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Effect of packaging material on storage ability of mango milk powder and the quality of reconstituted mango milk drink
Powder Technology 239 (2013) 86–93
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Effect of packaging material on storage ability of mango milk powder and the quality of reconstituted mango milk drink Anil Kumar Chauhan ⁎, Vaibhav Patil Centre of Food Science and Technology, Banaras Hindu University, Varanasi-221005, India
a r t i c l e
i n f o
Article history: Received 28 August 2012 Received in revised form 23 January 2013 Accepted 26 January 2013 Available online 1 February 2013 Keywords: Shelf life Mango milk powder Storage Packaging Products
a b s t r a c t Mango milk powder (MMP) was obtained after recirculatory convective drying, conditioning and grinding. The physico-chemical characteristics of fresh canned mango pulp and those of the finished product were estimated. The microbiological quality of the beverage showed the presence of low number of cfu (colony forming unit) as 2.5 × 10 3 and ymc (yeast and mold count) as 3 per gram. The product was free from coliform bacteria. MMP was packaged in pouches of high density polystyrene, tin can, metalized polyesters and four ply laminates polythene aluminum foil–polythene–paper. The shelf life of mango milk powder was predicted on the basis of free flowability of product under controlled storage condition and was found to be maximum in tin containers (10 and 11 months, respectively) at 30 ± 1 °C and 5 ± 1 °C. © 2013 Elsevier B.V. All rights reserved.
1. Introduction Packaging means placing a commodity into a protective wrapper or container for transport or storage. Package has three fold functions of containing, protecting and merchandising. It provides protection to the product against contamination or loss and damage or degradation due to microbial action, exposure to heat, light, moisture and oxygen, evaporation, etc. It also helps in selling the products. It constitutes an important link between the manufacturer and ultimate consumer for the safe delivery of the product through different stages of production, storage, transport, distribution and marketing. Mango pulp is the most utilized part for human consumption. This portion constitutes about 58 to 77% of the total fruit weight depending upon the variety. Prevention of cancer and heart diseases is possible by antioxidants (β-carotene and vitamin C) rich mango. Bioflavonoid present in mango help in building human immune system. The insoluble dietary fiber found abundantly in mango helps in the elimination of waste from the colon and prevents constipation. Mango milk shake is reported to be helpful in body weight gain especially in low weight persons. Mangoes may be used in a variety of preparations with milk forming as the base, viz., mango milk beverages, puddings, custards, ice creams etc. The availability of fresh milk and canned mango is abundant. Manufacture of mango milk powder will provide an alternate pathway for utilization of surplus milk solids. The specialty product, so manufactured, is likely to prove highly remunerative for industry and nutritious for all classes of consumers.
⁎ Corresponding author. Tel.: +91 9450658188; fax: +91 542 2368993. E-mail address: [email protected] (A.K. Chauhan). 0032-5910/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.powtec.2013.01.055
Standardization of manufacturing technology of mango milk powder (MMP) and type of packing material may affect the quality and safety of reconstituted drink. Therefore, evaluation of packaging materials for MMP and its reconstituted drink at different storage condition had undertaken mainly the fulfillment of the consumer demand for nutritional products with assurance of quality and safety. New methods of processing and packaging being developed to meet the growing demand of ready to eat convenience food products with long shelf stability, nutritional integrity and safety assurance. There is an increasing demand in the world for instant powder which could be reconstitute into variety of products. The present investigation has been planned with the objective to evaluate the suitability of certain packaging material and methods of packaging material on shelf of mango milk powder. The packages were pasteurized, dried and filled with inert gases, keeping in view the Metal can, 4-ply laminates (polyethylene-aluminium foil–polyethylene– paper), metalized polyester, polystyrene packages were used. 2. Materials and methods 2.1. Mango milk powder The mango milk powder (MMP) (Fig. 1) prepared was used for the present study. Standardization of spray drying process for mango milk powder was done with reference to optimum total solid concentration, inlet and outlet air temperature and speed atomization keeping the flow rate of the feed constant [1]. The ratio of mango (Totapari) pulp, pasteurized toned milk (Vita brand, 3% fat and 8.5% SNF) and refined cane sugar (ISI Mark) was kept constant at 30, 62 and 8%, respectively. Concentrated toned milk and one third of total
