Fresh beef was modified-atmosphere packaged in carbon monoxide or oxygen to prolong red surface color. After comparison of several packaging method using carbon monoxide, steaks pretreated with 5% carbon monoxide for 24 hours and then vacuum packaged had the best combination of color and microbial stability (5 weeks), with the least potential for carbon monoxide inhalation. In the evaluation of ground beef in high-oxygen, modified-atmosphere-packaging, thiobarbituric-acid numbers increased over time, and the flavor was disliked slightly after 6 or 10 days of storage at 2° Celsius. The antioxidant effect of milk-mineral was tested in raw and cooked ground pork stored refrigerated or frozen. Thiobarbituric-acid numbers were low for all raw treatments. For cooked ground pork, thiobarbituric-acid numbers were lower for samples with milk-mineral or sodium-tripolyphosphate, compared to control or samples with butylated-hydroxytoluene. Sodium-tripolyphosphate, a type 2 antioxidant (iron chelator), was also very effective in preventing heme degradation during refrigerated storage.

Amino acids derived from the degradation of casein in cheese serve as precursors for the generation of desirable and undesirable flavor compounds. Microbial degradation of aromatic amino acids is associated with the formation of aroma compounds that impart putrid-fecal, barny-utensil, and floral off-flavors in cheese, but pathways for their production had not been established. This study investigated Tyr and Phe catabolism by Lactobacillus casei and Lactobacillus helveticus cheese flavor adjuncts under simulated Cheddar cheese-ripening conditions (pH 5.2, 4% NaCl, 15°C, no sugar). Enzyme assays of cell-free extracts and micellar electrokinetic capillary chromatography of supernatants indicated that L. casei and L. helveticus strains catabolize Tyr and Phe by successive transamination and dehydrogenation reactions. Major products of Tyr and Phe catabolism included off-flavor compounds formed by chemical degradation of the α-keto acids, produced by transamination, and aromatic α-hydroxy acids derived from α-keto acids by α-hydroxy acid dehydrogenases. Action of Lacrococcus lactis aminotransferase enzymes on Trp, Tyr, and Phe also leads to the formation of α-keto acids, but unlike lactobacilli, the former bacteria do not express dehydrogenase activity under cheese-like conditions (pH 5.2, 4% NaCl, 15°C, no sugar). Since aromatic α-keto acids may degrade spontaneously into undesirable flavor compounds, α-hydroxy acid dehydrogenases may be useful in controlling off-flavor development via diversion of chemically labile α-keto acids to more stable a-hydroxy acids. To test this hypothesis, we investigated the effect of D-hydroxyisocaproate dehydrogenase overexpression by a L. casei adjunct on chemical and sensory properties of reduced-fat Cheddar cheese made with and without addition of 20 mM α-ketoglutarate. The D-hydroxyisocaproic acid dehydrogenase gene (D-HicDH) was cloned into a high copy number vector pTRKH2 and transformed into L. casei ATCC334. Reduced-fat Cheddar cheeses were made with Lactococcus lactis starter only, starter + L. casei ATCC334 with pTRKH2, and starter + L. casei ATCC334 with pTRKH2: D-HicDH, and then volatile analysis was performed by gas chromatography and mass spectrometry. Statistical analysis of volatile data after 3 mo of ripening at 7°C showed profiles of ketones, aldehydes, alcohols, esters, sulfur compounds, and benzaldehyde were significantly altered by culture treatments and α-ketoglutarate addition, and these treatments also affected sensory flavor attributes of experimental cheeses. Results also indicated overexpression of D-hydroxyisocaproic acid dehydrogenase can divert labile α-keto acids into more stable compounds, but the overall effect seemed to diminish both beneficial and detrimental flavor notes.

