The aim of the Food Chemistry & Technology Department is to help food processors maintain competitive advantage and secure premium markets. Our Dairy research focuses on cheese, infant formula and dairy based ingredients; Meat research, focusing on quality, whole chain management and recovering value from meat processing streams; Cereal research focusing on product quality and innovation in the bakery industry

Recent Submissions

  • Integration of high and low field 1H NMR to analyse the effects of bovine dietary regime on milk metabolomics and protein-bound moisture characterisation of the resulting mozzarella cheeses during ripening

    Boiani, Mattia; Sundekilde, Ulrik; Bateman, Lorraine M.; McCarthy, Daniel G.; Maguire, Anita R.; Gulati, Arunima; Guinee, Timothy P.; Fenelon, Mark; Hennessy, Deirdre; Fitzgerald, Richard; et al. (Elsevier, 2018-10-11)
    The influence of dairy cow feeding regime was investigated using 1H nuclear magnetic resonance (NMR). Two different NMR analytical systems were deployed: high field 1H NMR to investigate the influence on milk metabolomics and low field NMR to characterise proton relaxation linked to changes in the state of mozzarella cheese moisture during ripening. The metabolomics results showed that grass-based feeding increased the concentration of a biological marker that signifies near-organic milk production conditions. On the other hand, the investigation of cheese moisture distribution showed that grass-based diets reached final moisture partitioning in a shorter time, which implied the formation of a more compact protein structure in the cheese matrix. These results indicate that pasture-based dairying may be differentiated in terms of the provenance of milk produced along with the accrual of additional benefits during ripening of the resulting mozzarella cheeses.
  • Short communication: Multi-component interactions causing solidification during industrial-scale manufacture of pre-crystallized acid whey powders

    Drapala, Kamil P.; Murphy, Kevin M.; Ho, Quang Tri; Crowley, Shane V.; Mulcahy, Shane; McCarthy, Noel; O'Mahony, James A.; Technology Centres Programme; TC/2014/0016 (Elsevier, 2018-10-03)
    Acid whey (AW) is the liquid co-product arising from acid-induced precipitation of casein from skim milk. Further processing of AW is often challenging due to its high mineral content, which can promote aggregation of whey proteins, which contributes to high viscosity of the liquid concentrate during subsequent lactose crystallization and drying steps. This study focuses on mineral precipitation, protein aggregation, and lactose crystallization in liquid AW concentrates (∼55% total solids), and on the microstructure of the final powders from 2 independent industrial-scale trials. These AW concentrates were observed to solidify either during processing or during storage (24 h) of pre-crystallized concentrate. The more rapid solidification in the former was associated with a greater extent of lactose crystallization and a higher ash-to-protein ratio in that concentrate. Confocal laser scanning microscopy analysis indicated the presence of a loose network of protein aggregates (≤10 µm) and lactose crystals (100–300 µm) distributed throughout the solidified AW concentrate. Mineral-based precipitate was also evident, using scanning electron microscopy, at the surface of AW powder particles, indicating the formation of insoluble calcium phosphate during processing. These results provide new information on the composition- and process-dependent physicochemical changes that are useful in designing and optimizing processes for AW.
  • Evaluation of Vis-NIR hyperspectral imaging as a process analytical tool to classify brined pork samples and predict brining salt concentration

    Achata, Eva M.; Inguglia, Elena S.; Esquerre, Carlos A.; Tiwari, Brijesh; O'Donnell, Colm P.; Department of Agriculture, Food and the Marine; 13/FM/508 (Elsevier, 2018-10-20)
    Hyperspectral imaging in the visible and near infrared spectral range (450–1664 nm) coupled with chemometrics was investigated for classification of brined and non-brined pork loins and prediction of brining salt concentration employed. Hyperspectral images of control, water immersed and brined (5, 10 or 15% salt (w/v)) raw and cooked pork loins from 16 animals were acquired. Partial least squares (PLS) discriminative analysis models were developed to classify brined pork samples and PLS regression models were developed for prediction of brining salt concentration employed. The ensemble Monte Carlo variable selection method (EMCVS) was used to improve the performance of the models developed. Partial least squares (PLS) discriminative analysis models developed correctly classified brined and non-brined samples, the best classification model for raw samples (Sen = 100%, Spec = 100%, G = 1.00) used the 957–1664 nm spectral range, and the best classification model for cooked samples (Sen = 100%, Spec = 100%, G = 1.00) used the 450–960 nm spectral range. The best brining salt concentration prediction models developed for raw (RMSEp 1.9%, R2p 0.92) and cooked (RMSEp 2.6%, R2p 0.83) samples used the 957–1664 nm spectral range. This study demonstrates the high potential of hyperspectral imaging as a process analytical tool to classify brined and non-brined pork loins and predict brining salt concentration employed.
  • Preparation of modified whey protein isolate with gum acacia by ultrasound maillard reaction

