Effects of packaging systems and fat concentrations on microbiology,sensory and physical properties of ground beef stored at 4 ± 1 °C for 25 days

This study evaluated effects of modified atmosphere (MAP, 0.4% carbon monoxide [CO], 30% carbon dioxide, and 69.6% nitrogen), vacuum (VP) and polyvinyl chloride (PVC) packaging systems and fat levels (10, 20 and 30% fat) on ground beef stored at 4 ± 1 °C for 25 days for microbiology, sensory, pH, thiobarbituric acid reactive substances (TBARS), objective color, headspace and residual CO. As storage time increased, pH decreased (P < 0.05) for MAP and VP and increased (P < 0.05) for PVC. TBARS varied (P < 0.05) among MAP and VP treatments. Except for day 1, CO headspace concentrations were similar among fat concentrations, and residual CO absorption in meat increased (P < 0.05) for all MAP treatments. In all treatments, degree of lightness was similar, redness decreased and brown discoloration increased during storage. As psychrotrophic bacteria counts increased, panelists detected color and off-odor deterioration in all systems. The CO treatment had no effect on maintaining the carboxymyoglobin “cherry red” fresh meat color during meat spoilage.     

Implementation of the Bacillus cereus microbiological plate used for the screening of tetracyclines in raw milk samples with STAR protocol – the problem with false-negative results solved

In antibiotic residue analyses the first step of screening is just as important as the following steps. Screening methods need to be quick and inexpensive, but above all sensitive enough to detect the antibiotic residue at or below the maximum residue limit (MRL). In the case of a positive result, the next step is conducted and further methods are used for confirmation. MRLs stated in European Union Regulation 37/2010 for tetracyclines in raw milk are: 100 µg kg^–1 for tetracycline, 100 µg kg^–1 for oxytetracycline, 100 µg kg^–1 for chlortetracycline and no limit for doxycycline because it is prohibited for use in animals from which milk is produced for human consumption. The current five-plate microbiological screening method for the detection of antibiotic residues in raw milk was found to be simple and inexpensive, but not specific, sensitive and reliable enough to detect tetracycline at MRL in routine raw milk screening procedures. Spiking samples with tetracycline at the MRL level and applying them on Bacillus cereus ATCC 11778 microbiological plates often gave false-negative results, indicating that tetracyclines may have to be inactivated or masked. Tetracyclines seem to bind to a certain component in milk. Consequently, when applying samples to the B. cereus microbiological plate the antibiotic cannot inhibit the growth of B. cereus which disables the formation of inhibition zones on the test plate. After adding the appropriate amount of citric acid into the milk samples, we solved the problem of false-negative results. During the validation 79 samples of milk were spiked with tetracyclines at different concentrations: 100 µg kg^–1 for tetracycline, 100 µg kg^–1 for oxytetracycline, 80 µg kg^–1 for chlortetracycline and 30 µg kg^–1 for doxycycline. Concentrations used in the validation matched the requirements for MRLs (they were either at or below the MRLs) stated in European Union Regulation 37/2010. The sensitivity of the validation was 100%.     

Investigating the within-herd prevalence and risk factors for ketosis in dairy cattle in Ontario as diagnosed by the test-day concentration of β-hydroxybutyrate in milk

An observational study of 790 to over 3,000 herds was conducted to estimate the within-herd prevalence and cow-level risk factors for ketosis in dairy cattle in herds that participate in a Dairy Herd Improvement Association (DHIA) program. Ketosis or hyperketolactia (KET) was diagnosed as milk β-hydroxybutyrate ≥0.15 mmol/L at first DHIA test when tested within the first 30 d in milk. Seven hundred ninety-five herds providing at least 61 first milk tests from June 2014 to December 2015 were used to estimate the provincial within-herd prevalence of KET. All herds on DHIA in Ontario (n = 3,042) were used to construct cow-level multilevel logistic regression models to investigate the association of DHIA collected variables with the odds of KET at first DHIA milk test. Primiparous and multiparous animals were modeled independently. The cow-level KET prevalence in Ontario was 21%, with an average within-herd prevalence of 21% (standard deviation = 10.6) for dairy herds enrolled in a DHIA program. The prevalence of KET had a distinct seasonality with the lowest prevalence occurring from July to November. Automatic milking systems (AMS) were associated with increased within-herd prevalence, as well as increased odds of KET in multiparous animals at first test (odds ratio: 1.45; 95% confidence interval: 1.30 to 1.63). Jersey cattle had over 1.46 times higher odds of KET than Holstein cattle. Milk fat yield ≥1.12 kg/d at the last test of the previous lactation was associated with decreased odds of KET in the current lactation (odds ratio: 0.56; 95% confidence interval: 0.53 to 0.59). Increased days dry and longer calving intervals, for multiparous animals, and older age at first calving for primiparous animals increased the odds of KET at first test. This study confirms previous findings that increased days dry, longer calving intervals, and increased age at first calving are associated with increased odds of KET and is the first report of increased KET in herds with AMS and in relation to milk fat yield at the final test of the previous lactation. Feeding management on AMS herds likely contributes to the increased prevalence of KET and further work is required to investigate modifications to current management to minimize risk. Milk fat yield during the previous lactation may be representative of energy partitioning.     

