"Milk on Ice": A detailed analysis of Ernest Shackleton's century-old whole milk powder in comparison with modern counterparts.

Whole milk powder (WMP) manufactured in New Zealand in 1907 was sent to the Antarctic continent with the Shackleton-led British Antarctic Expedition from 1907 to 1909. This powder was stored at ambient conditions at Shackleton's Hut at Cape Royds, Antarctica, for over 100 yr before a sample was collected on behalf of Fonterra by the Antarctic Heritage Trust. Having spent most of its existence both dried and in frozen storage, any deleterious reactions within the WMP would have been markedly retarded. The composition and some properties of the roller-dried Shackleton's WMP are reported along with those of 2 modern spray-dried New Zealand WMP. The Shackleton powder was less white and more yellow than the modern WMP and was composed of flakes rather than agglomerated particles, consistent with that expected of a roller-dried powder. Headspace analysis showed lipolytic and oxidative volatile compounds were present in the Shackleton WMP, indicting some deterioration of the milk either before powder manufacture or on storage of the finished product. On a moisture-free basis, the Shackleton WMP had higher protein, higher fat (with a markedly higher free fat level), higher ash, and a lower lactose level than the modern WMP. The lysine level was lower in the Shackleton WMP compared with the spray-dried powders, whereas the fatty acid composition was relatively similar. The sodium level was markedly higher in the Shackleton WMP compared with the spray-dried powder, which is probably due to the addition of an alkaline sodium salt to adjust the pH of the milk before roller drying. Lead, iron, and tin levels were markedly higher in the Shackleton WMP compared with the spray-dried powders, possibly due to the equipment used in powder manufacture and the tin-plated cases used for storage. The proteins in the Shackleton WMP were more lactosylated than in the spray-dried powders. The Shackleton WMP had a higher ratio of κ-casein A to B variants and a higher ratio of ß-lactoglobulin B to A variants than the spray-dried powders, whereas the αS1-casein, ß-casein, αS2-casein, and α-lactalbumin protein variants were similar in all powders. The total phospholipid content was markedly lower in the Shackleton WMP than the spray-dried powders, primarily due to a lower phosphatidylethanolamine concentration. The molecular species distributions within the phospholipid classes were generally similar in the 3 powders. Claims are sometimes encountered that the milk of today is different from that consumed by previous generations. However, this comparative study has shown that the Shackleton WMP was generally similar to modern WMP. Although differences in some components and properties were observed, these were attributable to the manufacturing equipment and processes used in the pioneering years of WMP manufacture.

The influence of emulsion structure on the Maillard reaction of ghee.

Food systems, such as cream and butter, have an emulsion or emulsion-like structure. When these food emulsions are heated to high temperatures to make products such as ghee, the Maillard reaction forms a range of volatile flavour compounds. The objective of this paper was to unravel the specific influence of emulsion structure on the Maillard reaction pathways that occur during the cooking of ghee using model systems. Switching the dispersed phase from oil to water provided a means of altering the ratios of volatile compounds produced in the cooked samples. The oil-in-water emulsion generated a volatile compound profile similar to that of the fat containing two phase model matrix, whereas the water-in-oil emulsion produced a different ratio of these compounds. The ability to generate different volatile compound profiles through the use of inverted emulsion structures could point to a new avenue for control of the Maillard reaction in high temperature food systems.

Lipolysis within single culture and co-culture biofilms of dairy origin.

Bacteria in raw milk can produce heat-stable lipases, which survive pasteurisation and subsequently reduce the shelf life of dairy products because of their ability to break down the milk fat and increase rancidity. In this study, four bacteria, originating from the surfaces of raw milk transport tankers, and a known lipase-producing bacterium were evaluated for their ability to produce lipolysis in planktonic and biofilm cultures. Lipolysis was determined using two separate assays that measured hydrolysis of the ester p-nitrophenol palmitate (pnpp) and the lipid tributyrin. The hydrolysis of pnpp per CFU within biofilms and planktonic cultures ranged from 0.01 to 8.35 and 0.01 to 0.07 nU/CFU respectively. The amount of butyric acid released from hydrolysis of tributyrin per CFU within biofilms and planktonic cultures ranged from 0.1 to 1110.3 and 0.1 to 0.3 ng/CFU, respectively. The hydrolysis of pnpp and tributyrin per CFU within biofilms was at least 10 times higher compared with the corresponding planktonic cultures. This is the first study to show that lipolysis occurs within biofilms of bacteria that were originally isolated from the surfaces of raw milk tankers. This is relevant to the dairy industry, highlighting the importance of eliminating biofilms on milk tanker surfaces as a source of heat-stable lipases.

