The impact of viscosity on emulsion stability at pH 2 using 1% (w/w) rapeseed oil (RSO) with 0.2 ... more The impact of viscosity on emulsion stability at pH 2 using 1% (w/w) rapeseed oil (RSO) with 0.2 and 2% (w/w) whey protein concentrate (WPC) and 0.1 % (w/w) chitosan (CH) during 1 and 16 days of storage was investigated. The droplet size values obtained by image analysis were correlated with the viscosity values. All the emulsions behaved like non-Newtonian fluids, having shearthickening characteristics, as the flow behaviour index values were larger than 1. A reduction in emulsion droplet size from 2.24 (2% WPC) to 0.95 μm (2% WPC, 0.1% CH) was observed when chitosan was added to the emulsions containing WPC (day 1). Addition of chitosan to WPC-emulsions caused about 20% relative increase in the viscosity. An increase in viscosity with a decrease in droplet size was observed. During the storage for up to 16 days, no water separation of WPCchitosan emulsions was noticed, indicating that the stability of these emulsions was maintained at 4 oC. The stability observations were related ...
The effect of type of emulsifier, 2 w/w% whey protein concentrate (WPC) or 2 w/w% WPC and 0.1 w/w... more The effect of type of emulsifier, 2 w/w% whey protein concentrate (WPC) or 2 w/w% WPC and 0.1 w/w% chitosan (CH) on the rheological changes and droplet size distribution during the ex vivo digestion of oil in water emulsions (pH 2) containing 1 w/w% rapeseed oil (RSO) were investigated. The procedure was used to mimic the human gastro duodenal digestion in two steps, gastric phase at pH 2 for 30 min followed by the duodenal phase at pH 7 for 60 min. With regard to viscosity, the emulsion, either WPC or WPC-CH showed an increase from gastric phase to duodenal phase (p<0.001) and then it was stable until the end of digestion. The viscosity of WPC-CH emulsions during the whole digestion (with/without added HGJ/HDJ) process was higher than the respective WPC emulsions. At pH 7 (duodenal juice addition), the droplet diameters stabilized by WPC emulsion showed a bimodal distribution with droplet sizes in the range of 0.05-1.7 µm and 200-500 µm. A significant change (p<0.01) in the o...
The objective of the present study was twofold: first to compare the degradation patterns of capr... more The objective of the present study was twofold: first to compare the degradation patterns of caprine whey proteins digested with either human digestive juices (gastric or duodenal) or commercial porcine enzymes (pepsin or pancreatic enzymes) and second to observe the effect of gastric pH on digestion. An in vitro two-step assay was performed at 378C to simulate digestion in the stomach (pH 2, 4 or 6) and the duodenum (pH 8). The whey proteins were degraded more efficiently by porcine pepsin than by human gastric juice at all pH values. Irrespective of the enzyme source, gastric digestion at pH 2 followed by duodenal digestion resulted in the most efficient degradation. Lactoferrin, serum albumin and the Ig heavy chains were highly degraded with less than 6 % remaining after digestion. About 15, 56 and 50 % Ig light chains, b-lactoglobulin (b-LG) and a-lactalbumin remained intact, respectively, when digested with porcine enzymes compared with 25, 74 and 81 % with human digestive juices. For comparison, purified bovine b-LG was digested and the peptide profiles obtained were compared with those of the caprine b-LG in the digested whey. The bovine b-LG seemed to be more extensively cleaved than the caprine b-LG in the whey. Commercial enzymes appear to digest whey proteins more efficiently compared with human digestive juices when used at similar enzyme activities. This could lead to conflicting results when comparing human in vivo protein digestion with digestion using purified enzymes of non-human species. Consequently the use of human digestive juices might be preferred.
This study was conducted in Ethiopia on four goat breeds: Arsi-Bale, Somali, Toggenburg-Arsi-Bale... more This study was conducted in Ethiopia on four goat breeds: Arsi-Bale, Somali, Toggenburg-Arsi-Bale cross and Boer to assess milk yield and composition at different lactation stages, for the suitability of the milk for cheese production. Milk yield was measured once per week and milk samples were collected three times during the lactation period. Total solids, fat, protein, casein, whey-protein, non-protein nitrogen (NPN), lactose and minerals, (calcium, phosphorus, magnesium, potassium, sodium, zinc and iron) were analyzed. A higher daily milk yield, 1.41 kg, was recorded for Boer goats (P < 0.05), compared to 1.13, 0.93 and 0.85 kg produced by Arsi-Bale, Cross and Somali goats, respectively. Milk from Cross was lower in total solids 13.9% and fat 3.7% (P < 0.001), than Arsi-Bale, Boer and Somali which had 16.3, 15.4 and 14.5% total solids and 5.2, 4.7 and 4.9% fat, respectively. Arsi-Bale goats had significantly higher protein content, 4.8% (P < 0.001) than the rest of the breeds. Lactose content of milk was high in all goat breeds, 4.9% with no significant difference between them. Early and late lactation milk had significantly higher contents (P < 0.001) of milk components. Milk from all breeds was high in calcium, phosphorous and potassium: 1.62, 1.39 and 1.69 g kg −1 , respectively and Fe and Zn: 5.47 and 0.36 mg kg −1 , respectively. Superior chemical composition revealed the potential of milk from indigenous Ethiopian goats for cheese production.
Goat milk contributes significantly to human nutrition and has been used in functional food appli... more Goat milk contributes significantly to human nutrition and has been used in functional food applications in many parts of the world. Among the components in milk, lactoferrin (Lf) is a multifunctional glycoprotein that plays an important role in immune regulation and defence mechanisms against bacteria, fungi and viruses. The biological activity may be affected by thermal treatment during industrial processes. The production and content of Lf in milk from different species seems to vary a lot. This study aims to compare the thermal stability and structural differences in bovine (Blf) and caprine Lf (Clf) under conditions such as pH and iron content. The X-ray crystallography investigation has shown the presence of alpha helical and beta sheet contents to different degrees in Lf among both species which upholds stability to the molecule. In addition, the iron saturation was found to be important in Lf structure and stability. In the present investigation an attempt has been made to a...