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87
70 Packaging Material
60
Storage Period (months) 50 Flowability (q) 40
Wettability (sec) Solubiliy (ml)
30
Bulk Density (g/ml) 20
Sinkability 2 min Sinkability 4 min
10
Sinkability 6 min 0 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Fig. 1. Effect of different packaging materials on physical properties of mango milk powder stored at 30 ± 1 °C. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)
sugar were preheated to 70–75 °C and double stage homogenized at 1000/500 psi. The homogenized mix was pasteurized followed by cooling to 20 °C and mixing of canned mango pulp with pasteurized formulation. This mixture was spray dried with operating conditions of 185 °C inlet air temperature and an outlet temperature objective of about 85 °C. The resulting product moisture content was about 2.15%. The atomizer speed of 15000 rpm was used to maintain a constant flow rate with droplet size of about 250 μm. Spray dried product was collected and dry blended with the remaining two thirds of powdered cane sugar. The resultant mango milk powder (MMP) blend was collected in polyethylene lined powder bags. The bags were closed and sealed with a minimum headspace, then allowed to cool at room temperature before refilling into the different packaging material used in the study. Samples of MMP were tested at regular intervals of every 2 months up to 8 months and thereafter at monthly intervals up to 12 months. Fresh samples of MMP and those stored in different packages were reconstituted with 4.5 times its weight of potable water in a mixer. Chemical analysis of MMB was carried out by the methods described [2] for total solids, crude fiber content, total sugar and vitamin C. Total soluble solids of MMB were detected by hand refractometer at 20± 0.5 °C and viscosity was determined by a programmable coaxid cylinder viscometer with digital display (Controvac Rheomat 108 E/R Mettle Tolebo, Switzerland) with measuring system 1, 1 for MMB. Flow curve was obtained for shear at range of 100 to 1000 s−1 at 20 °C. MMP was analyzed. Moisture by ISI [3] methods, titratable acidity by AOAC [4], total protein by micro-Kjeldahl methods by AOAC [5] and total ash and fat contents as per ISI methods were described [6]. Fully ripe mangoes of the three selected varieties viz. Baneshan (BE), Suvarnarekha (SR), Totapuri (TT) were washed thoroughly, peeled and cut into pieces and stones were removed manually. The cut pieces were fed into the pulper with a sieve size of 1/1600. The extracted pulp was heated at 60 °C in steam jacketed kettle for 3 min, cooled and potassium metabisulphate was added at the rate of 0.2%. The pulp was then transferred to white high density polyethylene (HDPE) cans and kept in cold storage until use (less than a month) as per the procedure described [7]. Conventional types of mango products have been developed to a considerable extent but the mango industry is eager to develop new processed products [8].
the procedure. Color of reconstituted MMB was estimated by LAB mode lightness for white (L), greenness and redness (a) and yellowness and blueness (b). 2.3. Physical analysis of MMP Bulk density and flowability [9], solubility index [3], wettability [10], and sinkability [11] were determined as per prescribed methods. 2.3.1. Bulk density A 100 ml graduated cylinder of tarred weight was taken. The mouth of cylinder and the powder was allowed to flow freely to 100 ml mark. The net weight was obtained and results expressed as g/ml (loose density). The packed bulk density was determined by tapping the cylinder till the volume attained a constant level. The volume occupied was noted and result expressed as g/ml. 2.3.2. Flowability A plastic funnel with a narrow stem, cut at right angles, was mounted exactly 2 cm above a piece of butter paper positioned on a horizontal table. A sieve with 16-mesh size was fixed to a shaker (100 shakings per minute). Powder sample was placed on the sieve and allowed to go through the funnel in a fine stream at a controlled speed, so as to form a conical heap. When the top of the powder heap touched the end of funnel stem, the powder stream was stopped by switching off the shaker. The base of the powder heap was outlined with a pencil and powder was removed. After removing the powder, the outlined paper circle was cut and weighed. The radius was calculated and the angle of repose was estimated. 1 Tan θ ¼ h= r− =2 a Where, θ h r a
angle of repose, height of stem base (2 mm), radius of the base of powder heap, and diameter of funnel stem.