    Chen, Weijun; Ma, Xiobhin; Wang, Wenjun; Lv, Ruiling; Guo, Mingming; Ding, Tian; Ye, Xingqian; Miao, Song; Liu, Donghong; National Key Research and Development Program of China; et al. (Elsevier, 2018-10-18)
    Effect of ultrasound treatment on whey protein isolate (WPI)-gum Acacia (GA) conjugation via Maillard reaction was investigated. And the physicochemical properties of the conjugates obtained by ultrasound treatment were compared with those obtained by classical heating. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, high-performance size exclusion chromatography and fourier transform infrared spectroscopy provided evidence on the formation of the Maillard type conjugation. Compared with classical heating, ultrasound treatment could accelerate the glycation reaction between WPI and GA. A degree of graft of 11.20% was reached by classical heating for 48 h, whereas only 20 min was required by ultrasound treatment. Structural analyses suggested that the conjugates obtained by ultrasound treatment had less α-helix content, higher surface hydrophobicity and fluorescence intensity than those obtained by classical heating. Significantly lower level of browning intensity and significantly higher (p < 0.05) level of solubility (under alkaline conditions), thermal stability, emulsifying activity and emulsifying stability were observed for the conjugates obtained by ultrasound treatment as compared with those obtained by classical heating.
  • Comparison of the nutritional composition of experimental fermented milk:wheat bulgur blends and commercially available kishk and tarhana products

    O'Callaghan, Yvonne; Shevade, Ashwini V.; Guinee, Timothy P.; O'Connor, Tom P.; O'Brien, Nora M.; Department of Agriculture, Food and the Marine; 14/F/805 (Elsevier, 2018-11-05)
    Dried, fermented blends of dairy products and cereals, such as kishk and tarhana, are foodstuffs traditionally consumed in many regions as they possess good nutritional qualities and extended storage stability. This study examined the nutritional composition of kishk or tarhana type products and compared with experimental blends of fermented milk and wheat bulgur containing 60–80% milk. The blends with higher milk contents had levels of protein (18.9%) and fat (5.8%) at the concentrations specified in fortified blended foods as outlined by the World Food Program. Higher milk contents were also associated with higher contents of calcium (323.2 mg/100 g), phosphorus (335.3 mg/100 g), vitamin A (486.7 µg/100 g) and α-tocopherol (174.5 µg/100 g). The nutritional content of the experimental fermented milk:wheat bulgur blends compared favourably with that of the commercial samples. These blends may be suitable as base products, to be fortified with micronutrients, for the development of fortified blended foods (FBFs) for humanitarian distribution.
  • Modelling the changes in viscosity during thermal treatment of milk protein concentrate using kinetic data

    Ho, Quang Tri; Murphy, Kevin M.; Drapala, Kamil P.; Fenelon, Mark A.; O'Mahony, James A.; Tobin, John; McCarthy, Noel; Enterprise Ireland; TC/2014/0016 (Elsevier, 2018-10-24)
    This work aimed to model the effect of heat treatment on viscosity of milk protein concentrate (MPC) using kinetic data. MPC obtained after ultrafiltration was subjected to different time-temperature heat treatment combinations. Heat treatment at high temperature and short time (i.e., 100 or 120 °C×30 s) led to a significant increase in viscosity in MPC systems. Second-order reaction kinetic models proved a better fit than zero- or first-order models when fitted for viscosity response to heat treatment. A distinct deviation in the slope of the Arrhenius plot at 77.9 °C correlated to a significant increase in the rate of viscosity development at temperatures above this, confirming the transition of protein denaturation from the unfolding to the aggregation stage. This study demonstrated that heat-induced viscosity of MPC as a result of protein denaturation/aggregation can be successfully modelled in response to thermal treatment, providing useful new information in predicting the effect of thermal treatment on viscosity of MPC.
  • Using rejection thresholds to determine acceptability of novel bioactive compounds added to milk-based beverages

