The effect of different temperature-time combinations when ageing beef: Sensory quality traits and microbial loads

Microbial Profiles of Meat at Different Stages of the Distribution Chain from the Abattoir to Retail Outlets

Meat has been found to be a prime vehicle for the dissemination of foodborne pathogens to humans worldwide. Microbial meat contaminants can cause food-borne diseases in humans. The threat to consumers by microbial meat contaminants necessitates the studying of meat microbial loads to prevent potential illnesses in consumers. Studies investigating the meat microbial loads in South Africa are limited. The objective of this study was to compare microbial contamination of different meat types from low-throughput (LTA) and high-throughput abattoirs (HTA) at three stages of the distribution chain from abattoir to retail outlets. Beef, pork, and mutton (n = 216) carcasses were sampled: during the loading process at the abattoirs, when off-loading at the supply points and during marketing. All samples were subjected to total bacterial count (TBC), coliform count (CC), presumptive Escherichia coli (E. coli) (PEC) and Staphylococcus aureus (S. aureus) detection. In mutton, TBC dominated at loading, CC was similar across distribution chain stages, PEC was the predominant microbial contaminant at the offloading stage at the HTA, but TBC was affected at loading, CC was similar across distribution chain stages, PEC was affected at loading, and S. aureus was affected at the display stage at the LTAs. In beef, TBC had similar levels at loading; CC and PEC dominated at the display stage for the HTAs. However, TBC was affected at the display stage; CC was similar across stages; PEC was affected at the offloading stage at the LTAs. In pork, higher contamination levels were discovered at the display stage, CC dominated at the loading stage, with PEC detected at offloading at the HTAs but TBC, CC, PEC and S. aureus were similar across stages at the LTAs. TBC, CC and PEC were affected by the storage period and meat supplier to meat shop distance whereas distance affected the TBC, CC and PEC. Meat supplier to meat shop distance negatively correlated with meat distribution chain stage but positively correlated with TBC, CC and PEC such as temperature. Temperature positively correlated with meat distribution chain stage and shop class. Meat distribution chain stage was negatively correlated with storage period, TBC, CC and PEC but positively correlated with shop class. Shop class negatively correlated with storage period, TBC, CC and PEC. Storage period positively correlated with TB, CC and PEC. TBC and meat type positively correlated with CC and PEC. CC positively correlated with PEC but negatively correlated with S. aureus such as PEC. In conclusion, mutton, pork and beef meat are susceptible to microbial contamination at distribution chain stages in abattoirs.

Comparison of physiochemical attributes, microbial community, and flavor profile of beef aged at different temperatures

Beef aging for tenderness and flavor development may be accelerated by elevated temperature. However, little to no research has been undertaken that determines how this affects other important meat quality characteristics and microbial community. This study aims to decrease aging time by increasing temperature. Beef were aged and vacuum packaged at 10 and 15°C, and the effects of increased temperature on meat physiochemical attributes, microbial community, and flavor profile were monitored. The shear force decreased with aging in all temperature and showed the higher rate at elevated temperatures compare to 4°C. The beef aged at elevated temperatures (10 or 15°C) for 5 days showed equivalent shear force value to the beef aged at 4°C for 10 days (p  >  0.05), however, the final tenderness was not affected by the elevated temperature. The beef aged at elevated temperatures showed a significantly higher cooking loss and less color stability compared to 4°C (p  <  0.05). The total volatile basic nitrogen and aerobic plate count increased (p  <  0.05) faster at elevated temperatures compare to 4°C. Carnobacterium, Lactobacillus and Hafnia-Obesumbacterium were the dominant genus in the beef samples aged at 4, 10, and 15°C, respectively. In addition, the contents of isobutyraldehyde, 3-methylbutyraldehyde, 2-methylbutyraldehyde, and 3-methylbutanol were higher than aged at 4°C (p  <  0.05). Therefore, these results suggest that application of elevated aged temperatures could shorten required aging time prior while not adversely affecting meat quality. In turn, this will result in additional cost savings for meat processors.

Application of gamma radiation in the beef texture development during accelerated aging

This study aimed to evaluate the effects of gamma radiation (3 kGy) on the quality of post-rigor beef (M. longissimus lumborum) aged for up to 21 days at different temperatures (1, 7, and 15°C). Irradiation reduced the mesophilic and lactic acid bacteria counts, which were higher in the non-irradiated samples aged at 7 and 15°C. The water retention capacity was lower in the irradiated beef, resulting in higher values of exudation and cooking losses. High aging temperatures increased the exudation loss and myofibrillar proteolysis (lower fragmentation index; FI) and reduced the total and insoluble collagen contents and the beef Warner-Bratzler square Shear Force (WBsSF). However, irradiated beef had higher FI and SF than non-irradiated ones, increasing the time required for the beef tenderizing. Gamma irradiation (3 kGy) can be used to ensure the microbiological safety during short storage at high temperatures (up to 15°C) in order to accelerate the process of beef tenderizing.

