High Vacuum Level Research Articles

Effect of Packaging Film and Vacuum Level on Regular and Sorbate‐Cured Bacon

ABSTRACTBacon was produced with either 40 ppm NaNO2/0.26% potassium sorbate, or 120 ppm NaNO2. Slices were packaged in either nylon/Surlyn or nylon/Saran/Surlyn pouches and sealed at either a high or intermediate vacuum level. At 0, 10, 21 and 28 days after packaging, residual nitrite, rancidity, pH, residual salt and pigment conversion were measured. Residual nitrite and pH were lower while nitrosopigment conversion was higher in bacon packaged with the high‐barrier film. Vacuum level, however, had no effect on any measured characteristic. The sorbate/reduced nitrite cure resulted in lower pigment conversion, lower residual nitrite, and a higher TBA number.

Analysis of Instantaneous Milk Flow Rate Patterns

ABSTRACT MEASUREMENTS of instantaneous milk flow rates from unsupported teats (i.e., linerless teat cups) and corresponding analysis of flow charcteristics are presented in this report. Milk flow measurements were made with an ultrasonic flow meter, using techniques described in a previous report (Delwiche, Scott, and Drost, 1980). Data were gathered according to a V fac-torial experiment design, conducted over 16 days on four cows. Parameters investigated were pulsation frequency, 1.0 and 0.3 Hz; pulsation ratio, 63 and 42 percent milk-ing vacuum, 51 and 41 kPa; and quarter, front (right) and rear (left). Milk flow patterns from each test are divided into three stages: the low flow beginning stage (stage 1), the high average flow rate stage (stage 2), and the tapering off stage (stage 3). Within each stage, se-quences of four to 15 milk flow and vacuum pulses are analysed. Treatment effects during stages 1 to 3 are tested for significance by analysis of variance. Peak and average milk flow rates per pulsation cycle are significantly higher for the lower pulsation frequency (0.3 vs. 1.0 Hz). Similarly, the higher vacuum level (51 vs. 41 kPa) yielded significantly higher flow rates. Differences due to the ef-fects of pulsation frequency are greater than differences due to milking vacuum level. Milk flow rate patterns from unsupported teats show distinct smooth muscle ac-tivity affecting flow rate characteristics. Contractions of smooth muscles in the teat and at the teat end produce rhythmic oscillations of the peak milk flow rate from pulse to pulse and determine the overall shape of each milk pulse.

EFFECT OF SODIUM ERYTHORBATE AND PACKAGING CONDITIONS ON COLOR STABILITY OF SLICED BOLOGNA

ABSTRACTRetention of cured color and shelf life of sliced bologna manufactured with various erythorbate levels and packaged with different films and vacuum levels were studied. Good barrier films (7.0 ml/m2/24 hr or less oxygen permeability), film rigidity, and high vacuum levels (686‐737 mm) are most critical for less faded color, higher cured pigment conversion, and lower TBA numbers. Erythorbate aided curing developments but could not compensate for low barrier films or low vacuum levels during storage.

EFFECT OF SODIUM NITRITE CONCENTRATION AND PACKAGING CONDITIONS ON COLOR STABILITY AND RANCIDITY DEVELOPMENT IN SLICED BOLOGNA

ABSTRACTColor stability and shelf life of sliced bologna made with various nitrite levels and packaged with different films and vacuum levels have been studied. A maximum (686–737 mm Hg) initial vacuum levels combined with fiims of low oxygen permeability (7.0 ml/m2/24 hr or less) had higher color scores, greater cured pigment conversion and lower TBA numbers. A lower nitrite concentration (50 ppm) was possible while maintaining product characteristics if good barrier films (less than 7.0 ml oxygen/m2/24 hr) and high initial vacuum levels (686–737 mm Hg) were used.

A comparison of carbon contaminant buildup on conductors and insulators in X-ray photoelectron spectroscopy

In a spectrometer of high X-ray flux and moderate vacuum level, C 1 s buildup differed drastically on conducting and insulating samples. A model is proposed which depends on photoelectron hole-site lifetime differences on such samples leading to different probabilities of film-forming chemical reactions with constituents of the vacuum atmosphere.