    Murray, Niamh M.; Jacquier, Jean Christophe; O'Sullivan, Michael; Hallihan, Áine; Murphy, Eoin; Feeney, Emma L.; O'Riordan, Dolores; Enterprise Ireland; TC2013001 (Elsevier, 2018-11-03)
    This study aimed to identify the amount of crude casein-hydrolysate (HMW) and a low molecular weight sub-fraction (LMW) thereof that could be incorporated into strawberry- and vanilla-flavoured beverages before the bitterness/taste became objectionable to panellists. The beverages were spiked with increasing amounts of hydrolysate and a 2-alternative forced choice (2-AFC) design was employed to determine rejection thresholds (RjT). Results showed a higher amount of HMW, than LMW, could be incorporated into the beverages before the taste became objectionable and the type of flavouring did not have a significant effect on RjT. Following the 2-AFC, panellists rated the bitterness of the hydrolysates (in water) on a general Labelled Magnitude Scale (gLMS). Results showed no significant differences between the bitterness perception of the HMW and LMW. However, there was considerable variation in the panellists’ perception of bitterness, suggesting possible evidence for segmentation. Using this rationale, each panel was segmented into two groups: those who rated the bitterness of the hydrolysate samples as ≤20 on the gLMS and, those who rated the bitterness as ≥75 on the gLMS, and RjT were examined within them. Although a trend was seen for those most sensitive to bitterness in water, to have a lower acceptance for the level in the beverages, the RjT of the segmented groups were not significantly different from each other. Evaluation of hydrolysates in water does therefore not appear to be suitable for predicting consumer acceptance of hydrolysates in food matrices; highlighting the importance of testing food ingredients in the final food product.
  • The effect of buttermilk or buttermilk powder addition on functionality, textural, sensory and volatile characteristics of Cheddar-style cheese

    Hickey, Cian D.; O'Sullivan, Maurice; Davis, Jessica; Scholz, Dimitri; Kilcawley, Kieran N; Wilkinson, Martin G.; Sheehan, Jeremiah J.; Dairy Levy Trust; 6259 (Elsevier, 2017-09-28)
    The influence of buttermilk or buttermilk powder addition to cheese milk or cheese curds respectively on cheese functional properties, free fatty acid profiles and subsequent volatile and sensory characteristics was investigated. Buttermilk addition to cheese milk resulted in a softer cheese compared to other cheeses, with a significantly reduced flowability, while buttermilk powder addition had no influence on cheese firmness but cheese flowability was also reduced compared to the control cheese. Larger pools of free fat, higher levels of free fatty acids, volatile compounds and significant differences in sensory profiles associated with off-flavour were also observed with the addition of buttermilk to cheese milk. Application of light microscopy, using toluidine blue stain, facilitated the visualisation of fat globule structure and distribution within the protein matrix. Addition of 10% buttermilk powder resulted in significant increases in volatile compounds originating from proteolysis pathways associated with roasted, green aromas. Descriptive sensory evaluation indicated few differences between the 10% buttermilk powder and the control cheese, while buttermilk cheeses scored negatively for sweaty, barnyard aromas, oxidized and off flavors, correlating with associated volatile aromas. Addition of 10% buttermilk powder to cheese curds results in cheese comparable to the control Cheddar with some variations in volatile compounds resulting in a cheese with similar structural and sensory characteristics albeit with subtle differences in overall cheese flavor. This could be manipulated to produce cheeses of desirable quality, with potential health benefits due to increased phospholipid levels in cheese.
  • Paste structure and rheological properties of lotus seed starch–glycerin monostearate complexes formed by high-pressure homogenization

