Polysaccharide–protein interactions in dairy matrices,control and design of structures

Protein–polysaccharide interactions are of great importance in the design of dairy formulations, as they play a key role in the formation of structure and texture in dairy products. With a detailed understanding of the factors affecting the interactions, the ability of charged polysaccharides to associate with the milk proteins is continuously exploited to create functional complexes, novel ingredients and delivery systems. In addition, formulations containing non-interacting polysaccharides also need to be carefully controlled, as these biopolymers may give rise to segregative phase separation, with important consequences to the stability and quality of the final matrix. As casein micelles play a major role in imparting structure to dairy products, emphasis in this review will be given to the molecular details of the interactions between polysaccharides with these protein particles. Some of the most researched polysaccharides will be highlighted in this context, and the progress made in understanding their role during structure formation of dairy matrices will be discussed. The opportunity of creating novel microstructures provided by association or/and incompatibility of milk proteins and different polysaccharides will be assessed.     

Starch–protein interaction in the rumen of weaned dairy calves

The objectives of this study were to investigate the effect of starch and protein interaction on rumen environment, in situ digestion, and total-tract digestibility of nutrients in weaned dairy calves between 8 and 16 wk of age. Sixteen rumen-cannulated calves were randomly divided into 4 dietary treatment groups with 4 calves fed in each treatment. The treatment diets had 2 levels of starch [18%, low starch (LS), or 38%, high starch (HS)] and 2 levels of protein [16%, low protein (LP), or 22%, high protein (HP)] on a dry matter (DM) basis in calf grower: (1) LPLS, (2) LPHS, (3) HPLS, and (4) HPHS. Calves were fed for ad libitum intake (95% assigned grower and 5% grass hay), and refusals were collected weekly. Total-tract digestibility collection and in situ digestibility procedures were performed for each calf at 11 and 15 wk. Samples for in situ digestibility, grass hay (GH), soybean hulls (SBH), wheat middlings (WM), ground corn (GrC), and soybean meal (SBM) were incubated for 9 and 24 h. There was no starch and protein interaction on total-tract digestibility of calves. Total-tract DM, neutral detergent fiber (NDF) and acid detergent fiber (ADF) digestibility, and feed efficiency were affected by both protein and starch inclusion level in calf diet. Total-tract starch digestibility was lower for LS diets. Dry matter digestibility and feed efficiency were greater in calves fed HP and HS diets compared with calves fed LP and LS diets, respectively. Fiber digestibility (NDF and ADF) was less in calves fed HS diets compared with calves fed LS diets but was greater in calves fed HP diets compared with calves fed LP diets. Level of protein did not affect in situ DM and NDF disappearance of GH, but HP increased in situ DM and NDF disappearance of SBH. High-starch diets decreased DM and NDF disappearance of both GH and SBH. At 20 h after feeding, ruminal pH was 0.51 unit higher in calves fed HPHS compared with calves fed LPHS. Total ruminal VFA and proportion of propionate was greater with HS versus LS, whereas proportion of acetate was greater with LS versus HS. The DM disappearance of SBM and WM and NDF disappearance of WM was greater for calves fed HPHS compared with calves fed LPHS at 11 wk of age. In our study, when HP was fed with HS, rumen pH, in situ digestion of WM and SBM, and total-tract digestion of DM, NDF, and ADF increased. This provides evidence for starch–protein interaction in the rumen of recently weaned dairy calves. Improvements in total-tract and in situ digestibility suggest that both protein and starch levels are important for 8- to 16-wk-old calves.     

Symposium review: Host–rumen microbe interactions may be leveraged to improve the productivity of dairy cows

The rumen is a large bioreactor that enables dairy cattle to derive nutrition from otherwise indigestible plant polymers and compounds. Despite the direct contribution of the rumen's microbial community toward the nutrition of the dairy cow, only a general knowledge has been gained of the metabolic processes within the rumen, and less still is known about most of the individual microbial species that colonize the organ. What has been discovered is that the rumen contains a diverse community of microbial species from all of the major domains of life, and that the contents of the rumen can vary greatly among individual animals. Preliminary evidence also indicates that rumen microbial profiles are heritable and sustainable within an individual, and that rumen microbial community structure can revert to its original profile within a short period following substantial perturbation. Much progress has been made in recent years to identify the diversity of microbial species in the rumen; however, the most popular methods used to identify microbial species often lack the predictive power necessary to associate particular microbial profiles with rumen metabolic activity. This represents the most significant barrier to the design of models that can estimate the direct effects of rumen microbial content on downstream dairy production traits. If such challenges can be overcome, it is possible that rumen microbial content could be assessed as a new phenotypic trait in cattle. In the future, we may estimate dairy production using a “genotype × environment × microbial” interaction model that accurately combines all factors affecting milk production.     