2.2. Microbiological analysis Total viable count and yeast and mold count were done following the ISI methods mentioned [6] whereas spore count was done as per
2.3.3. Solubility index Fourteen grams of the powder was reconstituted in a 100 ml of distilled water. The sediment obtained from 50 ml by centrifugation
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Table 1 Effect of different packaging materials on physical properties of mango milk powder stored at 30 ± 1 °C. Packaging material
Tin can
Metalized polyester
4-Ply laminates
Polystyrene
Storage period (months)
Flowability (θ)
Wettability (s)
Solubility (ml)
Bulk density (g/ml)
Sinkability 2 min
4 min
6 min
Initial 2 4 6 8 2 4 6 8 2 4 6 8 2 4 6 8
58.50 58.50 60.20 61.40 62.10 58.90 60.00 61.20 63.90 59.10 60.60 61.30 63.95 59.40 62.80 64.10 65.6 0.10 0.29
31.20 31.90 33.10 35.10 35.50 31.60 34.50 36.90 39.10 31.80 34.30 36.40 39.00 31.70 35.20 39.30 42.2 0.10 0.29
0.97 0.97 1.05 1.25 1.40 0.97 1.20 1.42 1.62 0.97 1.20 1.41 1.65 0.99 1.67 1.80 1.90 0.03 0.08
0.70 0.70 0.72 0.73 0.75 0.71 0.73 0.75 0.77 0.72 0.73 0.73 0.77 0.78 0.82 0.86 0.89 0.01 0.03
24.33 24.77 25.27 26.87 28.79 24.50 26.43 28.33 30.93 24.63 26.87 28.67 30.30 25.37 28.87 30.00 32.00 0.10 0.29
18.33 18.57 18.90 19.00 21.30 18.60 20.57 22.50 24.63 18.80 20.37 22.50 24.30 19.43 23.50 24.17 25.00 0.10 0.29
14.23 14.50 15.33 15.83 17.20 14.67 17.80 18.77 20.87 14.83 17.20 18.43 20.53 15.40 18.63 20.50 21.50 0.10 0.29
SEM CD (5%) Number of replicates = 3. CD = critical difference. SEM = standard error mean.
of reconstituted product was measured and results expressed in milliliters.
2.3.4. Wettability A piece of satin-fabric measuring 10 × 10 cm was stretched over one end of the metallic can (open at both ends with 6.5 cm dia and 4.5 cm height) and fastened in position by a rubber band. Another one end can (5 cm dia and 7 cm height) was placed centrally on the cloth. The tray was filled with distilled water at 40 ± 1 °C to a height of 2.5 cm. A triangle made out of 0.4 cm thick glass rod with sides measuring 8 cm long was placed in the dish and served to prevent close contact of the cloth with the bottom of the dish. With the two cans assembled, and cloth resting on outer can, 1 g of powder was transferred to the inner can and spread over the 6 cm circle
of the cloth as evenly as possible with a soft sable hair brush. The inner can was then removed and the outer can lowered into the tray onto the glass triangle and held in place, until the water level in the can ceased to rise. A stopwatch was clicked as soon as the cloth touched the water and stopped when the powder got completely wet. The time taken for complete wetting of powder was recorded in seconds.
2.3.5. Sinkability In this test, 3.5 ml of distilled water at 20 °C was taken in the spectrophotometer cuvette and 10 mg sample of powder was then dusted on the surface of water and the percentage transmittance was measured at 760 nm in a spectrophotometer. The readings were recorded after 2, 4 and 6 min intervals. The mean of three replicate values was taken as the percentage transmittance.
Table 2 Effect of different packaging materials on physical properties of mango milk powder stored at 5 ± 1 °C. Packaging material
Tin can
Metalized polyester
4-Ply laminates
Polystyrene
SEM CD (5%) Number of replicates = 3. CD = critical difference. SEM = standard error mean.