The role of the Maillard reaction in the formation of flavour compounds in dairy products--not only a deleterious reaction but also a rich source of flavour compounds.

Dairy products are heated both during processing and by consumers during food preparation; consumers place a high level of importance on flavour when assessing product acceptability. Of particular importance to the flavour of heated dairy products is the highly complex network of Maillard reactions. Much focus has been placed on the undesirable flavours generated through the Maillard reaction and how to minimise the formation of these flavours. However, beneficial flavours can also be formed by the Maillard reaction; dairy products, such as ghee, are formed by heating and are characterised by the unique flavour generated by this chemistry. This review looks at the Maillard reaction as a source of beneficial flavours for cooked dairy products and the application of models to the study of flavour formation in food systems. Models are typically used to study complex reactions in a simplified way; however, they are not always applicable to food systems.

Proteolysis produced within biofilms of bacterial isolates from raw milk tankers.

In this study, six bacterial isolates that produced thermo-resistant enzymes isolated from the internal surfaces of raw milk tankers were evaluated for their ability to produce proteolysis within either single culture biofilms or co-culture biofilms. Biofilms were formed in an in vitro model system that simulated the upper internal surface of a raw milk tanker during a typical summer's day of milk collection in New Zealand. The bacterial isolates were further evaluated for their ability to form biofilms at 25, 30 and 37°C. Mutual and competitive effects were observed in some of the co-culture biofilms, with all isolates being able to form biofilms in either single culture or co-culture at the three temperatures. The proteolysis was also evaluated in both biofilms and corresponding planktonic cultures. The proteolysis per cell decreased as the temperature of incubation (20-37°C) increased. Furthermore, mutualistic interactions in terms of proteolysis were observed when cultures were grown as co-culture biofilms. This is the first study to show that proteolytic enzymes can be produced in biofilms on the internal surfaces of raw milk tankers. This has important implications for the cleaning and the temperature control of raw milk transport tankers.

Do arsenosugars pose a risk to human health? The comparative toxicities of a trivalent and pentavalent arsenosugar.

Seafood frequently contains high concentrations of arsenic (approximately 10-100 mg/kg dry weight). In marine algae (seaweed), this arsenic occurs predominantly as ribose derivatives known collectively as arsenosugars. Although it is clear that arsenosugars are not acutely toxic, there is a possibility of arsenosugars having slight chronic toxicity. In general, trivalent arsenicals are more toxic than their pentavalent counterparts, so in this work we examine the hypothesis that trivalent arsenosugars might be significantly more toxic than pentavalent arsenosugars in vitro. We compared the in vitro toxicity of (R)-2,3-dihydroxypropyl-5-deoxy-5-dimethylarsinoyl-beta-D-riboside, a pentavalent arsenosugar, to that of its trivalent counterpart, (R)-2,3-dihydroxypropyl-5-deoxy-5-dimethylarsino-beta-D-riboside. The trivalent arsenosugar nicked plasmid DNA, whereas the pentavalent arsenosugar did not. The trivalent arsenosugar was more cytotoxic (IC50 = 200 microM, 48 h exposure) than its pentavalent counterpart (IC50 > 6000 microM, 48 h exposure) in normal human epidermal keratinocytes in vitro as determined via the neutral red uptake assay. However, both the trivalent and the pentavalent arsenosugars were significantly less toxic than MMA(III), DMA(III), and arsenate. Neither the pentavalent arsenosugar nor the trivalent arsenosugar were mutagenic in Salmonella TA104. The trivalent arsenosugar was readily formed by reaction of the pentavalent arsenosugar with thiol compounds, including, cysteine, glutathione, and dithioerythritol. This work suggests that the reduction of pentavalent arsenosugars to trivalent arsenosugars in biology might have environmental consequences, especially because seaweed consumption is a significant environmental source for human exposure to arsenicals.

Plasmid DNA damage caused by stibine and trimethylstibine.