Casein–whey protein interactions in heated milk: the influence of pH

Heat-treatment of milk causes denaturation of whey proteins, leading to a complex mixture of whey protein aggregates and whey protein coated casein micelles. In this paper we studied the effect of pH-adjustment of milk (6.9–6.35) prior to heat-treatment on the distribution of denatured whey proteins in aggregates and coating of casein micelles. Proteins were fractionated using an alternative fractionation technique based on renneting. Acid- and rennet-induced gelation of these milks were used to obtain more information on the characteristics of the milk. Acid-induced gelation appeared to be mainly influenced by the presence of whey protein aggregates. Rennet-induced gelation was determined by the whey protein coating of the casein micelles. Both the quantity of whey proteins present on the surface of the casein micelles and the homogeneity of the coating were determining the renneting properties. These results extend the current knowledge on pH dependent casein–whey protein interactions. In order to present a clear picture of the changes occuring during heat treatment of milk at various pH, the results are summarized in a model. In this model we propose that heating at a pH>6.6 lead to a partial coverage of the casein micelles and the formation of separate whey protein aggregates. Heating at a pH<6.6 lead to an attachment of all whey proteins to the casein micelles. At pH 6.55 the coverage is rather homogeneous but lowering the pH further lead to an inhomogeneus coverage of the casein micelles. Surprisingly small changes of the pH at which the milk was heated had considerable effects on the gelation behaviour both in renneting and in acid gelation.     

Consumer perception of ice cream and frozen desserts in the “better-for-you” category

The consumption of ice cream and frozen desserts in the “better-for-you” (BFY) category has grown rapidly over the past few years, even as traditional ice cream sales remain stagnant. To better understand consumer preferences within the BFY category, an online survey (n = 1,051) was conducted with ice cream and frozen dessert consumers, followed by consumer acceptance testing of commercial BFY frozen dairy desserts. Consumers of BFY frozen desserts (n = 578) completed an adaptive choice-based conjoint survey and MaxDiff exercise to identify the attributes that drive purchase of BFY frozen desserts. MaxDiff exercises were also used to determine which attributes all frozen dessert consumers (n = 1,051) perceived to make a frozen dessert BFY and which stabilizers or emulsifiers were most attractive on an ice cream or frozen dessert label. Subsequently, a consumer acceptance test (n = 186) was conducted using 4 commercial vanilla-flavored frozen dairy desserts made with different sweetening systems (sugar, sucralose + acesulfame K, monk fruit + allulose, and stevia + erythritol). Half of consumers were primed or informed with the sweeteners and basic nutritional information for the frozen desserts before tasting, and the other half of consumers evaluated samples blinded, where they were only informed that they were tasting a vanilla-flavored frozen dessert. Sweetener type and base (dairy vs. plant) were the most important attributes to BFY consumers when selecting a BFY frozen dessert (n = 578). For all ice cream and BFY dessert consumers (n = 1,051), sweetener-related claims (naturally sweetened, reduced sugar, no added sugar), along with “all natural” and a short ingredient list, were the top attributes that contributed to perception of a “healthier” frozen dessert. When BFY frozen desserts were tasted by consumers, purchase intent decreased after tasting, suggesting that frozen desserts made with natural non-nutritive sweeteners did not meet consumer expectations. Flavor of BFY frozen desserts remains more important than perceived healthiness. Consumers perceive frozen desserts, even those in the BFY category, as an indulgence. Frozen dessert manufacturers should focus on naturally sweetened, dairy-based desserts with minimal sweetener-related flavor defects when designing products for the BFY category.     