This short review presents the developments in genetic improvement of Ethiopian goat breeds and t... more This short review presents the developments in genetic improvement of Ethiopian goat breeds and the impact of the crossbreeding programs on ␣s1-CN gene (CSN1S1). The influence of newly identified mutations on milk components and technological properties are considered. The indigenous Ethiopian goat breeds are low milk yielders with high percentage of milk organic component and thus with good technological properties. Crossbreeding programs were taken as an option to improve their genetic potential. The main objective of crossbreeding programs in Ethiopia were to increase milk yield and thus, to enhance protein consumption at household level. The success of crossbreeding programs was impaired due to high input requirements, incompatibility of the genotype with the farmers breeding objectives and the production system, owing mainly to less net benefit than expected from the crossbreeding. Evaluation of CSN1S1 gene revealed 36 mutations, which were not previously reported. Four of these mutations were detected in the exon region of CSN1S1: two synonymous (exons 4 and 12), one non-synonymous (exon 10) and a nonsense mutation (exon 15). The non-synonymous mutation was detected only in the indigenous goats and their crosses with exotic Boer goats. It involved amino acid exchange Gln77→Pro77. Goats carrying this mutation have higher ␣s1-CN, fat and protein content and good coagulation properties with exceptionally high gel strength. The nonsense mutation involved a transversion, at amino acid position Gln140, CAG→TAG giving rise to a premature stop codon. The mutation was found in three crossbred goats between the exotic Toggenburg buck and the local Arsi-Bale does. This mutation was not detected in any of the local goat breeds and therefore, we assume it originates from the exotic parent. The lesson is the need for careful evaluation of the exotic genes for milk quality in bucks chosen for crossbreeding programs, prior to introduction.
Very high casein content and good coagulation properties previously observed in some Ethiopian go... more Very high casein content and good coagulation properties previously observed in some Ethiopian goat breeds led to investigating the α s1 -casein (CSN1S1) gene in these breeds. Selected regions of the CSN1S1 gene were sequenced in 115 goats from 5 breeds (2 indigenous: Arsi-Bale and Somali, 1 exotic: Boer, and 2 crossbreeds: Boer × Arsi-Bale and Boer × Somali). The DNA analysis resulted in 35 new mutations: 3 in exons, 3 in the 5 untranslated region (UTR), and 29 in the introns. The mutations in exons that resulted in an amino acid shift were then picked to evaluate their influence on individual casein content (α s1 -, α s2 -, β-, and κ-CN), micellar size, and coagulation properties in the milk from the 5 goat breeds. A mutation at nucleotide 10657 (exon 10) involved a transversion: CAG→CCG, resulting in an amino acid exchange Gln 77 →Pro 77. This mutation was associated with the indigenous breeds only. Two new mutations, at nucleotide 6072 (exon 4) and 12165 (exon 12), revealed synonymous transitions: GTC→GTT in Val 15 and AGA→AGG in Arg 100 of the mature protein. Transitions G→A and C→T at nucleotides 1374 and 1866, respectively, occurred in the 5 UTR, whereas the third mutation involved a transversion T→G at nucleotide location 1592. The goats were grouped into homozygote new (CC), homozygote reference (AA), and heterozygote (CA) based on the nucleotide that involved the transversion. The content of α s1 -CN (15.32 g/kg) in milk samples of goats homozygous (CC) for this newly identified mutation, Gln 77 →Pro 77 was significantly higher than in milks of heterozygous (CA; 9.05 g/kg) and reference (AA; 7.61 g/kg) genotype animals. The α s2 -, β-, and κ-CN contents showed a similar pattern. Milk from goats with a homozygous new mutation had significantly lower micellar size. Milk from both homozygote and heterozygote new-mutation goats had significantly shorter coagulation rate and stronger gel than the reference genotype. Except the transversion, the sequence corresponded to allele A and presumably derived from it. Therefore, this allele is denoted by A 3 . All goats from the reference genotype (AA) were homozygous for the allele at nucleotide position 1374 and 1866, whereas all mutations in the 5 UTR existed in a heterozygous form in both heterozygous (CA) and the new mutation (CC) genotype. The newly identified mutation (CC) detected in some of the goat breeds is, therefore, important in selection for genetic improvement and high-quality milk for the emerging goat cheese-producing industries. The finding will also benefit farmers raising these goat breeds due to the increased selling price of goats. Further studies should investigate the effect of this amino acid exchange on the secondary and tertiary structure of the α s1 -CN molecule and on the susceptibility of peptide hydrolysis by digestive enzymes. Figure 3. Principal components (PC) analysis plot of different genotypes, caseins, micellar size, proteins, and TS. Gr = group; BR = Boer reference genotype; AN = Arsi-Bale new mutation; SN = Somali new mutation; ANZ = Boer × Arsi-Bale cross heterozygote; SHZ = Boer × Somali cross heterozygote.