    Chen, Bingyan; Guo, Zebin; Zeng, Shaoxiao; Tian, Yuting; Miao, Song; Zheng, Baodong; National Natural Science Foundation of China; Scientific and Technological Innovation Team Support Plan of Institution of Higher Learning in Fujian Province; Fujian Agriculture and Forestry University of China; 31501485; et al. (Elsevier, 2017-10-31)
    Starch–lipid complexes were prepared using lotus seed starch (LS) and glycerin monostearate (GMS) via a high-pressure homogenization (HPH) process, and the effect of HPH on the paste structure and rheological properties of LS–GMS was investigated. Rapid Visco Analyser (RVA) profiles showed that HPH treatment inhibited the formation of the second viscosity peak of the LS–GMS paste, and the extent of this change was dependent on the level of homogenized pressure. Analysis of the size-exclusion chromatography, light microscopy, and low-field 1H nuclear magnetic resonance results revealed that high homogenized pressure (70–100 MPa) decreased molecular weight and size by degrading the branch structure of amylopectin; however, intact LS–GMS granules can optimize the network structure by filler–matrix interaction, which causes free water to transition into immobile water in the starch paste. The steady-shear results showed that the LS–GMS pastes presented non-Newtonian shear-thinning behavior, with higher homogenized pressure producing a smaller hysteresis loop area. During the oscillation process, the LS–GMS pastes prepared at 100 MPa exhibited the lowest loss tangent values in all the complexes, indicating a stronger resistance to vibration.
  • Impact of ultrasound and blanching on functional properties of hot-air dried and freeze dried onions

    Ren, F.; Perussello, C. A.; Zhang, Z.; Kerry, J. P.; Tiwari, Brijesh; Department of Agriculture, Food and the Marine; FIRM 450 06/TNI/AFRC6 (Elsevier, 2017-08-22)
    The aim of this study was to investigate the effect of ultrasonic treatment and blanching prior to hot-air drying and freeze drying of onions on the retention of bioactive compounds (total phenolics, total flavonoids, and quercetin). Onion slices were treated either with ultrasound at 20 kHz and different amplitude levels (24.4–61 μm) for 1, 3 and 5 min or with blanching using hot water at 70 °C for 1, 3 and 5 min. The ultrasound treatment improved the retention of bioactive compounds (especially quercetin) and accordingly the antioxidant activity in onion slices dried either by freeze drying or hot-air drying. This is ascribed to the destruction of the original tissue structure by ultrasound and thus higher extraction ability of the studied phytochemicals. Comparing ultrasound treated samples, freeze dried onions had a higher retention of bioactive compounds than hot-air dried ones. Blanched and ultrasound treated dried onions exhibited similar colour change. Therefore, ultrasound treatment is a potential alternative to conventional blanching before drying of onion slices.
  • Bovine glycomacropeptide promotes the growth of Bifidobacterium longum ssp. infantis and modulates its gene expression

    O'Riordan, Noelle; O'Callaghan, J.; Buttò, L.F.; Kilcoyne, Michelle; Joshi, L.; Hickey, Rita M.; Teagasc Walsh Fellowship Programme (Elsevier, 2018-05-24)
    Bovine milk glycomacropeptide (GMP) is derived from κ-casein, with exclusively o-linked glycosylation. Glycomacropeptide promoted the growth of Bifidobacterium longum ssp. infantis in a concentration-dependent manner, and this activity was lost following periodate treatment of the GMP (GMP-P), which disables biological recognition of the conjugated oligosaccharides. Transcriptional analysis of B. longum ssp. infantis following exposure to GMP revealed a substantial response to GMP relative to bacteria treated with GMP-P, with a greater number of differentially expressed transcripts and larger fold changes versus the control. Therefore, stimulation of B. longum ssp. infantis growth by GMP is intrinsically linked to the peptide's O-linked glycosylation. The pool of differentially expressed transcripts included 2 glycoside hydrolase (family 25) genes, which were substantially upregulated following exposure to GMP, but not GMP-P. These GH25 genes were present in duplicated genomic islands that also contained genes encoding fibronectin type III binding domain proteins and numerous phage-related proteins, all of which were also upregulated. Homologs of this genomic arrangement were present in other Bifidobacterium species, which suggest it may be a conserved domain for the utilization of glycosylated peptides. This study provides insights into the molecular basis for the prebiotic effect of bovine milk GMP on B. longum ssp. infantis.
  • Effects of milk heat treatment and solvent composition on physicochemical and selected functional characteristics of milk protein concentrate