Technical note: Quantification of lignans in the urine,milk, and plasma of flaxseed cake–fed dairy sheep

Mammalian lignans are phytoestrogens with important bioactivities, and their concentrations in livestock milk may influence the health of consumers. This research aimed to establish a method to quantify multiple mammalian lignans in the biofluids of dairy sheep using ultra-HPLC-triple quadropole mass spectrometry with multiple-reaction monitoring. Secoisolariciresinol, 2-[(4-hydroxy-3-methoxyphenyl)methyl]-3-[(3-hydroxyphenyl)methyl]-1,4-butanediol, enterodiol (ED), enterolactone (EL), ED-sulfate (ED-S), and EL-sulfate (EL-S) were purified from the urine of flaxseed cake–fed dairy sheep. The structures of these lignans were identified by a combination of mass and nuclear magnetic resonance spectra. These purified lignans were used as standards to optimize their quantification conditions in urine, milk, and plasma of dairy sheep. On this basis, the lignan metabolites in biofluids were quantified. To improve analysis sensitivity, plasma and milk were pretreated with acetonitrile containing 1% formic acid and passed through a HybridSPE-PL 55261-U column (Supelco, Bellefonte, PA). The limit of quantification of the lignans ranged from 1.43 to 18.3 ng/mL in plasma, and from 1.01 to 18.7 ng/mL in milk. The linearity of the calibration curves ranged from their limit of quantification to at least 217 ng/mL in plasma, and 217 ng/mL in milk. Regression coefficient of the calibration curves were above 0.99 for secoisolariciresinol, 2-[(4-hydroxy-3-methoxyphenyl)methyl]-3-[(3-hydroxyphenyl)methyl]-1,4-butanediol, ED, EL, ED-S, and EL-S, indicating satisfactory relationships between the peak areas and concentrations in the quantification range. The relative concentrations of ED-glucuronide and EL-glucuronide (EL-G) in different biofluids were compared based on their chromatogram peak areas. The sheep plasma contained all forms of mammalian lignans (i.e., ED, EL, ED-S, EL-S, ED-glucuronide, and EL-G.); the urine contained ED, EL, ED-S, and EL-S; and the milk contained ED, EL, ED-S, EL-S, and EL-G. Milk-to-plasma concentration ratios of the mammalian lignans indicated that the free forms were more permeable than the sulfated conjugates. Mammalian lignans found in sheep plasma and milk may provide health benefits to the sheep and sheep-product consumers. The analytical method established in this work could be used to quantify mammalian lignans in livestock products.     

Mycoplasma bovis infection in dairy herds—Risk factors and effect of control measures

As Mycoplasma bovis spreads to new countries and becomes increasingly recognized as a disease with major welfare and economic effects, control measures on dairy farms are needed. To minimize the risk of infection spread to naive herds, all possible risk factors for M. bovis infection should be identified and controlled. Mycoplasma bovis was first diagnosed in dairy cattle in Finland in 2012, and by January 2020, 86 Finnish dairy farms (<1.5%) supporting M. bovis infections were identified. We evaluated risk factors for M. bovis infection using a questionnaire provided to 40 infected and 30 control dairy farms. Control measures were advised for 19 of the infected dairy farms during visits by a veterinarian. The course of the infection on those farms was followed by analyzing calf nasal swabs with PCR for presence of M. bovis 4 times at 6-mo intervals. Control measures included culling of M. bovis mastitic cows, isolation of new calves from older animals after initial M. bovis mastitic cows had been culled, prevention of nose-to-nose contact with infected animals, early detection of mastitis cases using M. bovis PCR, and hygiene measures mainly related to milking, calf pens, feeding buckets, and teats. Farms implemented the control measures related to the isolation of calves or avoidance of nose-to-nose contact in various ways, according to farm structures and financial circumstances. In our study, the control measures recommended to the dairy farms appeared effective, such that 13 of 19 farms reached a low risk level during at least 3 consecutive negative samplings from calves, with no M. bovis mastitis detected subsequently. Among risk factors, insemination with an M. bovis-positive bull indicated a trend of increasing the odds of M. bovis infection on the farm in a multivariable logistic model. In contrast, higher herd average milk yield had an association with lower odds for M. bovis infection. Occurrence of other infectious diseases affecting several animals on the dairy farm in the previous 6 mo before M. bovis infection were more frequent on M. bovis-infected farms.     

