Mixing milk

Food adulteration is an unsavoury fact of modern life. Many foodstuffs are targeted by criminal gangs because of their high value, so mixing them with cheaper alternatives while selling at the price of the pure material leads to higher profits. Pursue this tactic at the national or international scale and there is good money to be made.

One of the more surprising foods that have been targeted is milk. Not the common cows’ milk that we drink in the Western world, but milk from more exotic species likes the yak, buffalo or camel. These types have been mixed with milk from the cow or goat, and goat milk itself has been adulterated with cheaper cow milk. It is difficult to see or taste the difference when milk has been adulterated but scientific methods are available.

In particular, NMR and IR spectroscopy, mass spectrometry, capillary electrophoresis, ELISA and the polymerase chain reaction have been successfully employed. A further technique is 2D gel electrophoresis (2-DE) which has been reported recently for the characterisation of mammalian milk but there has been little work to study the differences in the 2-DE maps of different species.

This situation has now been rectified by Chinese researchers who have examined five types of milk. Jiaqi Wang and colleagues from the Institute of Animal Science at the Chinese Academy of Agricultural Sciences, Beijing, and the Institute of Animal Science and Veterinary Medicine at Anhui Academy of Agricultural Sciences, Hefei, used 2-DE backed up by mass spectrometry to help identify milk adulteration.

Well gel

Milk was collected from buffalos, yaks, camels, goats and cows at various farms in China. Samples of the same species were pooled to provide uniformity and the skimmed milk was prepared for analysis. Samples from one species alone or with up to 5% adulteration by one other type of milk were prepared.

All of the samples were subjected to 2-DE with isoelectric focussing over pH 4-7 followed by separation on polyacrylamide gels. This process separated the proteins across the gel in two dimensions and they were visualised by staining the gels with the dye Coomassie Brilliant Blue G-250. The intensities of the dye on the respective spots are a measure of the amount of protein in that spot.

Each pure milk was subjected three times to 2-DE and master gel maps for each species were created by comparing the 2-DE maps. Then, the researchers looked for proteins that were present in the milk mixtures but absent from the pure milks as a way to detect adulteration and these spots were identified by mass spectrometry.

Animal species identified

At first glance, the protein maps of cow, yak and buffalo milk were similar but those of camel and goat were different, as might be expected. Those differences not only allowed modified mixtures to be detected, but also revealed which type of milk had been added. They key proteins were β-lactoglobulin, α-lactalbumin and αS1-casein. 

For instance, β-lactoglobulin and α-lactalbumin from cow or goat milk mark the adulteration of camel milk. This is supported by the detection of the αS1-caseins from the cow and the goat, which have different molecular masses and isoelectric points from that of the camel, so appear in different positions on the gels.

Yak milk adulteration by cow milk was highlighted by a β-lactoglobulin variant which is absent in the yak but present in cow milk. Similarly, the β-lactoglobulin and α-lactalbumin of goat milk revealed its presence in yak milk. Conversely, goat milk adulteration with yak milk was marked by the presence of yak β-lactoglobulin and α-lactalbumin.

These three proteins from each species were sufficient to unearth the adulteration of one milk by another, down to contamination levels of 0.5%. The gels are reproducible for each species, with the proteins appearing in the same positions so, in theory, it is not necessary to identify the protein spots for successful tests. However, it would be wise to confirm their identities before establishing a lab test.

Researcher studies crystal growth that may lead to biomaterials for both and tooth repair

In nature, some organisms create their own mineralized body parts--such as bone, teeth and shells--from sources they find readily available in their environment. Certain sea creatures, for example, construct their shells from calcium carbonate crystals they build from ions found in the ocean.

"The organism takes brittle carbonate and turns it into a structural shape that protects it from predators, and from being bashed against the rocks," says Lara Estroff, an associate professor of materials science and engineering at Cornell University. "There is much scientific interest in how the organism controls the crystal growth, and what mechanisms are involved in strengthening and toughening the shells, especially in comparison to their components, which are brittle."