This study sought to investigate the role of the C55 undecaprenol lipid carrier in the production of exopolysaccharide (EPS), the effect of exopolysaccharide producing (EPS+) starter cultures on the viscosity of Mozzarella cheese whey, and the possible protective characteristics of capsular EPS against freezing and freeze drying. Efforts to investigate the role of the lipid carrier in EPS production employed pAMbacA, a plasmid that encodes an enterococcallipid kinase that confers bacitracin resistance by increasing intracellular levels of undecaprenol phosphate lipid carrier. Unfortunately, this avenue of study was thwarted by the inability to demonstrate bacA expression in a model dairy lactic acid bacterium, Lactococcus lactis. To study the effect of EPS+ cultures on cheese whey, Mozzarella cheese was made with starters consisting of Lactobacillus helveticus (LH100) paired with one of four Streptococcus thermophilus strains. These strains included a capsular EPS producer (Cps+) MR-1C; a non-exopolysaccharide producing negative mutant (EPS-) of MR-1C, DM10; a ropy EPS producer, MTC360; and a non-EPS producing industrial strain, TA061. Results showed that Mozzarella cheese made with a Cps+ or ropy EPS+ S. thermophilus strain had significantly higher moisture levels than cheese made with non-exopolysaccharide producing (EPS-) streptococci. Melt properties were also better in cheeses with higher moisture. Viscosity measurements of unconcentrated and ultrafiltered (5-fold concentrated) whey showed that ultrafiltered whey from cheeses made with S. thernzophilus MTC360 was significantly higher in viscosity than whey from cheeses made with MR-1C, TA061, or DM10. There was no significant difference in the viscosity of unconcentrated or concentrated whey from cheese made with S. thermophilus MR-1C and cheese made with the commercial starter culture TA061. The results indicated that non-ropy, encapsulated exopolysaccharideproducing S. thermophilus strains can be used to achieve higher cheese moisture levels and to improve the melt properties of Mozzarella cheese without significantly increasing cheese whey viscosity. Finally, S. thermophilus MR-1C and DM10 were subjected to freezing and freeze drying to test for possible protective effects of the capsular exopolysaccharide. Analysis of variance of cell counts taken before and after freezing or freeze drying cycles revealed there was no significant difference between the viability of these strains.

Whey permeate was anaerobically digested in laboratory scale upflow anaerobic sludge blanket reactors. Nine hydraulic retention times between 5 and 0.2 days were examined with a fixed influent concentration of 10.6 ± 0.2 g COD/L. Chemical oxygen demand removal efficiency ranged from 99.0 to 18.9% and maximum production rate of methane gas was 2.67 L/L/day at a hydraulic loading rate of 12.97 kg COD/m3/day. About 70% of the chemical oxygen demand removed was converted to methane. Both the nonlinear least square method with 95% confidence interval and linear regression were used to evaluate kinetic coefficients. The maximum substrate utilization rate, k, and half saturation coefficient, KL, were determined to be 1.269 ± 0.163 Kg COD/kg VSS/day and 1.000 ± 0.179 kg COD/kg VSS/day. The yield coefficient, Y, and biomass decay rate coefficient, Kd, were also determined to be 0.160 ± 0.012 kg VSS/kg COD and 0.027 ± 0.004 day-1, respectively.

Experiment A explored the influence of sodium on direct acid, nonfat Mozzarella cheese. Cheeses with differing salt levels were obtained by varying dry salt applications (none, 0.5%, and 1.0% NaCl w/w) and hot brine stretching (0%, 5%, and 10% NaCl wt/v). Salt application and salt content influenced cheese moisture, meltability, expressible serum, micro- and ultra-structure, and color. Moisture was highest when cheese was salted before stretching (P = 0.03) . Melt was lowest in cheeses that were unsalted (P = 0.05). Cheeses stretched in salt brine had < 1% of the amount of expressible serum found in unsalted cheese (P < 0.0001). Unsalted cheeses had a more open structure with pockets of serum distributed throughout the protein matrix giving it an opaque, white appearance. Salted cheeses had a more homogeneous protein matrix lacking light scattering surfaces, resulting in a translucent cheese. Neither salt concentration nor method of salting affected the calcium content of the cheeses (P > 0.05). Experiment B explored the influence of calcium, moisture, and pH on cheese structure and functionality. Cheeses were manufactured using combinations of citric and acetic acids. Addition of EDTA to the whey during cooking, CaCl2 fortification, and extended drain times were used to produce eight cheeses in a 23 factorial design with target pH levels of 5.8 and 5.3, 70% and 66% moisture, and 0.6% and 0.3% calcium levels. EDTA was unsuccessful in removing calcium from pH 5.8 cheese. Adding CaCh successfully increased the calcium level of pH 5.3 cheese. Cheese with 0.3% calcium had greatest melt, decreased hardness and increased adhesiveness. Cheese with 0.6% calcium had decreased melt and adhesiveness, and increased hardness. When calcium content was held at 0.6% there was no significant difference in melting even when pH was varied from pH 5.8 to pH 5.3 . The microstructure of the 0.6% calcium cheeses had an increase in protein folds and serum pockets. Low calcium cheeses had a very homogeneous structure. Directly acidified nonfat Mozzarella cheese manufactured with 1.0% dry salt and hot water stretching produced the best cheese. This cheese contained 0.4% salt, 0.4% calcium, no expressible serum, and good meltability.