    Lin, Yingchen; Kelly, Alan L.; O’Mahony, James A.; Guinee, Timothy P.; Dairy Levy Trust Co-Operative Society Limited (Elsevier, 2018-05-24)
    Milk protein concentrate (MPC) powders (∼81% protein) were made from skim milk that was heat treated at 72°C for 15 s (LHMPC) or 85°C for 30 s (MHMPC). The MPC powder was manufactured by ultrafiltration and diafiltration of skim milk at 50°C followed by spray drying. The MPC dispersions (4.02% true protein) were prepared by reconstituting the LHMPC and MHMPC powders in distilled water (LHMPCw and MHMPCw, respectively) or milk permeate (LHMPCp and MHMPCp, respectively). Increasing milk heat treatment increased the level of whey protein denaturation (from ∼5 to 47% of total whey protein) and reduced the concentrations of serum protein, serum calcium, and ionic calcium. These changes were paralleled by impaired rennet-induced coagulability of the MHMPCw and MHMPCp dispersions and a reduction in the pH of maximum heat stability of MHMPCp from pH 6.9 to 6.8. For both the LHMPC and MHMPC dispersions, the use of permeate instead of water enhanced ethanol stability at pH 6.6 to 7.0, impaired rennet gelation, and changed the heat coagulation time and pH profile from type A to type B. Increasing the severity of milk heat treatment during MPC manufacture and the use of permeate instead of water led to significant reductions in the viscosity of stirred yogurt prepared by starter-induced acidification of the MPC dispersions. The current study clearly highlights how the functionality of protein dispersions prepared by reconstitution of high-protein MPC powders may be modulated by the heat treatment of the skim milk during manufacture of the MPC and the composition of the solvent used for reconstitution.
  • Effects of depleting ionic strength on 31P nuclear magnetic resonance spectra of micellar casein during membrane separation and diafiltration of skim milk

    Boiani, Mattia; McLoughlin, Padraig; Auty, Mark; Fitzgerald, Richard J.; Kelly, Phil M.; Irish Department of Agriculture Food Institution Research Measure; Teagasc Walsh Fellowship Programme (Elsevier, 2017-07-06)
    Membrane separation processes used in the concentration and isolation of micellar casein-based milk proteins from skim milk rely on extensive permeation of its soluble serum constituents, especially lactose and minerals. Whereas extensive literature exists on how these processes influence the gross composition of milk proteins, we have little understanding of the effects of such ionic depletion on the core structural unit of micellar casein [i.e., the casein phosphate nanocluster (CPN)]. The 31P nuclear magnetic resonance (NMR) is an analytical technique that is capable of identifying soluble and organic forms of phosphate in milk. Thus, our objective was to investigate changes to the 31P NMR spectra of skim milk during microfiltration (MF) and diafiltration (DF) by tracking movements in different species of phosphate. In particular, we examined the peak at 1.11 ppm corresponding to inorganic phosphate in the serum, as well as the low-intensity broad signal between 1.5 and 3.0 ppm attributed to casein-associated phosphate in the retentate. The MF concentration and DF using water caused a shift in the relevant 31P NMR peak that could be minimized if orthophosphate was added to the DF water. However, this did not resolve the simultaneous change in retentate pH and increased solubilization of micellar casein protein. The addition of calcium in combination with orthophosphate prevented micellar casein solubilization and simultaneously contributed to preservation of the CPN structure, except for overcorrection of retentate pH in the acidic direction. A more complex DF solution, involving a combination of phosphate, calcium, and citrate, succeeded in both CPN and micellar casein structure preservation while maintaining retentate pH in the region of the original milk pH. The combination of 31P NMR as an analytical technique and experimental probe during MF/DF processes provided useful insights into changes occurring to CPN while retaining the micellar state of casein.
  • Technical note: Fourier transform infrared spectral analysis in tandem with 31P nuclear magnetic resonance spectroscopy elaborates detailed insights into phosphate partitioning during skimmed milk microfiltration and diafiltration

