Physicochemical properties, degradation kinetics, and antioxidant capacity of aqueous anthocyanin-based extracts from purple carrots compared to synthetic and natural food colorants.

As a means to evaluate the potential of carrot anthocyanins as food colorants and nutraceutical agents, we investigated the physicochemical stability and antioxidant capacity of purple carrot extracts under different pH (2.5-7.0) and temperature (4-40 °C) conditions, in comparison to a commercial synthetic (E131) and a natural grape-based (GRP) colorant. During incubation, the colorants were weekly-monitored for various color parameters, concentration of anthocyanins and phenolics, and antioxidant capacity. Carrot colorants were more stable than GRP; and their thermal stability was equal (at 4 °C) or higher than that of E131 (at 25-40 °C). Carrot anthocyanins had lower degradation rate at low pH and temperature, with acylated anthocyanins (AA) being significantly more stable than non-acylated anthocyanins (NAA). Anthocyanins acylated with feruloyl and coumaroyl glycosides were the most stable carrot pigments. The higher stability of carrot colorants is likely due to their richness in AA and -to a lesser extent- copigmentation with other phenolics.

Effect of high-pressure treatment on hard cheese proteolysis.

The application of high hydrostatic pressure (HHP) treatment has been proposed to reduce the ripening time of cheese via modifications in the enzymatic activities or the substrate reactivity. Investigations on the effect of HHP on cheese proteolysis have been undertaken with either encouraging results or little effect according to the treatment conditions and the type of cheese, but information concerning the effect of HHP on the ripening of hard cooked cheese is still lacking. In this report, we describe the effect of HHP treatment on Reggianito cheese proteolysis. For that purpose, 1-d-old miniature cheeses (5.5-cm diameter and 6-cm height) were treated at 100 or 400MPa and 20°C for 5 or 10min, and control cheeses in the trial were not pressurized. All cheeses were ripened at 12°C during 90d. The HHP did not affect gross composition of the cheeses, but microbial load changed, especially because the starter culture count was significantly lower at the beginning of the ripening of the cheeses treated at 400MPa than in controls and cheeses treated at 100MPa. Cheeses treated at 400MPa for 10min had significantly higher plasmin activity than did the others; the residual coagulant activity was not affected by HHP. Proteolysis assessment showed that most severe treatments (400MPa) also resulted in cheeses with increased breakdown of αS1- and ß-CN. In addition, nitrogen content in soluble fractions was significantly higher in cheeses treated at 400MPa, as well as soluble peptides and free AA production. Peptide profiles and individual and total content of free AA in 60-d-old treated cheese were as high as in fully ripened control cheeses (90d). Holding time had an effect only on pH-4.6-soluble nitrogen fraction and plasmin activity; cheese treated for 10min showed higher values than those treated for 5min, at both levels of pressure assayed. We concluded that HHP treatments at 400MPa applied 1d after cheesemaking increased the rate of proteolysis, leading to an acceleration of the ripening process in Reggianito Argentino cheese, whereas 100-MPa treatments did not lead to significant changes.

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.