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SHELF-LIFE OF MILDLY/MINIMALLY PROCESSED APPLE DESSERTS
D. F. Keenan1, T. R. Gormley1, F. Butler2
1Ashtown Food Research Centre (Teagasc), Ashtown, Dublin 15 and 2Biosystems Engineering, School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Dublin 2
Functional food products are a growing feature in retail outlets, due to increasingly health conscious consumers. This study involved testing processed apple (Bramley’s Seedling) puree desserts containing healthy functional ingredients added at levels of 8 (BeneoTM HSI; ORAFTI, Belgium), 5 (apple pomace; Polish Shampion) and 5% (w/w) [alcohol-insoluble-solids (AIS)]. BeneoTM HSI is a prebiotic, while apple pomace and AIS are rich in dietary fibre and help lower cholesterol. Samples were vacuum packed, sous vide processed (Barriquand Steriflow retort; P90>10 min), cooled, sieved (1.4 mm mesh), held at 2-4°C, and tested (days 1, 15 and 30) for microbiological stability (TVC), rheological properties (Brookfield rheometer and TAXT2i texture analyser), colour (Hunter Lab), pH, titratable acidity, and soluble solids. pH values fell (P<0.001) during storage (3.19, 3.09 and 3.05 on days 1, 15 and 30 respectively). L/b ratios were influenced (P<0.001) by inclusions (lowered L/b ratios) and storage times with the day 30 AIS (3.20) and control (3.12) purees giving the highest L/b ratios. Pomace and AIS purees had higher (P<0.001) consistency values than control or Beneo purees. Shear thinning was observed in all purees. Microbiological stability was maintained in all purees (TVCs <10cfu/g after 30 days).
Apples are inherently ‘functional’ or healthy, i.e. they are a good source of pectin (dietary fibre that also reduces cholesterol), monosaccharides, minerals, vitamins, and various bioactive compounds, such as vitamin C along with phenolic compounds, which are known to act as natural antioxidants1. A food can be considered ‘functional’ if demonstrated to have physiological benefits and/or reduce the risk of chronic disease beyond that of basic nutrition2. A functional food can be (a) a conventional natural food consumed as part of a normal diet, or (b) a food in which a positive component has been added, or from which a deleterious compound has been modified or removed3. This study was carried out to exploit opportunities that focus on the importance of health in the diet by developing ready- desserts with added functional ingredients. It embraced the addition of three types of functional ingredients, namely, oligofructose (Beneo HSI™), apple pomace or alcohol-insoluble-solids (AIS). Oligofructose acts as a dietary fibre and prebiotic and is a non-digestible food ingredient that beneficially affects the host by selectively stimulating growth and/or activity of one or a limited number of colonic bacteria, thus, improving host health4. AIS remain relatively unused as a food inclusion but have potential functional properties such as the ability to lower serum cholesterol in humans and help modulate late-maturity-onset diabetes. These inclusions, combined with the inherent functionality of apple5,6 and mild sous vide processing7 should maximise retention of bioactive compounds and produce a value-added, healthy, ready-dessert.
MATERIALS AND METHODS
Purees were prepared from stewed (95°C; 15 min) Bramley’s Seedling apple slices (+33% H2O) and inclusions were Beneo HSI™ (8), apple pomace (5), or (AIS 5%w/w). Samples were cooled, sieved (1.4 mm), vacuum packed (200g) and sous vide processed (Barriquand Steriflow retort: P90>10 min) and stored (2-4°C) for 30 days. Sous vide samples were tested on days 1, 15 and 30. Measurements included soluble solids, pH, colour (HunterLab), Brookfield viscometer TAXT2i texture analyser and total viable counts (TVC).
RESULTS AND DISCUSSION
Moisture values were lowest (P<0.001) in Beneo HSI™ purees (i.e. highest w/w addition of the inclusions) and were also lower (P<0.001) on day 30 compared to days 1 and 15 compared to controls. pH values fell (P<0.001) during storage (3.19, 3.09 and 3.05 on days 1, 15 and 30 respectively). Soluble solids were higher (P<0.001) in Beneo HSI™ purees compared to pomace, AIS and control purees. As Beneo HSI™ is a fructo-oligosaccharide and is used as a sugar replacer, this observation was expected. L/b ratios were influenced (P<0.001) by inclusions (lower values) and storage times with the day 30 AIS (3.20) and control (3.12) purees giving the highest L/b ratios. Pomace and AIS purees had higher (P<0.001) consistency values than control or Beneo purees. Shear thinning was observed in all purees. Microbiological stability was maintained in all purees (TVCs <10cfu/g after 30 days).
Different nutraceuticals and minimal processing were used to produce a range of healthy apple ready-desserts with a shelf-life of approximately 30 days. Beneo HSI™ inclusions increased puree sweetness and dry matter content. AIS and pomace inclusions increased puree viscosity. Pomace inclusions decreased colour values (L/b ratios) which was undesirable in the final products. pH values decreased during storage due to loss of buffering capacity. Microbiological stability was maintained in all purees throughout the shelf-life period.
This research was part-funded (ISAFRUIT project) by the European Commission [Thematic Priority 5:- Food Quality and Safety of the 6th Framework Programme of RTD (Contract No. FP6-FOOD 016279)].
1Gormley, T. R., Keenan, D. F., and Roessle, C. (2008). Horticulture Week. 29/05/2008, 31-33.
