School of Applied Sciences, RMIT University, Melbourne VIC 3000, Australia
Changes in breads, cakes, doughnuts and other similar foods that are not attributed to microbial spoilage are referred to as staling, a process that leads to a decrease in consumer acceptance of a product (Eliasson and Larsson 1993).
The primary purpose of microencapsulation is to produce particles that control mass transport behaviour in some manner. The coating of a microcapsule is designed to prevent diffusion of material either from within or from the exterior into a microcapsule (Reineccius 2001).
The aim of the current study has been to investigate procedures for preparation of microcapsules incorporating various food acids and then to assess and compare the impact of these acids on the characteristics of both Arabic and loaf breads.
BW= beeswax, CW= carnauba wax, AA= ascorbic acid, TA= tartaric acid, USA= United states of America
Wheat flour, instant dry yeast, cooking salt, white sugar, beeswax (BDH Laboratory supplies, England), carnauba wax,tartaric acid (McKenzie Pty Ltd, Australia), ascorbic acid (BDH Laboratory supplies, England).
Bread making formula
The preparation of Arabic bread method used was as described by Quail et al. (1990). Flour 300g, yeast 3g, salt 4.5g, sugar 4.5g were mixed with and without acids. Water (160g) was mixed with the dry ingredients for 6 min. After mixing, the dough was transferred to covered plastic bowl and placed in a proof cabinet, and allowed 60 min fermentation at 30 °C.
After fermentation, the dough was scaled off into 60g sections. The pieces were rounded by hand into balls and covered with plastic. The dough rested for 10 min then dough pieces were lightly dusted with flour and flattened by gentle hand pressure and passed through a roll sheeter. The sheeted dough was transferred to stainless steel board and covered with a piece of cloth. Then the dough was transferred for a final proofing of 30 min at 30 °C. The dough was baked at 400 °C for 90 sec., in a preheated aluminium tray. After baking, the bread was cooled for 10 min and stored in clear polyethylene bags. After 2 hr, the loaves were assessed.
The loaf bread formulation used was 450g flour, 9g sugar, 8g instant yeast, 7.5g salt, 9g vegetable oil and 283.5mL water and was processed in an automatic breadmaker (Panasonic SD-253, Matsushita Electric Ind. Co. Ltd.), using a rapid cycle of 1 h and 55 min. Twelve test loaves were baked from each treatment (4 loaves with acid, 4 loaves with encapsulated acid and 4 control loaves). Baked loaves were allowed to cool for 1 h at 25°C before storage, and stored in sealed polyethylene bags at room temperature for periods of up to 5 days.
Acids were emulsified into a molten wax phase. This molten mixture was then added to the heated external water phase with vigorous stirring. The emulsion was agitated for 20s and cooled rapidly using an ice bath to form microparticles. These were collected by filtration, vacuum dried, and stored in sealed vials at room temperature.
Scoring of Arabic bread
The scoring system method used was as described by (Qarooni et al.1987, Quail et al.1990). Four loaves were scored two hours after baking (first day), and four loaves 24 hours after baking (second day).
Bread firmness measurements were made with a Texture Analyser (TA-XT2, Stable Micro Systems, England). Slices (25mm thickness) were compressed to 40% (10 mm) using a 35-mm diameter aluminium plunger with a 5 kg load cell. The rate of compression was 1.7 mm/s. The compression curves of the bread crumb (distance vs. force) were plotted, and the force readings (in Newtons) at 25% compression were taken as a measure of firmness in accordance with AACC method 74-09 (AACC, 2000). Two slices were analyzed from each loaf.
Bread loaf volume was estimated from the sum of two circumference values of the loaf. The second measurement was taken perpendicular to the first. All measurements were taken after one hour of cooling at room temperature and the sum expressed in centimeters
The effect of adding 10 ppm AA and 0.1% TA into formulations of Arabic bread is shown in Figure 1. The external characteristics were generally improved in comparison to the control. The least enhancement was achieved using BW to encapsulate AA. In the Arabic bread samples with added 10 ppm AA encapsulated using CW there was a significant increase in the external scores compared with both the control and the sample with unencapsulated AA. Internal features for the Arabic bread were enhanced by AA at 10 ppm level in comparison with the control. Similarly when AA encapsulated using CW was incorporated further improvement in the internal characteristics was consistently observed.