Lactoferrin (LF) is a protein present in milk and other body fluids that plays important biologic... more Lactoferrin (LF) is a protein present in milk and other body fluids that plays important biological roles. As part of a diet, LF must survive gastrointestinal conditions or create bioactive fragments to exert its effects. The degradation of LF and formation of bioactive peptides is highly dependent on individual variation in intraluminal composition. The present study was designed to compare the degradation and peptide formation of bovine LF (bLF) following in vitro digestion under different simulated intraluminal conditions. Human gastrointestinal (GI) juices were used in a 2-step model digestion to mimic degradation in the stomach and duodenum. To account for variation in the buffering capacity of different lactoferrin-containing foods, gastric pH was adjusted either slowly or rapidly to 2.5 or 4.0. The results were compared with in vivo digestion of bLF performed in 2 volunteers. High concentration of GI juices and fast pH reduction to 2.5 resulted in complete degradation in the gastric step. More LF resisted gastric digestion when pH was slowly reduced to 2.5 or 4.0. Several peptides were identified; however, few matched with previously reported peptides from studies using nonhuman enzymes. Surprisingly, no bovine lactoferricin, f(17-41), was identified during in vitro or in vivo digestion under the intraluminal conditions used. The diversity of enzymes in human GI juices seems to affect the hydrolysis of bLF, generating different peptide fragments compared with those obtained when using only one or a few proteases of animal origin. Multiple sequence analysis of the identified peptides indicated a motif consisting of proline and neighboring hydrophobic residues that could restrict proteolytic process-ing. Further structure analysis showed that almost all proteolytic cutting sites were located on the surface and mainly on the nonglycosylated half of lactoferrin. Digestion of bLF by human enzymes may generate different peptides from those found when lactoferrin is digested by nonhuman enzymes. The degradation of LF in the GI tract should be taken into consideration when health effects are proposed, because LF has now been approved by the European Food Safety Authority as a dietary supplement in food products.
A rapid spectroscopic method to determine total protein in bovine and buffalo milk using UV spect... more A rapid spectroscopic method to determine total protein in bovine and buffalo milk using UV spectra of guanidine-hydrochloride mixed milk has previously been reported and validated. The method was based on mixed calibration samples and univariate calibrations of fourth derivative (4D) spectra. In this study the same method was compared and tested for determination of total protein in goat milk. Calculations based on multivariate calibration (partial least squares regression) on full spectra of goat milk were used. The method was tested on 2 UV instruments. The comparison resulted in a significantly more robust (i.e., better) transferability between UV instruments for the partial least squares regression method on full spectra compared with previous univariate calibration of 4D spectra. Local (1 instrument) calibrations gave similar, significantly not different (chi-squared test) cross-validated prediction error results for the 2 methods. It can be concluded that there is no need for fourth derivation. Partial least squares regression on full spectra was equal or superior to using the 4D spectra.
The economic output of the dairy industry is to a great extent dependent on the processing of mil... more The economic output of the dairy industry is to a great extent dependent on the processing of milk into other milk-based products such as cheese.
In this study, we analysed the impact of carboxymethylcellulose (CMC) on lipid digestion and phys... more In this study, we analysed the impact of carboxymethylcellulose (CMC) on lipid digestion and physicochemical properties of whey proteins (WP)-stabilised emulsions during in vitro digestion with either artificial or human gastrointestinal juices. The emulsions were made by adsorbing WP on the fat droplets and subsequently adding CMC, which does not interact with the adsorbed proteins. The limited hydrolysis of lipids and their higher physical stability was recorded for WP-stabilised emulsions in the presence of CMC under simulated gastrointestinal conditions. The possible mechanism by which CMC lowers the digestion of WP-stabilised emulsions is related to the limited interaction of fat droplets with gastrointestinal fluids due to the extended thickening network formed by CMC in the continuous phase. The digestion of WP- and CMC-stabilised emulsions in the in vitro model with human gastric fluids led to greater lipid hydrolysis, although the enzymatic activity in both in vitro models ...
The objective of the present study was twofold: first to compare the degradation patterns of capr... more The objective of the present study was twofold: first to compare the degradation patterns of caprine whey proteins digested with either human digestive juices (gastric or duodenal) or commercial porcine enzymes (pepsin or pancreatic enzymes) and second to observe the effect of gastric pH on digestion. An in vitro two-step assay was performed at 378C to simulate digestion in the stomach (pH 2, 4 or 6) and the duodenum (pH 8). The whey proteins were degraded more efficiently by porcine pepsin than by human gastric juice at all pH values. Irrespective of the enzyme source, gastric digestion at pH 2 followed by duodenal digestion resulted in the most efficient degradation. Lactoferrin, serum albumin and the Ig heavy chains were highly degraded with less than 6 % remaining after digestion. About 15, 56 and 50 % Ig light chains, b-lactoglobulin (b-LG) and a-lactalbumin remained intact, respectively, when digested with porcine enzymes compared with 25, 74 and 81 % with human digestive juices. For comparison, purified bovine b-LG was digested and the peptide profiles obtained were compared with those of the caprine b-LG in the digested whey. The bovine b-LG seemed to be more extensively cleaved than the caprine b-LG in the whey. Commercial enzymes appear to digest whey proteins more efficiently compared with human digestive juices when used at similar enzyme activities. This could lead to conflicting results when comparing human in vivo protein digestion with digestion using purified enzymes of non-human species. Consequently the use of human digestive juices might be preferred.
Milk from 94 Ethiopian goats (four breeds) was assessed for casein level, micellar size, coagulat... more Milk from 94 Ethiopian goats (four breeds) was assessed for casein level, micellar size, coagulation properties and whey syneresis to evaluate cheese-making potential. Casein content (g/kg) ranged from 6.84 to 8.94 (␣ s1 ); 4.16-4.98 (␣ s2 ); 12.51-15.37 () and 6.89-8.93 (). Arsi-Bale goats had the highest ␣ s1 -casein (8.94 g/kg) followed by the Somali goats (7.90 g/kg); and were higher than Boer (7.05 g/kg) and Cross (6.84 g/kg) (P < 0.001). Milk from Arsi-Bale and Somali goats had significantly (P < 0.05) smaller micelles; 207.47 and 209.29 nm respectively than Boer (230.30 nm) and Cross (228.71 nm). Significantly stronger gels (P < 0.05) were obtained from milk samples with higher ␣ s1 -CN level and smaller micelles (Arsi-Bale 37.99 mm and Somali 36.19 mm) than samples with lower ␣ s1 -CN level and larger micelles (Boer 31.13 mm and Cross 33.51 mm). Syneresis was significantly higher (P < 0.001) in milk with good coagulation properties. Curd firmness was negatively correlated with coagulation rate (R, −0.832) and micellar size (R, −0.647). Milk from Arsi-Bale and Somali goats had significantly higher ␣ s1 -CN level, smaller micelle and better cheese making property than the cross and Boer goats. This study shows that there exists high potential among indigenous goats for cheese production.