Water–disaccharides interactions in saturated solution and the crystallisation conditions

This paper reports solubility data and measurements of viscosity of the saturated aqueous solutions of sucrose, maltitol, and trehalose. Likewise, the metastable zone width and velocity of nucleation of the three disaccharides are compared. The narrowest metastable zone is observed for maltitol and the largest for trehalose. Such behaviour is due to a higher affinity of trehalose for water. Moreover, the crystallisation of anhydrous disaccharides in aqueous solution necessitates that hydration water be removed and evacuated from crystal integration surface to the bulk of solution to allow the growth of crystals. This step of disassociation and diffusion of hydration water proves to be the controlling step of the crystallisation process. Structural features at the origin of the differences between the three sugars are studied by FTIR spectroscopy. Modifications of frequencies and intensities of the vibrations around the glycosidic bond are interpreted in terms of conformational flexibility. Arguments like H-bond strength or conformational flexibility of the two monomers around the glycosidic oxygen were evoked as possible explanations of the behaviour of disaccharides. Likewise stability of hydration of the disaccharides is derived from the interpretation of FTIR spectra. These structural features help in interpreting the differences in crystallisation conditions and to hypothesize about the cryoprotective ability of the studied molecules.     

Sweet–bitter interactions and the solution properties of chlorinated sugars

Among chlorinated sugars, some are intensely sweet, some are bitter and others are tasteless. Although chlorination of sugars provokes an increase in lipophilicity, a certain hydrophilic/lipophilic balance is needed for sweeteners to be perceived. Two chlorinated sugars, sucralose (trichlorogalactosucrose) and methyldichlorogalactoside, respectively known for their enhanced sweetness (650×) and inhibitory effect on the sweetness of sucrose, are studied. Their sapid properties are interpreted on the basis of their physicochemical properties (intrinsic viscosity, apparent specific volume, surface tension, contact angle and vibrational spectra). It is particularly shown that the perturbation of the structure of water by these molecules, compared with that by simple sugars, helps in understanding their taste mechanism.     

Influence of buffer type and concentration on the peptide composition of trypsin hydrolysates of β-lactoglobulin

Proteins acquire conformation in aqueous media due to the influence of the buffer salt composition and concentration. Such influence may have impact on the enzyme–substrate interaction and somehow steer the enzyme attack properties, leading to release of dissimilar products. Our group has sought to investigate the influence of the hydrolysis environment on the trypsinolysis of a model protein, β-lactoglobulin (β-Lg). This work was aimed at investigating the effect of different buffers and their concentrations on the trypsinolysis patterns of β-Lg. The traditional NaOH-buffered water, in comparison to Tris–HCl and potassium-phosphate buffer at 62.5 mM–1.0 M were used at pH 8.5 for the pH drop and pH 7.8 for the hydrolysis. Bovine trypsin (EC 3.4.21.4) was used at an enzyme-to-substrate ratio of 1%. The samples were analysed for mass composition, using LC-ESI-TOF/MS and MALDI-TOF/MS for monitoring time-dependence of peptide evolution. In all buffer types and concentrations, peptides f(1–8), f(15–40, f(125–138) and f(142–148) were detected, implicating ease of hydrolysis of the terminal regions of β-Lg. A peptide from f(9–14), with sequence Gly-Leu-Asp-Ile-Gln-Lys, was detected at >0.5 M Tris–HCl only, while peptide f(71–75) was unique to <125 mM Tris–HCl and >250 mM potassium-phosphate buffer. Hydrolysis under buffer produced trypsin-specific peptides, numerous chymotrypsin-like non-specific peptides but no disulphide-linked peptides. Trypsinolysis shifted to the N-terminal region of lysine under some conditions. Hydrolysis under buffer holds potential for the avoidance of some peptides with undesirable characteristics while preserving a diversity of different peptides with possible bioactive properties.     

Effect of ionising radiation treatment on the specific migration characteristics of packaging–food simulant combinations: effect of type and dose of radiation