The effects of micrococci on sensory characteristics of different batches of summer sausages were determined. Sixty four salt-tolerant indigenous isolates were selected from beef or mutton treated with 1.5 or 3.0% sodium chloride and 120 ppm sodium nitrite, and held at 5 or 10 C for 5 days. These isolates (61/64) were identified as staphylococci and micrococci. Summer sausages were made from several lamb, ewe, and ram carcasses which were hand deboned and blended after grinding to contain 22% fat. Six summer sausage treatments were prepared using two different sources of commercial starter cultures including Micrococcus species or Micrococcus varians and Lactobacillus plantarum, an indigenous Micrococcus isolate, a microbial lipase, or encapsulated lactic acid. Three sensory panel sessions rated these products for consumer acceptability. Sensory panel results indicated that starter culture treatments did not improve sensory characteristics of the summer sausage over the treatment containing encapsulated lactic acid. Lipase addition caused a general reduction in sensory panel ratings for flavor, texture, appearance, and overall acceptability of the summer sausage (p = 0.05).

Essential oils (EOs) or their isolated components, such as eugenol and carvacrol, have strong antimicrobial activities against both Gram-positive and Gram-negative bacteria and are generally recognized as safe by the FDA. However their hydrophobic properties limit their dispersion and stabilization in aqueous food systems. This requires higher concentrations, which in turn negatively affect the quality of foods. The objective here was to determine the effect of the natural emulsifier lecithin on the antimicrobial activity of eugenol and carvacrol and possible food applications. Escherichia coli K12 and E. coli O157:H7 strains ‘Cider’ and ATCC 43889 were used. Homogenized eugenol and carvacrol, with and without lecithin, were screened for antimicrobial activity. The stability of the samples measured by particle size and zeta potential was not affected by different concentrations of lecithin. For all strains, the antimicrobial activity of carvacrol and eugenol was enhanced significantly (P<0.05) by low concentration of lecithin. The D-value (time at a specific concentration of antimicrobial necessary to cause a 90% reduction in viable cells) for E. coli K12 exposed to 0.047% v/v eugenol or 0.015 % v/v carvacrol was reduced from 13.3 to 6.3 min and 17.4 to 9.7 min, respectively, with the addition of 0.0025% lecithin (w/v). Similarly 0.0025% w/v lecithin in the presence of 0.058% v/v eugenol or 0.0188% v/v carvacrol, caused the D-value to decrease from 4.0 to 1.2 min and 10.2 to 6.9 min, respectively, for E. coli strain ‘Cider’ and from 6.2 min to 3.6 min and 9.9 to 5.4 min, respectively, for E. coli ATCC 43889. Higher lecithin concentrations (> 0.005% w/v) increased D-values compared to lower concentrations. Similar results were found in vegetable juice. The results showed that a small amount of lecithin can enhance the antimicrobial activities of essential oils. Addition of lecithin had no effect on oil-water emulsion droplet particle size and the stability of the samples was not affected by different concentration of lecithin. We believe that lecithin enhances the antimicrobial activity of eugenol and carvacrol droplets by improving the ionic interactions between the positively charged lecithin-containing essential oil components and negatively charged bacterial cells.

Scientific evidence shows that dietary intake of the omega-3 polyunsaturated fatty acids is beneficial to human health. Fish oil is a rich source of omega-3 fatty acids. However, fish oil with high levels of omega-3 PUFA is very susceptible to oxidative deterioration during storage. The objective of this study was to investigate the effect of xanthan gum (XG)-locust bean gum (LBG) mixtures on the physicochemical properties of whey protein isolate (WPI) stabilized oil-in-water (O/W) emulsions containing 20% v/v menhaden oil. The O/W emulsions containing XG/LBG mixtures were compared to emulsions with either XG or LBG alone. The emulsions were prepared using a sonicator by first mixing menhaden oil into the WPI solution and then either XG, LBG or XG/LBG mixtures were added. WPI solution (2 wt%) and gum solutions (0.0,0.05, 0.1, 0.15, 0.2 and 0.5 wt%) were prepared separately by dissolving measured quantities of WPI in distilled water. XG and LBG gums were blended in a synergistic ratios of 50:50 for the mixture. The emulsions were evaluated for apparent viscosity, microstructure, creaming stability and oxidative stability. Addition of 0.15, 0.2 and 0.5 wt% XG/LBG mixtures greatly decreased the creaming of the emulsion. The emulsion with 0.15, 0.2 and 0.5 wt% XG/LBG mixtures showed no visible serum separation during 15 d of storage. The apparent viscosity of the emulsions containing XG/LBG mixtures was significantly higher (p < 0.05) than the emulsions containing either XG or LBG alone. The viscosity was sharply enhanced at higher concentrations of XG/LBG mixtures. Microstructure images showed depletion flocculation for LBG (0.05-0.5 wt%), XG (0.05- 0.2 wt%) and XG/LBG mixtures (0.05 and 0.1 wt%) emulsions. Flocculation was decreased with the increased biopolymer concentration in the emulsion. The decrease in flocculation was much pronounced for the emulsion containing XG/LBG mixtures. The rate of lipid oxidation for 8 week storage was significantly (p < 0.05) lower in emulsions containing XG/LBG mixtures than in emulsions containing either of the biopolymer alone. The results suggested that the addition of XG/LBG mixtures greatly enhanced the creaming and oxidative stability of the WPI-stabilized menhaden O/W emulsion as compared to either XG or LBG alone.