Effect of a 10-day ageing at 30 °C on the texture of dry-cured hams processed at temperatures up to 18 °C in relation to raw meat pH and salting time

The aim of this study was to investigate the effect of a 10-day ageing at 30 ± 2 °C on the texture of dry-cured hams processed at temperatures up to 18 ± 2 °C for 12 months in relation with raw ham pH and salting time. Three pH groups (semimembranosus muscle at 24 h post-mortem: Low pH < 5.7, Medium pH = 5.7 ⩽ pH ⩽ 5.9, and High pH > 5.9), three salting times (6 d, 10 d and 14 d) and two ageing temperatures (18 °C and 30 °C) were investigated. Physicochemical characteristics, instrumental and sensory texture and product sliceability were evaluated on biceps femoris and semimembranosus muscles. Hams with pH_SM24 < 5.7 should be avoided in order to reduce the incidence of texture problems in dry-cured ham elaboration. Texture problems are especially important in hams with a reduced salt content that are mechanically sliced (not frozen). A 10-day ageing at 30 °C could be useful for reducing the soft texture problems in dry-cured hams processed at temperatures up to 18 °C for 12 months without affecting the product flavour.     

Lactose hydrolysis in milk as affected by neutralizers used for the preparation of crude β-galactosidase extracts from Lactobacillus bulgaricus 11842

Three different neutralizers (NaOH, KOH, NH₄OH) were employed for pH maintenance during the growth of Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842, used as a source of β-galactosidase extracts. The crude enzymatic extract (CEE) was obtained by bead milling of the cell paste, collected from the cultivation of the source microorganism in skim milk at 43 °C and constant pH. Lactose hydrolysis kinetics in skim milk and proteolytic activity during the hydrolysis were evaluated. The use of NH₄OH as a neutralizer resulted in significantly (P<0.05) higher enzyme activity of the CEE than that obtained using NaOH or KOH. The kinetic parameters, k_cat and K_m, of the Michaelis–Menten model were determined for lactose hydrolysis in skim milk using 1% (v/v) addition of a CEE. There was no significant (P>0.05) difference in k_cat among the different extracts, with a clear temperature dependence following Arrhenius kinetics. The rate of lactose hydrolysis was dependent on the initial enzyme activity and temperature. The highest initial rate was observed at 65 °C; however, the enzyme deactivation occurred within 1–1.5 h. The proteolytic activity determined by HPLC peptide mapping was significantly (P<0.05) higher in the moderate temperature range (20 and 37 °C) than at 7 or 55 °C. Industrial relevance: Since lactose intolerance affects a large proportion of the world's population, an economically feasible and effective process with a cheap source of β-galactosidase may have a substantial potential. The use of crude β-galactosidase extracts from Lactobacillus bulgaricus 11842 appears to be a promising approach for development of a technologically feasible process of lactose hydrolysis for food or non-food uses.     

Application of one injection of prostaglandin F2α in the five-day Co-Synch + CIDR protocol for estrous synchronization and resynchronization of dairy heifers

The objective was to determine if the 5-d Co-Synch + CIDR (controlled internal drug releasing insert) protocol can be used in dairy heifers for a synchronized timed artificial insemination (TAI) with one injection of PGF_2α for first and second services. In experiment 1, heifers were assigned randomly to receive 1 (n = 295) or 2 (n = 298) injections of PGF_2α in the 5-d Co-Synch + CIDR protocol. Corpus luteum (CL) regression was measured in one replicate (n = 218). No difference in pregnancy per TAI (P/TAI; 46.1 and 48.6%) or CL regression (86.9 and 92.8%) was detected for 1 versus 2 injections of PGF_2α, respectively. In experiment 2, nonpregnant heifers (n = 86) were assigned to a resynchronized 5-d Co-Synch + CIDR with 1 PGF_2α/TAI or insemination at detected estrus. There was no difference in P/TAI (52.2 and 55%) between groups. In experiment 3, nonpregnant heifers (n = 110) were assigned randomly to receive a CIDR (n = 54) or no CIDR insert (n = 56) in the 5-d Co-Synch protocol for resynchronization of TAI. Pregnancy per TAI was lower without the CIDR device (39.3 vs. 51.8%). In a commercial field evaluation, 416 heifers were synchronized for the first and resynchronized TAI with the 5-d Co-Synch + CIDR protocol with 1 injection of PGF_2α. Pregnancy per TAI on d 60 was 58.2 and 47.5% for first and second TAI, respectively; there was a sire effect to the second TAI. In conclusion, the 5-d Co-Synch + CIDR protocol with 1 injection of PGF_2α is an effective reproductive management program for first and second TAI in dairy heifers.     

Green tea – A potential preservative for extending the shelf life of fresh mutton at ambient temperature (25 ± 2 °C)

This investigation was taken up to evaluate the feasibility of using green tea (GT) to extend the shelf life of fresh mutton, at ambient storage conditions (25 ± 2 °C and 85 ± 5% RH). The ethanolic extract of GT (GTE) was found to significantly inhibit (P < 0.01) spoilage microflora, including certain pathogens of acidulant treated mutton (pH 3.8) for up to 4 days. Application of GTE did not cause any deleterious change in sensorial and physical quality and the mutton was acceptable for up to 4 days. While the control samples showed initial signs of spoilage between 20 and 24 h and registered an increase in free fatty acids (FFA) from 1.24 g to 4.1 g/100 g lipid and biogenic amine index (BAI) from 0.27 mg to 4.63 mg/100 g mutton, at the end of two days of storage, the GTE treated sample showed FFA levels of 1.5 g/100 g lipid and BAI of 0.25 mg/100 g mutton at the end of the 4 days. GTE treatment could be effectively used to extend the shelf life of fresh mutton for up to 4 days in Indian climatic conditions, since it significantly (P < 0.01) inhibits the formation of these lipolytic and proteolytic degradation products, which are responsible for sensorial spoilage.