M.W. Schilling

Relationships between sensory descriptors, consumer acceptability and volatile flavor compounds of American dry-cured ham

The relationships between volatile flavor compounds, sensory descriptors and consumer acceptability were determined for eight commercial American dry-cured hams using external preference and flavor mapping. The majority of consumers preferred (p<0.05) hams that had more intense caramelized, smoky, savory and molasses aromas as well as more intense sweet and savory flavors. Sixteen aroma impact compounds were identified from the headspace volatiles of dry-cured hams. The majority of consumers preferred (p<0.05) hams that were characterized by 4-methyl-2-methoxyphenol (sweet ham), 4-ethyl-2-methoxyphenol (sweet ham), 2-methoxyphenol (smoky, cocoa), 2,6-dimethoxyphenol (smoky ham, savory) and 2-furanmethanol (burnt meat, vitamin). Fourteen percent of consumers preferred (p<0.05) two hams that were characterized by methional (baked potato). Consumer acceptability scores were lower for hams either characterized by methanethiol (sulfur), carbon disulfide (sulfur), 2-butanone (sweet), 3-methylbutanal (malty, fermented), 2-heptanone (burnt meat, vitamin), hexanal (cut grass), benzeneacetaldehyde (floral), 1-octen-3-ol (mushroom) or characterized by benzaldehyde (burnt meat, cooked meat) and limonene (citrus). This study revealed how relationships between sensory descriptors, consumer acceptability and volatile flavor compounds could be determined using external preference mapping and used to comprehend the nature of dry-cured ham flavor as it is perceived by a consumer panel.

Bactericidal activity of lauric arginate in milk and Queso Fresco cheese against Listeria monocytogenes cold growth

Lauric arginate (LAE) at concentrations of 200 ppm and 800 ppm was evaluated for its effectiveness in reducing cold growth of Listeria monocytogenes in whole milk, skim milk, and Queso Fresco cheese (QFC) at 4°C for 15 to 28 d. Use of 200 ppm of LAE reduced 4 log cfu/mL of L. monocytogenes to a nondetectable level within 30 min at 4°C in tryptic soy broth. In contrast, when 4 log cfu/mL of L. monocytogenes was inoculated in whole milk or skim milk, the reduction of L. monocytogenes was approximately 1 log cfu/mL after 24 h with 200 ppm of LAE. When 800 ppm of LAE was added to whole or skim milk, the initial 4 log cfu/mL of L. monocytogenes was nondetectable following 24 h, and no growth of L. monocytogenes was observed for 15 d at 4°C. With surface treatment of 200 or 800 ppm of LAE on vacuum-packaged QFC, the reductions of L. monocytogenes within 24 h at 4°C were 1.2 and 3.0 log cfu/g, respectively. In addition, the overall growth of L. monocytogenes in QFC was decreased by 0.3 to 2.6 and by 2.3 to 5.0 log cfu/g with 200 and 800 ppm of LAE, respectively, compared with untreated controls over 28 d at 4°C. Sensory tests revealed that consumers could not determine a difference between QFC samples that were treated with 0 and 200 ppm of LAE, the FDA-approved level of LAE use in foods. In addition, no differences existed between treatments with respect to flavor, texture, and overall acceptability of the QFC. Lauric arginate shows promise for potential use in QFC because it exerts initial bactericidal activity against L. monocytogenes at 4°C without affecting sensory quality.

Dietary Digestible Lysine Requirements of Male and Female Broilers from Forty-Nine to Sixty-Three Days of Age

Experiments were conducted to evaluate digestible (dig) Lys requirements of male and female broiler chickens from 49 to 63 d of age. A dose-response diet consisting of corn, soybean meal, and corn gluten meal was formulated to be adequate in dig amino acid concentrations with the exception of Lys. L-Lysine . HCl was added to the dose-response diet to create 7 experimental diets. Concentrations of dig Lys of experimental diets ranged from 0.50 to 1.04% in increments of 0.09%. Variables measured consisted of standardized dietary Lys digestibility, feed intake, dig Lys intake, BW gain, feed conversion, mortality, abdominal fat weight and percentage, carcass weight and yield, and total breast meat weight and yield. In experiment 1, dig Lys of the dose-response diet was determined as 0.51% with cecectomized roosters. In experiment 2, dig Lys requirements of male broilers for BW gain, feed conversion, breast meat weight, and breast meat yield were 0.86, 0.88, 0.90, and 0.90%, respectively, based on 95% of the responses. From 49 to 63 d of age, male broilers optimized growth and meat yield measurements with approximately 3.0 g of dig Lys intake. In experiment 3, dig Lys requirements of female broilers were estimated as 0.79 and 0.83%, respectively, for BW gain and feed conversion. Digestible Lys intake necessary to optimize growth performance was 2.8 g/bird during 49 to 63 d of age. These results indicate that dig Lys requirements for male broilers were 0.87 and 0.90% of the diet, respectively, for growth performance and breast meat yield. Conversely, the dig dietary Lys requirement for females was 0.81% based only on growth performance.