Researchers such as Estroff are very interested in synthesizing this kind of biology in the lab, and creating new organic and inorganic materials that mimic the "biomineralization" that occurs in nature, so they can gain a better understanding of how these natural processes work.

"We are trying to learn the techniques from the organisms, and apply them in the laboratory," says the National Science Foundation (NSF)-funded scientist, a synthetic chemist by training. "Part of it is creating simplified systems so that we can tease apart the more complicated mechanisms that are going on in biology. I am not recreating biology in the lab. I am learning from biology to create new materials."

Estroff's primary research focus is to discover the role of gels in crystal formation. Hydrogels, which are gels made in water, similar to Jell-O®, are involved in a number of natural biological systems, including the mother-of-pearl in mollusk shells, tooth enamel in mammals, even otoconia, which are tiny particles found in human ears. These substances are composed of both organic and inorganic materials; often the organic components form a gel. Estroff wants to know their purpose.

"Is there something special about a hydrogel in directing crystal growth?" she asks. "Does it change properties? Is it somehow responsible for giving rise to organic-inorganic composites?"

Understanding and controlling crystal growth is very important in many industrial fields, chief among them the manufacture of pharmaceuticals, since many drugs are in crystalline form, and "it's of vast importance to know how to modulate the solubility of crystals and how they pack into tablets," she says.

There also may be potential applications in producing biomaterials for bone and tooth repair, and in creating more functional inorganic materials, such as substances structured at the nanoscale that could enhance energy storage, for example in batteries. "Being able to manipulate these crystal structures down to the nanoscale opens up a lot of opportunities," she says.

Estroff is conducting her research under an NSF Faculty Early Career Development (CAREER) award, which she received in 2009. The award supports junior faculty who exemplify the role of teacher-scholars through outstanding research, excellent education and the integration of education and research within the context of the mission of their organization. NSF is funding her work with $472,773 over five years.

The project focuses on observations, both in nature and in the laboratory, of macroscopic, single crystals with incorporated polymer fibers and other macromolecules. The project aims to understand the mechanisms by which these polymer networks become incorporated into macroscopic, single crystals.

Her lab, in studying crystal growth mechanisms in gels and their relationship to biomineralization, is trying to answer at least three questions. "First, what is the internal structure of these crystals, and where does the gel material become trapped?" she asks. "Second, can we understand the mechanism of how it is trapped to control how much is trapped? And, third, what effect does this material have on the mechanical properties of the crystals?"

To find the answers, her team developed a synthetic analog to the biological system. Using agarose, a more purified form of the gel agar-agar, they grew their own crystals in the lab, then compared them to crystals grown without gel in an ordinary water-based solution, and later to natural biological crystals.

During the process, they ran a high resolution electron tomography scan of their samples, creating a three-dimensional image of the gel-grown crystal, which "was the first time that people had actually seen how the organic phase can be incorporated in the crystal," she says. "A crystal is an order array of ions, and a polymer is a floppy, poorly-defined blob. How do you accommodate this floppy blob into this ordered array?"

In comparing their synthetic crystals to natural ones, "there were similarities and differences," she says. "We now have the best image of how these objects are incorporated and now can start asking questions about the structure-property relationships, including how this internal structure translates into changes in the mechanical properties. We've been poking at the crystals and looking at the response."

As it turns out, "these organic inclusions mechanically strengthen and toughen the material in both biological crystals and synthetic crystals," she says. "The organic material that is trapped within the crystals makes them stronger and harder--more resistant to fracture--than their geologic counterparts with no organic material."

The researchers' next step is to synthesize other materials. "We'd like to find out if we can grow different types of crystals in different types of gels," she says. "We're now pursuing that route."