    Boiani, Mattia; Fitzgerald, Richard J.; Kelly, Philip M.; Department of Agriculture, Food and the Marine; Teagasc Walsh Fellowship Programme (Elsevier, 2018-09-27)
    Our previous study identified peaks in the 31P nuclear magnetic resonance (31P NMR) spectra of skim milk, denoting the interaction of different phosphate species such as inorganic and casein-associated phosphate during the separation of colloidal and serum phases of skim milk by microfiltration (MF) and diafiltration (DF). In the current study, we investigated the same samples generated by the aforementioned separation using attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy analysis. The results confirmed that the technique was not only capable of differentiating between the mineral equilibrium of the casein phosphate nanocluster (CPN) and milk serum, but also complemented the application of 31P NMR. An ATR-FTIR broad band in the region of 1,055 to 1,036 cm−1 and a specific band at 1,076 cm−1 were identified as sensitive to the repartitioning of different phosphate species in milk in accordance with the 31P NMR signals representing casein-associated phosphate and inorganic phosphate in the serum. A third ATR-FTIR signal at 1,034 cm−1 in milk, representing precipitated inorganic calcium phosphate, had not previously been detected by 31P NMR. Thus, the results indicate that a combination of ATR-FTIR and 31P NMR spectroscopies may be optimally used to follow mineral and protein phase changes in milk during membrane processing.
  • Invited review: Whey proteins as antioxidants and promoters of cellular antioxidant pathways

    Corrochano, Alberto R.; Buckin, Vitaly; Kelly, Philip M.; Giblin, Linda; Department of Agriculture, Food and the Marine; Teagasc Walsh Fellowship Programme; 13 F 454-WheyGSH (Elsevier, 2018-03-28)
    Oxidative stress contributes to cell injury and aggravates several chronic diseases. Dietary antioxidants help the body to fight against free radicals and, therefore, avoid or reduce oxidative stress. Recently, proteins from milk whey liquid have been described as antioxidants. This review summarizes the evidence that whey products exhibit radical scavenging activity and reducing power. It examines the processing and treatment attempts to increase the antioxidant bioactivity and identifies 1 enzyme, subtilisin, which consistently produces the most potent whey fractions. The review compares whey from different milk sources and puts whey proteins in the context of other known food antioxidants. However, for efficacy, the antioxidant activity of whey proteins must not only survive processing, but also upper gut transit and arrival in the bloodstream, if whey products are to promote antioxidant levels in target organs. Studies reveal that direct cell exposure to whey samples increases intracellular antioxidants such as glutathione. However, the physiological relevance of these in vitro assays is questionable, and evidence is conflicting from dietary intervention trials, with both rats and humans, that whey products can boost cellular antioxidant biomarkers.
  • Effect of milk centrifugation and incorporation of high heat-treated centrifugate on the microbial composition and levels of volatile organic compounds of Maasdam cheese

    Lamichhane, Prabin; Pietrzyk, Anna; Feehily, Conor; Cotter, Paul D.; Mannion, David T.; Kilcawley, Kieran N; Kelly, Alan L.; Sheehan, Jeremiah J.; Dairy Levy Trust; Teagasc Walsh Fellowship Programme; et al. (Elsevier, 2018-03-15)
    Centrifugation is a common milk pretreatment method for removal of Clostridium spores which, on germination, can produce high levels of butyric acid and gas, resulting in rancid, gassy cheese. The aim of this study was to determine the effect of centrifugation of milk, as well as incorporation of high heat-treated centrifugate into cheese milk, on the microbial and volatile profile of Maasdam cheese. To facilitate this, 16S rRNA amplicon sequencing in combination with a selective media-based approach were used to study the microbial composition of cheese during maturation, and volatile organic compounds within the cheese matrix were analyzed by HPLC and solid-phase microextraction coupled with gas chromatography–mass spectrometry. Both culture-based and molecular approaches revealed major differences in microbial populations within the cheese matrix before and after warm room ripening. During warm room ripening, an increase in counts of propionic acid bacteria (by ∼101.5 cfu) and nonstarter lactic acid bacteria (by ∼108 cfu) and a decrease in the counts of Lactobacillus helveticus (by ∼102.5 cfu) were observed. Lactococcus species dominated the curd population throughout ripening, followed by Lactobacillus, Propionibacterium, and Leuconostoc, and the relative abundance of these accounted for more than 99% of the total genera, as revealed by high-throughput sequencing. Among subdominant microflora, the overall relative abundance of Clostridium sensu stricto was lower in cheeses made from centrifuged milk than control cheeses, which coincided with lower levels of butyric acid. Centrifugation as well as incorporation of high heat-treated centrifugate into cheese milk seemed to have little effect on the volatile profile of Maasdam cheese, except for butyric acid levels. Overall, this study suggests that centrifugation of milk before cheesemaking is a suitable method for controlling undesirable butyric acid fermentation without significantly altering the levels of other volatile organic compounds of Maasdam cheese.
  • Phenotypic, fermentation characterization, and resistance mechanism analysis of bacteriophage-resistant mutants of Lactobacillus delbrueckii ssp. bulgaricus isolated from traditional Chinese dairy products

