Effects of high hydrostatic pressure on physico-chemical and structural properties of two pumpkin species

The effects of high pressure treatments (200, 400, 600MPa for 5 min) and a thermal treatment (85°C for 5 min) were evaluated on cubes of two pumpkin species (Cucurbita maxima L. var. Delica and Cucurbita moschata Duchesne var. Butternut) up to 2 months of refrigerated storage. Increasing the pressure, small parenchyma cells from the pumpkin tissue exhibited collapses and separations, especially for Butternut. This species showed a lower hardness than Delica at time 0. For both species, 400MPa and thermal treatment were the most effective in the inactivation of pectinmethylesterase, which reactivated after 2 months, especially for Butternut. Colorimetric parameters decreased after all treatments. Antioxidant activity resulted affected by pressure, showing a significant increase during storage especially for the samples treated at 200MPa after 2 months, comparable to the thermal treated ones. Among the tested treatments, 400MPa may be considered as the best option for the quality retention during storage

High pressure and thermal processing on the quality of zucchini slices

AbstractIn response to the market demand for low processed vegetables, high-pressure treatments (400,600 MPa; 1,5 min) were applied on zucchini slices and compared to a traditional blanching treatment. Histological observations, texture and color analysis, pectinmethylesterase (PME) and antioxidant (DPPH) activities were measured and compared to untreated samples. The histological observations revealed that the longer high-pressure treatments (5 min) led to more extended cell lysis and dehydration than the shorter ones (1 min) and blanching. High-pressure treatments resulted less effective than blanching on PME inactivation, with the best results obtained at 400 MPa for 1 min. Comparable texture parameters were observed for high-pressured and blanched samples. The negative correlation found between PME activity and the texture parameter 'distance of the first peak force' revealed an effect of PME on the texture recovery after treatments. High pressure led to a general browning of zucchini parenchyma and to DPPH drop. The correlations found between DPPH and color suggest the common nature of the phenomena. The influence of pressure and time on the studied parameters was revealed by two-way ANOVA. Principal component analysis clustered together the four high-pressure-treated samples, being clearly divided by blanched and untreated ones

Shelf life of donkey milk subjected to different treatment and storage conditions

The aim of this study was to investigate the effects of different treatment conditions on microbiological indicators of donkey milk hygiene and their evolution during shelf life at 4 and 12\ub0C from 3 to 30 d, simulating a farm-scale pasteurization and packing system. Four treatment conditions were tested: no treatment (raw milk), pasteurization (65\ub0C 7 30 min), high-pressure processing (HPP), and pasteurization plus HPP. The microbiological quality of the raw donkey milk investigated was not optimal; our results highlight the importance of raw milk management with the need for animal hygiene management and good dairy farming practices on donkey farms to improve handling procedures. The raw milk treated with HPP alone showed visible alterations with flocks, making the milk unfit for sale. The microbiological risk posed by consumption of raw donkey milk was significantly reduced by heat treatment but farm-scale packing systems cannot guarantee an extended shelf life. In contrast, the pasteurization plus HPP treatment was the most effective method to maintain microbiological milk quality. Microflora growth had little effect on pH in donkey milk: pH values were significantly different only between raw milk and pasteurized and pasteurized plus HPP milk stored at 12\ub0C for 3 d. Alkaline phosphatase activity and furosine could be used as indicators of proper pasteurization and thermal processing in donkey milk. Moreover, the presence and growth of Bacillus cereus in the case of thermal abuse hamper the wide-scale marketing of donkey milk due to the potential consequences for sensitive consumers and therefore further tests with time/temperature/high-pressure protocols associated with B. cereus are needed. Finally, our study shows that an HPP treatment of pasteurized milk after packing extends the shelf life of donkey milk and assures its microbial criteria up to 30 d if properly stored at 4\ub0C until opening; therefore, combined heat treatment and storage strategies are recommended to enhance the shelf life of donkey milk

Improved Physicochemical and Structural Properties of Blueberries by High Hydrostatic Pressure Processing

The use of high pressure on fruits and vegetables is today widely studied as an alternative to the traditional thermal preservation techniques, with the aim of better preserving nutritional and organoleptic properties. The use of high hydrostatic pressures (400–600 MPa; 1–5 min; room temperature) was tested on the physicochemical and structural properties of blueberries, in comparison to raw and blanched samples. High hydrostatic pressures led to higher tissue damages than blanching, related to the intensity of the treatment. The cellular damages resulted in leakage of intracellular components, such as bioactive molecules and enzymes. As a consequence, among the high pressure treatments, the resulting antioxidant activity was higher for samples treated for longer times (5 min). Pectinmethyl esterase (PME), deactivated by blanching, but strongly barotolerant, was more active in blueberries treated with the more intense high pressure conditions. Blueberry texture was better retained after high pressure than blanching, probably because of the PME effect. Blueberry color shifted towards purple tones after all of the treatments, which was more affected by blanching. Principal component analysis revealed the mild impact of high pressure treatments on the organoleptic properties of blueberries