Glassware Taper Joint Measurement

Years of work outside laboratory environment seemed made me clueless about many simple laboratory terms and methods. I think I have forgotten many important rules and protocols. I feel that I am not fit for this kind of work anymore. I wish my doubt is not true.

I need to order three flat bottom boiling flask as replacement part for traditional Soxhlet Extraction System – an equipment to measure crude fat or simply oil content.

The problem! I forgot how to measure the glass standard taper joint, the ground inner/outside finish for easily connecting glasswares together. The joint size is usually permanently written on surface but I cannot find it anywhere.  Or, maybe I never knew how to measure it from the very start. I was absent when our Chemistry professor discussed it.

At times like this, back reading is my best friend.

Glassware standard taper joint looks like this.

flat bottom flask ground jointAfter reviewing few paragraphs: The size is expressed by two numbers separated by forward slash. The joint size 19/22 means 19 mm width of the joint widest portion and 22 mm taper length. Get outside width  for male joint and inner for female socket.

It is recommended to use vernier caliper for accurate measurement. Search for matching product on-line or on catalog books. If no similar products are found, then it is probably out of stock or you have made a wrong measurement.

vernier caliper soxhlet and flask

Marvin is the lead chocolate maker of Ben and Lyn Chocolate Inc. Has strong background in food research and development. Occasionally conducts training and lectures. Lecturer of Cocoa Foundation of the Philippines. Do coaching and consultancy services on his free time.

Measuring Food Protein Content

While reviewing one of the laboratory analytical procedures, I am jotting down some important notes. I am trying to make it shorter and easier for me to understand.

The popular method for measuring food protein content is by Kjeldahl procedure. The analytical method developed by Johan Kjeldahl. Most modern and current procedures are also based on his work.

The procedure is not 100 percent accurate. That is why the specific method name is Crude Protein. The procedure specifically targets the element N. Proteins contain N but the food may contain other nitrogen containing compounds. So all N collected might be expressed as protein.

As I said, the following are written specifically as my quick reference. Anyone wanting to learn the protein analysis process should consult the complete procedure approved by Association of Official Analytical Chemist (AOAC) or any reputable institution.

Kjeldahl Method. The shortened procedure

REAGENTS

95-98% sulfuric acid, nitrogen free
Copper catalyst – CuSO4-5H2O
Potassium sulfate – nitrogen free
Sodium hydroxide solution – 50% w/w
Boiling chips – high purity amphoteric alundum granules
zinc granules/chips
Methyl red/bromocresol green indicator solution
Ammonium sulfate – 99.9%
Tryptophan or lysine hydrochloride
Sucrose, nitrogen free

REAGENTS PREPARATION

Indicator: Dissolve 0.2 g methyl red and dilute to 100 ml 95% ethanol. Dissolve 1 g bromocresol green and dilute to 500ml 95% ethanol. Mix one part methyl red solution with 5 parts bromocresol green.

Boric acid solution: 4% boric acid with 3 ml methyl red/bromocresol green.

1 M HCl … Seed standard preparation.

DIGESTION

Add 15 grams potassium sulfate, 8-10 boiling chips, 1 ml copper sulfate pentahydrate, 1 g sample recorded to nearest 0.0001 g and 25 ml sulfuric acid to kjeldahl flask

Heat requirement – 250 ml water rolling boil within 5-6 minutes. Pre-heat the the heating equipment, place the flask containing water then record time. Adjust and repeat.

Place digestion flask on heating apparatus in inclined position. Set to low. Digest for 20 minutes or until white fumes appear in flasks.

Increase heat half-way to maximum. Heat for another 15 minutes.

Set to maximum then continue boiling for 1 to 1.5 hours.

Cool approximately 25 minutes.  Large amount of crystallization should not be observed. Refer to full reference if so.

Add 300 ml distilled water and swirl. Cool to room temperature.

DISTILLATION

Assemble the distillation apparatus.

Add 50 ml Boric acid solution to 500 ml Erlenmeyer flask. Place it under condenser tip. The tip should be submerged in solution.

To kjeldahl flask, carefully add 75ml 50% sodium hydroxide solution with no agitation. Add few zinc chips – it will prevent bumping during distillation. Connect it to system immediately.

Distill until sufficient volume has been collected. 150ml to 200ml.

TITRATION

Titrate the boric acid solution with 0.1000M HCl to first trace of pink.

CHECK SAMPLE PREPARATION

Nitrogen loss. Use 0.12 g ammonium sulfate and 0.85 g sucrose. Subject to kjeldahl test. Recovery should be at least 99%.

Digestion efficiency. Use 0.16 g lysine hydrochloride or 0.18 g tryptophan and 0.67 g sucrose.  Subject to kjeldahl test. Recovery should be 98%.

COMPUTATION

% Nitrogen = (1.4007x[Vs -Vb]xM)/W

where Vs and Vb = ml HCl titrant used for test portion and blank, respectively; M = molarity of HCl solution; and W = test portion weight, g.

Then the percent N is multiplied by factor appropriate for the food analyzed.

coffee bean for protein analysis

Marvin is the lead chocolate maker of Ben and Lyn Chocolate Inc. Has strong background in food research and development. Occasionally conducts training and lectures. Lecturer of Cocoa Foundation of the Philippines. Do coaching and consultancy services on his free time.