    Deng, Kaibo; Fang, Wei; Zheng, Baodong; Miao, Song; Huo, Guicheng; International Technological Cooperation and Exchange Plan of Fujian Agriculture and Forestry University; National Natural Science Funds of China; Scientific and Technological Innovation Team Support Plan of Fujian Agriculture and Forestry University; KXGH17001; 31171717; et al. (Elsevier, 2017-12-21)
    Bacteriophage infection is a large factor in dairy industrial production failure on the basis of pure inoculation fermentation, and developing good commercial starter cultures from wild dairy products and improving the environmental vigor of starter cultures by enhancing their phage resistance are still the most effective solutions. Here we used a spontaneous isolation method to obtain bacteriophage-resistant mutants of Lactobacillus delbrueckii ssp. bulgaricus strains that are used in traditional Chinese fermented dairy products. We analyzed their phenotypes, fermentation characteristics, and resistance mechanisms. The results showed that bacteriophage-insensitive mutants (BIM) BIM8 and BIM12 had high bacteriophage resistance while exhibiting fermentation and coagulation attributes that were as satisfying as those of their respective parent strains KLDS1.1016 and KLDS1.1028. According to the attachment receptor detection, mutants BIM8 and BIM12 exhibited reduced absorption to bacteriophage phiLdb compared with their respective bacteriophage-sensitive parent strains because of changes to the polysaccharides or teichoic acids connected to their peptidoglycan layer. Additionally, genes, including HSDR, HSDM, and HSDS, encoding 3 subunits of a type I restriction-modification system were identified in their respective parent strains. We also discovered that HSDR and HSDM were highly conserved but that HSDS was variable because it is responsible for the DNA specificity of the complex. The late lysis that occurred only in strain KLDS1.1016 and not in strain KLDS1.1028 suggests that the former and its mutant BIM8 also may have an activatable restriction-modification mechanism. We conclude that the L. bulgaricus BIM8 and BIM12 mutants have great potential in the dairy industry as starter cultures, and their phage-resistance mechanism was effective mainly due to the adsorption interference and restriction-modification system.
  • Effect of different forage types on the volatile and sensory properties of bovine milk

    Faulkner, Hope; O’Callaghan, Tom F.; McAuliffe, Stephen; Hennessy, Deirdre; Stanton, Catherine; O’Sullivan, Maurice G.; Kerry, Joseph; Kilcawley, Kieran N; Department of Agriculture, Food and the Marine; 13SN401 (Elsevier, 2017-12-08)
    The effect of 3 diets (grass, grass/clover, and total mixed ration) on the volatile and sensory properties of bovine milk was assessed over an entire lactation season. Little evidence was found of direct transfer of terpenes into raw milk from the different diets, and it is likely that the monocultures of ryegrass used with and without white clover were factors as these contained very few terpenes. Evidence of direct transfer of nonterpene volatiles from forage to the subsequent raw milks was probable; however, differences in the protein carbohydrate availability and digestion in the rumen appeared to have a greater contribution to volatile profiles. Pasteurization significantly altered the volatile profiles of all milks. A direct link between the milk fatty acid content, forage, and volatile products of lipid oxidation was also evident and differences in fatty acid content of milk due to forage may also have influenced the viscosity perception of milk. Irish sensory assessors preferred pasteurized milk produced from grass-fed cows, with least preference from milk produced from total mixed ration diets. β-Carotene content was significantly higher in milks derived from grass or grass/clover and appears to have directly influenced color perception. Toluene and p-cresol are both degradation products of β-carotene and along with β-carotene were identified as potential biomarkers for milk derived from pasture. The only correlation that appeared to influence the flavor of milk as determined using ranked descriptive analysis was p-cresol. P-Cresol appears to be responsible for the barnyard aroma of milk and is also likely derived from the deamination and decarboxylation of tryptophan and tyrosine due to the higher levels of available protein in the grass and grass/clover diets. The highest levels of p-cresol were in the grass/clover diets and are likely due to the degradation of the isoflavone formononetin in the rumen, which is present in white clover swards.
  • Inhibition of lactose crystallisation in the presence of galacto-oligosaccharide

