LETTERS
Excellent coverage of technology
Your last two issues (October and November) were especially good. Your articles on ozone, magnetic thermometry for aseptic processing, convenient foods, outsourcing, nutraceuticals, and other food engineering topics are timely and appreciated. Did you read my mind? Your magazine’s excellent coverage on the latest food technology is the main reason I intend to resubscribe. Thanks.
—Kirk Dolan, PHF Specialists, Inc., Sierra Vista, Ariz.
Nutraceutical information timely
I’m writing to tell you how much I appreciated Don Pszczola’s article, “Nutraceuticals That Take the Form of Candy and Snacks” (October, p. 74). One of my co-workers with cardiovascular problems has been eating the HeartBar during these past months. The information on the package label doesn’t say much at all about the product. We were aware that the bar is enriched with L-arginine. The information in the article is timely and of particular interest to me and my co-worker. Thank you also for including information on John Cooke, developer of the bar. I e-mailed him at Stanford U. and asked if he has either a reprint or summary of his presentation at Nutracon ’99, which your article also mentions.
—Pamela Tom, Program Representative–Sea Grant Extension Program, Dept. of Food Science & Technology, University of California, Davis
Additional clarification regarding packaging
Like Dr. Doar at Clemson in the article, “Predicting Permeability and Transmission Rate for Multilayer Materials” by Kay Cooksey, Kenneth S. Marsh, and Leroy H. Doar (September, p. 60), I was similarly confused after consulting various packaging textbooks and refereed literature while developing a packaging course for our department’s IFT accreditation application. The situation is such that, in what are otherwise good textbooks, the authors’ confusion (or neglect) over terms and units for permeance and permeability renders calculations on shelf life useless for technologists and obfuscating for students. Although the article will help to dispel some of the confusion, two amendments to their article would improve matters further.
First, of the terms permeance and permeability, the permeance (or transmission rate) of the film is met first, because a manufacturer or a student cannot measure the film’s permeability experimentally, only its permeance. After measuring how much vapor passes through the film in a given time (its permeance), we derive the permeance capacity of a unit thickness of that film (its permeability) by multiplying the measured permeance by film thickness. Thus, these extensive and intensive properties of the film are analogous to the feeling and capacity of feeling exhibited by Jane Austen’s characters in Sense and Sensibility.
Second, the absence of parentheses in Table 1 would mean that a strict adherence to their units would lead to erroneous values for permeability and transmission rate, since all their terms except for film area are expressed as numerators; parentheses after the divisor symbol are recommended to eliminate this error (see Dodd, I. S. 1997. The ACS Style Guide, 2nd ed. Am. Chem. Soc., Washington, D.C.). However, a more desirable method of expressing units is to adhere to a rationalized coherent system of units (SI) and express denominators with a negative exponent, although in packaging applications we prevent canceling of units so that the contributing physical mechanisms are expressed in the units. In this way, permeance has units of kg m–2 s–1 Pa–1, while permeability has units of kg m m–2 s–1 Pa–1 (since at a given temperature gases of interest have a certain density). Such strict formalism in expressing units may seem unwieldy, but correct usage will insulate our profession from the vilification expressed by some physical scientists (see Chatwin, P. and Katan, L. 1997. Migration from packaging into food. Math. Today, Oct., pp. 142-145.) when we get our dimensions wrong.
—Martin Scanlon, Associate Professor, Dept. of Food Science, University of Manitoba, Winnepeg, Manitoba, Canada
Misspelling noted
I enjoyed the article, “Probiotics” by Mary Ellen Sanders (November, p. 67), except for one minor typo at the bottom of the first column on p. 73. “Chron’s” is incorrect. “Crohn’s,” to my knowledge, is the correct spelling.
—Norm Harris, Sangerville, Maine
No formal connection
In the Ingredients column, “Choosing Ingredients for the Time Capsule” (September, p. 132), the item on p. 134 entitled “Ingredient blocks sweetness in nonfat peanut butter spread,” discussed use of a Domino Specialty Ingredients product, Envision® Flavor and Texture Modifier, in a nonfat peanut butter spread called GoNuts™. Envision provides the functionality of sucrose and simultaneously controls sweetness. We would like to clarify that Domino Specialty Ingredients has no formal connection with the GoNuts product.
—Carolyn Ruhlow, Rossé & Associates, Inc., Advertising/Marketing Communications, Sparks, Md.