The effect of extended refrigerated storage on the physicochemical, structural, and microbial quality of sous vide cooked biceps femoris treated with ginger powder (zingibain)

The aim of the study was to investigate quality and shelf life of beef meat cooked under sous vide conditions then extended refrigerated storage for 10 weeks. Biceps femoris (n = 6) from six to seven year old cows were treated with 2 g/L ginger powder (GP) containing zingibain or control (no injection) and were then cooked in sous vide conditions at 65 °C for 1 h or 8 h. Cooked samples were evaluated for physicochemical (pH, total water content, cooking loss, Warner-Bratzler shear force (WBSF), texture profile analysis (TPA), L*, a*, b* properties and thiobarbituric acid reactive substance (TBARS)), microstructure (scanning electron microscopy) and microbiological (Brochothrix thermospacta, Clostridium perfringens, Lactic acid bacteria, Listeria monocytogenes, Salmonella spp, and yeasts and moulds) quality after vacuum packing, cooking, then refrigerated storage at 4 °C for 0, 2, 4, 8 or 10 weeks. Physicochemical parameters were improved by GP treatment (P < 0.05) while there was no effect of storage time on WBSF, TPA or microstructure. The microbial quality of sous vide cooked meat in refrigerated storage appeared to be four weeks and oxidation shelf life of the cooked meat was found to be two weeks under refrigerated storage.

The Applicability of Total Color Difference ΔE for Determining the Blooming Time in Longissimus Lumborum and Semimembranosus Muscles from Holstein-Friesian Bulls at Different Ageing Times

This study was conducted to determine the optimal blooming time in beef muscles based on ΔE, and to analyze the effects of muscle type and ageing time on beef color and blooming. Beef color was determined on freshly cut longissimus lumborum (LL, n = 8) and semimembranosus (SM, n = 8) muscles on days 1, 9, and 14 of ageing during 60 min blooming at 5 min intervals. It was found that ΔE0, representing the difference in color between freshly cut muscles and subsequently analyzed samples, supported the determination of the optimal blooming time, which varied across ageing times (15, 20, 25 min for the LL muscle, and 10, 15, 20 min for the SM muscle on days 1, 9, and 14 of ageing, respectively). Beef color was affected by both muscle type and ageing. The values of color parameters increased between days 1 and 9 of ageing. The results may have practical applications because beef should be presented to consumers and restaurant owners approximately 25 min after cutting, when its color has fully developed.

Temperature-time combination effects on aged beef volatile profiles and their relationship to sensory attributes

Beef ageing (in vacuo) for tenderisation and flavour development may be accelerated by favourable temperature-time combinations (TTCs), however the effect of such manipulations on volatile organic compounds (VOCs) that are generated during cooking, is unknown. We compared VOCs from grilled beef longissimus lumborum muscle samples which had been subjected to different TTCs. The TTCs consisted of combinations of temperatures (~ 3, 5, or 7 °C) and ageing time periods (6, 8, 10 or 12 d); as well as control samples, which were held at 0-2 °C for a total of 14 d. Sensory quality attributes of these same samples were measured by untrained consumer panellists. Generally, it was found that TTCs had negligible effects on grilled beef VOCs and were comparable to controls. Furthermore, many VOCs were significantly related to flavour intensity, flavour liking and overall liking. These findings support the use of TTCs as a viable means to accelerate the rate of beef ageing without compromising quality.

Moisture content, fatty acid profile and oxidative traits of aged beef subjected to different temperature-time combinations

Temperature-time combinations (TTC) effects on beef fatty acid (FA) composition, moisture content and oxidative traits were investigated. TTC were designed so temperatures were constant over each time period, and there was at most one variation in temperature within a sample's combined (total) time period. Therefore, three temperatures (~ 3, 5 and 7 °C) and five time periods (6, 8, 10 and 12 d) resulted in 72 different TTC, which were compared to control samples held for 14 d at ~ 1 °C. It was found that moisture losses increased as TTC temperature and time periods increased. There were negligible effects of TTC on FA composition. Sample TBARS and vitamin E content did not respond to TTC. A positive relationship between beef vitamin E and long chain polyunsaturated FA contents was observed. We concluded that TTC could be applied to accelerate the rate of ageing for beef and achieve comparable yield, oxidative and FA characteristics compared to conventional ageing approaches.