Migration levels of acetyl tributyl citrate (ATBC) plasticiser from polyvinyl chloride (PVC) film into the European Union specified aqueous food simulants (distilled water, 3% w/v acetic acid and 10% v/v ethanol) were monitored as a function of time. Migration testing was carried out at 40°C for 10 days. Determination of the analyte was performed by applying an analytical methodology based on surfactant (Triton X-114) mediated extraction prior to gas chromatographic-flame ionisation detection. PVC cling film used was subjected to ionising treatment with a [⁶⁰Co] source, as well as to electron-beam irradiation at doses equal to 5, 15 and 25 kGy, with the aim to compare the effect of type and dose of radiation on the specific migration behaviour of PVC. Equilibrium concentrations of acetyl tributyl citrate into the aqueous solvents covered the ranges 173–422?µg?l^?1 and 296–513?µg?l^?1 for gamma- and electron-irradiated PVC, respectively. Hence, e-beam irradiation resulted in significantly higher ATBC migration compared with gamma treatment. The highest extraction efficiency of the 10% ethanol solution was common in both gamma and e-beam treatments; distilled water demonstrated the lowest migration. Gamma-irradiation at intermediate doses up to 5 kGy produced no statistically significant (p?>?0.05) effect on ATBC migration into all three aqueous simulants; however, this does not apply for high-energy electrons. Both ionising treatments were similar in that they resulted in statistically significant (p?<?0.05) differences in plasticiser migrating amounts between non-irradiated and irradiated at doses of 15 and 25 kGy samples. Gamma-radiation did not affect the kinetics of plasticiser migration. On the contrary, electron-beam radiation produced shorter equilibration times for all food-simulating solvents tested at 40°C. The above values regarding ATBC migration into aqueous food simulants are far below the European Union restriction (1?mg?kg^?1 body weight) for both types of ionising radiation. Thus, PVC cling film may be used in food irradiation applications in contact with aqueous foodstuffs.     

Aroma–taste interactions between a model cheese aroma and five basic tastes in solution

The flavour perception of cheese results from complex sensory interactions between tastes and aromas. Using a model cheese solution, this study investigated perceived interactions between each of five basic tastes and a cheese aroma mixture containing ten volatile compounds commonly found in cheese. The five tastes – sucrose (sweetness), sodium chloride (NaCl) (saltiness), monosodium glutamate (MSG) (umami), lactic acid (sourness), and caffeine (bitterness) – were individually mixed with cheese aroma in water using a 5 taste level (0.2 log series) by 3 aroma level (0.5 log series) design. Aroma controls with no added taste were also included. This resulted in 18 samples for each single taste–aroma combination. An additional 18 samples were produced using a mixture of all 5 tastes with the 3 aroma levels. A panel of trained assessors (n = 10) evaluated cheese flavour intensity and taste intensity using 100 point line scales. Evaluation was carried out in duplicate, with samples grouped by taste type; 1 evaluation session per taste per replicate. Within type, order of presentation was balanced, and taste type order was randomised between replicates. Cheese flavour intensity was enhanced by sucrose and NaCl, while being suppressed by lactic acid. NaCl enhanced cheese flavour intensity the most at high aroma level, while lactic acid suppressed the most at low aroma level. When MSG level was increased, cheese flavour intensity was enhanced at both low and medium aroma levels, but was suppressed at the high aroma level. The greatest enhancement of cheese flavour intensity was found with the mixture of 5 tastes. Aroma significantly enhanced umami and bitterness, but did not enhance sweetness, saltiness, or sourness. This study showed that the perceived interaction between taste and cheese aroma depended on taste type and on the concentration levels of both taste type and aroma. The mixture of tastes was more effective at enhancing cheese flavour intensity than single tastes. This study provides knowledge that will underpin further study of taste–aroma interactions in a model cheese that aims to optimise cheese flavour intensity and character.     

The effect of protein concentration and heat treatment temperature on micellar casein–soy protein mixtures

The objective of this study was to investigate the effect of concentration and temperature on the rheological properties of soy proteins (SP) and micellar casein (MCN) systems. Individual and mixed (1:1) protein systems of 2–15% concentration were prepared and heat treated for 5 min at 40–90 °C. After cooling to 20 °C, their rheological properties were determined using steady-shear rheology. Zeta potential and particle size measurements were also conducted. Both proteins were negatively charged under all experimental conditions, but the absolute values of zeta potential and thus the stability of the protein solutions decreased with temperature and concentration. For SP solutions, viscosity and apparent yield stress increased with concentration. Shear thinning behavior was prevalent, becoming more pronounced with increasing concentration. Heat treatments at T ≥ 80 °C induced glycinin denaturation, followed by aggregation and network formation when C ≥ 7.5%. Heat treatment did not significantly affect viscosity of MCN systems, while increasing concentration resulted in a significant increase in apparent viscosity and apparent yield stress. Most MCN systems exhibited Newtonian flow behavior, with the exception of systems with C ≥ 12.5% treated at T ≥ 80 °C, which became slightly shear thickening. Mixed SP–MCN systems mimicked the behavior of SP, with most values of rheological parameters intermediate between SP and MCN-only systems. Mixtures of 7.5–12.5% concentration treated at 90 °C displayed local phase separation, low viscosity and apparent yield stress, while 15% mixtures treated at 90 °C showed protein aggregation and incipient network formation. The data generated in this study can be used to develop a range of protein based products with unique flow characteristics and storage stability.     