Many infant formulas are enriched with lactoferrin (Lf) because of its claimed beneficial effects... more Many infant formulas are enriched with lactoferrin (Lf) because of its claimed beneficial effects on health. Native bovine Lf (bLf) is known to inhibit in vitro replication of human enteroviruses, a group of pathogenic viruses that replicate in the gut as their primary infection site. On the basis of a model digestion and human gastrointestinal enzymes, we hypothesized that bLf could retain its antiviral properties against enterovirus in the gastrointestinal tract, either as an intact protein or through bioactive peptide fragments released by digestive enzymes. To test our hypothesis, bLf was digested with human gastric juice and duodenal juice in a 2-step in vitro digestion model. Two gastric pH levels and reduction conditions were used to simulate physiological conditions in adults and infants. The antiviral activity of native bLf and of the digested fractions was studied on echovirus 5 in vitro, using various assay conditions, addressing several mechanisms for replication inhibition. Both native and digested bLf fractions revealed a significant inhibitory effect, when added before or simultaneously with the virus onto the cells. Furthermore, a significant stronger sustained antiviral effect was observed when bLf was fully digested in the gastric phase with fast pH reduction to 2.5, compared with native bLf, suggesting the release of antiviral peptides from bLf during the human digestion process. In conclusion, this study demonstrates that bLf may have a role in the prevention of human gastrointestinal virus infection under physiological conditions and that food containing bLf may protect against infection in vivo.
Milk samples of 59 cows of the Norwegian Red Cattle breed receiving three di!erent supplementary ... more Milk samples of 59 cows of the Norwegian Red Cattle breed receiving three di!erent supplementary concentrates, were analysed for genotypes of caseins and whey proteins, the content of di!erent milk salts (Ca>, Ca, Mg and citrate), the content of total protein, casein and whey protein and the mean micellar size of native and heated casein micelles. The genotype of -casein had a statistically signi"cant e!ect on the content of protein and casein, and the content of whey protein and the casein number were signi"cantly in#uenced by di!erent feeding regimes, and the content of citrate. The mean size of native and heated casein micelles was signi"cantly in#uenced by the feeding regimes, genotype of -casein (native mean size only) and -casein, pH and the content of casein, whey protein and casein number. The heat-induced changes in mean micellar size were signi"cantly a!ected by the calcium ion activity which accounted for approximately 40% of the total variation.
... recently been an increased attention on cows' milk allergy, particularly among infants (... more ... recently been an increased attention on cows' milk allergy, particularly among infants (Paupe, Paty, de Blic, & Scheinmann, 2001; Sampson, 2004). ... Bovine milk has nine different genetic variants, however, type B is dominant in Europe (Bech & Kristiansen, 1990; Lien et al., 1999 ...
The influence of milk protein genetic variants on the quality, composition and technological prop... more The influence of milk protein genetic variants on the quality, composition and technological properties of milks from Norwegian Red cattle has been studied. Results are reported for a small sample of 55 cows.
The structure of human salivary parotid proteins has been compared to that of the casein micelle ... more The structure of human salivary parotid proteins has been compared to that of the casein micelle in bovine milk. Although both salivary particles and casein micelles were stabilised by calcium, the parotid micelle-like structures tended to aggregate into clusters on storage.
a b s t r a c t Antiviral activity of Ragusano donkeys' milk proteins was investigated for the ef... more a b s t r a c t Antiviral activity of Ragusano donkeys' milk proteins was investigated for the effect on echovirus type 5, known to infect the gastrointestinal tract of humans. Three protein fractions were tested; casein (CN), whey protein (WP) and a low molecular whey protein fraction (LWP; <30,000 Da). The antiviral activity of WP and LWP was tested on echovirus type 5 at three concentrations (1, 5 and 10 mg mL À1 ); CN was assessed only at the lower concentration. All donkey milk protein fractions showed significant inhibition on virus replication at the concentration of 1 mg mL À1 , and both WP and LWP fractions showed significant inhibition on the virus replication at all concentrations tested. The strongest antiviral effect was observed for the WP fraction. These findings show that the different whey proteins in donkey milk, probably acting in synergy, exert antiviral activity on echovirus 5 and might contribute to prevent gastrointestinal virus infections in humans.
Qualitative and quantitative analysis of the protein profile of milk samples from 14 Ragusano don... more Qualitative and quantitative analysis of the protein profile of milk samples from 14 Ragusano donkeys was carried out. Isoelectric focusing (IEF) analysis revealed three IEF protein patterns: individual variability was related both to casein (one deviating sample, without a S1 -casein) and whey proteins (two deviating samples, without b-lactoglobulin II). The observed polymorphism reflected the different distribution of the protein fractions (casein or whey protein content) but did not affect the size and zetapotential of casein micelles. A simulated in vitro digestion, carried out in a two-step digestion assay with human gastric juice and duodenal juice, was also performed to provide a direct estimation of donkey milk protein digestibility. Individual IEF variability had an effect on digestibility only in the two samples lacking the b-lactoglobulin II, revealing a more rapid degradation of the b-lactoglobulin fraction when it consists of the single b-lactoglobulin I, particularly in the gastric digestion.