Storage period (months)
Flowability (θ)
Wettability (s)
Solubility (ml)
Bulk density (g/ml)
Sinkability 2 min
4 min
6 min
Initial 2 4 6 8 2 4 6 8 2 4 6 8 2 4 6 8
58.50 58.90 60.10 61.00 62.10 58.80 62.80 63.70 62.90 59.00 60.30 62.00 62.95 59.30 61.60 63.90 65.00 0.10 0.29
31.20 31.40 32.80 34.70 36.10 32.40 33.10 36.60 37.90 31.70 33.00 36.40 37.90 33.50 35.00 38.80 41.00 0.10 0.29
0.97 0.97 1.03 1.20 1.40 0.97 1.30 1.40 1.52 0.97 1.20 1.38 1.48 0.98 1.21 1.69 1.80 0.01 0.03
0.70 0.70 0.72 0.72 0.73 0.71 0.73 0.74 0.74 0.71 0.73 0.73 0.74 0.77 0.79 0.82 0.86 0.01 0.03
24.27 24.23 24.64 25.09 26.66 24.41 25.35 26.11 27.79 24.43 25.38 26.15 27.82 25.22 28.79 29.75 30.50 0.10 0.29
18.33 18.11 18.76 18.93 21.05 18.55 19.45 20.39 22.51 18.59 19.47 20.41 22.56 19.23 23.15 23.98 24.5 0.10 0.29
14.23 14.25 15.06 15.59 17.02 14.59 16.72 17.69 18.68 14.61 16.74 17.68 18.69 15.16 18.23 19.97 24.55 0.10 0.29
A.K. Chauhan, V. Patil / Powder Technology 239 (2013) 86–93
89
70
60 Packaging Material 50
Storage Period (months) Flowability (q)
40 Wettability (sec) 30
Solubility (ml) Bulk Density (g/ml)
20 Sinkability 2 min Sinkability 4 min
10
Sinkability 6 min 0 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
-10 Fig. 2. Effect of different packaging materials on physical properties of mango milk powder stored at 5 ± 1 °C. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)
Sediment in reconstituted MMB was measured by filling reconstituted MMB in 100 ml cylinder and level was brought up to 100 ml mark. The sediment at the bottom was measured in milliliters after keeping overnights in refrigerator. A digital pH meter (LAB India Instruments Pvt. Ltd., Mumbai) was used for measuring pH of the reconstituted MMP at 30 °C. A panel comprising seven trained judges did sensory evaluation of fresh MMB and reconstituted MMB by using 9-points hedonic scale scorecard.
and 5 ± 1 °C for storage studies. The mango pulps were stored with higher levels of sulfur dioxide [12]. With additional packing such as bag-in-box (a polyethylene pouch placed in a cardboard box) or the aluminium laminated high-density polyethylene, the loss of b-carotene can be further reduced. Baneshan, Suvarnarekha varieties showed that the results of mango powders can be safely stored in metalized polyester/polyester poly packaging for a period of up to 6 months. For storage beyond 6 months additional packaging may be required [13].
2.4. Storage of powder
2.5. Statistical analysis
The samples of MMP were separately packaged in tin, 4-ply laminates, polystyrene and metalized polystyrene and stored at 30 ± 1 °C
Statistical analysis was done by using factorial randomized design of ANOVA. The one factor with four levels that is tin containers,
Table 3 Effect of different packaging materials on microbiology of mango milk powder stored at 30 ± 1 °C and at 5 ± 1 °C. 30 ± 1 °C
5 ± 1 °C cfu × 103
YMC × 101
Spore count × 101
cfu × 103
YMC × 101
Spore count × 101
Packaging material
Storage period (months) Initial
16.0
6.0
12.0
Initial
16.0
6.0
12.0
Tin can
2 4 6 8 2 4 6 8 2 4 6 8 2 4 6 8
12.2 9.5 8.1 7.3 12.0 9.2 7.8 6.0 12.0 9.1 8.0 6.9 11.0 9.2 7.0 6.7 0.10 0.29
4.9 3.0 2.5 1.1 5.1 4.0 2.1 1.2 5.0 3.9 2.1 1.0 5.1 4.0 2.0 0.7 0.10 0.28
11.6 9.5 9.2 7.1 11.2 9.8 7.8 5.0 11.6 9.4 8.6 6.6 11.8 11.2 9.2 10.4 0.10 0.29
2 4 6 8 4 6 8 2 6 8 2 4 2 4 6 8
12.4 9.8 8.4 7.6 9.3 7.9 6.9 12.0 8.2 7.0 11.2 9.4 11.2 9.4 8.0 6.8 0.10 0.29
5.0 3.1 2.8 1.2 4.2 2.4 1.3 5.1 2.2 1.1 5.1 4.0 5.1 4.0 2.2 0.9 0.10 0.28
11.8 11.1 9.8 8.2 11.3 10.1 8.4 11.6 8.6 6.7 11.8 11.3 11.8 11.3 10.1 9.40 0.10 0.29
Metalized polyester
4-Ply laminates
Polystyrene
SEM CD (5%) Number of replicates = 3. CD = critical difference. SEM = standard error mean.
