Abstract
Thermal processing affects sensory attributes and causes a loss in nutritional values of fruit
juice products. This preliminary study was to clarify the effect of high pressure processing
(HPP) as a non-thermal treatment on quality changes in ‘Nanglae’ pineapple juice. Fresh
‘Nanglae’ pineapple juice (100% juice) was prepared and treated under pressure at 400
and 600 MPa for 5 min. The condition of 80°C for 10 min was selected as conventional heat
treatment (CHT). Changes in physical and chemical quality as well as microbiological quality
in terms of aerobic plate count (APC) and yeast and mold (YM) were determined after
treatment (0 day) and during storage at 5+1°C for 2, 4 and 6 days. The results were compared
with the non-treated juice (control). It was found that after treatment, both HPP and CHT
significantly reduced (P<0.05) APC and YM in juice samples from 6.71+0.14 and 5.89+0.13
log CFU/mL to less than 1.48 and 1.18 log CFU/mL, respectively. APC and YM were still
detected at the same amount until 6 days of storage. In addition, CHT significantly degraded
(P<0.05) ascorbic acid content in juice while HPP showed lower effect to ascorbic acid
degradation. Lightness and yellowness were not significantly different (P>0.05) between
HPP treatment and control. In contrast, yellowness of sample with CHT significantly
decreased (P<0.05) from 3.47+0.40 to 2.90+0.44 at day 2 of storage. Moreover, TSS in HPP
treated juice did not significantly change (P>0.05) compared to non-treated one while in
CHT sample the TSS significantly increased (P<0.05) from 17.10+0.00 to 18.00+0.10 °Brix.
In addition, pH and TA of juice were not significantly different (P>0.05) between HPP and
CHT, while non-treated sample had higher pH and lower TA than HPP and CHT after 6 days
of storage. According to the results, it may conclude that HPP can preserve quality and
maintain freshness of ‘Nanglae’ pineapple juice and is an alternative way for the juice
production. However, further study should be carried on the optimization of HPP condition
and its effect on other characteristics such as bioactive compound and nutrition value should
be further studied.