Dietary inclusion level effects of distillers dried grains with solubles on broiler meat quality.

A completely randomized design with 7 replications (n = 7, treatments = 5 with 8 subsamples per treatment) was used to evaluate the effects of feeding various levels of distillers dried grains with solubles (DDGS; 0, 6, 12, 18, and 24%) on broiler breast and thigh meat quality. Broilers were harvested in a pilot scale processing plant with commercial prototype equipment at 42 d of age. The right half of each breast was evaluated for pH, instrumental color, cooking loss, proximate analysis, and tenderness. The left half of each breast was used for consumer acceptability testing. Thigh meat was evaluated for proximate composition, fatty acid composition, and TBA reactive substances. Breast meat from broilers that were fed DDGS had a higher (P < 0.05) pH than those from the control diet. In addition, the 18 and 24% DDGS treatments yielded breast meat with higher (P < 0.05) pH values than the 6% DDGS treatment. No differences existed (P > 0.05) among breast meat from the different treatments with respect to cooking loss, instrumental color, and consumer acceptability, but breast meat from the control (0% DDGS) treatment had slightly lower (P < 0.05) shear force than breast meat from the 18 and 24% DDGS treatments. In addition, no differences (P > 0.05) existed among proximate composition of breast and thigh meat from the control and DDGS treatments. As DDGS concentration increased, there was a linear increase (P < 0.05) in linoleic and polyunsaturated fatty acids, which indicates a greater potential for lipid oxidation. The TBA reactive substances values were greater (P < 0.05) for the 18 and 24% DDGS treatments at d 5 when compared with the control and 6% DDGS treatments, which indicates increased oxidation. Overall, data suggest that all treatments yielded high-quality breast meat and that thigh meat quality was similar among treatments containing 0 to 12% DDGS, but higher inclusion levels led to thigh meat that was more susceptible to oxidation.

Inhibition and inactivation of Salmonella typhimurium biofilms from polystyrene and stainless steel surfaces by essential oils and phenolic constituent carvacrol.

Persistence of Salmonella biofilms within food processing environments is an important source of Salmonella contamination in the food chain. In this study, essential oils of thyme and oregano and their antimicrobial phenolic constituent carvacrol were evaluated for their ability to inhibit biofilm formation and inactivate preformed Salmonella biofilms. A crystal violet staining assay and CFU measurements were utilized to quantify biofilm cell mass, with evaluating factors such as strain variation, essential oil type, their concentrations, exposure time, as well as biofilm formation surface. Of the three Salmonella strains, Salmonella Typhimurium ATCC 23564 and Salmonella Typhimurium ATCC 19585 produced stronger biofilms than Salmonella Typhimurium ATCC 14028. Biofilm formation by different Salmonella strains was 1.5- to 2-fold higher at 22°C than at 30 or 37°C. The presence of nonbiocidal concentrations of thyme oil, oregano oil, and phenolic carvacrol at 0.006 to 0.012% suppressed Salmonella spp. biofilm formation 2- to 4-fold, but could not completely eliminate biofilm formation. There was high correlation in terms of biofilm inactivation, as determined by the crystal violet-stained optical density (at a 562-nm wavelength) readings and the viable CFU counts. Reduction of biofilm cell mass was dependent on antimicrobial concentration. A minimum concentration of 0.05 to 0.1% of these antimicrobial agents was needed to reduce a 7-log CFU biofilm mass to a nondetectable level on both polystyrene and stainless steel surfaces within 1 h of exposure time.

The effect of pasteurization temperature on consumer acceptability, sensory characteristics, volatile compound composition, and shelf-life of fluid milk.

The relationship among consumer acceptability, descriptive sensory attributes, and shelf-life was determined for 2% milk pasteurized at 77, 79, 82, and 85 degrees C. Sensory descriptive attributes and volatile compound composition were monitored over the shelf-life of the products to determine if treatments could be differentiated at various times through out the shelf-life of the product. Consumers preferred 79 degrees C milk over other treatments on d 0; however, at d 6 postpasteurization, 79 and 82 degrees C milks were preferred over the 77 degrees C treatment. Consumers were grouped into 8 clusters based on product liking for both d 0 and d 6 evaluations. The largest cluster liked all pasteurization treatments, and 79 degrees C milk was highly acceptable to all consumers who liked milk. Similar sensory descriptors indicated the end of shelf-life for all pasteurization treatments even though treatments could be differentiated by descriptors on d 0. This research reveals that altering the pasteurization temperature from 79 degrees C may cause a decrease in consumer acceptability to some consumers. Also, altering pasteurization temperature did not affect shelf-life or sensory descriptors and volatile compound composition at the end of shelf-life.