Storage period (months)
90
A.K. Chauhan, V. Patil / Powder Technology 239 (2013) 86–93
metalized polyester, 4-ply laminates and polystyrene containers also second factor with 4 levels that is 2, 4, 6 and 8 months. Critical difference (CD) is the least significance difference, greater than which all the differences are significant. The data for each parameter were collected in three replicates. The statistical analysis shows that the effect of different packaging materials and the effect of storage period on physical properties of mango milk powder were stored at 30 ± 1 °C and at 5 ± 1 °C.
3. Results and discussion 3.1. Comparative assessment of packaging materials for mango milk powder The packaging material and storage temperature are known to influence the physical, chemical, microbiological and sensory properties of dried milk products. The selection criteria of a suitable packaging material for mango milk powder was essentially based on the shelf life. The suitability of the packaging materials on quality of mango milk powder during storage are presented and discussed below.
3.2. Chemical properties Moisture, acidity, fat, protein and ash content in MMP stored at 30 ± 1 °C and 5± 1 °C have been presented in Tables 1 and 2 respectively. Comparative value of constituents during storage showed about 0.41% increase in moisture content over a period of six-month storage at 30 °C in the sample of mango milk powder packaged in polystyrene. Samples packed in 4-ply laminates showed an increase of moisture to about 0.21% in 6 months. These results are consistent with those reported by Ardito et al. and Mrithyunjaya and Bhanumurthi [14,15]. It is difficult to ascertain whether the slight increase in moisture percentage in the samples was due to ingress of moisture or the chemical changes occurring during storage. However, there is a gradual increase in moisture content in dried whole milk during storage. Titratable acidity showed a minor increase during the storage irrespective of packaging used, suggesting the interplay of various constituents and resulting chemical changes. A gradual decrease in pH value was noted during storage. Increasing moisture levels caused a slight reduction in total protein content in the sample during storage. There was no change in protein content during storage on dry
(a) 18 16 14 12
30 ± 1°C
10
cfu
8
YMC
6
Spore 4
Count
2 0
Packaging Material Tin can -2
Metallized polyester
4-Ply Laminates
Polystyrene
(b) 14
12
10
5 ± 1°C Storage Period (months)
8
5 ± 1°C cfu 6
5 ± 1°C YMC 5 ± 1°C Spore Count
4
2
0
Tin can
Metallized polyester 4-Ply Laminates
Polystyrene
-2 Fig. 3. (a) Effect of different packaging materials on microbiology of mango milk powder stored at 30 ± 1 °C. (b) Effect of different packaging materials on microbiology of mango milk powder stored at 5 ± 1 °C. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)
A.K. Chauhan, V. Patil / Powder Technology 239 (2013) 86–93
matter basis. These results are consistent with those reported by Furukava and Yamamanaka [16], in kulfi mix powder titratable acidity increased over a period of 8 months storage at 30 °C when packed in the different kinds of packaging materials. Irrespective of type of packaging material, chemical changes occurred faster at 30 °C than those at 5 °C. These results are consistent with those reported by Driscoll [17], chemical deterioration in milk powders was faster at 21 °C at temperature of storage than at 10 °C. Increase in fat content with storage periods with corresponding increase in moisture may be due to liberation of fat from lipo-protein complexes in MMP. Ash content is nearly constant. However, slight decrease in protein content may be owing to its degradation with corresponding changes in moisture. Mango pulp carbohydrates and lactose content in MMP have not been estimated and their contribution to acidity during storage may be the contributing factors. 