Oil-in-water emulsions have wide range of applications in food industry because of their structure-forming properties, and as delivery systems of polyunsaturated fatty acids into foods. The thermodynamic instability of oil and water, and high susceptibility of unsaturated fatty acids to oxidation lead to physical and oxidative stability in oil-in-water emulsions. These instability processes are generally controlled by incorporating proteins and polysaccharides into oil-in-water emulsions. The objective of this study was to evaluate xanthan/enzymatically modified guar (XG/EMG) polysaccharides on the physical and oxidative stability of 2 wt% whey protein stabilized oil-in-water emulsions containing 20% v/v menhaden fish oil. Enzymatic modified guar gum was obtained by hydrolyzing native guar gum using α-galactosidase enzyme. Emulsions were prepared for guar gum (GG), xanthan gum (XG), xanthan/guar (XG/GG), and xanthan/enzymemodified guar (XG/EMG) gum mixtures using 0, 0.05, 0.1, 0.15, 0.2, and 0.3% gum concentrations. Emulsions were then evaluated for creaming, viscosity, particle size, and microstructure to evaluate the physical stability, and peroxide value, TBARS value and GC-MS solid phase micro extraction (SPME) experiments were performed to evaluate the oxidative stability. Emulsions containing XG/EMG gum mixtures exhibited better creaming stability and higher viscosity of all the emulsion types. However, XG/EMG gum concentrations did not affect the droplet size of the emulsions. The microstructures revealed decreased flocculation in emulsions with XG/EMG mixtures. The primary and secondary lipid oxidation measurements indicated that emulsions containing XG/EMG gum mixtures were more effective in preventing the lipid oxidation of all the emulsion types. From the results, it is evident that XG/EMG gum mixtures can be used as emulsifiers in oil-in-water emulsions to increase both physical and oxidative stability.

This study investigated the antiviral, chemoprotective and proliferative effects of strawberry anthocyanins on herpes simplex virus type-1, cancerous cell lines HT-29 and AGS, and normal cell lines Hs 738.St/Int and CCD-18Co. Antiviral properties were measured by infecting vero cells from adult grivet (Cercopithecus aethiops) with herpes simplex virus type-1 (HSV-1) and treating with a concentration of 1.25-20 µg/mL of strawberry anthocyanins. Infectivity and replication were quantified for herpes simplex virus type-1 using the direct plaque assay and reporting PFU/mL. Strawberry anthocyanins (>20 µg/mL) inhibited the herpes simplex virus infectivity in vero cells by 100% (p<0.05). Strawberry anthocyanins at concentrations of 5, 10 and 20 μg/mL were reduced to 75.36, 57.98, and 31.46 percent of the control (100%) (p<0.05). Chemoprotective and proliferative effects of strawberry anthocyanins were analyzed for the human cell lines AGS, Hs 738.St/Int, HT-29, and CCD-18Co at a concentration of 25-200 µg/mL and quantified using the sulforhodamine-B assay. Growth inhibition occurred at a level of ≥87% for treatment concentrations 100 and 200 µg/mL for the cancerous AGS and HT-29 cell lines (p<0.0001). Proliferation rates for the normal Hs 738.St/Int and CCD-18Co cell lines increased at all treatment concentrations of 25-200 μg/mL (p<0.0001); suggestingthat the observed proliferative activity may be associated with anthocyanin treatment.Strawberry anthocyanin treatment concentration worked in a dose dependent manner for the HSV-1 and the cancerous AGS and HT-29 cells. The caspase-3 assay was performed to demonstrate potential mechanism of action and confirmed thatanthocyanin treatments play a role in apoptosisby the up regulation of caspase-3.Significantdifferences were seen between the growth characteristics of cancerous cell linescompared to their equivalent normal cell lines (p<0.0001). In summary, the antiviral findings suggest that strawberry anthocyanin extracts could be an effective topical treatment and/or prophylactic agent for oral herpetic infections (HSV-1). Also, the in vitro chemoprotective effect of strawberry anthocyanins found may be relevant to in vivo work in the future because when anthocyanins are consumed in the diet they come in direct contact with the gastrointestinal tract and may provide chemoprotection upon contact with the stomach and gastrointestinal tract’s epithelial cell layer.