Overall the general effect on Arabic bread quality of using 0.1% TA was negative. The results show that average score for the internal characteristics decreased on addition of unencapsulated TA. In comparison, encapsulated TA was the same as the control and the effect on external characteristics showed enhancement with encapsulated TA at the 0.1% level. The scores for quality scores for Arabic bread on the second day using TA at the same level were decreased compared to the control, whereas using encapsulated TA showed a little improvement on the second day
Figure 1. The effect of addition of 10ppm AA and 0.1% TA on Arabic bread characteristics,
1- external features (first day); 2- internal feature (first day); 3- second day
Note: Scores are presented as mean ± sd
The effect of adding 10 ppm of AA and 0.1% TA on overall score for Arabic bread is demonstrated in Table 1. The results show that adding AA at this level improved the overall bread quality compared to the control, and particularly with AA encapsulated in CW. The overall characteristics of Arabic bread were improved by using encapsulated TA in comparison with the control for both CW and BW. TA had a negative effect on the overall scores for the Arabic bread samples.
Table 1. The effect of addition of 10ppm AA and 0.1% TA on overall characteristics of Arabic bread
76.4 ± 0.3
76.4 ± 0.3
84 ± 1
72.6 ± 0.3
AA & CW
88 ± 1
TA & CW
83.1 ± 0.3
AA & BW
81.6 ± 0.3
TA & BW
82.6 ± 0.3
Note: Scores are presented as mean ± sd
Maximum possible score was 100
The results obtained for the effect of AA and TA on loaf bread firmness are presented in Figure 2 These results show that the bread incorporating AA and encapsulated AA were both softer than the control when measured immediately after the baked loaf had cooled (zero days). When assessed 24 h later, samples with encapsulated AA had softer texture than the sample with AA alone and this was softer than the control which was relatively firm. During storage for a period of 5 days the samples with encapsulated AA using BW firmed less than the control and the sample with unencapsulated AA and the control firmed more than the sample with AA.
For the effect of TA used at a level of 0.1% in loaf bread formulations, immediately after baking all samples had the same firmness values and then samples with TA firmed more than the control during the 5 day storage period. Samples with TA encapsulated using carnauba wax firmed at the same rate as the control during the first 24 h. At 3 days of storage the loaves with encapsulated TA had the same level of firmness as 24 h which means it had a lower staling rate over the 3 day period compared with the control and the encapsulated TA samples. From day three until day five the sample with encapsulated TA firmed less compared with the control.
Figure 2. The effect of addition of 10 ppm AA and 0.1% TA on loaf bread firmness
Note: Scores are presented as mean ± sd
Added AA improved the volume of loaf bread compared with the control and upon addition of AA encapsulated with CW the volume significantly increased compared with the control and samples with unencapsulated AA (Figure3). In addition, when using BW as the encapsulation coat, the volume improved compared with the control and AA sample.
The effect of adding 0.1% TA on loaf bread volume was studied and the results are shown in Figure 3. Upon incorporation of TA at this level, the volume was improved compared with the control. When TA encapsulated with carnauba wax was used the volume showed a greater improvement compared with the control and bread with un-encapsulated TA. The results for beeswax had the greatest impact upon the loaf volume compared with all of the other treatments.
Figure 3. The effect of addition of 10ppm AA and 0.1% TA on loaf bread volumes,
A=control; B=AA; C=encapsulated AA with CW; D=encapsulated AA with BW; F=TA; G= encapsulated TA with CW; H= encapsulated TA with BW
Note: loaf volumes are presented as mean ± sd
AA and TA appeared to have positive effects when it was incorporated into both Arabic and loaf bread in encapsulated forms. AA encapsulated by CW had the highest potential to provide fresh products for Arabic bread. TA encapsulated by BW showed the greatest potential to provide fresh products for loaf bread, and AA encapsulated by CW showed the maximum loaf volumes with minimal deterioration during storage for loaf bread.
American Association of Cereal Chemists, Approved Methods. Method, 10th Edition. (2000) Approved Method 74-10. Bread Firmness by Universal Testing Machine.
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Reineccius, G.A. (2001) Multiple core encapsulations: the spray drying of food ingredients. Vilstrup, P.(eds) Microencapsulation of food ingredients. Leatherhead: Leatherhead RA Publishing. 151-185.