Oxidation of marine oils during in vitro gastrointestinal digestion with human digestive fluids – Role of oil origin, added tocopherols and lipolytic activity

The formation of malondialdehyde (MDA), 4-hydroxy-2-hexenal (HHE), 4-hydroxy-2-nonenal (HNE), and 4-oxo-2-nonenal (ONE) in cod liver-, anchovy-, krill-, and algae oil during in vitro digestion with human gastrointestinal fluids was investigated. Adding rabbit gastric lipase, lipase inhibitor (orlistat) and tocopherols to cod liver oil, lipolysis and oxidation was also studied. Among the marine oils, the highest aldehyde levels (18 \ub5M MDA, 3 \ub5M HHE and 0.2 \ub5M HNE) were detected after digestion of cod liver oil, while the lowest levels were detected in krill and algae oils. Addition of rabbit gastric lipase significantly increased the release of HNE during the digestion. Orlistat significantly reduced lipolysis and MDA formation. Formation of MDA and HHE was delayed by tocopherols, the tocopherol mix Covi-ox\uae T 70 EU being more effective than pure α-tocopherol

Principal Milk Components in Buffalo, Holstein Cross, Indigenous Cattle and Red Chittagong Cattle from Bangladesh

The aim of the present study was to get a total physical and chemical characterization and comparison of the principal components in Bangladeshi buffalo (B), Holstein cross (HX), Indigenous cattle (IC) and Red Chittagong Cattle (RCC) milk. Protein and casein (CN) composition and type, casein micellar size (CMS), naturally occurring peptides, free amino acids, fat, milk fat globule size (MFGS), fatty acid composition, carbohydrates, total and individual minerals were analyzed. These components are related to technological and nutritional properties of milk. Consequently, they are important for the dairy industry and in the animal feeding and breeding strategies. Considerable variation in most of the principal components of milk were observed among the animals. The milk of RCC and IC contained higher protein, CN, β-CN, whey protein, lactose, total mineral and P. They were more or less similar in most of the all other components. The B milk was found higher in CN number, in the content of αs2-, κ-CN and α-lactalbumin, free amino acids, unsaturated fatty acids, Ca and Ca:P. The B milk was also lower in β-lactoglobulin content and had the largest CMS and MFGS. Proportion of CN to whey protein was lower in HX milk and this milk was found higher in β-lactoglobulin and naturally occuring peptides. Considering the results obtained including the ratio of αs1-, αs2-, β- and κ-CN, B and RCC milk showed best data both from nutritional and technological aspects

A standardised static in vitro digestion method suitable for food – an international consensus

peer-reviewedSimulated gastro-intestinal digestion is widely employed in many fields of food and nutritional sciences, as conducting human trials are often costly, resource intensive, and ethically disputable. As a consequence, in vitro alternatives that determine endpoints such as the bioaccessibility of nutrients and non-nutrients or the digestibility of macronutrients (e.g. lipids, proteins and carbohydrates) are used for screening and building new hypotheses. Various digestion models have been proposed, often impeding the possibility to compare results across research teams. For example, a large variety of enzymes from different sources such as of porcine, rabbit or human origin have been used, differing in their activity and characterization. Differences in pH, mineral type, ionic strength and digestion time, which alter enzyme activity and other phenomena, may also considerably alter results. Other parameters such as the presence of phospholipids, individual enzymes such as gastric lipase and digestive emulsifiers vs. their mixtures (e.g. pancreatin and bile salts), and the ratio of food bolus to digestive fluids, have also been discussed at length. In the present consensus paper, within the COST Infogest network, we propose a general standardised and practical static digestion method based on physiologically relevant conditions that can be applied for various endpoints, which may be amended to accommodate further specific requirements. A frameset of parameters including the oral, gastric and small intestinal digestion are outlined and their relevance discussed in relation to available in vivo data and enzymes. This consensus paper will give a detailed protocol and a line-by-line, guidance, recommendations and justifications but also limitation of the proposed model. This harmonised static, in vitro digestion method for food should aid the production of more comparable data in the future.COST action FA1005 Infogest22 (http://www.cost-infogest.eu/) is acknowledged for providing funding for travel, meetings and conferences

Importance of casein micelle size and milk composition for milk gelation.

