Fruit and vegetables are important components of a healthy balanced diet, especially as sources of antioxidants and polyphenols, yet individuals fail to comply with the recommended five portions daily(Reference Henderson, Gregory and Irving1). The demand for ‘smoothies’ has grown from none to >£20×106 over the last 5 years(2). Smoothies are potentially a convenient and palatable way of assisting compliance with the recommended ‘5-a-day’ guideline for fruit and vegetable intake. The aim of the present study was to determine whether nutritional components present in fresh fruit are retained during the production of a fruit-based drink and to elucidate whether a home-made fruit-based drink would be a satisfactory substitute for the commercial smoothie drink.
Pear, apple and kiwifruit (Actinidia delicious), along with the corresponding smoothie (v/v; 45% pear, 29.6% apple, 25% kiwifruit) were collected from a manufacturer. The fruits were analysed individually and these values used to calculate the expected nutritional composition of the final smoothie. Additionally, the fruits were also used to make a home-made fruit-based drink following the smoothie manufacturer's recipe, without the addition of ascorbate. The nutritional composition of the home-made smoothie was then compared with the commercial equivalent. The following nutritional components were determined by established methods: vitamin C using the Boehringer Mannheim assay(3); antioxidant capacity by the ferric-reducing antioxidant power (FRAP) assay(Reference Benzie and Strain4) and the oxygen radical absorbance capacity (ORAC) assay(Reference Huang, Ou and Hampsch-Woodill5); polyphenolic content by the Folin-Ciocalteau(Reference Forrest and Bendall6)method. β-Carotene was measured by extraction into hexane/acetone, absorbance measured and carotene quantified using ε450 nm=138 730 M−1·cm−1. Total sugars were assessed using the d-glucose–fructose–sucrose Boehringer Mannheim assay (3). All assays were carried out in triplicate and statistical analysis was by SPSS (SPSS Inc., Chicago, IL, USA) using an independent t test.
The nutritional composition of pear, apple and kiwifruit extracts and home-made and commercial smoothies are shown in the Table (n 3).
TE, Trolox equivalent; GAE, gallic acid equivalent. Mean values were significantly different from those for home-made:
*** P<0.001. Mean values were significantly different from those for home-made:
††† P<0.001.
Sugars and β-carotene levels for both smoothies were as predicted. The home-made drink had the expected vitamin C content, whilst that of the commercial drink was much higher, reflecting the addition of 4 g ascorbic acid/l. The phenolic content of the commercial smoothie was much higher than expected (P<0.001), which may reflect a greater efficiency of homogenisation in the manufacturing process. The commercial smoothie also contained the highest antioxidant capacity. Thus, smoothies, both home-made and commercial, appear to be beneficial in assisting compliance with the ‘5-a-day’ recommendation.
