Eur Food Res Technol (2003) 218:79–82 DOI 10.1007/s00217-003-0800-6

ORIGINAL PAPER

O. O. Alaka · J. O. Aina · K. O. Falade

Effect of storage conditions on the chemical attributes of Ogbomoso mango juice Received: 24 March 2003 / Revised: 27 July 2003 / Published online: 7 November 2003
Springer-Verlag 2003

Abstract Mango juices were extracted from Ogbomoso variety using the method of Brekke et al. (1972). Mango juices were packaged in polyethylene films, polyethylene tetraphthalate (PET or plastic) bottles and transparent glass bottles and stored at 6 C, 26 C and 34 C. Percentage ascorbic acid loss, browning index, titratable acidity, pH and soluble solids were evaluated at 2-week intervals for 8 weeks. Percentage ascorbic acid loss, nonenzymatic browning and titratable acidity increased with storage time in all packaging materials. However, pH decreased with storage time and soluble solids remained constant. Higher percentage ascorbic acid loss, browning index and titratable acidity occurred in juices packaged in polyethylene film, than in PET and glass bottles. Percentage ascorbic acid, browning index and pH increased with increased storage temperature. However, titratable acidity decreased with increased storage temperature and soluble solids remained constant throughout the period of storage. Keywords Mango juices · Ogbomoso variety · Packaging materials · Chemical attributes · Storage temperature

Introduction Mango (Mangifera indica L.) of the family Anacardiaceae is a big flesh drupe with edible pulp and a stony layer around the seed. It is known to be among the most nutritious fruits. Over 1000 varieties of mango exist, among which are Alphonso, Pairi, Banganpalli, Bombai, Palmer, Saigon, Edward and Julie [1]. Each variety of mango is distinct from others in colour and flavour and therefore, vary in its suitability in processing into different products like juices and chutney [2 ,3, 4]. In Nigeria, Ogbomoso mango is a popular cultivar. However, Ogbomoso mango faces post harvest losses of O. O. Alaka ()) · J. O. Aina · K. O. Falade Department of Food Technology, University of Ibadan, Ibadan, Nigeria e-mail: [email protected]

up to 50% due to the high relative humidity, temperature and poor handling techniques and facilities [5, 6]. The successful production of Ogbomoso mango juice by small and medium scale factories in the fruit juice industry has increased its utilization and preservation. Moreover, packaging environment established by producers and storage/handling conditions influenced by wholesalers and retailers, effect the quality and subsequent shelf life of juice produced, due to different product-package interactions that take place during storage. The objective of this study is to evaluate the effect of different packaging materials (glass, PET and polyethylene film) and temperature on chemical attributes of Ogbomoso mango juice during storage.

Materials and methods Mango (variety Ogbomoso) was obtained from a local village near Ogbomoso town, Oyo state, Nigeria. The 35-cL transparent glass bottles and 40-micron polyethylene film were obtained from a local market in Ibadan, Oyo state, Nigeria. The polyethylene tetraphthalate (PET) bottle was obtained from the Kushils Production Company in Otta, Ogun State, Nigeria. Mango juices were extracted from fresh ripe fruits according to the method of Brekke et al. [7]. The mango fruits were peeled, pulped and clarified using muslin cloth. Sodium benzoate (0.35 g/L) and citric acid (1 g/L) were added to the mango juice as preservatives. The juice was then packaged in polyethylene film, PET and glass bottles. The packaged juices were maintained at refrigerated (6 C), ambient (26 C) and elevated (34 C) temperatures. Chemical analysis Ascorbic acid, browning index, titratable acidity, pH and soluble solids were analysed initially and at regular interval of 2 weeks and for 8 weeks. pH was measured using pH meter (model E-520). Titratable acidity was determined according to the method of AOAC [8]. Soluble solids were determined with a refractometer (Abbe 60 series), according to the method of Ruck [9]. Using the method of AOAC [10], ascorbic acid content was determined with a spectrophotometer (Jenway 6405 UV/VIS). Browning index was measured according to the method of Meydar et al. [11], using a spectrophotometer (Jenway 6405 UV/VIS).

80 Table 1 Effect of packaging material on titratable acidity, pH and soluble solids of Ogbomoso mango juices stored at 34 C

Packaging material

Polyethylene film

Plastic bottles

Glass bottles

Parameter

TTA PH Soluble solids TTA PH Soluble solids TTA PH Soluble solids

Storage period (weeks) 0

2

4

6

8

0.71 3.34 12 0.71 3.34 12 0.71 3.34 12

0.63 3.41 12 0.49 3.69 12 0.63 3.40 12

0.46 3.70 12 0.42 3.80 12 0.46 3.70 12

0.87 3.33 12 0.50 3.39 12 0.51 3.29 12

1.02 3.18 12 0.52 3.42 12 0.49 3.43 12

Results and discussion Table 1 shows the effect of packaging material on titratable acidity, pH and soluble solids of the stored Ogbomoso mango juices at 34 C. Generally, titratable acidity of the juices increased in the order polyethylene film >PET bottles >glass bottles. However, the pH increased in the order glass bottles >PET bottles >polyethylene film. Similar results were obtained in juices stored at 6 C and 25 C. Figure 1 shows the effect of packaging material on percentage ascorbic acid loss in Ogbomoso mango juices stored at 34 C. Percentage ascorbic acid loss was lower in juices packaged in glass bottles. Similar trend was observed in juices stored at 26 C and 6 C. Juices stored

