Fibrous Cellular Structures are Found in a Commercial Fruit Smoothie and Remain Intact during Simulated Digestion

Jin Chu,Caroline Orfila,Bridget Dooshima Igbetar

doi:10.4172/2155-9600.1000576

Abstract

The intactness of cell wall structures in foods has important repercussions for nutrient digestion and availability. In this study, we show the presence of intact cell wall structures in a commercial fruit smoothie (blend of banana, mango, orange and apple) and fruit puree (banana, mango), but not in fruit juices (apple or orange). Small clusters of cells were observed in fresh crushed fruit (banana, mango, and apple), the size of the cluster dependent on the type of fruit. When the smoothie was subjected to simulated gastro-intestinal digestion, cell wall structures were found abundantly even after 16 hrs of agitated incubation with digestive enzymes (protease, amylase and amyloglucosidase). Total dietary fibre (TDF) content of the smoothie was measured using the AOAC (991.43) and integrated fibre (IF) analysis methods. TDF-AOAC value was significantly lower (1.61%) than the TDF-IF (2.22%), but the ratio of insoluble to soluble dietary fibre (IDF: SDF) was consistently 1:3. Disruption of the cell wall structures in the smoothie by high shear homogenisation led to a 68% reduction in viscosity, 30% reduction in TDF content and a 10% increase in SDF. These experiments suggest that cell wall structures similar to those observed in crushed fruit are preserved during commercial smoothie manufacture and are retained during digestion. Their presence may have implications for fibre quantification and fibre functionality in the gut. We discuss the need to consider fibre structure, as well as content, when evaluating the nutritional properties of fruit and their products.

Highlights

Consumption of fruit and fruit products has been associated with a reduced risk of overall mortality and some non-communicable diseases, leading to intake recommendations of least 3 to 4 portions of fruit a day for the general population [1,2]
The aim of this study was to observe whether cell wall structures are present in a commercial fruit smoothie as well as two purées and two juices, and to compare those structure to those found in crushed fruit
Cell walls are natural structures that occur in plant foods that offer a natural barrier to molecular exchange and enzymatic digestion of cellular contents [18]

Summary

Introduction

Consumption of fruit and fruit products has been associated with a reduced risk of overall mortality and some non-communicable diseases, leading to intake recommendations of least 3 to 4 portions of fruit a day for the general population [1,2]. Intact cellular structures and cell clusters were observed following chewing of mango and banana fruits [8]. Fermentation of carrot cell clusters showed that particles measuring approximately 150-300 μm were more rapidly fermented than smaller clusters or single cells [9] These studies suggest that the intactness of cellular structures may affect fruit and vegetable functionality in the gut. While consumption of whole fruits would ensure ingestion of cellular structures, food consumption data indicates that around two thirds of adults do not consume enough fruit (Public Health England, 2016) Fruit beverages such as smoothies have been suggested as convenient and cost effective foods that provide similar nutrient and functionality to whole fruit [13]. The effect of food processing on cellular structures needs further investigation

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