Antimony is classified as "possibly carcinogenic to humans" and there is also sufficient evidence for antimony carcinogenicity in experimental animals. Stibine is a volatile inorganic antimony compound to which humans can be exposed in occupational settings (e.g., lead-acid battery charging). Because it is highly toxic, stibine is considered a significant health risk; however, its genotoxicity has received little attention. For the work reported here, stibine was generated by sodium borohydride reduction of potassium antimony tartrate. Trimethylstibine is a volatile organometallic antimony compound found commonly in landfill and sewage fermentation gases at concentrations ranging between 0.1 and 100 microg/m3. Trimethylstibine is generally considered to pose little environmental or health risk. In the work reported here, trimethylstibine was generated by reduction of trimethylantimony dichloride using either sodium borohydride or the thiol compounds, dithioerythritol (DTE), L-cysteine, and glutathione. Here we report the evaluation of the in vitro genotoxicities of five antimony compounds-potassium antimony tartrate, stibine, potassium hexahydroxyantimonate, trimethylantimony dichloride, and trimethylstibine-using a plasmid DNA-nicking assay. Of these five antimony compounds, only stibine and trimethylstibine were genotoxic (significant nicking to pBR 322 plasmid DNA). We found stibine and trimethylstibine to be about equipotent with trimethylarsine using this plasmid DNA-nicking assay. Reaction of trimethylantimony dichloride with either glutathione or L-cysteine to produce DNA-damaging trimethylstibine was observed with a trimethylantimony dichloride concentration as low as 50 microM and L-cysteine or glutathione concentrations as low as 500 and 200 microM, respectively, for a 24 h incubation.

Dimethylarsine and trimethylarsine are potent genotoxins in vitro.

The mechanism of arsenic carcinogenesis is unclear. A complicating factor receiving increasing attention is that arsenic is biomethylated to form various metabolites. Eleven different arsenicals were studied for in vitro genotoxicity to supercoiled DNA (pBR 322 and phiX174). Five arsenicals showed various degrees of positivity-monomethylarsonous acid, dimethylarsinous acid, monomethylarsine, dimethylarsine, and trimethylarsine. Supercoiled DNA, blotted on nitrocellulose filter paper, was exposed to gaseous arsines by suspending the filter paper above aqueous reaction mixtures of sodium borohydride and an appropriate arsenical. All three methylated arsines damaged DNA; inorganic arsine did not. Arsines were generated in situ in reaction mixtures containing DNA by reaction of sodium borohydride with arsenite, monomethylarsonous acid, dimethylarsinous acid, and trimethylarsine oxide, at pH 8.0. Both dimethylarsine and trimethylarsine (generated from 200 micro M dimethylarsinous acid and trimethylarsine oxide, respectively) damaged DNA in less than 30 min. Under certain conditions, the two most potent genotoxic arsines, trimethylarsine and dimethylarsine, are about 100 times more potent than dimethylarsinous acid (the most potent genotoxic arsenical previously known). There was no evidence to suggest that anything other than the arsines caused the DNA damage. Possible models for the biological production of arsines were examined. The coenzymes, NADH and NADPH, are biological hydride donors. When NADH or NADPH (5 mM) were incubated with dimethylarsinous acid (0-2 mM) for 2 h, DNA damage was increased by at least 10-fold. A possible explanation for this result is that these compounds react with dimethylarsinous acid to generate dimethylarsine. DNA was incubated with a dithiol compound, dithioerythritol (5 mM), and trimethylarsine oxide (0.5 mM) for 2 h, and the reduction of trimethylarsine oxide to trimethylarsine resulted in DNA damage.

Sensory properties of virgin olive oil polyphenols: identification of deacetoxy-ligstroside aglycon as a key contributor to pungency.

Polyphenols are an important functional minor component of virgin olive oils that are responsible for the key sensory characteristics of bitterness, pungency, and astringency. Polyphenols were isolated from virgin olive oils by using liquid/liquid extraction and then separated by using reverse phase HPLC followed by fraction collection. The sensory qualities of the isolated polyphenols were evaluated, and almost all fractions containing polyphenols were described as bitter and astringent. However, the fraction containing deacetoxy-ligstroside aglycon produced a strong burning pungent sensation at the back of the throat. In contrast, the fraction containing the analogous deacetoxy-oleuropein aglycon, at an equivalent concentration, produced only a slight burning/numbing sensation, which was perceived more on the tongue. No other polyphenol fractions from the analyzed oils produced the intense burning sensation; thus, deacetoxy-ligstroside aglycon is the polyphenol responsible for the majority of the burning pungent sensation found in pungent extra virgin olive oils.