| Resum: |
In the last years the almond beverage has experimented an increase on the consume, therefore, the commercialization area has been expanded, almost all around the world. This beverage further than be an alternative to milk for people with lactose intolerance, it is claimed because of its functional qualities that can contribute to reduce or prevent diseases, which are besetting society; this mainly due thanks to the content of the fatty acids, monounsatured and polyunsatured, and the antioxidants just like E vitamin, phenolic compounds and polyamines. This thesis project was focused on the application of an emerging technology, Ultra High Pressure Homogenization (UHPH), in the production of almond beverage. This non-thermal technology consists of a high pressure machine capable of applying pressures of up to 400 MPa using a special homogenizing system designed to produce a conserving effect, improving the colloidal and microbial stability while maintaining good nutritional and sensory qualities. Considering this hypothesis, UHPH could be an alternative technology to those commonly applied in the food industries. For that, a comparative study of UHPH with thermal treatments (pasteurization) was carried out in this work. This investigation has been conducted through four successive studies. The first study was aimed to optimize processing conditions of the elaboration of a base product of almond beverage for being used in subsequent studies. Moreover, influence of the addition of lecithin as an emulsifier in the stability of pasteurized beverage was studied and the most relevant analytical parameters related to the overall quality of the food were analyzed. In the second study, the influence of the UHPH treatments (200 and 300 MPa, 55, 65 and 75 ºC) were evaluated in the almond beverage characteristics, and they were compared with samples treated with convectional pasteurization, UHT and with based crude product. UHPH at 200 MPa 55 and 75 ºC of inlet temperature were revealed as alternative treatments to pasteurization, and 300 MPa 65 y 75ºC as alternative to UHT. The UHPH condition of 300 MPa and 65 and 75ºC inlet temperature was able to produce commercial sterile almond beverages. The third study was the identification of potentially contaminating spoilage microorganisms in treated almond beverage, to evaluate subsequently the lethality produced by UHPH treatments 300 MPa, 55, 65, 75 and 85 °C, in microorganisms with higher resistance to UHPH and most frequently isolated. These microorganisms were Bacillus cereus, Bacillus subtilis and Lysinibacillus spp. Lethality was complete when treatment was used 300 MPa and 75 and 85°C inlet temperatures. The second part consisted in the shelf-life evaluation of soymilk treated by UHPH using the selected optimal conditions determined in the previous step Finally, with the selected conditions of UHPH treatments (200 MPa, 55 and 75 ºC), was studied the microbiological, physical and chemical quality of the almond beverage during cold storage time and it was compared with pasteurized almond beverage. Monitoring was conducted every 7 days for 3 weeks. During cold storage, almond beverage samples treated by UHPH at both inlet temperatures had generally better characteristics than pasteurized ones. |
visitant ::
identificació
dir. (Universitat Autònoma de Barcelona. Departament de Ciència Animal i dels Aliments)
