Effect Of Hhp On

LWT - Food Science and Technology 45 (2012) 50e57

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LWT - Food Science and Technology
journal homepage: www.elsevier.com/locate/lwt

Effect of high hydrostatic pressure and thermal processing on the nutritional
quality and enzyme activity of fruit smoothies
Derek F. Keenan a, *, Christian Rößle a, Ronan Gormley b, Francis Butler c, Nigel P.Brunton a
a

Teagasc, Food Research Centre, Ashtown, Dublin 15, Ireland
UCD Institute of Food and Health, University College Dublin, Dublin 4, Ireland
c
Biosystems Engineering, UCD School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Dublin 4, Ireland
b

article info

abstract

Article history:
Received 7 January 2011
Received in revised form
10 June2011
Accepted 5 July 2011

Fruit smoothie samples were thermally (P70 > 10 min) or high hydrostatic pressure (HHP) processed
(450 MPa/20  C/5 min or 600 MPa/20  C/10 min) and the total antioxidant capacity (TAC), levels of
antioxidant groups [total phenols (TP), anthocyanins and ascorbic acid], instrumental colour, polyphenol
oxidase (PPO) enzyme activity and dissolved oxygen were examinedover a storage period of 10 h at 4  C.
Thermal processing of smoothies reduced (p < 0.001) TAC and TP values, ascorbic acid and L and a colour
attributes (lightness and redness respectively) compared to fresh and HHP-450 processed samples.
Conversely, it did result in complete inactivation of PPO enzyme, with no activity detected. Of the HHP
treatments, HHP-450 samples had higher (p < 0.001)levels of total antioxidant, phenols and anthocyanin content than HHP-600 samples. However, the latter was more effective in reducing (p < 0.001) the
endogenous enzyme activity of the smoothies. .Ascorbic acid content degraded over the storage for all
smoothies. HHP-600 samples had high initial values, which declined slowly over storage, while thermal
samples had the lowest initial value (0.5h) that fell below detectable limits by 10 h. Despite these data,
less pronounced effects were observed for storage. No significant effects were observed for total
anthocyanin and phenolic contents as well as L and colour change (DE) variables. Overall, HHP processing
of smoothies at moderate temperatures may be a suitable alternative to traditional thermal processing.
Ó 2011 Elsevier Ltd. Allrights reserved.

Keywords:
Fruit smoothies
High hydrostatic pressure processing
PPO
Dissolved oxygen
Antioxidants
Colour

1. Introduction
Fruit smoothies are a popular and convenient way of consuming
fruit. Smoothies are blended beverages, containing fruit, fruit juice,
ice, yoghurt and milk. Smoothie consumption may significantly
contribute to daily antioxidant intakes and the UKmarket estimated
to be worth £282 (V354) million in 2008 (Safefood, 2009). Antioxidants are bioactive molecules, naturally occurring in many fruits
that are capable of inhibiting the oxidation of other compounds.
They have been implicated in protective biological effects against
degenerative diseases (Serafini, 2006). As smoothies contain
a mixture of intracellular contents from the differentfruit components, the mixture may exhibit very different biochemical behaviours to those of their individual components. While most authors
have reported that high hydrostatic pressure (HPP) helps retain
antioxidant activity of individual fruits, we recently reported that
retention of ascorbic acid, antioxidant and polyphenols contents in

* Corresponding author. Tel.: þ353 18059505; fax: þ35318059550.
E-mail address: derek.keenan@teagasc.ie (D.F. Keenan).
0023-6438/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.lwt.2011.07.006

high hydrostatic pressure (HHP) processed smoothies was no better
than for thermally processed samples (Keenan et al., 2010). HHP has
been extensively researched in recent years (Rastogi, Raghavarao,
Balasubramaniam,...