Comparative analysis of thermal-assisted high pressure and thermally processed mango pulp: Influence of processing, packaging, and storage

High-Pressure Processing Effects on Microbiological Stability, Physicochemical Properties, and Volatile Profile of a Fruit Salad

Nowadays, consumers are more aware of the effects of their diet on their health, and thus demand natural or minimally processed food products. Therefore, research has focused on processes that assure safe products without jeopardizing their nutritional properties. In this context, this work aimed to evaluate the effects of high-pressure processing (550 MPa/3 min/15 °C, HPP) on a fruit salad (composed of melon juice and pieces of Golden apple and Rocha pear) throughout 35 days of storage at 4 °C. For the physicochemical properties analysed (browning degree, polyphenol oxidase activity, antioxidant activity (ABTS assay), and volatile profile), a freshly made fruit salad was used, while for the microbiological tests (total aerobic mesophiles, and yeast and moulds) spoiled melon juice was added to the fruit salad to increase the microbial load and mimic a challenge test with a high initial microbial load. It was determined that processed samples were more microbiologically stable than raw samples, as HPP enabled a reduction of almost 4-log units of both total aerobic mesophiles and yeasts and moulds, as well as an almost 1.5-fold increase in titratable acidity of the unprocessed samples compared to HPP samples. Regarding browning degree, a significant increase (p < 0.05) was observed in processed versus unprocessed samples (roughly/maximum 68%), while the addition of ascorbic acid decreased the browning of the samples by 29%. For antioxidant activity, there were no significant differences between raw and processed samples during the 35 days of storage. An increase in the activity of polyphenol oxidase immediately after processing (about 150%) was confirmed, which was generally similar or higher during storage compared with the raw samples. Regarding the volatile profile of the product, it was seen that the compounds associated with melon represented the biggest relative percentage and processed samples revealed a decrease in the relative quantity of these compounds compared to unprocessed. Broadly speaking, HPP was shown to be efficient in maintaining the stability and overall quality of the product while assuring microbial safety (by inactivating purposely inoculated microorganisms), which allows for longer shelf life (7 versus 28 days for unprocessed and processed fruit salad, respectively).

Effect of high hydrostatic pressures on microorganisms, total phenolic content and enzyme activity of mamey (Pouteria sapota) nectar

Mamey (Pouteria sapota) is a Mexican native fruit of sweet flavor and high content of antioxidants. Some of these antioxidants are  sensitive to high temperatures. Nonthermal technologies such as high hydrostatic pressures (HHP) could be an adequate alternative to traditional thermal pasteurization. Mamey nectars were treated under different HHP conditions and the effects on native microorganisms (mesophilic bacteria, molds and yeast), pectinmethylesterase (PME) and polyphenoloxidase (PPO) activities as well as on total phenolic content (TPC), were evaluated. Most HHP treatments conditions were equally effective to inactive native microorganisms. The application of HHP improved the extraction of TPC showing increments of 24% (400 MPa/2 min) to 64% (500 MPa/2 min) compared with the control samples. At 500 MPa/5 and 10 min maximum inactivation levels of PPO of about 40% were obtained, while PME activity showed decrements up to 70% at 400 MPa/5 min. HHP showed to be a potential technology to preserve mamey nectar, but more conditions should be tested to reach higher enzyme inactivation.