S.R. Vaudagna

Conventional freezing plus high pressure–low temperature treatment: Physical properties, microbial quality and storage stability of beef meat

Meat high-hydrostatic pressure treatment causes severe decolouration, preventing its commercialisation due to consumer rejection. Novel procedures involving product freezing plus low-temperature pressure processing are here investigated. Room temperature (20°C) pressurisation (650MPa/10min) and air blast freezing (-30°C) are compared to air blast freezing plus high pressure at subzero temperature (-35°C) in terms of drip loss, expressible moisture, shear force, colour, microbial quality and storage stability of fresh and salt-added beef samples (Longissimus dorsi muscle). The latter treatment induced solid water transitions among ice phases. Fresh beef high pressure treatment (650MPa/20°C/10min) increased significantly expressible moisture while it decreased in pressurised (650MPa/-35°C/10min) frozen beef. Salt addition reduced high pressure-induced water loss. Treatments studied did not change fresh or salt-added samples shear force. Frozen beef pressurised at low temperature showed L, a and b values after thawing close to fresh samples. However, these samples in frozen state, presented chromatic parameters similar to unfrozen beef pressurised at room temperature. Apparently, freezing protects meat against pressure colour deterioration, fresh colour being recovered after thawing. High pressure processing (20°C or -35°C) was very effective reducing aerobic total (2-log(10) cycles) and lactic acid bacteria counts (2.4-log(10) cycles), in fresh and salt-added samples. Frozen+pressurised beef stored at -18°C during 45 days recovered its original colour after thawing, similarly to just-treated samples while their counts remain below detection limits during storage.

Warmed-over flavour analysis in low temperature–long time processed meat by an “electronic nose”

The ability of an electronic nose, comprising 32 conducting polymer sensors, to identify and classify warmed-over flavour (WOF) aroma in bovine semitendinosus muscle, processed by vacuum cook-in-bag/tray technology (VCT) and storage under refrigerated conditions, was evaluated. The VCT process employed low temperature-long time (50°C-390 min) thermal treatments. Multivariate analysis showed that VCT processed beef aroma profiles were sorted into two groups, one included samples stored for up to 20 days and the other included samples with 34 to 45 days of storage. WOF odour standard samples were recognised to have similar aroma as samples of the second group. Lipid oxidation results, measured by thiobarbituric acid reactive substances, showed an increment in oxidation level for samples stored for 34 days or more (P<0.05). This study shows that electronic nose technology can be applied to WOF odour identification and classification in VCT beef meat, complementing chemical and sensory techniques used in this field.

Effect of whey protein concentrate and sodium chloride addition plus tumbling procedures on technological parameters, physical properties and visual appearance of sous vide cooked beef

Beef muscles cooked by the sous vide system were evaluated for the effects of pre-injection tumbling, brine addition and post-injection tumbling on technological parameters, physical properties, visual appearance and tissue microstructure. The muscles were injected at 120% (over original weight) with a brine formulated to give a concentration of 3.5% whey protein concentrate and 0.7% sodium chloride on an injected raw product basis. Pre-injection tumbling did not affect most of the evaluated parameters. Brine addition reduced significantly the cooking and total weight losses. Total weight loss was 7.2% for injected muscles, and significantly higher (28.2%) for non-injected ones. Brine incorporation increased pH and reduced shear force values of cooked muscles. Extended post-injection tumbling (5rpm-10h) improved brine distribution and visual appearance, and also diminished the shear force values of cooked muscles. However, this treatment increased the weight losses of post-injection tumbling and cooking-pasteurization stages.

