Microwave Pasteurised Pear Snack: Quality and Microbiological Stability

William Bartlett (Pyrus communis) pears were diced, packaged and subjected to a short continuous microwave treatment (4.7 min) which increased the temperature from 19.92 ± 1.36 to 101.11 ± 2.50 °C. Retorted samples were processed at 95.40 °C for 18.0 min for comparison. Recorded temperature data were used to calculate C, D and F values. Brix, pH, colour, texture, microbial counts, microstructure and volatile profiles of both treated samples were analysed immediately after process and after 1, 2, 4 and 6 weeks of storage at 4 °C. The C, D and F values of microwaved pears were significantly (p < 0.05) lower compared to those of retorted samples. Both methods of processing resulted in products with standard plate count of < 10 cfu/g during 6 weeks of storage at 4 °C. Microwave processing offered a final product with a total colour difference in the same range as the retorted samples. Polyphenol oxidase enzyme was inactivated below the detection level by both microwave processing and retorting. Microwaved samples also maintained cell wall integrity, although the intercellular intactness was slightly weakened and prevented the final product from developing water-soaked appearance. During storage, volatile profiles of microwaved samples showed significant (p < 0.05) differences, whereas the retort samples showed minimal changes. In comparison to conventional retorting, a short microwave treatment can result in a superior quality end-product with a comparable microbiological quality and a minimum shelf life of 6 weeks at 4 °C.