2Food Safety Authority of Ireland. (2001).Available at:
3Roberfroid, M. B. (2000). In: Functional foods, Concept to product. Gibson, G, R, & Williams, C, M., eds. Woodhead Publishing Limited, Cambridge, England. 9-27.
4Coussement, P. A. A. (1999). J. Nutrition. 129: 1412S-1417S.
5Asenjo, F., and Figuerola, F. (2004). Food Chem. 91(3): 395-401.
6Mayne, P. D., McGill, A. R., Gormley, T. R., Tomkin, G. H., Jullan, T. R., and O’Moore, R. R. (1982). Irish J. Medical Sci. 151, 36-41.
7Tansey, F. S., and Gormley, T.R. (2002). Farm & Food Research. 12(1): 18-22.
Influence of dietary vitamin E (-tocopherol) on expression of genes involved in vitamin E and lipid metabolism in liver.
A Lejeune1, S. McGettrick1, A.P. Moloney2, T. Sweeney1, and F.J. Monahan1.
1UCD School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Dublin 4; 2Teagasc, Grange Beef Research Centre, Dunsany, Co. Meath
Vitamin E is an antioxidant which plays an essential role in animal health and in the postmortem stability of meat. It may also regulate expression of genes coding for proteins involved in its own metabolism. The objective of this study was to measure gene expression of the alpha-tocopherol transfer protein (aTTP), cytochrome P450 3A4 (CYP3A4) and multidrug resistance protein-1 (MDR1) involved in liver metabolism of vitamin E in cattle fed a concentrate-based diet with or without vitamin E supplementation. Previous work in our laboratory suggested putative regulation by vitamin E of the stearoyl-CoA desaturase (SCD) gene, a key enzyme in the synthesis of conjugated linoleic acid and mono-unsaturated fatty acids. As these lipids are beneficial for human health, the expression of the SCD gene was also characterized using an in vitro human HepG2 hepatocyte cell line model. Results showed that low vitamin E supplementation tended to increase the aTTP gene expression (P=0.07) but expression of the other genes was not modified by vitamin E supplementation. With regard to the SCD1 and SCD5 genes and the HepG2 cell line, there was no evidence to suggest regulation by vitamin E.
Dietary vitamin E (-tocopherol) is an important antioxidant in animal health, preventing oxidation of biomolecules such as DNA, lipids and proteins. Vitamin E also has non-antioxidant functions in transcriptional regulation. It could regulate expression of genes involved in its own metabolism in liver (see figure 1). Previous work carried out by our group also suggests an involvement of vitamin E in stearoyl-CoA desaturase (SCD) gene expression, a key enzyme in the synthesis and regulation of conjugated linoleic acid and unsaturated fatty acids.
Figure 1. Vitamin E transport and metabolism in liver. TTP (Tocopherol Transfer Protein), CYP3A4 (Cytochrome P450 3A4), MDR1 (MultiDrug Resistance protein-1). This figure depicts previously suggested gene regulation by vitamin E (•) at the mRNA (+) or protein level (++).
MATERIALS AND METHODS
Four groups of 8 continental heifers received diets with 0, 500, 1000, 3000 I.U. vitamin E supplementation/day for 160 days. RNA was extracted from liver and TTP, CYP3A4, MDR1 and SCD gene expression was measured using quantitative PCR. The effect of -tocopherol (50 M, 500 M) was also tested on a human hepatocyte cell line (HepG2) over 24h. Arachidonic acid (200 M) was used as positive control of SCD1 and SCD5 gene regulation as it is known to inhibit SCD gene expression1. RNA was extracted and gene expression measured using quantitative PCR.
Results and Discussion
Figure 2. Effect of vitamin E supplementation on liver gene expression.
Figure 3. Regulation of human SCD1 and SCD5 in HepG2 cell by -tocopherol.
Low vitamin E supplementation (500 I.U./day) tended to increase TTP gene expression (P < 0.1) and decrease MDR1 gene expression (P < 0.1) in comparison with the control (unsupplemented) group but no effect on these genes was observed with higher vitamin E supplementation (Figure 2). The high level of vitamin E (3000 I.U./day) tended to decrease SCD gene expression (P < 0.1). Expression of CYP3A4 was not affected by vitamin E supplementation. As expected, figure 3 showed a trend toward a decrease of SCD gene expression upon treatment with arachidonic acid with SCD1 gene being more down-regulated than SCD5. No clear evidence of a down-regulation in SCD1 or SCD5 gene in response to -tocopherol at either 50 M or 500 M was observed.
The study did not reveal a strong association between vitamin E supplementation in cattle and the expression of genes involved in its own metabolism in liver. High levels of vitamin E supplementation could potentially decrease the expression of SCD, a key-enzyme in the synthesis and regulation of conjugated linoleic acid and unsaturated fatty acids. As these lipids are highly beneficial for human health, further work should be carried out to assess their level in vitamin E supplemented cattle. The preliminary study on a human hepatocyte cell line did not reveal clear evidence of modification of SCD1 and SCD5 genes following incubation with varying levels of -tocopherol.
This research was funded under the Food Institutional Research Measure of the Department of Agriculture, Fisheries and Food.
1Tebbey, P.W. and Buttke, T.M. (1992). Biochim. Biophys. Acta. 1171: 27-34.
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