Fig. 2 Effect of packaging material on non-enzymatic browning in Ogbomoso mango juice stored at 34 C

Fig. 1 Effect of packaging materials on % ascorbic acid loss in Ogbomoso mango juice stored at 34 C

at 26 C showed ascorbic acid loss of 45%, 63% and 70% in juices stored in glass, PET and polyethylene film, respectively. Juices stored at 6 C showed ascorbic acid loss of 11%, 50% and 68% in glass bottles, PET bottles and polyethylene film, respectively. The better protective capability of glass bottles may be due to the impervious property of glass to environmental oxygen and exclusion of other components of the environment [10]. Figure 2 shows the effect of packaging material on non-enzymatic browning in Ogbomoso mango juice stored at 34 C. Non-enzymatic browning occurred in juices in all packaging materials. Generally, non-enzymatic browning increased for 6 weeks after which it became constant. Non-enzymatic browning increased in the order polyethylene >PET bottles >glass bottles. Similar trends were observed in juices stored at 26 C and 6 C. Juices stored at 26 C showed browning index

81 Table 2 Effect of storage temperature on titratable acidity, pH and soluble solids of Ogbomoso mango juices packaged in polyethylene

Storage temperature

Parameter

34 C

TTA PH Soluble solids TTA PH Soluble solids TTA PH Soluble solids

26 C

6 C

Fig. 3 Effect of storage temperature on % ascorbic acid loss in Ogbomoso mango packaged in polyethylene during storage

of 0.27, 0.25 and 0.23 in polyethylene film, plastic and glass bottles respectively after 8 weeks of storage. Moreover, juices stored at 6 C showed browning index of 0.27, 0.23 and 0.22 in polyethylene film, PET and glass bottles, respectively after 8 weeks of storage. According to Labuza [12], the extent of non-enzymatic browning in food depends on the food’s exposure to oxygen, which in turn depends on the type of packaging material used [13]. Table 2 shows the effect of storage temperature on titratable acidity, pH and soluble solids of Ogbomoso mango juices packaged in polyethylene film. Generally, titratable acidity of stored juices decreased with increased storage temperature. However, pH increased with increased storage time. Soluble solids remained constant throughout the period of storage. Similar results were observed in juices packaged in PET and glass bottles.

Storage period (weeks) 0

2

4

6

8

0.71 3.34 12 0.71 3.34 12 0.71 3.34 12

0.63 3.41 12 0.88 3.10 12 0.67 3.40 12

0.46 3.70 12 0.91 2.89 12 0.53 3.32 12

0.87 3.33 12 2.64 2.16 12 1.49 2.27 12

1.02 3.18 12 2.17 2.42 12 2.10 2.62 12

Fig. 4 Effect of storage temperature on non-enzymatic browning in Ogbomoso mango juice packaged in glass bottles

Figure 3 shows the effect of storage temperature on percentage ascorbic acid loss in Ogbomoso mango juice packaged in polyethylene film. Percentage ascorbic acid loss increased with increased storage temperature and time. Greater loss was observed in mango juices stored at 34 C than juices stored at 26 C and 6 C. A similar trend was observed in mango juices stored in PET and glass bottles. Juices packaged in PET bottles showed ascorbic acid loss of 50, 63 and 67% in juices stored at 6, 26 and 34 C, respectively. Meanwhile, juices packaged in glass bottles showed ascorbic acid loss of 11, 45 and 62% in juices, stored at 6, 26 and 34 C, respectively. Higher percentage ascorbic acid loss at higher temperatures may be due to increased chemical reactions associated with ascorbic acid degradation. Biochemical reactions associated with ascorbic acid degradation. Biochemical reac-

82

Fig. 5 Effect of storage temperature on non-enzymatic browning in Ogbomoso mango juice packaged in PET bottles

Fig. 6 Effect of storage temperature on non-enzymatic browning in Ogbomoso mango juice packaged in polyethylene film

tions proceed faster at high temperature than at low temperature [14]. Figure 4 shows the effect of storage temperature on non-enzymatic browning in Ogbomoso mango juice packaged in glass bottles. Non-enzymatic browning, measured at 420 nm, increased with increased storage temperature and time. Similar trends were observed in juices packaged in PET (plastic) bottles and polyethylene films (Figs. 5 and 6). Juices packaged in plastic bottles showed browning index of 0.23, 0.25 and 0.27 in mango juices stored at 6, 26 and 34 C, respectively. Meanwhile, juices packaged in polyethylene showed a browning index of 0.27, 0.27 and 0.28 in juices stored at 6 C, 26 C and 34 C at the end of storage period. The extent of nonenzymatic browning in foods depends on storage temperature and time [15].

References

Conclusion Ogbomoso mango juice packaged and stored at the refrigeration temperature of 6 C retained the desired quality attributes in juices better than juices stored at 26 C and 34 C. Glass bottles gave greater protection against degradation of the chemical attributes of the mango juices. Packaging Ogbomoso mango juices in glass bottles and storing them at 6 C will give good protection against quality degradation of mango juices.

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