10. Laboratory Analysis of Food

Transkript

1 10. Laboratory Analysis of Food Food is analysed for many reasons. Some of the key applications that food testing analyzers are used for are food chemistry analysis (e.g. moisture, fat, protein, ph, salt, minerals, sugar, contaminants, etc.), food microbiology analysis (e.g. Lactobacillus, Salmonella, Pseudomonas, Listeria, E. coli, Staphylococcus aureus, yeast, mould, etc.), food allergen analysis (e.g. peanut, egg, soy, etc.), food nutrition analysis (determining the nutritional content), natural food toxin analysis (e.g. histamine), food shelf-life studies or food quality control determination (e.g. GMO analysis, wheat adulteration, etc.). Food analysis is often provided to ensure the food safety. It would be very undesirable for the both consumer and the manufacturer if unwholesome or toxic products were sold. Hence it is essential that the harmful substances like microorganisms, toxic chemicals or extraneous matter were absent or effectively eliminated. This should be achieved by observing good manufacture practice and regulations laid down by the government for specific food products as well as using analytical techniques that are capable of detecting unauthorized substances. Sometimes it is necessary to employ high sensitivity analytical techniques that can reliably detect very low levels of harmful substances. Food analysis is conducted by scientists of all major sectors of the food industry including food manufacturers, ingredient suppliers and many types of laboratories (analytical service, national or university research). Thus different analytical methods are available for various purposes. They are chosen according to the property to be measured, the type of foodstuff to be analysed or the reason for the testing. Typically, foods are tested in laboratories to determine their safety for consumption, composition or to help food manufacturers in understanding the shelf life and stability of a food product or ingredient. Every laboratory should be lit and ventilated properly, with adequate room temperature for a consistent environment and large enough to accommodate all the necessary equipment as well as to provide comfortable work area. Although there are many types of laboratories due to various purposes, every laboratory has certain components that are common for all. Such equipment includes sinks with a source of running water where specimens and reagents are rinsed, drained or stained and fluids are discarded. Sufficient storage space as drawers and cabinets must be available for reagents and supplies to prevent clutter on the laboratory counter space. As some reagents or specimens must be kept cool or frozen, a refrigerator and freezer are essential. One of the necessary things of a laboratory of the 21 st century is an Internet access as it offers the possibility to use the or fax to report the critical results of submitted diagnostic tests or send photographic images. Internet may also serve as a diagnostic aid in laboratories with digital camera attachment to a compound microscope. Another important type of laboratory equipment comprises laboratory glassware such as beakers, graduated cylinders, flasks, thermometer, reagent bottles, test tubes, glass rods, evaporating dish, watch glass and the like. Central to food testing analysis are spectrometers, alcohol analyzers, refractometers, titrators, moisture analyzers, and other standard lab equipment. Specialized analyzers and meters are also available per specific methods and applications, while others can be used for various food analysis requirements. The analysis of food products for presence of pathogenic microorganisms is one of the basic steps to control safety and quality of food. Most of the microorganisms encountered in the laboratory are potentially pathogenic, thus all specimens should be handled as potentially

2 contagious. The safety of every person working in the laboratory depends on strict observance of safety and hygienic rules. Staff must wear personal protective equipment (PPE) during their work and materials contaminated with potentially infectious agents must be decontaminated before disposal. Moreover, all accidents must be reported immediately to the laboratory supervisor or other competent authority. The first stage of microbiological analysis of food consists in taking and preparing a sample for testing. Incorrect sampling may result into obtaining false negative or false positive results. The representative sample should reflect the image of the product from which it originates as precisely as possible. There is a variety of methods used for microbe detection; some of them being more traditional like culture collection, whereas, the others are newer and faster and include e.g. polymerase chain reaction (PCR), infrared devices that detect bacteria in food, and rapid scans that detect bacterial contamination in blood platelets. One traditional technique of bacterial detection is to take a sample, grow a bacteria culture, and count the bacteria that grow. This method is effective but can take hours or days to show results and may miss some types of bacteria. Other traditional culture method detects changes in oxygen levels indicating the presence of bacteria but obtaining results can take seven days. Among the newer, more rapid systems to detect bacteria belong e.g. solid-phase cytometry which detects and counts all fluorescently labelled bacteria within three minutes, or PCR (polymerase chain reaction) characteristic for high sensitivity, specificity, and rapid results. It is an enzymatic reaction replicating a DNA molecule, thus a critical condition of the PCR course is the presence of an enzyme, thermostable DNA polymerase. Variants of the conventional PCR method are a real-time PCR (an improved method observed in real time) and multiplex PCR (two or more loci are simultaneously amplified in the same reaction). Task. Answer the following questions. What types of food analysis do you know? Who conducts food analysis? What is a laboratory? What typical equipment and instruments can you name? Are there some tools or appliances necessary for food testing? What does the abbreviation PPE stand for? What is a representative sample? Can you name some rapid methods of detecting microorganism in the food? What does the word thermostable mean?