3.3. Physical properties The effect of packaging materials on physical properties of mango milk powder is presented in Tables 1 and 2 and Figs. 1 and 2. It can be noted that there was a gradual loss of solubility, flowability, wettability, whereas, bulk density and sinkability increased during storage at 30 °C. The losses in flowability, wettability and solubility were faster in samples packed in polystyrene than those in metalized polyester, 4-ply laminates and tin cans. These results are consistent with those reported by Pijanowski [18], an increase in amount of free fat might be responsible for the loss in wettability and flowability and inverse relation between free fat and wettability. The increase in wetting time of MMP samples during storage may be attributed partly to increase in free fat content and native quality of proteins. Considerable increase in wetting time of dried milks attributed this to increased liberation of free fat during storage [19,20]. Loss in wettability in pre-term infant formula, khoa powder and kulfi mix powder after storage at 30 °C has been reported [21]. Besides, similar observations have also been reported in cheddar cheese, whey powder, whey based mushroom soup powder and whey kinnow juice powder, respectively [22,23]. A progressive increase in solubility index of MMP may be attributed to the formation of water insoluble compounds caused by increased casein micelles size due to hydrogen bonding [24] consequent to protein–protein interactions or sugar–protein interaction [25]. The changes in protein structure due to Maillard reaction and protein– protein interaction during storage could be responsible for the loss of solubility [26]. Gradual increase in solubility index from 1.07 to 1.80 ml in WMP after storage for 6 months at 30 °C is reported by Mrithyunjaya and Bhanumurthi [15]. Solubility index of khoa powder [21] and kulfi mix powder also increased from 1.2 to 2.0 ml over a period of 8 months storage at 30 °C; in similar studies on dried milks [16,27,28] an increase in solubility index with the progress of storage time is also observed. Bulk density of mango milk powder increased with the storage period irrespective of packaging materials used. Increase in bulk density with increased moisture content was also observed [29] in dried milk powder and ice-cream mix powder, respectively. An increase in bulk density may be attributed to increased cohesiveness caused by absorption of moisture during storage. Sinkability of mango milk powder increased with the storage period. Changes occurred faster at 30 °C than those at 5 °C. Flowability decreased with increasing storage period more so at higher temperatures. Irrespective of storage temperatures, samples packed in polystyrene registered a high loss of flowability during storage. Angle of repose (tan θ) increased from 62.93 to 66.16 in spray dried malted milk food on storage at 30 °C for 12 months. A gradual loss of flowability in lactose hydrolyzed infant formula on storage at 30 °C for 12 months. These results are consistent with those reported by Peleg [30]; increase in free fat content and changes
91
Table 4 Effect of different packaging materials on physico-chemical properties of reconstituted mango milk powder stored at 30 ± 1 °C. Packaging material
Tin can
Metalized polyester
4-Ply laminates
Polystyrene
Storage period (months)
Total solids (%)
pH
Initial 2 4 6 8 2 4 6 8 2 4 6 8 2 4 6 8
19.78 19.76 19.78 19.74 19.75 19.75 19.77 19.79 19.78 19.76 19.78 19.77 19.77 19.79 19.77 19.78 19.8 0.10 0.29
6.05 6.01 5.97 5.82 5.75 5.99 5.86 5.63 5.59 5.98 5.87 5.65 5.60 5.92 5.68 5.45 5.32 0.11 0.30
SEM CD (5%)
Color L
a
b
70.10 70.12 70.25 70.25 70.28 70.27 70.28 70.36 70.41 70.28 70.28 70.36 70.42 70.32 70.37 70.45 70.52 0.10 0.29
8.01 8.01 8.02 8.02 8.04 8.03 8.04 8.07 8.08 8.04 8.04 8.07 8.08 8.06 8.07 8.09 8.11 0.11 0.30
42.23 42.17 42.14 42.07 41.99 42.10 42.05 41.95 41.86 42.11 42.06 41.95 41.87 42.08 41.98 41.88 41.88 0.11 0.31
Sediments (ml) 5.08 5.10 5.16 5.30 5.42 5.11 5.20 5.41 5.72 5.11 5.20 5.42 5.75 5.14 5.67 5.80 5.96 0.10 0.29
Number of replicates = 3. CD = critical difference. SEM = standard error mean.