As part of the grant's educational component, Estroff teaches a course on biomineralization for both graduate students and undergraduates. "One of my goals is to get them reading primary literature and analyzing it," she says. "They also go out and look for biomineralizing organisms on campus. They go to local streams and bring them back to the lab."

She also is trying to recruit more female students to her department. She is the faculty advisor to a group known as WIMSE, which stands for Women in Materials Science and Engineering, and has organized a mentoring program where freshmen and sophomores are paired with juniors and seniors who, in turn, are paired with graduate students. The enrollment of women in the materials science and engineering major has grown from 10 percent to 30 percent during the last five years.

"Having a group creates a critical mass," she says. "It's really had a positive impact."

--   Marlene Cimons, National Science Foundation

Investigators

Lara Estroff

Related Institutions/Organizations

Cornell University

Related Awards

#0845212 CAREER: Synthesis, Characterization, and Application of Gel-Grown, Polymer-Reinforced Single Crystals

Total Grants

$472,773

SINGAPORE: Opp til 600 tonn fisk fra 55 gårder her har gått tapt på grunn av en alge blomstrer i de siste ukene. En plankton blomst koste fjor 53 gårder ca 500 tonn fisk.

Chief Minister of State (National Development) Maliki Osman fortalte parlamentet forrige uke at Agri-Food and Veterinary Authority (AVA) vil hjelpe bønder utvikle planer for å redusere tap i fremtidige episoder. AVA ikke vil pålegge et minimum produksjon krav på berørte gårder i år, la han til.

Dr Maliki, som talte i årlige økt å granske hans departement budsjett, også pekte ut behovet for å bedre forstå vitenskapen bak fenomenet, legger til at AVA arbeider med ulike etater, National Environment Agency, nasjonalparker bord, vann agency PUB og National University of Singapores tropiske Marine Science Institute, å studere forholdet mellom plankton blomster og fisk dødsfall.

Dette er en rettidig utlysing.

Episoder av plankton blomst skjedde i Singapore siden 2009, men det er fortsatt en mangel vitenskap-minst i public domain-på denne naturlige forekomsten, fører til ubesvarte spørsmål.

For eksempel var dødsårsaker fisk i West Johor stredet av Lim Chu Kang (som skjedde to helger siden) og Øst Johor stredet av Pasir Ris (som skjedde tre helger siden) forskjellige? Hvordan har plankton blomst episoder gjennom årene, og arter involvert, forskjellig? Et mer avansert system for vann overvåking trengs?

Medvirkende faktorer foreslått av publikum, som brukt av Punggol vannvei og mangel på vannføring på grunn av moloen, også fortjene svar.

HVA VI VET SÅ LANGT

AVA sa foreløpige funnene peker mot Karlodinium veneficum arter av alger bak øst Johor stredet blomstring. Men noen nyanser i fortellingen at bønder som LED de tyngste tap ikke ta forholdsregler tidlig nok trenger fleshing ut.

Myndighet sendt et varsel til bønder på Feb 16 og 17 informere dem om forhøyet plankton nivåer og rådet dem til å distribuere lerret poser, høste fisk tidlig for å redusere tap og overføre lager upåvirket områder.

Bønder sa tidlig advarsel var bra. Mange hadde lerret poser klar til å distribueres på sine gårder, samt beredskapsplan som tauing gårdene fra de berørte områdene. Men djevelen er i tidsberegningen og gjennomføring av tiltak.

"Det er ganske lett å planlegge, men vanskelig å gjøre det... Du kan sette fisk i lerret poser for et par dager, men du må vite et par dager på forhånd (for å gjøre det) og du kan ikke ha så mye fisk,"sa en bonde.

Tegn vises i denne episoden var også forskjellige fra fjorårets, oppdrettere sa i dag. Lav oppløst oksygen nivåer var skylden i fjorårets blomst, men det var ikke en faktor denne gangen går av egne tester, sa de. Noen hevdet ikke å vite mye om skadelige alge blomstrer.