Reduction of Listeria monocytogenes Biofilms on Stainless Steel and Polystyrene Surfaces by Essential Oils

Plant-derived essential oils were tested for their ability to eliminate biofilms of Listeria monocytogenes on polystyrene and stainless steel surfaces. Various concentrations of essential oils were tested with different contact times on biofilms of various ages. Preliminarily screening of nine essential oils and related phenolic compounds in a disk diffusion assay revealed that thyme oil, oregano oil, and carvacrol had the highest antimicrobial activity. Further screening of these three compounds against 21 L. monocytogenes strains representing all 13 serotypes indicated some strain-specific variations in antimicrobial activity. For 1-day-old biofilms of mixed L. monocytogenes strains produced at 22°C on polystyrene microtiter plates, only 0.1% concentrations of thyme oil, oregano oil, and carvacrol were needed to eliminate 7 log CFU per well. On the stainless steel coupons, a 0.5% concentration of these compounds was adequate to completely eliminate 4-day-old biofilms at 7 log CFU per coupon. Our findings indicate that these compounds are potential candidates for elimination of L. monocytogenes biofilms on stainless steel and polystyrene surfaces.

The effects of broiler catching method on breast meat quality

Mechanical and hand catching of broilers (n=24 per treatment for each trial) were performed to determine if differences existed in breast meat quality among catching methods. Two trials (summer and winter 2005) were conducted, and it was determined that there was greater variation in meat quality in the summer in comparison to the winter within treatments in both catching methods. Neither catching method yielded breast meat with significant quality issues. Therefore, either catching method should be acceptable for catching broilers in respect to meat quality. However, mechanical catching and crating for 2h yielded slightly better (P<0.05) quality meat than hand catching in respect to averages and individual quality problems. These slight improvements in meat quality included higher (P<0.05) 15min pH, lower (P<0.05) drip loss, and lower (P<0.05) incidence of pale meat with a rapid pH decline in the summer.

Effects of sodium lactate and acetic acid derivatives on the quality and sensory characteristics of hot-boned pork sausage patties

Sodium lactate and acetic acid derivatives were evaluated for their effects on color retention, microbial growth, and sensory attributes of hot-boned pork sausage patties. Treatments included: (a) sodium lactate (L), (b) buffered vinegar (V), (c) sodium lactate and vinegar mixture (LV), (d) control with BHA/BHT (C), and (e) negative control (NC). Treatments L and LV decreased TPC at day 14 and day 16 when compared to control samples and reduced bacterial numbers up to 18 days. In addition, use of lactate and vinegar increased (P<0.05) acceptability and juiciness and reduced (P<0.05) off-flavor and rancidity when compared to control treatments at day 14. These results revealed that the L and LV sausage patties retained sensory acceptability and shelf-life quality from day 14 through day 17 as opposed to other treatments. Additionally, sausage patties with LV maintained redness and sensory quality throughout 17 days of shelf-life, as compared to other treatments that retained color and quality for 14 days.

Effects of ionizing irradiation and hydrostatic pressure on Escherichia coli O157:H7 inactivation, chemical composition, and sensory acceptability of ground beef patties.

A randomized complete block design with three replications was utilized to determine the effects of ionizing irradiation and hydrostatic pressure on the inactivation of Escherichia coli O157:H7, volatile composition, and consumer acceptability (n=155) of frozen ground beef patties. E-beam and X-ray irradiation (2kGy) inactivated E. coli O157:H7 below the limit of detection, while hydrostatic pressure treatment (300mPa for 5min at 4°C) did not inactivate this pathogen. Solid-phase microextraction (SPME) was used to extract volatile compounds from treated ground beef patties. Irradiation and hydrostatic pressure altered the volatile composition (P<0.05) of the ground beef patties in respect to radiolytic products. However, results were inconclusive on whether these differences were great enough to use this method to differentiate between irradiated and non-irradiated samples in a commercial setting. Irradiation did not affect (P>0.05) consumer acceptability of ground beef patties when compared to untreated samples, but hydrostatic pressure caused decreased acceptability (P<0.05) when compared to other treatments.