Instrument for Rapid Moisture and Protein Determination

What you see is a parcel of instrument that has been grabbing most of my time. I cannot show full pictures yet as the patenting is underway. The process may take up to a year so please bear with me.

predicted moisture contentThe instrument works like this on the user point of view. The in-charge has to get a representative sample from batch. Place it in glass type sample holder. Install the sample cap with the sample on top of instrument. Click the command “scan” and the moisture or protein content of the sample will be displayed on the computer screen after approximately six seconds. It sounds too good to be true but it is indeed real!

The instrument gets rid of laborious and often long sample preparations. No grinding of sample and mixing of expensive chemicals. Chemicals that are often harmful to human and environment, a.k.a hydrochloric acid, mercury and ammonia and sulfuric acid. The instrument is easy to use. Almost anybody with average educational background can operate the equipment after short orientation. It performs rapid analysis that could be made faster by in-line process installation.

Food Tech Knowledge for Other Purposes

I have been tinkering with this important experiment for few weeks now. I need a set of corn samples with varying protein content.

The first problem I had was easy. Corn samples with varying moisture content. I bought some cracked corn from my favorite feed supply store. Sifted it to remove fine powders caused by milling. Soaked in generous amount of water for two hours. Drained for 30 minutes. Scattered the wetted corn evenly on trays, about one cm thick. Set the electric fan in front of it for air drying. Got measured amount every hour for ten hours. That’s it I had ten corn samples with varying amount of moisture. It was 11 in all including the control sample. I stored them in chiller for two days to let the moisture equilibrate.

It was easy but it took me several trials before arriving to a satisfactory results. Keeping the corn in humid area will encourage moisture gain, but, it took too long and the molds were already grown before getting acceptable moisture. Rapid oven drying of wetted samples caused gelatinization of starch. Gelatinized corn is useless for our setup. I found out later that air blow drying gives excellent outcome and could be way faster than oven.

Then, as I said. I need another set of corn samples with varying protein content. For the start it should have 30 % moisture content. Add 4-6 grams urea per 100 grams corn. Ferment for two weeks at 30 to 40 ⁰C. Expect protein content gain after two weeks. That is if the spoilage organisms such as mold won’t penetrate the measures I set.

corn protein enrichment with ureaUrease producing bacteria is necessary for successful fermentation. It is found almost everywhere including the urea and corn samples I have. Heating is good for destroying spoilage organisms but might as well kill the needed microbes. Hermetically sealing the mixture is a nice solution. It’s gonna keep beneficial bacteria alive while keeping aerobes away and those that already in dormant.

The protein enrichment experiment has been going for four days now with no sign of molds, bacterial growth and discoloration. I am hoping it last until the target period.

My job description has going out of line lately. However, my stored knowledge on food processing often come in handy.

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