in particle structure due to moisture absorption during storage could increase cohesiveness of powder leading to reduction in flowability. Moist powder exhibited higher angle of repose (mainly due to cohesion), despite the fact that the angle of internal friction usually decreases with increase in moisture level. 3.4. Microbiological quality The microbial counts in fresh mango milk powder were SPC 16.0 × 10 3, YMC 6.0 × 10 1 and spore count 12.0 × 10 1 per gram of product. The microbial counts largely depend upon the quality of raw materials used in the product preparation and the methods of processing. The type of package and temperature of storage showed significant influence on the growth and survival of microorganisms
Table 5 Effect of different packaging materials on physico-chemical properties of reconstituted mango milk powder stored at 5 ± 1 °C. Packaging Material
Storage Period Total solids pH (months) (%)
Initial 2 4 6 8 Metalized 2 polyester 4 6 8 4-Ply 2 laminates 4 6 8 Polystyrene 2 4 6 8 SEM CD (5%) Tin can
Number of replicates = 3. CD = critical difference. SEM = standard error mean.
19.78 19.79 19.78 19.76 19.77 19.77 19.78 19.78 19.76 19.78 19.79 19.76 19.77 19.77 19.77 19.78 19.78 0.10 0.29
6.05 6.03 5.99 5.87 5.81 6.01 5.93 5.87 5.76 6.02 5.92 5.88 5.77 5.95 5.71 5.52 5.37 9.90 28.51
Color L
a
b
70.10 70.20 70.21 70.24 70.29 70.23 70.25 70.31 70.35 70.22 70.25 70.30 70.35 70.29 70.34 70.42 70.45 0.10 0.29
8.01 8.01 8.02 8.03 8.04 8.02 8.03 8.05 8.07 8.02 8.02 8.04 8.06 8.04 8.05 8.07 8.09 0.10 0.29
42.23 42.19 42.18 42.15 42.11 42.14 42.11 42.07 42.01 42.13 42.12 42.07 42.02 42.05 42.01 41.93 41.82 0.10 0.29
Sediments (mg) 5.08 5.08 5.11 5.20 5.40 5.09 5.30 5.40 5.52 5.09 5.20 5.38 5.48 5.11 5.31 5.70 4.92 0.10 0.29
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80 70 60
Packaging Material 50
Storage Period (months)
40
Total Solids (%)
30
pH Colour
20
Sediments (mg) 10 0 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
-10 Fig. 4. Effect of different packaging materials on physico-chemical properties of reconstituted mango milk powder stored at 30 ± 1 °C. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)
in mango milk powder (Table 3 and Fig. 3). While yeast and mold counts decreased rapidly during storage, spores exhibited a great resistance. The death rate of bacteria was slower at 5 °C than at 30 °C. Low water activity in the product coupled with antibacterial nature of some of the chemical compounds released in various degradation reactions may have caused rapid destruction of microbial cells during storage [31]. As the rate of chemical reactions is slow at lower temperatures of storage, the decline in microbial number was found to be slow. A decrease in microbial counts from initial numbers of 4.1 × 10 3 to 2.2 × 10 3 was also reported [32] in SMP after storage for 6 months at 30 °C. The spore counts in MMP showed insignificant decrease during storage at 30 °C and 5 °C. Spores survive even in most adverse conditions [33]. An insignificant reduction in spore count from an initial number of 4.5 × 10 2 to 4.0 × 10 2 in high heat SMP after storage for 6 months at 30 °C is observed by Muir et al. [32]. The YMC also showed a declining trend during the entire storage period, becoming almost negligible at the end of storage study both at 30 °C and 5 °C. Yeast and mold grow at aw above 0.6. Lower aw
should be one reason for the accelerated death of yeast and mold during storage. These results are consistent with those reported by Ranganadham [21].
3.5. Sensory quality Packaging material and temperature of storage had marked influence on the sensory quality of mango milk powder. Mango milk samples packed in polystyrene were acceptable up to 150 days of storage at 30 °C and 5 °C. The 4-ply laminates containers and metalized polyester offered almost equal storage quality to the product. Samples were acceptable up to 8 months of storage at 30 °C and for 9 months at 5 °C. Among the four packaging materials studied. Tin cans offered the highest protection against loss in sensory scores of mango milk powder. The samples packed in tin cans were acceptable up to 8 months of storage at 30 °C and for 8 months at 5 °C. On the basis of above results, it could be recommended that tin cans are most useful for long storage of MMP.
