STORAGE BEHAVIOUR OF APPLES TREATED WITH WAX EMULSION
H. B. RAM and W. B. DATE
Fruit Preservation and Canning Institute, Lucknow
Received on December 4, 1969
SuMMARY
Waxol-W and Waxol-0 treatments were compared in relation to storage life of red delicious variety of apples. The former had a deleterious effect whereas the latter was satisfactory.
INTRODUCTION
Wax-coating prolongs the storage lifC of mangoes (Bose
et al., 1954; Mathur et al., 1955) and apples (Dalal, 1961-62).
Martin (1960) has reported successful use of skin-coatings in reducing the incidence of bitter pit in apples during storage. Hallet al. (1953) recorded an increase of about. 50 per cent in
storage life with the application of 8-10 per cent alcoholic solution containing castor oil and wax-free shellac in the ratio of 2 : 1.
Firm texture, natural gloss and absence of surface-shrivelling in addition to eating qualities are important consi-derations in apple trade. The present investigation was under-taken to study the efficacy of two wax emulsions, viz., Waxol-0 and Waxol-W developed by the Central Food Techno-logical Research Institute, Mysore in relation to storage behaviour of apples under non-refrigerated conditions.
MATERIALS AND METHODS
STORAGE BEHAVIOUR OF APPLES 169 at room temperature (25-30° C; 55-90 per cent R.H.). There were 50 fruits under each treatment.
Treated and untreated fruits were analysed for respiratory activity, acidity and the contents of total soluble solids, sugars and ascorbic acid.
Respiration rates were measured by the continuous current method using N/10 barium hydroxide solution. The acidity was determined by titrating the water extract of fruit samples against a standard alkaline solution. Reducing and non-reducing sugars were determined from the fruit pulp by following the Lane and Eynon's copper reduction method (1960). The ascorbic acid was estimated by titration against a standard solution of 2 : 6-di-chlorophenol"indophenol. The total soluble solids were estimated with the help of a refractometer.
RESULTS AND DISCUSSION
The results are presented in Tables I-III and Fig. 1.
Loss in weight.-Thc per cent loss in weight due to
respira-tion and transpirarespira-tion in apples coated with vVaxol-W was more than the loss in control fruits. The samples treated with Waxol-0 showed very little loss in weight (Table I).
Table I. Losses due to respiration and transpiration in weight of apples during storage at room temperature (percentage over initial weight)
- - - -- - - -_" ______
Treated with (8%) of
Storage period
-(days) Control Waxol-0 Waxol-W
4 1·0 0·8 1·2
8 2·0 1·8 3·0
12 3·1 2·5 3·5
15 4·2 3·4 4·5
18 5·2 4·1 6·0
21 6·2 5·0 6·8
24 7·2 5·7 7·7
Table
II.
Storage period (days)
Reducing Control W-0 W-W Initial 7·00 7·00 7·00 12 9·80 9·50 9·90 18 10·50 9·70 10·00 25 II· 10 II ·60 10·80 32 II ·00 12·40 10·40 Changes in the chemical composition
if
apple fruits during storage Ascorbic acid content Acidify% Sugar content (%) (mg/100 g fresh (as malic acid) weight) Non-reducing Total Control W-0 W-W Control W-0 W-W Control W-0 W-W Control W-0 W-W 2·56 2·56 2·56 9·69 9·69 6·69 2·50 2·50 2·50 0·22 0·22 0·22 4·96 2·18 3·32 15· 2 11·78 13·38 I ·50 I ·80 I ·25 0· 18 0·22 0· 17 3· 10 2·20 3· 13 13·75 13·98 13·29 1·50 1·70 I ·25 0· 15 0· 19 0· 15 2·37 2·28 I ·61 13·58 14·00 12·49 I ·40 I ·60 I ·20 0· 15 0· 18 0· 14 1·14 I ·52 0·76 12·49 14·00 I I ·20 I ·25 1·40 I ·20 0· 14 0·18 0· 14STORAGE BEJ{AVIOUR OF APPLES 171
Table Ill. Changes tn total soluble solids (%)
Storage period Control Waxol-0 Waxol-W
(days)
0 11·0 11·0 11·0
12 15·0 14·0 14·5
18 15·5 15·0 15·0
25 15·5 15·0 15·0
32 16·0 15·5 13·5
Sugar content.-The percentage of reducing as well as non-reducing sugars in the control and Waxol-W treated samples during 18-day storage period, was higher as compared to a slow and steady rise in reducing sugar content of the fruits coated with Waxol-0 (Table II). This may be due to delayed ripening process in the fruits receiving Waxol-0 treatment.
Ascorbic acid.-Fruits treated with Waxol-0 showed a better retention of ascorbic acid as compared to control samples as well as the samples treated with Waxol-W which reduced the ascorbic acid content to some extent.
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172 H. B. RAM AND W. B. DATE
Acidity and total soluble solids.-In the fruits coated with
Waxol-0, per cent acidity was higher than in those treated with Waxol-W and the rate of increase in total soluble solids was lower in the samples treated with Waxol-0 as compared to its faster rise in control and Waxol-W treated ones.
Respiration rates.-The rate of respiration was the highest
in control fruits, followed by Waxol-W treated samples and was the least in Waxol-0 coated ones (Fig. 1).
Under the normal conditions obtaining with the fruit vendors, use of Waxol-0 would be beneficial as is evident from the results in the present experiment. There is a distinct gain of about a week in the storage life of apples treated with Waxol-0. From marketability point of view, firm texture, natural gloss and absence of surface shrivelling com-bined with more desirable eating qualities are the special features of consideration in apple trade. In so far as red delicious variety of apples is concerned, Waxol-0 treatment is suitable for fresh fruit trade. On the basis of this laboratory trial, treatment of the fruits in larger quantities in the market was also carried out during the last season and the effect of Waxol-0 was found to be satisfactory as compared to Waxol-W. The results of these investigations indicate that Waxol-W has a deleterious effect on the storage life of the experimental fruits.
This observation is in contradiction of the recommenda-tions made by Dalal ( 1962) who reported that both wax compo-sitions were usable for apple fruits. The varietal difference might be responsible for these contrary observations.
REFERENCES
Bose, A. N. and Basu, G. (1954): Studies on the use of coating for extension of storage life of fresh (Fazli) mango. Food Research 19: 424.
Dalal, V. B. (1962): Role of skin coating in the extension of storage life of fresh fruits and vegetables. Proc. Association Fruit Technologists in
II: 38.
- - - . A brief note on wax-emulsion for coating fresh fruits and vegetables to extend their storage life; C.F.T.R.I., Mysorc (a personal communication). Hall, E. G., Sykes, S. M. and Trout, S. A. (1953): Effect of skin coatings on the behaviour of apples in storage II. Common storage investigation:
Australian ]. Agric. Res., 4: 264-482.
Lane Eynon. (1960): Official Methods of Analysis of the Assoc. Official Agr. Clzem.,
9th edition pp. 417.
Martin, D. (1960): Diseases due to physiological disorders in fruits: Proc. 3rd
Conference Australian Technological Officers Engaged irz Fruit & Vegetable Storage Research.
