of fats are important for the snap of chocolate and confectionery products. This study demonstrates how the breakage sound intensity is significantly correlated with the negative part of the second derivate of force curves, which can be related to a rigid structure due to strong intraparticle links. [ABSTRACT FROM AUTHOR]

The aim of the study was to evaluate mussel meal and starfish meals as protein sources for organic layers by studying the effect on production performance, nutrient digestibility and egg quality. A total of 300 Hisex white laying hens (20-week old) were distributed randomly to 6 dietary treatment groups, each with five replicates, including a control diet providing fish meal, 3 diets providing mussel meal (4, 8 and 12 g/100 g) and 2 diets providing starfish meal (4 and 8 g/100 g). Laying rate, egg mass, feed conversion ratio, mortality and live weight of the hens did not differ among treatments. The egg weight was not different from the egg weights of control diets, but the inclusion of 4 g mussel meal resulted in a lower ( P < 0.05) egg weight than 8 g and 12 g mussel meal per 100 g feed. The egg shell strength was not affected by any of the diets. The egg yolk colour was lower ( P < 0.05) in lightness (L*) and higher ( P < 0.05) in redness (a*) for each increase in mussel meal concentration, but was not affected by starfish meal. The albumen dry matter content was not significantly different among diets, whereas the albumen gel fracture stress was lower ( P < 0.05) in eggs from hens fed 4 g mussel meal/100 g diet compared to the starfish diets. Eggs from hens fed 12 g mussel meal/100 g diet showed a fishy smell in the sensory evaluations. The retention of nitrogen was significantly higher in hens receiving 12 g mussel meal and 8 g starfish meal than in control hens ( P < 0.05). Increasing the dietary mussel meal concentrations increased the total tract nitrogen corrected apparent metabolisable energy (AMEn) ( P < 0.001). Diets with 8 g and 12 g mussel meal/100 g diet showed the highest apparent metabolisable energy, whereas the lowest was observed in diets providing 4 and 8 g starfish meals/100 g. The apparent total tract amino acid digestibility was higher ( P < 0.05) in the diets with 8 and 12 g mussel meal and 4 g starfish meal compared with the control diet. Compared to the control diet, the apparent digestibility of methionine was higher ( P < 0.05) in hens fed with 8 and 12 g mussel meal, and the apparent digestibility of lysine was higher in hens fed 4, 8 and 12 g mussel meal and 4 g starfish meal/100 g diet. Fat digestibility was higher ( P < 0.05) in diets with 4, 8 and 12 g mussel meal compared with the control diet. In conclusion, up to 8 g mussel meal and starfish meal per 100 g feed can be used in diets as a high quality protein source for egg production. These meals can replace fish meal; however, an inclusion level higher than 8 g/100 g of mussel or starfish meal may result in a fishy smell of the eggs. [ABSTRACT FROM AUTHOR]

In this study, the impact of high intensity ultrasound (HIU) on proteins in whey protein isolates was examined. Effects on thermal behavior, secondary structure and nature of intra- and intermolecular bonds during heat-induced gelling were investigated. Ultrasonication (24 kHz, 300 W/cm 2 , 2078 J/mL) significantly reduced denaturation enthalpies, whereas no change in secondary structure was detected by circular dichroism. The thiol-blocking agent N-ethylmaleimide was applied in order to inhibit formation of disulfide bonds during gel formation. Results showed that increased contents of α-lactalbumin (α-La) were associated with increased sensitivity to ultrasonication. The α-La:β-lactoglobulin (β-Lg) ratio greatly affected the nature of the interactions formed during gelation, where higher amounts of α-La lead to a gel more dependent on disulfide bonds. These results contribute to clarifying the mechanisms mediating the effects of HIU on whey proteins on the molecular level, thus moving further toward implementing HIU in the processing chain in the food industry. [ABSTRACT FROM AUTHOR]

In this study, the degree of inhomogeneity in crystallized fat samples was evaluated in terms of texture, solid fat content, microstructure, and triacylglycerol (TAG) composition. Four different cocoa butter alternatives based on symmetric or asymmetric monounsaturated TAGs and with different contents of palmitic acid (a POP-rich fat and a PPO-rich fat) and steric acid (a SOS-rich fat and a PSO-rich fat) were studied. Significant differences ( P < 0.001) in hardness between top and bottom was observed for all fats except the PSO-rich fat. The inhomogeneous consistency was shown to be a consequence of microstructural variation within the crystallized fats. No differences in solid to liquid ratio, melting points, or polymorphic behavior between top and bottom of fats were found. Sedimentation during the crystallization process could explain the observed inhomogeneity. Although sedimentation most likely is limited to the early stages of the crystallization process due to network formation, sedimented crystals influence the crystallization kinetics and thus introduce microstructural variations. This hypothesis is supported by findings of a higher amount of trisaturated TAGs in the bottom compared with the top of crystallized fats. The PSO-rich fat crystallizes fast compared with the other evaluated fats, which explains the more homogeneous texture of the PSO-rich fat compared with the other evaluated fats. Practical applications: Fat crystallization plays an important role for the texture of many food products such as chocolates, confectioneries, margarine, and butter. Correct analysis of texture is thus critical when evaluating fats for the food industry. This study emphasizes that inhomogeneity in the consistency could be of practical importance for evaluation of the mechanical and textural properties of crystallized fats for instance by compression tests or small deformation rheological testing of fat samples prepared in molds or with needle penetration tests, which only include the top of a fat sample. This study shows an inhomogeneous consistency of crystallized fat samples due to microstructural variation within the fat. [ABSTRACT FROM AUTHOR]

The initial stage of the Maillard reaction, protein lactosylation, occurs during heat treatment of milk and continues during subsequent storage. We compared the initial lactosylation as well as the rate of lactosylation of milk proteins during storage in UHT milk subjected to direct or indirect heat treatment using liquid chromatography ( LC) coupled with electrospray injection mass spectrometry ( ESI- MS). Furosine content was used as an overall marker to allow for a quantitative correlation of lactosylation measured by LC- ESI- MS in the UHT milks. Protein lactosylation increased during the storage period of 6 months at 20 °C. Both the initial extent and the rate of lactosylation positively correlated with the number of lysine residues in the different proteins. An exponential or linear correlation with furosine concentration could be established for major and minor lactosylated proteins, respectively. [ABSTRACT FROM AUTHOR]

Inthis study, immediate and long-term effects of high intensity ultrasoundon crystallization mechanisms of anhydrous milk fat were examined.Short time (5 s) ultrasound treatment (24 kHz, 300 W/cm2, 17.5 J/mL) of milk fat induced crystallization onset at highertemperatures and a longer temperature interval between the crystallizationof the high and low melting fractions. The solid fat content in ultrasonicatedmilk fat was higher during cooling to 5 °C and for the first20 min of incubation at this temperature. After 20 min, the increasediminished, and during further storage, the solid fat content in theultrasonicated fat remained lower than in the nontreated fat. Ultrasoundtreatment promoted the formation of spherulite structures and a highdegree of size uniformity. Nano- and microscopic changes lead to alteredmacroscopic properties, where a softer and less brittle milk fat materialwas obtained, and the effects were sustained during storage. Theseresults contribute to clarify the mechanisms underlying the effectsof ultrasound treatment on fat crystallization and shed light on thepotential use of ultrasound in the processing chain to tailor productswith desired textural properties. [ABSTRACT FROM AUTHOR]