The impact of viscosity on emulsion stability at pH 2 using 1% (w/w) rapeseed oil (RSO) with 0.2 ... more The impact of viscosity on emulsion stability at pH 2 using 1% (w/w) rapeseed oil (RSO) with 0.2 and 2% (w/w) whey protein concentrate (WPC) and 0.1 % (w/w) chitosan (CH) during 1 and 16 days of storage was investigated. The droplet size values obtained by image analysis were correlated with the viscosity values. All the emulsions behaved like non-Newtonian fluids, having shearthickening characteristics, as the flow behaviour index values were larger than 1. A reduction in emulsion droplet size from 2.24 (2% WPC) to 0.95 μm (2% WPC, 0.1% CH) was observed when chitosan was added to the emulsions containing WPC (day 1). Addition of chitosan to WPC-emulsions caused about 20% relative increase in the viscosity. An increase in viscosity with a decrease in droplet size was observed. During the storage for up to 16 days, no water separation of WPCchitosan emulsions was noticed, indicating that the stability of these emulsions was maintained at 4 oC. The stability observations were related ...
The effect of type of emulsifier, 2 w/w% whey protein concentrate (WPC) or 2 w/w% WPC and 0.1 w/w... more The effect of type of emulsifier, 2 w/w% whey protein concentrate (WPC) or 2 w/w% WPC and 0.1 w/w% chitosan (CH) on the rheological changes and droplet size distribution during the ex vivo digestion of oil in water emulsions (pH 2) containing 1 w/w% rapeseed oil (RSO) were investigated. The procedure was used to mimic the human gastro duodenal digestion in two steps, gastric phase at pH 2 for 30 min followed by the duodenal phase at pH 7 for 60 min. With regard to viscosity, the emulsion, either WPC or WPC-CH showed an increase from gastric phase to duodenal phase (p<0.001) and then it was stable until the end of digestion. The viscosity of WPC-CH emulsions during the whole digestion (with/without added HGJ/HDJ) process was higher than the respective WPC emulsions. At pH 7 (duodenal juice addition), the droplet diameters stabilized by WPC emulsion showed a bimodal distribution with droplet sizes in the range of 0.05-1.7 µm and 200-500 µm. A significant change (p<0.01) in the o...
The objective of the present study was twofold: first to compare the degradation patterns of capr... more The objective of the present study was twofold: first to compare the degradation patterns of caprine whey proteins digested with either human digestive juices (gastric or duodenal) or commercial porcine enzymes (pepsin or pancreatic enzymes) and second to observe the effect of gastric pH on digestion. An in vitro two-step assay was performed at 378C to simulate digestion in the stomach (pH 2, 4 or 6) and the duodenum (pH 8). The whey proteins were degraded more efficiently by porcine pepsin than by human gastric juice at all pH values. Irrespective of the enzyme source, gastric digestion at pH 2 followed by duodenal digestion resulted in the most efficient degradation. Lactoferrin, serum albumin and the Ig heavy chains were highly degraded with less than 6 % remaining after digestion. About 15, 56 and 50 % Ig light chains, b-lactoglobulin (b-LG) and a-lactalbumin remained intact, respectively, when digested with porcine enzymes compared with 25, 74 and 81 % with human digestive juices. For comparison, purified bovine b-LG was digested and the peptide profiles obtained were compared with those of the caprine b-LG in the digested whey. The bovine b-LG seemed to be more extensively cleaved than the caprine b-LG in the whey. Commercial enzymes appear to digest whey proteins more efficiently compared with human digestive juices when used at similar enzyme activities. This could lead to conflicting results when comparing human in vivo protein digestion with digestion using purified enzymes of non-human species. Consequently the use of human digestive juices might be preferred.
This study was conducted in Ethiopia on four goat breeds: Arsi-Bale, Somali, Toggenburg-Arsi-Bale... more This study was conducted in Ethiopia on four goat breeds: Arsi-Bale, Somali, Toggenburg-Arsi-Bale cross and Boer to assess milk yield and composition at different lactation stages, for the suitability of the milk for cheese production. Milk yield was measured once per week and milk samples were collected three times during the lactation period. Total solids, fat, protein, casein, whey-protein, non-protein nitrogen (NPN), lactose and minerals, (calcium, phosphorus, magnesium, potassium, sodium, zinc and iron) were analyzed. A higher daily milk yield, 1.41 kg, was recorded for Boer goats (P < 0.05), compared to 1.13, 0.93 and 0.85 kg produced by Arsi-Bale, Cross and Somali goats, respectively. Milk from Cross was lower in total solids 13.9% and fat 3.7% (P < 0.001), than Arsi-Bale, Boer and Somali which had 16.3, 15.4 and 14.5% total solids and 5.2, 4.7 and 4.9% fat, respectively. Arsi-Bale goats had significantly higher protein content, 4.8% (P < 0.001) than the rest of the breeds. Lactose content of milk was high in all goat breeds, 4.9% with no significant difference between them. Early and late lactation milk had significantly higher contents (P < 0.001) of milk components. Milk from all breeds was high in calcium, phosphorous and potassium: 1.62, 1.39 and 1.69 g kg −1 , respectively and Fe and Zn: 5.47 and 0.36 mg kg −1 , respectively. Superior chemical composition revealed the potential of milk from indigenous Ethiopian goats for cheese production.
Goat milk contributes significantly to human nutrition and has been used in functional food appli... more Goat milk contributes significantly to human nutrition and has been used in functional food applications in many parts of the world. Among the components in milk, lactoferrin (Lf) is a multifunctional glycoprotein that plays an important role in immune regulation and defence mechanisms against bacteria, fungi and viruses. The biological activity may be affected by thermal treatment during industrial processes. The production and content of Lf in milk from different species seems to vary a lot. This study aims to compare the thermal stability and structural differences in bovine (Blf) and caprine Lf (Clf) under conditions such as pH and iron content. The X-ray crystallography investigation has shown the presence of alpha helical and beta sheet contents to different degrees in Lf among both species which upholds stability to the molecule. In addition, the iron saturation was found to be important in Lf structure and stability. In the present investigation an attempt has been made to a...
