Response of Listeria monocytogenes and Vibrio parahaemolyticus to High Hydrostatic Pressure

Listeria monocytogenes Scott A and CA, were subjected at 23°C to hydrostatic pressures ranging from 2,380 to 3,400 atm and Vibrio parahaemolyticus T-3765-1 from 680 to 1,700 atm. For L. monocytogenes Scott A, pressurization in ultra-high temperature-processed (UHT) milk and raw milk appeared to provide a protective effect and lessened cell death as compared to pressurization in phosphate-buffered saline (100 mM, pH 7.0). A population of about 10⁶ CFU/mL L. monocytogenes was killed by exposure to 3,400 atm within 80 min at 23°C in UHT milk. A population of about 10⁶ CFU/mL V. parahaemolyticus was killed by exposure to 1,700 atm within 10 min at 23°C in clam juice.     

OPTIMIZING STABILITY OF ORANGE JUICE FORTIFIED WITH WHEY PROTEIN AT LOW pH VALUES

Abstract The influence of temperature, heating time and pH on the stability of whey protein-fortified Valencia orange juice was determined by uronic acid content, degree of esterification (DE), % transmission measurements (%T) and capillary electrophoretic analysis of the juice-protein supernatants. Uronic acid content and charge of pectins showed no significant change in heat-treated samples with added proteins. The %T decreased with decreasing pH and increasing temperature and heating time for α-lactalbumin (α-lac), β-lactoglobulin (β-lg) and whey protein isolate (WPI). The lowest transmission values were shown at pH 3.0 and 85C. Capillary electropherograms confirmed more extensive juice-protein interactions in WPI and β-lg added juices than in those containing α-lac, especially at low pH, resulting in more stable juice-protein mixtures.     

VALIDATION OF HEATING CONDITIONS IN PRODUCTION OF DIRECT ACIDIFIED BEEF SUMMER SAUSAGE FOR ELIMINATION OF ESCHERICHIA COLI O157:H7

The effectiveness of a typical production process for eliminating Escherichia coli O157:H7 in directly acidified all‐beef summer sausage was evaluated for formulations of different fat contents (approximately 8 and 17%) and types of direct acidulant (encapsulated citric or lactic acid). Raw batter inoculated with E. coli O157:H7 to an initial level of ca. 7.4 log cfu/g was stuffed into 64‐mm casings and processed according to a thermal processing schedule used by a small commercial processor for directly acidified summer sausage products (maximum internal product temperature of 70C, followed by cold showering). For all‐beef summer sausage, log reductions ranged from 5.3 to 5.5 cfu/g when product reached 64.4C (148F) internal temperature (IT) and 70C (158F) IT, and from 6.3 to 6.5 log cfu/g reductions when product reached 37.8C (100F) IT after thermal processing and cold showering. No differences in E. coli O157:H7 counts were observed for products with different fat or acid contents.     

INCIDENCE OF CAMPYLOBACTER IN PROCESSED POULTRY: IS IT A CONCERN FOR HUMAN HEALTH?

In Australia, over 15,000 cases of campylobacteriosis occur annually; however, recent findings from case-control studies suggest that poultry may not be the primary etiological agent. To determine the incidence of Campylobacter species on Australian poultry, a qualitative and quantitative survey of different poultry products was undertaken. The qualitative study examined 428 poultry carcasses from 42 processors. Overall, 93.7% of the carcasses were found to be positive for Campylobacter species, of which 84.1% were identified as Campylobacter jejuni by hippurate hydrolysis, and 9.6% as other Campylobacter species. A longitudinal study over 6 weeks on 27 broiler carcasses from a single processor found an average Campylobacter species count of 163 cfu/cm², with a range of 5–1,850 cfu/cm² excluding one carcass that was negative. The real health risk of this carriage, however, cannot be determined accurately without further investigation of the presence of virulence factors and more accurate species identification.

PRACTICAL APPLICATIONS

This article identifies that the incidence of Campylobacter species on processed poultry remains at levels recognized to be potentially infectious to humans. This suggests that current changes in processing control in the Australian poultry industry primarily established for Salmonella species may not necessarily reduce all potential human pathogens to safe levels.
Using current literature, this article also debates whether the simple identification of presence and absence of a particular pathogen is sufficient for assumptions to be drawn on risk of infection. The discussion questions the real role of poultry in cases of campylobacteriosis, and suggests that based on case-history data, poultry may be not be the common cause of the disease.     

FATTY ACIDS AND MEAT CHARACTERISTICS OF DIFFERENT BIOLOGICAL TYPES OF BEEF CATTLE DEVELOPED UNDER A MANAGEMENT-INTENSIVE GRAZING SYSTEM

ABSTRACT

Beef steers representing four biological types were evaluated for fatty acid profiles and meat characteristics in muscle tissue developed on grazed forages. Biological types included six large‐framed, late maturing, nine medium‐framed, late maturing, nine medium‐framed, intermediate maturing, and nine medium‐framed, early maturing steers. Longissimus dorsi muscles were removed and frozen after 7 days of dry aging. Tenderness and cook loss were similar between biological types. Significant differences (P < 0.05) in fatty acid profiles were found between biological types. The medium‐framed, early maturing animals scored highest (P < 0.05) in marbling, had the highest (P < 0.05) concentration of total n‐3 fatty acids, and had the lowest n–6/n–3 ratio at 1.03:1. All biological types had a mean n–6/n–3 ratio well below the recommended <4:1 for human cardiovascular health. Under this dietary management system, medium‐framed, early maturing beef steers should be considered for producing grass‐fed beef based on both carcass merit and fatty acid composition.

PRACTICAL APPLICATIONS

Beef cattle that reach physiological maturity (i.e. puberty) earlier than their contemporaries should be selected for the production of grassfed beef if fully developed on forages. Those animals have the ability to deposit fat earlier than their later‐maturing contemporaries. Additionally, medium‐framed beef animals should be selected over larger‐framed animals as skeletal frame does not contribute to meat quality but requires more nutritional input for growth and maintenance. This ability to deposit fat exclusively on forage nutrients, without energy or protein supplementation, should be exploited when developing grassfed beef. Fat deposition, particularly intramuscularly (IM), contributes positively to meat quality. Fatty acids, especially the ratio of n‐6/n‐3, are optimized when beef animals have been fully developed on nutrient‐dense forages. Forages must be managed in such a way to capture those nutrients for animal intake and protect the plants for regrowth in a pasture setting.     

Protein Recovery from Veal Bones by Enzymatic Hydrolysis

Enzymatic hydrolysis (commercial enzyme) was applied to crushed bones in a batch reactor. The extraction was modeled using a Doehlert design. The effects of temperature (five levels ranging from 40 to 60°C), pH (seven levels from 5.7 to 7.5), enzyme concentration (seven levels from 20 to 80 g.kg^-1 protein), hydrolysis time (seven levels from 30 to 180 mn) and protein concentration (three levels from 60 to 90 g.kg^-1 mixture) were studied. Response surface methodology (RSM) predicted changes in protein yield and hydrolysis degree. Duration and enzyme concentration were the most important parameters, whereas pH and temperature exhibited no significant effects. Inhibition was observed over 80 g.kg^-1 of protein concentration.