Pectinesterase activity and the texture of Jalapeño pepper

Jalapeño pepper (Capsicum annuum), a vegetable used in many Mexican dishes, is usually blanched at 90°C for 1–5 min to inactivate enzymes that degrade its quality when it is subsequently canned in vinegar. But this process affects its texture which is undesirable. Food technologists have experienced great difficulty in processing foods so that they closely simulate native foods. The turgor that provides much of the crispness of fresh fruit and vegetables arises from the physiological activity of the living tissue. Pectinesterase (PE) is an enzyme in vegetable tissue that demethyloxylates pectins. This reaction allows interaction of carboxylic groups with calcium ions in the tissue, producing calcium pectates, which impart a firmer texture to the tissue. The main objective of this work was to improve the textural attributes of Jalapeño pepper by means of in situ thermal activation of PE. The temperatures tested were 60 and 65°C over 20, 40, and 60 min. PE activity (Kertesz method), texture (puncture with flat-end punch), and color (parameters L, a, b) were determined. The results indicated that maximum PE activity was achieved when the pepper was immersed in distilled water at 60°C for 40 and 60 min (27.9 and 29.5 U/mL, respectively). The highest resistance force to the puncture test was obtained in the sample treated at 60°C for 40 min (1.83±0.3 kg-f, approximately 6% more than untreated pepper). Pepper treated in this manner also showed the least variation in color (L, +2.64; a, –0.61; b, +3.07) with respect to the untreated control (L, +0.52, a, –0.16, b, +0.61). These results indicate that thermal activation of Jalapeño pepper at 60°C for 40 min enhances the PE activity and thus the firmness of the vegetal tissue, and preserves its original color better than the other pre-treatments.     

Does iodine supplementation of the prepartum dairy cow diet affect serum immunoglobulin G concentration,iodine, and health status of the calf?

Absorption of adequate IgG from colostrum is critical to provide the newborn calf with adequate immunological protection and resistance to disease. Excessive iodine supplementation of the prepartum ewe reduces IgG absorption of her offspring; it is possible that excessive iodine supplementation of the prepartum dairy cow may similarly impair the ability of the calf to acquire immunological protection. The objectives of this study were to determine whether the iodine status, health status, and ability of calves to absorb IgG from colostrum were affected by prepartum iodine supplementation strategies of their dams. Dairy cows (n = 127) received one of the following levels of iodine supplementation precalving: 15 mg of iodine/kg of dietary dry matter (DM) (HI); no additional iodine supplementation (MI); 5 mg/kg of dietary DM (SI); and 15 mg of iodine/kg of DM for the first 3.5 wk of the precalving period and no additional supplementation for the second 3.5 wk (HMI). Calves were assigned to 1 of 6 experimental treatments, based on the prepartum iodine supplementation treatment of their dam and the precalving treatment group of the cows from which the colostrum fed was obtained: (1) HI_HI: born to HI dams, fed HI colostrum (i.e., colostrum produced by cows in the HI group); (2) MI_MI: born to MI dams, fed MI colostrum; (3) SI_SI: born to SI dams, fed SI colostrum; (4) HI_MI: born to HI dams, fed MI colostrum; (5) MI_HI: born to MI dams, fed HI colostrum; and (6) HMI_HMI: born to HMI dams, fed HMI colostrum. Concentration of calf serum IgG and plasma inorganic iodine (PII) was measured at 0 and 24 h of age. Apparent efficiency of absorption for IgG was determined. Health scores were assigned to calves twice weekly and all episodes of disease were recorded. Cow experimental treatment group affected calf PII at 0 h of age; the PII of calves born to HI dams (987.2 µg/L) was greater than that of calves born to MI dams (510.1 µg/L), SI (585.2 µg/L), and HMI dams (692.9 µg/L). Calf experimental treatment group affected calf PII at 24 h of age; the PII of HI_HI (1,259.2 µg/L) and HI_MI (1,177.8 µg/L) calves was greater than MI_MI (240.7 µg/L), SI_SI (302.2 µg/L), HMI_HMI (320.7 µg/L), and MI_HI (216.3 µg/L) calves. No effect of experimental treatment was observed on the concentration of IgG measured in calf serum at 24 h of age, or on apparent efficiency of absorption. Experimental treatment had no effect on the likelihood of a calf being assigned a worse nasal, eye and ear, cough, or fecal score within the study period, nor did it affect the probability of a calf receiving treatment for a disease a greater number of times. Prepartum iodine supplementation of cows at 15mg/kg of DM increased the iodine levels in their calves at birth and 24 h of age, but did not affect their ability to absorb IgG from colostrum. Supplementation with iodine above the minimum requirements established by the National Research Council was unnecessary to ensure appropriate iodine levels in calves at birth.     