This short review presents the developments in genetic improvement of Ethiopian goat breeds and t... more This short review presents the developments in genetic improvement of Ethiopian goat breeds and the impact of the crossbreeding programs on ␣s1-CN gene (CSN1S1). The influence of newly identified mutations on milk components and technological properties are considered. The indigenous Ethiopian goat breeds are low milk yielders with high percentage of milk organic component and thus with good technological properties. Crossbreeding programs were taken as an option to improve their genetic potential. The main objective of crossbreeding programs in Ethiopia were to increase milk yield and thus, to enhance protein consumption at household level. The success of crossbreeding programs was impaired due to high input requirements, incompatibility of the genotype with the farmers breeding objectives and the production system, owing mainly to less net benefit than expected from the crossbreeding. Evaluation of CSN1S1 gene revealed 36 mutations, which were not previously reported. Four of these mutations were detected in the exon region of CSN1S1: two synonymous (exons 4 and 12), one non-synonymous (exon 10) and a nonsense mutation (exon 15). The non-synonymous mutation was detected only in the indigenous goats and their crosses with exotic Boer goats. It involved amino acid exchange Gln77→Pro77. Goats carrying this mutation have higher ␣s1-CN, fat and protein content and good coagulation properties with exceptionally high gel strength. The nonsense mutation involved a transversion, at amino acid position Gln140, CAG→TAG giving rise to a premature stop codon. The mutation was found in three crossbred goats between the exotic Toggenburg buck and the local Arsi-Bale does. This mutation was not detected in any of the local goat breeds and therefore, we assume it originates from the exotic parent. The lesson is the need for careful evaluation of the exotic genes for milk quality in bucks chosen for crossbreeding programs, prior to introduction.
Very high casein content and good coagulation properties previously observed in some Ethiopian go... more Very high casein content and good coagulation properties previously observed in some Ethiopian goat breeds led to investigating the α s1 -casein (CSN1S1) gene in these breeds. Selected regions of the CSN1S1 gene were sequenced in 115 goats from 5 breeds (2 indigenous: Arsi-Bale and Somali, 1 exotic: Boer, and 2 crossbreeds: Boer × Arsi-Bale and Boer × Somali). The DNA analysis resulted in 35 new mutations: 3 in exons, 3 in the 5 untranslated region (UTR), and 29 in the introns. The mutations in exons that resulted in an amino acid shift were then picked to evaluate their influence on individual casein content (α s1 -, α s2 -, β-, and κ-CN), micellar size, and coagulation properties in the milk from the 5 goat breeds. A mutation at nucleotide 10657 (exon 10) involved a transversion: CAG→CCG, resulting in an amino acid exchange Gln 77 →Pro 77. This mutation was associated with the indigenous breeds only. Two new mutations, at nucleotide 6072 (exon 4) and 12165 (exon 12), revealed synonymous transitions: GTC→GTT in Val 15 and AGA→AGG in Arg 100 of the mature protein. Transitions G→A and C→T at nucleotides 1374 and 1866, respectively, occurred in the 5 UTR, whereas the third mutation involved a transversion T→G at nucleotide location 1592. The goats were grouped into homozygote new (CC), homozygote reference (AA), and heterozygote (CA) based on the nucleotide that involved the transversion. The content of α s1 -CN (15.32 g/kg) in milk samples of goats homozygous (CC) for this newly identified mutation, Gln 77 →Pro 77 was significantly higher than in milks of heterozygous (CA; 9.05 g/kg) and reference (AA; 7.61 g/kg) genotype animals. The α s2 -, β-, and κ-CN contents showed a similar pattern. Milk from goats with a homozygous new mutation had significantly lower micellar size. Milk from both homozygote and heterozygote new-mutation goats had significantly shorter coagulation rate and stronger gel than the reference genotype. Except the transversion, the sequence corresponded to allele A and presumably derived from it. Therefore, this allele is denoted by A 3 . All goats from the reference genotype (AA) were homozygous for the allele at nucleotide position 1374 and 1866, whereas all mutations in the 5 UTR existed in a heterozygous form in both heterozygous (CA) and the new mutation (CC) genotype. The newly identified mutation (CC) detected in some of the goat breeds is, therefore, important in selection for genetic improvement and high-quality milk for the emerging goat cheese-producing industries. The finding will also benefit farmers raising these goat breeds due to the increased selling price of goats. Further studies should investigate the effect of this amino acid exchange on the secondary and tertiary structure of the α s1 -CN molecule and on the susceptibility of peptide hydrolysis by digestive enzymes. Figure 3. Principal components (PC) analysis plot of different genotypes, caseins, micellar size, proteins, and TS. Gr = group; BR = Boer reference genotype; AN = Arsi-Bale new mutation; SN = Somali new mutation; ANZ = Boer × Arsi-Bale cross heterozygote; SHZ = Boer × Somali cross heterozygote.