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. The yield and quality of cheese are dependent on both the composition and technological properties of milk. The objective of this study was to evaluate the importance and effects of casein (CN) micelle size and milk composition on milk gelation characteristics in order to evaluate the possibilities for enhancing gelation properties through breeding. Milk was collected on 4 sampling occasions at the farm level in winter and summer from dairy cows with high genetic merit, classified as elite dairy cows, of the Swedish Red and Swedish Holstein breeds. Comparisons were made with milk from a Swedish Red herd, a Swedish Holstein herd, and a Swedish dairy processor. Properties of CN micelles, such as their native and rennet-induced CN micelle size and their zeta-potential, were analyzed by photon correlation spectroscopy, and rennet-induced gelation characteristics, including gel strength, gelation time, and frequency sweeps, were determined. Milk parameters of the protein, lipid, and carbohydrate profiles as well as minerals were used to obtain correlations with native CN micelle size and gelation characteristics. Milk pH and protein, CN, and lactose contents were found to affect milk gelation. Smaller native CN micelles were shown to form stronger gels when poorly coagulating milk was excluded from the correlation analysis. In addition, milk pH correlated positively, whereas Mg and K correlated negatively with native CN micellar size. The milk from the elite dairy cows was shown to have good gelation characteristics. Furthermore, genetic progress in relation to CN micelle size was found for these cows as a correlated response to selection for the Swedish breeding objective if optimizing for milk gelation characteristics. The results indicate that selection for smaller native CN micelles and lower milk pH through breeding would enhance gelation properties and may thus improve the initial step in the processing of cheese

Degradation of β-casomorphin-7 through in vitro gastrointestinal and jejunal brush border membrane digestion

This work aimed to study the opioid peptide β-casomorphin-7 (BCM7) degradation or stability during digestion using human gastrointestinal (GI) juices and porcine jejunal brush border membrane (BBM) peptidases. Synthetic BCM7 was subjected to in vitro digestion by GI fluids obtained from human volunteers for 180 min, and to downstream degradation with porcine BBM vesicles. The BCM7 was sampled at 4 time points over 24 h after BBM addition. The digests were profiled by HPLC-electrospray ionization mass spectrometry (ESI/MS) to monitor BCM7 during GI digestion, and intact BCM7 through BBM digestion was quantified by reverse-phase (RP)-HPLC. We found that BCM7 was partly digested with human GI enzymes, as 3 proteolytic fragments in addition to f(60–66) YPFPGPI were detected: f(62–66) FPGPI, f(60–65) YPFPGP and f(61–66) PFPGPI. The RP-HPLC analysis revealed that 42% of the initial peptide was degraded after only 2 h of BBM digestion, and as much as 79% was degraded after 4-h digestion with supplementation of BBM. In conclusion, this study showed that most of BCM7 was degraded during GI and BBM digestion, although a small amount (5%) was still detected after 24-h digestion. It remains to be studied whether the small amount of intact BCM7 detected after in vitro digestion is transported via active transceptors in the human intestinal epithelial cells and enters blood circulation

A comparison of effects of pH on the thermal stability and conformation of caprine and bovine lactoferrin

Thermal stability and structural changes in caprine lactoferrin (cLF) and bovine lactoferrin (bLF) at pH 2.0-8.0 were measured using thermal denaturation temperature (Tm) analysis, fluorescence spectroscopy and circular dichroism (CD). Thermal stability analysis indicated a Tm of 70°C for bLF and 67°C for cLF at pH 7.0. From pH 7.0 to 3.0, a gradual reduction in the Tm of both bLF and cLF was observed and reached a value of 39°C and 30°C, respectively. At pH 2.0-3.0, a partly unfolded structure of bLF and cLF was observed with a relatively low content of α-helix structure (3% and 7%, respectively), but still rich in β-structure (54% and 57%, respectively). A higher exposure of hydrophobic surfaces at low pH for bLF compared with cLF was proved by fluorescence studies. In conclusion, the structure of cLF was more affected by pH and showed lower temperature stability than bLF

Comparison of the digestion of caseins and whey proteins in equine, bovine, caprine and human milks by human gastrointestinal enzymes

The aim of this study was to compare the digestion of milk proteins from different species using an in vitro gastrointestinal model. Raw and heated milks from bovine, caprine, human and equine species were digested by human digestive enzymes. Digestion was performed in two 30-min sequential steps by digestive juices from the stomach (pH 2.5/37 °C) and from the duodenum (pH 8.0/37 °C). The degradation patterns of the milk proteins were visualized by SDS-PAGE and quantified using the ImageQuant program. Caseins in the equine milk were rapidly digested by the gastric juice in contrast to the caseins from the other species. During the subsequent digestion by the duodenal juice most of the caseins from all species were degraded within 5 min, and within 30 min only traces of caseins were detected. The mean casein micellar size varied between species in the range of 146.0–311.5 nm (equine > caprine > bovine > human). The α-lactalbumin from all species appeared to be very resistant to both gastric and duodenal digestions. A similar trend was shown for β-lactoglobulin from bovine and caprine milks, of which ~ 60% intact protein remained, while only 25% remained intact in equine milk after total digestion. Equine milk contained a high amount of lysozyme, of which 60% remained intact in the present study. In heated milks from all species, only α-lactalbumin degradation increased approximately 12–20% in comparison to the raw milk. This study shows that equine milk with fast digestible proteins could be considered as a replacement for bovine milk in the diet of people with special needs, such as infants and the elderly