Soy protein isolate added to vacuum-packaged chorizos: effect on drip loss, quality characteristics and stability during refrigerated storage

Chorizo is a raw sausage, which is manufactured with beef, pork meat and pork fat, additives and spices. In Argentina, the expenditure of chorizo is through butchery and supermarkets where the product can be found packaged in both polyethylene films and vacuum sealed pouches. In the latter type of packaging an appearance problem has been detected in relation to drip loss. The aim of the work was to solve such problem through the incorporation of soy protein isolate (SPI). The sensory, microbiological and chemical stability of the product and its drip loss during a storage period of 14 days were studied. By adding a 2.5% SPI, the drip loss was prevented without introducing any change in the flavour, aroma and juiciness characteristics of the product. These sensory attributes were kept stable during the storage period studied. Chemical composition, oxidative and microbiological stability were not affected by the addition of SPI during the storage period, being similar for added and non-added SPI samples. Finally, SPI can be used in chorizos to improve their overall appearance during refrigerated storage while the product quality characteristics are not altered.

Effect of salt addition on sous vide cooked whole beef muscles from Argentina

Sodium chloride (NaCl, 0-1.4%) and sodium tripolyphosphate (STPP, 0-0.5%) were added to Semitendinosus muscles and submitted to sous vide cooking at different temperatures (55-75°C). The effects of these three factors on pH, cooking loss, instrumental colour parameters, protein solubilization and distribution, and micro- and ultra-structure were evaluated. Quadratic surface responses equations were obtained from data (pH, cooking loss and colour parameters) as a function of the salts concentrations and cooking temperature. Both salts - alone or in combination - successfully reduced cooking loss. The best results were obtained for the combinations 0.25%STPP+1.20%NaCl and 0.25%STPP+0.70%NaCl, and temperatures between 60 and 65°C. Under these conditions, cooking loss was reduced close to 0%. pH was only dependent on STPP concentration, with a threshold concentration value of 0.25%. Temperature increment and NaCl addition produced a redness reduction. STPP incorporation recovered partially this parameter in comparison to non-added samples. Microscopy and SDS-PAGE results support the effect of the selected combinations of factors, suggesting that both salts together induced protein solubilization and gelation upon heating.

The effects of high hydrostatic pressure at subzero temperature on the quality of ready-to-eat cured beef carpaccio.

We compared the application of high hydrostatic pressure (HHP) on unfrozen carpaccio (HHP at 20 °C) and on previously-frozen carpaccio (HHP at -30 °C). HHP at 20 °C changed the color. The pressure increase from 400 to 650 MPa and the time increment from 1 to 5 min at 400 MPa increased L* and b*. a* decreased only with 650 MPa for 5 min at 20 °C. The prior freezing of the carpaccio and the HHP at -30 °C minimized the effect of the HHP on the color and did not change the shear force, but increased expressible moisture as compared to the untreated carpaccio. HHP at 20 °C was more effective in reducing the counts of microorganisms (aerobic total count at 30 °C, Enterobacteriaceae, psychrotrophs viable at 6.5 °C and lactic acid bacteria) than HHP at -30 º C. With HHP at 20 °C, we observed a significant effect of pressure and time on the reduction of the counts.

High pressure treatments combined with sodium lactate to inactivate Escherichia coli O157:H7 and spoilage microbiota in cured beef carpaccio.

High-pressure treatments (400 and 600 MPa) combined with the addition of sodium lactate (1 and 3%) were tested to reduce Escherichia coli O157:H7 (STEC O157) and spoilage microbiota contamination in a manufactured cured beef carpaccio in fresh or frozen conditions. Counts of spoilage microorganisms and STEC O157 were also examined during the curing step to prepare the carpaccio. STEC O157 counts remained almost unchanged through the curing process performed at 1 ± 1 °C for 12 days, with a small decrease in samples with 3% of sodium lactate. High-pressure treatments at 600 MPa for 5 min achieved an immediate reduction of up to 2 logarithmic units of STEC O157 in frozen carpaccio, and up to 1.19 log in fresh condition. Counts of spoilage bacteria diminished below detection limits in fresh or frozen carpaccio added with sodium lactate by the application of 400 and 600 MPa. Maximum injury on STEC O157 cells was observed at 600 MPa in carpaccio in fresh condition without added sodium lactate. Lethality of high-pressure treatments on STEC O157 was enhanced in frozen carpaccio, while the addition of sodium lactate at 3% reduced the lethality on STEC O157 in frozen samples, and the degree of injury in fresh carpaccio.