3 Useful phrases and expressions Basic laboratory equipment balance /scales váhy beaker kádinka boiling flask varná baňka Bunsen burner Bunsenův kahan burette (buret) byreta crucible tavicí kelímek Erlenmeyer flask/conical flask Erlenmeyerova baňka evaporating dish odpařovací miska forceps kleště funnel nálevka glass rod skleněná tyčinka graduated cylinder odměrný válec hand lens/magnifying glass lupa microscope mikroskop mortar and pestle třecí miska s tloučkem pipette (pipet)/chemical dropper pipeta ring stand/clamp stand (univerzální) laboratorní stojan test tube holder držák na zkumavky test tube zkumavka thermometer teploměr tongs kleště tripod trojnožka wash bottle střička watch glass hodinové sklíčko wire gauze drátěná síťka Equipment and instruments specific for the microbiology laboratory syringes and needles stříkačky a jehly inoculating loops and wires očkovací kličky scissors and forceps nůžky a kleště sterile cotton-tipped swabs sterilní štětičky collection tubes odběrové zkumavky glass slides and cover tips podložní sklíčka a krycí sklíčka various culture media různá kultivační média gram stain or other stain Gramovo barvení a jiné barvení incubator inkubátor discard jar with disinfectant odpadní nádoba s desinfekcí Lab. personal protective equipment (PPE) laboratory coat/gown laboratorní plášť safety goggles ochranné brýle face shield ochranný štít disposable gloves jednorázové rukavice face masks/ respirator obličejová maska Terms used to describe lab results g/l (gram per litre), L/L (litres per litre), U/L (units per litre), mmol/l (millimols per litre), umol/l (micromols per litre) Terms used to describe lab values within normal limits/normal v normě/normální elevated/raised zvýšené reduced snížené

4 Vocabulary part 1. Label the following laboratory equipment. a long thin glass container that is open at one end and is used in laboratories a glass tube marked with a scale and with a tap at the bottom a tube wide at the top and narrow at the bottom, used for pouring liquid a piece of equipment used for weighing people or things a glass or plastic container with straight sides a bowl in which you crush substances into a powder a container used for heating substances or melting metals special glasses that protect your eyes a piece of equipment producing a gas flame, used for scientific experiments an object with three legs that is used for supporting something T. T. B.. F.. S.. B.. M. C G.. B B.. T 2. Translate the following phrases into English. provádět pokusy a výzkum.. objevit nebezpečné bakterie.. zkoumat přítomnost enzymu.. řádně odebrat vzorek.. zvýšené hodnoty bílkovin.. analýza na potravinové alergeny.. vypěstovat bakteriální kulturu.. sledovat změny v hodnotách kyslíku.. získat výsledky během pár minut.. nebezpečí falešně pozitivních výsledků.. Below are the steps describing the procedure of operating the microscope. Put them into the correct order. 1. Place the slide on the stage. 2. Lower the stage to its lowest point. 3. Turn on the light. 4. Move the objective into position by turning the turret or revolving nosepiece. 5. Go home 6. Use the coarse and fine adjustment knobs to get the image into focus. 7. Remove the slide. 8. Adjust the condenser and the diaphragm following the manufacturer s instructions. 9. Check the eyepieces, objectives and condenser lens and clean them if necessary. 10. Turn the light off and lower the stage completely.