Marine ekspert Lim Po Teen av universitetet av Malaya sier forskjellige svar er nødvendig for forskjellige alger arter. Fysiske barrierer som lerret poser er nytteløst hvis de ikke er definert før blomst treff, sier han.

Noen alger arter irritere fisk gjellene, forårsaker gjellene dekkes med Slim og fisken gisp for luften like vannflaten og kveles. For disse arter, sier filtrering og lufting tendens til å være nyttig, førsteamanuensis Lim.

Men andre alger arter (fureflagellater) produsere noen form for nervegifter som direkte kan drepe fisk og lufting vil ikke hjelpe i slike situasjoner, sa han. "Det er avgjørende å vite hva vi arbeider med. Hvis ikke vi kan bekrefte hva er årsaken til fiskedød, så vi ikke er klar til å administrere den."

Eksperter sa også at mens akvakultur i områder med vanlige skadelige alge blomstrer kan prekær, den negative effekten kan reduseres med bedre overvåking og prediktiv evner.

AVA sa det rutinemessig undersøkelser vanntemperatur, pH, saltholdighet og oppløst oksygen rundt oppdrett områder, oppmuntrer bønder til å bli varslet av uvanlig fisk eller vannforhold og gir tidlig varsler. Men det si ikke hvis rutinemessig målingene er delt med bønder.

Singapore kunne se på overvåking programmer brukes av havbruksnæringen i New Zealand (gjort av private forskning med kostnader dekkes av bøndene) og Japan (gjort av fiskeri kooperativer og de lokale myndighetene), foreslo Assoc Prof Lim.

Noen reduksjonsalternativer foreslått i vitenskapelig litteratur inkluderer fjernmåling å oppdage klorofyll-en (en spesifikk form av klorofyll i oxygenic fotosyntesen) og alger tilpasninger i vannet, sa Dr. Angela Capper James Cook University's College of Marine og miljøfag.

"Molekylær tilnærminger er en progressiv verktøyet spiller en nøkkelrolle i identifikasjon av skadelige alge blomstrer arter. Satellitt og prediktiv modellering basert på en rekke... parametere inkludert klimatiske forhold og havoverflaten temperaturer også bistå i gjennomføringen av tiltak, sa hun.

PSI FOR VANN?

Kanskje kan det myndighetene har gjort med luften kvalitet dataene replikeres for vannkvaliteten. Forurensende standarder indeks målinger er offentlig tilgjengelig online og luft-kvalitet rapportering ble forbedret i fjor. Med bedre og tilgjengelige data, ha bønder med en appetitt for mer informasjon, og forskere og marine entusiaster - som har gjort utrettelig shore turer for å overvåke død fisk - nytte.

Betimelig forbruker varsler vil også informere offentligheten og forhindre ryktet-mongering under plankton blomstrer.

AVA har informert publikum at fisk prøver fra berørte gårder ikke inneholder marine biotoxins og at fisk høstet fra lokale gårder er trygt å spise, men offentligheten bør også vite årsakene til fisk dødsfall, plankton arten, enten det er trygt å spille i vannet nær berørte områder og hva utviklingen å forvente.

Den lukket forvaring akvakultur systemer utviklet vil være del av løsningen, men en bonde sa det kan være for kostbart å bruke for hele varigheten av fiskens liv og at kjøttet av fisk i åpent farvann er bedre.

Mat-oppdrett fiskeindustrien og fortjener mens relativt liten, en passende injeksjon av forskning og hovedstaden hvis innsatsen er å holde den flytende.

Allmennheten burde bli bedre informert om maten de spiser og utfordringer som leverer at mat.

On-the-bakken innsats marine entusiaster bør suppleres av akademisk forskning og funn som deles åpent.

Klart, vi trenger mer vitenskap i det offentlige kan gjøre fremskritt på fisk drepe episoder slik at når den neste plankton eller alger blomstrer oppstår i Singapore farvann, fisk vil være bedre rustet til å håndtere.

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