EFFECT OF DEGREE OF VACUUM AND LENGTH OF STORAGE ON THE PHYSICAL CHARACTERISTICS OF VACUUM PACKAGED BEEF WHOLESALE CUTS

ABSTRACTWholesale beef cuts were vacuum packaged at low, intermediate or high degrees of vacuum and stored at l‐3°C for 7, 14, 21, 28 or 35 days. Purge loss, trim loss, muscle color and odor were not generally affected by degree of vacuum. Fat appearance and surface discoloration ratings for primal cuts favored the use of a high level of vacuum in three of five storage intervals. Total desirability ratings for primal cuts packaged with high vacuum were higher than those for primal cuts packaged with low vacuum at all five storage intervals. Cuts from the low vacuum treatment had consistently higher numerical values for trim loss than did cuts from intermediate or high vacuum level groups, but these differences were not statistically significant. Degree of vacuum used during storage of primal cuts did not generally affect the peripheral discoloration, surface discoloration or total desirability of subsequent retail steaks. However, among primal cuts stored for 21 days, peripheral discoloration and total desirability scores were lowest (P < 0.05) for retail cuts from the low vacuum treatment. Differences in juiciness, flavor desirability, overall satisfaction and Warner‐Bratzler shear values for retail steaks were not related to the degree of vacuum used to store primal cuts.

The influence of suction catheter tip design on tracheobronchial trauma and fluid aspiration efficiency.

The suctioning efficiency and trauma-producing characteristics of five commercially available tracheobronchial suction catheters (Pharmaseal Tri-Flo, NCC Gentle-Flo, Argyle Aero-Flo, Argyle Dual Side-Hole, and Pharmaseal Whistle-Tip) were experimentally evaluated in anesthetized healthy dogs. The tendency of catheters to invaginate or "grab" tracheobronchial mucosa was observed with a bronchofiberscope during suctioning. Mucosal grabbing was seldom seen even at high (greater than 300 torr) vacuum levels with the cateter tip in the trachea. All catheters were observed to invaginate mucosa in lobar and segmental bronchi, with the frequency of grabbing being a function of airway anatomy, airway size, catheter orientation, tip design, and vacuum level. Catheters with multiple side-holes appeared to invaginate mucosa less frequently than the single side-hole catheter. Repeated suctioning of anesthetized healthy dogs followed by tracheobronchial excision, gross observation, and histologic examination of mucosal tissue biopsies demonstrated significant differences in the frequency and severity of lesions caused by the tracheobronchial suction procedure. All catheters were observed to damage airway lining, the damage related to multiple side-hole catheters appearing to be associated entirely with the act of cateter insertion and not with the application of vacuum. Only the Whistle-Tip design produced measurable damage beyond that related to catheter insertion. The average tip-suctioning effectiveness for each catheter, determined in vitro by aspirating a thin, uniform layer of simulated mucus, was found to be significantly higher for the Tri-Flo and Whistle-Tip catheters than the others, the Aero-Flo being least effective. Preliminary attempts to demonstrate this difference in suctioning effectiveness by comparing the performance of the catheters which displayed the highest and lowest tip suction effectiveness in a standardized clinical suctioning procedure revealed no significant difference in the percentage of mucus removed by either catheter. Additional studies should clarify this apparent contradiction.

The High Resolution Scanning Transmission Electron Microscope

The high resolution STEM is now a fact of life. I think that we have, in the last few years, demonstrated that this instrument is capable of the same resolving power as a CEM but is sufficiently different in its imaging characteristics to offer some real advantages.It seems possible to prove in a quite general way that only a field emission source can give adequate intensity for the highest resolution^ and at the moment this means operating at ultra high vacuum levels. Our experience, however, is that neither the source nor the vacuum are difficult to manage and indeed are simpler than many other systems and substantially trouble-free.

The Rate of Machine Milking of Dairy Cows. II. Effect of Vacuum and Pulsation Rate

Summary Eighteen randomly selected slow-milking cows were milked with a machine operated at various vacuum levels (10, 12.5, and 15) and pulsation rates (20, 50, and 80) for a 27-day experimental period. The nine treatments were assigned at random at the start of each of the three replications included in the above experimental period. Increasing the vacuum level increased the speed of milking and the effect was greater from 10 to 12.5 than from 12.5 to 15 in. Increasing the pulsation rate increased the speed of milking, but the magnitude of its effect was much less than that of increasing the vacuum. Most of the effect of pulsation on increasing the speed of milking occurred from 20 to 50. Increasing the pulsation rate appeared to be more important at low levels of vacuum than it was at high-vacuum levels. Most of the effects of vacuum and pulsation on increasing milking rate were additive. A few treatment interaction terms were significant. In these cases the increases in milking rate expected, had the effects of vacuum and pulsation been additive, were not obtained as a result of this interaction. Changing the vacuum level or pulsation rate affected the cows differently. In general, increasing the vacuum or pulsation caused greater increases in milking rate, percentage-wise, for the slowest-milking group of cows than it did for the fastest-milking group of cows.