Changes in the expression of α-tocopherol-related genes in liver and mammary gland biopsy specimens of peripartum dairy cows

Blood α-tocopherol (α-Toc) concentrations decline gradually throughout the prepartum period, reaching the nadir after calving in dairy cows. The 6 α-Toc–related molecules [α-Toc transfer protein (TTPA); afamin; scavenger receptor class B, Type I; ATP-binding cassette transporter A1; tocopherol-associated protein (SEC14L2); and cytochrome P450 family 4, subfamily F, polypeptide 2 (CYP4F2)] are expressed in liver and other peripheral tissues. These molecules could regulate α-Toc transport, blood concentrations, and metabolism of α-Toc. Therefore, the aim of this study was to evaluate the changes in the expression of α-Toc–related genes in liver and mammary gland tissues of dairy cows around calving, which have remained elusive until now. In experiment (Exp.) 1, 28 multiparous Holstein cows were used (from ?5 to 6 wk relative to parturition) to monitor the changes in dietary α-Toc intake, blood concentrations of α-Toc, and lipoproteins; in Exp. 2, 7 peripartum Holstein cows were used (from ?4 to 4 wk relative to parturition) for liver tissue biopsy; and in Exp. 3, 10 peripartum Holstein cows were used (from ?8 to 6 wk relative to parturition) to carry out the mammary gland tissue biopsy and milk sampling. In Exp. 1, the serum α-Toc concentrations declined gradually with decreasing amount of α-Toc intake and plasma high-density lipoprotein concentrations toward calving time. However, in the early lactation period after calving, serum α-Toc concentrations remained at a lower concentration despite the recovery of α-Toc intake and plasma high-density lipoprotein concentrations. In Exp. 2, just after calving, the TTPA, SEC14L2, afamin, and albumin mRNA expression levels in the liver were temporarily downregulated, and the hepatic mRNA levels of endoplasmic reticulum stress-induced unfolded protein response markers and acute-phase response marker increased at calving. In Exp. 3, the concentrations of α-Toc in colostrum were greater than those in precolostrum (samples were collected at wk ?1 relative to parturition) and mature milk. The expression of TTPA, SEC14L2, and CYP4F2 mRNA in bovine mammary gland tissue was detected. However, TTPA and SEC14L2 mRNA expressions showed the opposite trends: the expression levels of TTPA mRNA peaked whereas SEC14L2 mRNA reached a nadir at calving. These results indicate that the expression of α-Toc–related genes involved in specific α-Toc transfer and metabolism in the liver and mammary gland are altered during calving. Moreover, these changes might be associated with the maintenance of lower serum α-Toc concentrations after calving.     

Secondary adsorption of milk proteins from the continuous phase to the oil–water interface in dairy emulsions

Low protein surface concentration emulsions are susceptible to secondary protein adsorption where protein moves from the continuous phase to the existing, oil–water interface. The resulting increase in protein surface concentration can greatly alter emulsion properties. Butteroil was emulsified with whey proteins and the emulsion was combined with a solution of dissolved skim milk powder (SMP), producing mixes with fat and protein levels representative of ice cream. The primary adsorbed layer was modified by heating the whey protein solution prior to emulsion formation (70°C, 80°C, 90°C), by heating the emulsion (70°C, 80°C, 90°C) or by pH adjustment of the emulsion (6–8). Modifications of the SMP solution included heat treatment (80°C, 95°C) or sugar addition with or without κ-carrageenan. The effect of addition of SMP solution on the protein surface concentration and shear stability of the diluted emulsions was determined. Addition of untreated solution to the control, heated or pH adjusted emulsions greatly reduced shear destabilization and increased the protein surface concentration. Addition of heat treated or sugar containing SMP solution to the control emulsion produced the same result. However, sugar and carrageenan in the mix maintained the susceptibility to partial coalescence and reduced the secondary adsorption of caseins and whey proteins.