    Fu, Shishan; Miao, Song; Ma, Xiaobin; Ding, Tian; Ye, Xinqian; Liu, Donghong (Elsevier, 2018-10-02)
    The stabilization of lactose in the form of amorphous (i.e. non-crystalline form) is the basic requirement to maintain the quality of relevant food and pharmaceutical products. The physiochemical properties of amorphous lactose mixed with galacto-oligosaccharide (GOS) were investigated. Water sorption, glass transition temperature, and crystallisation behaviour of lactose in the present of GOS (1:1 w/w) were measured at various water activity (0.11–0.75 aw, 25 °C) and lactose mutarotation was also evaluated. All of them were compared with the physiochemical properties of trehalose-lactose (1:1 w/w). The addition of GOS to lactose increased the hygroscopicity of the mixture, as well as slightly increased the glass transition temperature compared to lactose alone. The critical water activity (at 0.68 aw) of lactose crystallisation was increased by the addition of GOS as compared to that of trehalose-lactose (1:1 w/w) (at 0.58 aw) or lactose alone (at 0.44 aw). The dramatical inhibition of lactose crystallisation with a lower crystallisation kinetic constant and the alternation of lactose crystal forms in the presence of GOS was observed as compared to the crystallisation behaviour of trehalose-lactose (1:1 w/w) and pure lactose at 0.68 and 0.75 aw, 25 °C. Without affecting its Tg, the significantly delayed crystallisation of lactose in GOS-lactose mixture (1:1 w/w) was more likely due to the change of lactose mutarotation. As comparing to trehalose that is an effective inhibitor, GOS has a stronger ability to prevent lactose from crystallisation in hydrous matrices.
  • Outdoor grazing of dairy cows on pasture versus indoor feeding on total mixed ration: Effects on gross composition and mineral content of milk during lactation

    Gulati, Arunima; Galvin, Norann; Lewis, Eva; Hennessy, Deirdre; O'Donovan, Michael; McManus, Jennifer J.; Fenelon, Mark A.; Guinee, Timothy P.; Department of Agriculture, Food and the Marine; Dairy Levy Trust Co-Operative Society Limited; et al. (Elsevier, 2017-08-15)
    The influence of feeding system and lactation period on the gross composition, macroelements (Ca, P, Mg, and Na), and trace elements (Zn, Fe, Cu, Mo, Mn, Se, and Co) of bovine milk was investigated. The feeding systems included outdoor grazing on perennial ryegrass pasture (GRO), outdoor grazing on perennial ryegrass and white clover pasture (GRC), and indoors offered total mixed ration (TMR). Sixty spring-calving Holstein Friesian dairy cows were assigned to 3 herds, each consisting of 20 cows, and balanced with respect to parity, calving date, and pre-experimental milk yield and milk solids yield. The herds were allocated to 1 of the 3 feeding systems from February to November. Milk samples were collected on 10 occasions over the period June 17 to November 26, at 2 or 3 weekly intervals, when cows were on average 119 to 281 d in lactation (DIL). The total lactation period was arbitrarily sub-divided into 2 lactation periods based on DIL, namely mid lactation, June 17 to September 9 when cows were 119 to 203 DIL; and late lactation, September 22 to November 26 when cows were 216 to 281 DIL. With the exception of Mg, Na, Fe, Mo, and Co, all other variables were affected by feeding system. The GRO milk had the highest mean concentrations of total solids, total protein, casein, Ca, and P. The TMR milk had the highest concentrations of lactose, Cu, and Se, and lowest level of total protein. The GRC milk had levels of lactose, Zn, and Cu similar to those of GRO milk, and concentrations of TS, Ca, and P similar to those of TMR milk. Lactation period affected all variables, apart from the concentrations of Fe, Cu, Mn, and Se. On average, the proportion (%) of total Ca, P, Zn, Mn, or Se that sedimented with the casein on high-speed ultracentrifugation at 100,000 × g was ≥60%, whereas that of Na, Mg, or Mo was ≤45% total. The results demonstrate how the gross composition and elemental composition of milk can be affected by different feeding systems.

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