Lactoferrin (LF) is a protein present in milk and other body fluids that plays important biologic... more Lactoferrin (LF) is a protein present in milk and other body fluids that plays important biological roles. As part of a diet, LF must survive gastrointestinal conditions or create bioactive fragments to exert its effects. The degradation of LF and formation of bioactive peptides is highly dependent on individual variation in intraluminal composition. The present study was designed to compare the degradation and peptide formation of bovine LF (bLF) following in vitro digestion under different simulated intraluminal conditions. Human gastrointestinal (GI) juices were used in a 2-step model digestion to mimic degradation in the stomach and duodenum. To account for variation in the buffering capacity of different lactoferrin-containing foods, gastric pH was adjusted either slowly or rapidly to 2.5 or 4.0. The results were compared with in vivo digestion of bLF performed in 2 volunteers. High concentration of GI juices and fast pH reduction to 2.5 resulted in complete degradation in the gastric step. More LF resisted gastric digestion when pH was slowly reduced to 2.5 or 4.0. Several peptides were identified; however, few matched with previously reported peptides from studies using nonhuman enzymes. Surprisingly, no bovine lactoferricin, f(17-41), was identified during in vitro or in vivo digestion under the intraluminal conditions used. The diversity of enzymes in human GI juices seems to affect the hydrolysis of bLF, generating different peptide fragments compared with those obtained when using only one or a few proteases of animal origin. Multiple sequence analysis of the identified peptides indicated a motif consisting of proline and neighboring hydrophobic residues that could restrict proteolytic process-ing. Further structure analysis showed that almost all proteolytic cutting sites were located on the surface and mainly on the nonglycosylated half of lactoferrin. Digestion of bLF by human enzymes may generate different peptides from those found when lactoferrin is digested by nonhuman enzymes. The degradation of LF in the GI tract should be taken into consideration when health effects are proposed, because LF has now been approved by the European Food Safety Authority as a dietary supplement in food products.
A rapid spectroscopic method to determine total protein in bovine and buffalo milk using UV spect... more A rapid spectroscopic method to determine total protein in bovine and buffalo milk using UV spectra of guanidine-hydrochloride mixed milk has previously been reported and validated. The method was based on mixed calibration samples and univariate calibrations of fourth derivative (4D) spectra. In this study the same method was compared and tested for determination of total protein in goat milk. Calculations based on multivariate calibration (partial least squares regression) on full spectra of goat milk were used. The method was tested on 2 UV instruments. The comparison resulted in a significantly more robust (i.e., better) transferability between UV instruments for the partial least squares regression method on full spectra compared with previous univariate calibration of 4D spectra. Local (1 instrument) calibrations gave similar, significantly not different (chi-squared test) cross-validated prediction error results for the 2 methods. It can be concluded that there is no need for fourth derivation. Partial least squares regression on full spectra was equal or superior to using the 4D spectra.
The economic output of the dairy industry is to a great extent dependent on the processing of mil... more The economic output of the dairy industry is to a great extent dependent on the processing of milk into other milk-based products such as cheese.
In this study, we analysed the impact of carboxymethylcellulose (CMC) on lipid digestion and phys... more In this study, we analysed the impact of carboxymethylcellulose (CMC) on lipid digestion and physicochemical properties of whey proteins (WP)-stabilised emulsions during in vitro digestion with either artificial or human gastrointestinal juices. The emulsions were made by adsorbing WP on the fat droplets and subsequently adding CMC, which does not interact with the adsorbed proteins. The limited hydrolysis of lipids and their higher physical stability was recorded for WP-stabilised emulsions in the presence of CMC under simulated gastrointestinal conditions. The possible mechanism by which CMC lowers the digestion of WP-stabilised emulsions is related to the limited interaction of fat droplets with gastrointestinal fluids due to the extended thickening network formed by CMC in the continuous phase. The digestion of WP- and CMC-stabilised emulsions in the in vitro model with human gastric fluids led to greater lipid hydrolysis, although the enzymatic activity in both in vitro models ...
The objective of the present study was twofold: first to compare the degradation patterns of capr... more The objective of the present study was twofold: first to compare the degradation patterns of caprine whey proteins digested with either human digestive juices (gastric or duodenal) or commercial porcine enzymes (pepsin or pancreatic enzymes) and second to observe the effect of gastric pH on digestion. An in vitro two-step assay was performed at 378C to simulate digestion in the stomach (pH 2, 4 or 6) and the duodenum (pH 8). The whey proteins were degraded more efficiently by porcine pepsin than by human gastric juice at all pH values. Irrespective of the enzyme source, gastric digestion at pH 2 followed by duodenal digestion resulted in the most efficient degradation. Lactoferrin, serum albumin and the Ig heavy chains were highly degraded with less than 6 % remaining after digestion. About 15, 56 and 50 % Ig light chains, b-lactoglobulin (b-LG) and a-lactalbumin remained intact, respectively, when digested with porcine enzymes compared with 25, 74 and 81 % with human digestive juices. For comparison, purified bovine b-LG was digested and the peptide profiles obtained were compared with those of the caprine b-LG in the digested whey. The bovine b-LG seemed to be more extensively cleaved than the caprine b-LG in the whey. Commercial enzymes appear to digest whey proteins more efficiently compared with human digestive juices when used at similar enzyme activities. This could lead to conflicting results when comparing human in vivo protein digestion with digestion using purified enzymes of non-human species. Consequently the use of human digestive juices might be preferred.
Milk from 94 Ethiopian goats (four breeds) was assessed for casein level, micellar size, coagulat... more Milk from 94 Ethiopian goats (four breeds) was assessed for casein level, micellar size, coagulation properties and whey syneresis to evaluate cheese-making potential. Casein content (g/kg) ranged from 6.84 to 8.94 (␣ s1 ); 4.16-4.98 (␣ s2 ); 12.51-15.37 () and 6.89-8.93 (). Arsi-Bale goats had the highest ␣ s1 -casein (8.94 g/kg) followed by the Somali goats (7.90 g/kg); and were higher than Boer (7.05 g/kg) and Cross (6.84 g/kg) (P < 0.001). Milk from Arsi-Bale and Somali goats had significantly (P < 0.05) smaller micelles; 207.47 and 209.29 nm respectively than Boer (230.30 nm) and Cross (228.71 nm). Significantly stronger gels (P < 0.05) were obtained from milk samples with higher ␣ s1 -CN level and smaller micelles (Arsi-Bale 37.99 mm and Somali 36.19 mm) than samples with lower ␣ s1 -CN level and larger micelles (Boer 31.13 mm and Cross 33.51 mm). Syneresis was significantly higher (P < 0.001) in milk with good coagulation properties. Curd firmness was negatively correlated with coagulation rate (R, −0.832) and micellar size (R, −0.647). Milk from Arsi-Bale and Somali goats had significantly higher ␣ s1 -CN level, smaller micelle and better cheese making property than the cross and Boer goats. This study shows that there exists high potential among indigenous goats for cheese production.