Effect of the addition of conventional additives and whey proteins concentrates on technological parameters, physicochemical properties, microstructure and sensory attributes of sous vide cooked beef muscles.

Beef muscles submitted to four enhancement treatments (1.88% whey protein concentrate (WPC)+1.25% sodium chloride (NaCl); 1.88% modified whey protein concentrate (MWPC)+1.25%NaCl; 0.25% sodium tripolyphosphate (STPP)+1.25%NaCl; 1.25%NaCl) and a control treatment (non-injected muscles) were sous vide cooked. Muscles with STPP+NaCl presented a significantly higher total yield (106.5%) in comparison to those with WPC/MWPC+NaCl (94.7% and 92.9%, respectively), NaCl alone (84.8%) or controls (72.1%). Muscles with STPP+NaCl presented significantly lower shear force values than control ones; also, WPC/MWPC+NaCl added muscles presented similar values than those from the other treatments. After cooking, muscles with STPP+NaCl or WPC/MWPC+NaCl depicted compacted and uniform microstructures. Muscles with STPP+NaCl showed a pink colour, meanwhile other treatment muscles presented colours between pinkish-grey and grey-brown. STPP+NaCl added samples presented the highest values of global tenderness and juiciness. The addition of STPP+NaCl had a better performance than WPC/MWPC+NaCl. However, the addition of WPC/MWPC+NaCl improved total yield in comparison to NaCl added or control ones.

Optimization of whey protein concentrate and sodium chloride concentrations and cooking temperature of sous vide cooked whole-muscle beef from Argentina

Response surface methodology was used to optimize the effect of cooking temperature (CT: 65-75°C) and the incorporation of whey protein concentrate (WPC: 0-3.5%) and sodium chloride (NaCl: 0-2.5%) on technological, physical and sensory characteristics of cooked whole-muscle beef. Post-injection weight loss diminished when NaCl concentration increased. Moreover, the increment of both additives produced a reduction of cooking loss. An opposite effect was observed with the increment of CT. As it was expected, a total yield improvement was achieved by increasing both ingredients and diminishing CT. Equivalent yields are achieved complementing both ingredients, meaning that if one ingredient concentration is reduced the other has to be increased. Shear force values were not affected by the studied factors. Instead, lightness was reduced by their increment. At 65°C, injected muscles had lower flavour and odour scores than control. At all CT analyzed, the incorporated brines improved juiciness and tenderness-related attributes. Present results recommend the use of a CT of 70°C and maxima WPC and NaCl concentrations of 2.6% and 1.9%, respectively.

Effect of whey protein concentrate and sodium chloride concentrations on the odour profile of sous vide cooked whole-muscle beef from Argentina.

Semitendinosus muscles added with whey protein concentrate (WPC) and sodium chloride (NaCl) were submitted to sous vide cooking. Four enhancement treatments and a control were tested: 0.875% WPC (w/w)+0.625% NaCl, 2.625% WPC+0.625% NaCl, 0.875% WPC+1.875% NaCl, 2.625% WPC+1.875% NaCl, and control (non-injected muscles). Odour analyses were carried out with an electronic nose (EN) system. EN data were evaluated applying Principal Component Analysis, Linear Discriminant Analysis and Partial Least Squares algorithm. EN was able to discriminate the odour profiles of cooked enhanced beef as a function of the amount of WPC added. No significant differences in odour profiles were observed regarding NaCl concentration. These results agreed with those obtained when odour profiles were analysed in WPC dispersions. The reported results support the applicability of EN methodology for analysing the impact of processing parameters on beef odour profiles.