5 Grammar part Reported (Indirect) speech Key points: Back shift: Tenses shift back in time after a past tense reporting verb. present simple I work in a laboratory. present continuous I am working in a laboratory. present perfect simple I have worked in a laboratory. present perfect continuous I have been working in a laboratory. Present past simple He said he worked in a laboratory. past continuous He said he was working in a laboratory. past perfect simple He said he had worked in a laboratory. past perfect continuous He said he had been working in a laboratory. past simple I worked in a laboratory. past continuous I was working in a laboratory. past perfect simple/continuous I had worked/been working in a laboratory. Past past perfect simple/past simple He said he had worked/ worked in a laboratory. past perfect continuous He said he had been working in a laboratory. past perfect simple/continuous - NO CHANGE!!! He said he had worked/been working in a laboratory. Will I will work in a laboratory. be going to I am going to work in a laboratory. Future Would He said he would work in a laboratory. was/were going to He said he was going to work in a laboratory. can I can work in a laboratory. may I may work in a laboratory. will I will work in a laboratory. shall I shall work in a laboratory. must I must work in a laboratory. needn t Modal verbs could He said he could work in a laboratory. might He said he might work in a laboratory. would He said he would work in a laboratory. would He said he would never work in a laboratory. must or had to He said he must/had to work in a laboratory. needn t/didn t have to

6 I needn t work in a laboratory. He said he needn t/didn t have to work in a laboratory. now today, this week, this month, etc. yesterday, last week, last year, etc. tomorrow, next week ago here Reference words (place and time adverbials, pronouns, etc.) then, at the moment that day, that week, that month the day before, the previous week, the previous year the following day, the following week before there Indirect questions: Reporting questions - Yes/No questions are reported using if. The verb does not have a question form but has the form of a normal statement. There is no question mark. e.g. Do I have to wear a lab coat during the experiment? He asked me if he had to wear a lab coat during the experiment. Wh- questions are reported using the question word. The verb has the form of a normal statement. There is no question mark. e.g. Why do I have to wear a lab coat during the experiment? He asked me why he had to wear a lab coat the experiment. No back shift: If the reporting verb is in present tense. e.g. I sample the blood if necessary. The doctor says he samples the blood if necessary. If the present (e.g. today) in the direct speech is still the present in the reported speech. e.g. I am in a lab. He said he is in a lab today. If the future in the direct speech is still the future in the reported speech. e.g. I will phone you the results. He said he will phone me the results. (I am still waiting for his phone call). If the reported words are always true. e.g. Salmonellosis is an infection with bacteria called Salmonella. He said salmonellosis is an infection with bacteria called Salmonella. If the sentences are commands (imperatives) or requests; they are reported with tell or ask + infinitive. e.g. Avoid distress and unnecessary pain and suffering to the experimental animals! He told us to avoid distress and unnecessary pain and suffering to the experimental animals.

7 1. Rewrite each sentence as reported speech. Start with the supervisor said/asked/ordered, etc. The diagnosis is based on laboratory criteria of salmonella infection. Reference laboratory will build up and store diagnostic agents. The handling of live FMD virus for research has been carried out only in the approved laboratory. Look it up in the Manual of Standards for Diagnostic Tests and Vaccines! Laboratory waste was categorised in specific waste groups yesterday. Are you cooperating with any medical laboratory technicians these days? Where did you buy all the equipment for laboratory diagnostics? Can we recruit more laboratory assistants the next week? The tests must comply with the relevant requirements for protection of laboratory animals. What do you know about research laboratories? 2. Underline the most suitable verb form in each sentence. Sometimes both possibilities are correct. 1. The manager asked me if the food producer would need some time to test the meat products. The manager asked: Does the food producer need/ Will the producer need some time to test the meat products? 2. My colleague told me the raw milk had been exposed to microbial contamination. My colleague said: The raw milk was exposed/has been exposed to microbial contamination. 3. They told us to ensure that foodstuffs are not contaminated. Ensure/You ensure that foodstuffs are not contaminated! 4. The laboratory workers told us that Listeria is able to multiply in various foods at temperatures. They said: Listeria is able/will be able to multiply in various foods at temperatures! 5. The inspector asked them who might be responsible for the research. The inspector asked: Who may be/must be responsible for the research?