Four Reasons Why Compare Different Recipes and Methods

I am going to conduct an array of Kjeldahl Nitrogen  and Moisture Determination activities. I am downloading and reading methods recommended by different organizations. I have gotten more than five procedures each of the same type but still looking for more. I am comparing every procedures, for the following reasons:

1) All of the downloaded files are basically the same but they are uploaded at different times. Methods may changed through the work of different experts. I might find a significant improvement. The use of less chemicals, cheaper reagents or more affordable equipment.

2) Some files are easier to interpret than others, rewritten for better understanding. A recipe with very specific ingredient listing and more elaborate step-by-step instructions. An analytical procedure in translated in less technical manner.

3) Additional information. Safety precautions such as careful handling of sulfuric acid. Proper waste disposal. Other uses – the same Kjeldahl method for determining chlorophyll content and caffeine. A general nata recipe for coconut, kalabasa, mango and banana.

4) Merging of data. It happened to me several times when I cannot made a food product perfectly. Several tries produced the same failed results. Eventually, I managed getting what I want by reading methods from other sources.

Marvin is the lead chocolate maker of Ben and Lyn Chocolate Inc. Has strong background in food research and development. Occasionally conducts training and lectures. Lecturer of Cocoa Foundation of the Philippines. Do coaching and consultancy services on his free time.

Easy, Routine and Economical Moisture Analysis

These method is useful for routine drying where the moisture content of product is crucial. Laboratory moisture analysis is costly and time consuming. On the other hand, moisture content of sample can be approximated using weighing scale and a piece of sturdy container.  This is rapid and economical.a glass of water

Follow these steps:

1) Secure a container of known volume like a one or two liters metal can.  A sturdy durable can is preferred. It will be used for a routine moisture analysis.

2) Verify the exact volume of the chosen container. Fill it with water up to brim and transfer to a graduated cylinder – use only graduated cylinder. Record the exact volume.  Lets assume that volume is really two liters. Weigh the can.

3) Prepare three to ten batches of sample. Each batch should be more than enough to fit the container from number “2” and provide adequate for laboratory moisture analysis. Lets assume four kilograms for each batch.

4) Dry the samples using whatever method specified ( sun drying, oven drying, vacuum oven, etc….). Gather some literature about the drying time of the specified  sample, need a wild guess otherwise.

5) Set your drying period. e.g. 1 day, 2 days, 3 days, 4 days etc….  at specified temperature or 2 hours, 4 hours, 6 hours, 8 hours etc… at specified temperature. Drying period and temperature are sample dependent.

6) Get a part of each sample for moisture analysis after the first specified interval (e.g. after one day).  Send it to trusted laboratory for moisture analysis.

7) If your target moisture content is attained (e.g. 12 %), then stop drying. Otherwise continue drying and moisture testing until the desired moisture content is attained.

8) Fill each sample to the test container (container from “2“, the metal can). Filling should be free fall. Then scrape the top gently with a straight ruler or rod.  Weigh the sample and container then subtract the container weight.

9) Get the average moisture content. e.g. 12 %.

10) Get the average sample weight of all batches or the average weight of 2-liter sample (from method “8“). e.g. 1.5 kilograms.

11) Get the average drying time at specified temperature. e.g. one day at 70 °C.

So the specific commodity should be dried for one day at 70 °C. As quality check, a 2-liter can of sample should weigh 1.5 kg. Excess weight means insufficient drying while underweight is over drying. Adjust drying time accordingly.

Please never ask me for sources/references cause I personally got the idea when I was working as Food Research Assistant.  Comments, suggestions and recommendations are welcome!

The method is commodity specific. If you set parameters for drying ampalaya seeds then you should set another method for corn seeds. You need to shed sweats setting the parameters but the next routine analysis will be very very easy.

Marvin is the lead chocolate maker of Ben and Lyn Chocolate Inc. Has strong background in food research and development. Occasionally conducts training and lectures. Lecturer of Cocoa Foundation of the Philippines. Do coaching and consultancy services on his free time.

Water Activity of Meat Products and Limiting Values for Microbial Growth

Water activity ( aw) is the term for the amount of free (not chemically or physically bound) water, which is available for the growth of microorganisms. This information is particularly important, as higher amounts of free water favour the growth of microorganisms, while lower amounts (drier products) result in less microbial growth. Bacteria usually require at least aw 0.91 and fungi at least aw 0.71.

Aw can be measured by means of water activity meter.

Typical aw in Meat Products

Product aw range
Fresh meat 0.99 (0.99 to 0.98)
Cooked ham 0.97 (0.98 to 0.96)
Raw-cooked sausages 0.97 (0.98 to 0.93)
Liver sausages 0.96 (0.97 to 0.95)
Blood sausages 0.96 (0.97 to 0.86)
Raw-fermented ham 0.92 (0.96 to 0.80)
Raw-fermented sausages 0.91 (0.96 to 0.70)
Dried meat 0.70 (0.90 to 0.60)

water-activity-meter

Limiting aw for the Growth of Microorganisms

Microorganisms aw
Pseudomonas 0.93
E. coli 0.93
Salmonella species 0.91-0.95
Listeria 0.93
Cl. botulinum types 0.91-0.95
Cl. perfringens 0.93-0.95
Bacillus species 0.90-0.95
Lactobacillus 0.90
Staph. aureus 0.86-0.90
Most yeasts 0.87-0.90
Most moulds 0.80-0.85

Most bacteria between aw 0.91 – 0.96

Gunter Heinz & Peter Hautzinger – Meat Processing Technology

Marvin is the lead chocolate maker of Ben and Lyn Chocolate Inc. Has strong background in food research and development. Occasionally conducts training and lectures. Lecturer of Cocoa Foundation of the Philippines. Do coaching and consultancy services on his free time.