Many infant formulas are enriched with lactoferrin (Lf) because of its claimed beneficial effects... more Many infant formulas are enriched with lactoferrin (Lf) because of its claimed beneficial effects on health. Native bovine Lf (bLf) is known to inhibit in vitro replication of human enteroviruses, a group of pathogenic viruses that replicate in the gut as their primary infection site. On the basis of a model digestion and human gastrointestinal enzymes, we hypothesized that bLf could retain its antiviral properties against enterovirus in the gastrointestinal tract, either as an intact protein or through bioactive peptide fragments released by digestive enzymes. To test our hypothesis, bLf was digested with human gastric juice and duodenal juice in a 2-step in vitro digestion model. Two gastric pH levels and reduction conditions were used to simulate physiological conditions in adults and infants. The antiviral activity of native bLf and of the digested fractions was studied on echovirus 5 in vitro, using various assay conditions, addressing several mechanisms for replication inhibition. Both native and digested bLf fractions revealed a significant inhibitory effect, when added before or simultaneously with the virus onto the cells. Furthermore, a significant stronger sustained antiviral effect was observed when bLf was fully digested in the gastric phase with fast pH reduction to 2.5, compared with native bLf, suggesting the release of antiviral peptides from bLf during the human digestion process. In conclusion, this study demonstrates that bLf may have a role in the prevention of human gastrointestinal virus infection under physiological conditions and that food containing bLf may protect against infection in vivo.
Milk samples of 59 cows of the Norwegian Red Cattle breed receiving three di!erent supplementary ... more Milk samples of 59 cows of the Norwegian Red Cattle breed receiving three di!erent supplementary concentrates, were analysed for genotypes of caseins and whey proteins, the content of di!erent milk salts (Ca>, Ca, Mg and citrate), the content of total protein, casein and whey protein and the mean micellar size of native and heated casein micelles. The genotype of -casein had a statistically signi"cant e!ect on the content of protein and casein, and the content of whey protein and the casein number were signi"cantly in#uenced by di!erent feeding regimes, and the content of citrate. The mean size of native and heated casein micelles was signi"cantly in#uenced by the feeding regimes, genotype of -casein (native mean size only) and -casein, pH and the content of casein, whey protein and casein number. The heat-induced changes in mean micellar size were signi"cantly a!ected by the calcium ion activity which accounted for approximately 40% of the total variation.
... recently been an increased attention on cows' milk allergy, particularly among infants (... more ... recently been an increased attention on cows' milk allergy, particularly among infants (Paupe, Paty, de Blic, & Scheinmann, 2001; Sampson, 2004). ... Bovine milk has nine different genetic variants, however, type B is dominant in Europe (Bech & Kristiansen, 1990; Lien et al., 1999 ...
The influence of milk protein genetic variants on the quality, composition and technological prop... more The influence of milk protein genetic variants on the quality, composition and technological properties of milks from Norwegian Red cattle has been studied. Results are reported for a small sample of 55 cows.
The structure of human salivary parotid proteins has been compared to that of the casein micelle ... more The structure of human salivary parotid proteins has been compared to that of the casein micelle in bovine milk. Although both salivary particles and casein micelles were stabilised by calcium, the parotid micelle-like structures tended to aggregate into clusters on storage.
a b s t r a c t Antiviral activity of Ragusano donkeys' milk proteins was investigated for the ef... more a b s t r a c t Antiviral activity of Ragusano donkeys' milk proteins was investigated for the effect on echovirus type 5, known to infect the gastrointestinal tract of humans. Three protein fractions were tested; casein (CN), whey protein (WP) and a low molecular whey protein fraction (LWP; <30,000 Da). The antiviral activity of WP and LWP was tested on echovirus type 5 at three concentrations (1, 5 and 10 mg mL À1 ); CN was assessed only at the lower concentration. All donkey milk protein fractions showed significant inhibition on virus replication at the concentration of 1 mg mL À1 , and both WP and LWP fractions showed significant inhibition on the virus replication at all concentrations tested. The strongest antiviral effect was observed for the WP fraction. These findings show that the different whey proteins in donkey milk, probably acting in synergy, exert antiviral activity on echovirus 5 and might contribute to prevent gastrointestinal virus infections in humans.
Qualitative and quantitative analysis of the protein profile of milk samples from 14 Ragusano don... more Qualitative and quantitative analysis of the protein profile of milk samples from 14 Ragusano donkeys was carried out. Isoelectric focusing (IEF) analysis revealed three IEF protein patterns: individual variability was related both to casein (one deviating sample, without a S1 -casein) and whey proteins (two deviating samples, without b-lactoglobulin II). The observed polymorphism reflected the different distribution of the protein fractions (casein or whey protein content) but did not affect the size and zetapotential of casein micelles. A simulated in vitro digestion, carried out in a two-step digestion assay with human gastric juice and duodenal juice, was also performed to provide a direct estimation of donkey milk protein digestibility. Individual IEF variability had an effect on digestibility only in the two samples lacking the b-lactoglobulin II, revealing a more rapid degradation of the b-lactoglobulin fraction when it consists of the single b-lactoglobulin I, particularly in the gastric digestion.
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