8 Vocabulary accommodate (v) /əˈkɒmədeɪt/ vyhovovat, přizpůsobit adjust (v) /əˈdʒʌst/ seřídit, nastavit agar (n) /ˈeɪɡɑː(r)/ agar allergen (n) /ˈælə(r)ˌdʒen/ alergen analyser (n) /ˈænəlaɪzə/ analyzátor, analytik beaker (n) /ˈbiːkə(r)/ kádinka cabinet (n) /ˈkæbɪnət/ skříňka clutter (n) /ˈklʌtə(r)/ nepořádek contaminant (n) /kənˈtæmɪnənt/ znečišťující látka count (n) /kaʊnt/ množství, počet ve vzorku counter space (phr) /ˈkaʊntə(r) speɪs/ pracovní prostor current (n) /ˈkʌrənt/ proud cylinder (n) /ˈsɪlɪndə(r)/ válec decontaminate (v) /ˌdiːkənˈtæmɪˌneɪt/ dekontaminovat, odmořit discard (v) /dɪsˈkɑː(r)d/ vyhodit disposal (n) /dɪˈspəʊz(ə)l/ likvidace drain (v) /dreɪn/ odtéct, vylít drawer (n) /ˈdrɔːə(r)/ zásuvka, šuplík encounter (v) /ɪnˈkaʊntə(r)/ setkat se s, narazit na extraneous (adj) /ɪkˈstreɪniəs/ nepodstatný; vnější eyepiece (n) /ˈaɪˌpiːs/ okulár (mikroskop) flask (n) /flɑːsk/ baňka harmful (adj) /ˈhɑː(r)mf(ə)l/ škodlivý histamine (n) /ˈhɪstəmiːn/ histamin image (n) /ˈɪmɪdʒ/ snímek, obrázek Lactobacillus /ˌlæktəʊbəˈsɪləs/ laktobacil Listeria /lɪsˈtɪərɪə/ listerie meter (n) /ˈmiːtə(r)/ měřicí přístroj moisture (n) /ˈmɔɪstʃə(r)/ vlhkost peanut (n) /ˈpiːˌnʌt/ arašíd platelet (n) /ˈpleɪtlət/ krevní destička polymerase (n) /pəˈlɪməreɪz/ polymeráza Pseudomonas /sjuːˈdɒmənəs/ pseudomonáda reagent (n) /riˈeɪdʒ(ə)nt/ činidlo, reagens reflect (v) /rɪˈflekt/ odrážet revolving nosepiece (phr) /rɪˈvɒlvɪŋ ˈnəʊzˌpiːs/ otočná hlavice mikroskopu rinse (v) /rɪns/ opláchnout rod (n) /rɒd/ tyčinka running water (phr) /ˈrʌnɪŋ ˈwɔːtə(r)/ tekoucí voda sink (n) /sɪŋk/ umyvadlo, výlevka slide (n) /slaɪd/ podložní sklíčko specimen (n) /ˈspesəmɪn/ vzorek spectroscopy (n) /spekˈtrɒskəpɪ/ spektroskopie

9 stage (n) /steɪdʒ/ stolek (mikroskop) stain (v) /steɪn/ vybarvovat (preparáty) Staphylococcus aureus /ˌstæfɪləʊˈkɒkəs ˈɔːrɪəs/zlatý stafylokok submit (v) /səbˈmɪt/ předložit, podat, odevzdat test tube (n) /test tjuːb/ zkumavka thermometer (n) /θə(r)ˈmɒmɪtə(r)/ teploměr thermostable (adj) /ˌθɜːməʊˈsteɪbəl/ odolný proti teplu turret (n) /ˈtʌrɪt/ revolverová hlava (mikroskop) unwholesome (adj) /ʌnˈhəʊls(ə)m/ nezdravý, zdravý škodlivý