80 70 60
Packaging Material Storage Period (months)
50
Total Solids (%) 40
pH Colour
30
Colour 20
Colour Sediments (mg)
10 0 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
-10 Fig. 5. Effect of different packaging materials on physico-chemical properties of reconstituted mango milk powder stored at 5 ± 1 °C. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)
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3.6. Physico-chemical properties of reconstituted mango milk drink Fresh samples of MMP and those stored in different package were reconstituted with of 4.5 times its weights potable water in mixer. The stored dried mango milk powder samples were reconstituted after every 2 months of storage up to 8 months. The physico-chemical properties of reconstituted mango milk drink (RMMD) are presented in Tables 4 and 5 and Figs. 4 and 5. The pH of mango milk drink reconstituted from mango milk powder decreased with advancing storage period. The change in pH was faster in samples packed in polystyrene containers than those in metalized polyester, 4-ply laminates and tins. These results are consistent with those reported by Ranganadham [21]; amino groups of protein get blocked in the Maillard reaction leading to decreased pH. There was an increase in l and a value and decrease in b value for color in reconstituted mango milk drink. Change in color occurred faster at 30 °C than that a 5 °C. 3.7. Sensory quality of reconstituted mango milk beverage The sensory score of mango milk drink prepared from stored reconstituted MMP was significantly different from those of the samples prepared from fresh MMP. These results are consistent with those reported by Radayevam et al. [34]; the flavor scores of reconstituted mango milk drink decreased steadily with the progress of storage period. The rate of deterioration was faster at 30 °C than at 5 °C. The rate of deterioration was slightly faster in samples packed in polystyrene than those packed in metalized polyester, 4-ply laminates and tins. The rapid decline in flavor scores after 5 months storage could be expected due to oxidative changes. The body and texture score also decreased with increased storage period. There was a steady reduction in color and appearance scores of mango milk prepared from progressively stored MMP. Reduction in color and appearance may be due to oxidation of pigments. The statistical analysis has shown that tin can has significant difference as compared to other packaging material because the difference between the mean value of tin can and other treatment is more than the critical difference (CD) value. 4. Conclusion It is concluded that mango milk powder packed in tin containers, metalized polyester, 4-ply laminates and polystyrene containers can be preserved for 2, 4, 6 and 8 months at 30 °C and at 5 °C respectively. Therefore, the most suitable packaging material for long storage of MMP is tin can, whereas the least suitable materials is polystyrene under both the temperature conditions studied. This shelf life was achieved without addition of any preservative or antioxidant. References [1] C.G. Hill, An Introduction to Chemical Engineering Kinetics and Reactor Design, John Wiley and Sons Publication, New York, 1977. [2] S. Ranganna, Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2nd ed. Tata McGraw Hill Publications Co Ltd. Replika Press Pvt Ltd., Delhi, 2001. [3] ISI, Handbook of Food Analysis, Dairy Products Part-XI Indian Standards Institution Manak Bhavan New Delhi India, 1981. [4] AOAC, Official Methods of Analysis, Association of Official Analytical Chemist, Washington DC, 1995.
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[5] AOAC, Official Methods of Analysis, 16th ed., Association of Official Analytical Chemist, Washington DC, 1970. [6] SP:18 (Part-XI), ISI Handbook of Food Analysis, Dairy Products Indian Standards Institution Manak Bhavan New Delhi India, 1981. [7] D. Amba, P.G. Adsule, Bulk Preservation of Mango Pulp in High Density Polyethylene (HDPE) Containers, Indian Food Packer, Nov–Dec 1979, pp. 34–37. [8] M. Hassan, J. Ahmed, Physico-chemical and Sensory Characteristics of Mango-Milk Beverage, Indian Food Packer, March–April 1998, pp. 32–36. [9] A. Sjollema, Some investigations on the free flowing properties and porosity of milk powders, Neth Milk and Dairy Journal 17 (1963) 245–253. [10] M.M. Muers, M.A. House, A simple method for comparing the wettability of instant spray dried separated milk powders, XVI International Dairy Congress B, 1962, pp. 923–930. [11] E. Sammhammer, A method for measuring instant properties of milk powder, Milchwissenschaft 21 (1966) 413. [12] D.V. Sudhakar, S.B. Maini, Stability of carotenoids during storage of mango pulp, Journal of Food Science and Technology 31 (1994) 228–230. [13] T.V. Hymavathi, V. Khader, Carotene, ascorbic acid and sugar content of vacuum dehydrated ripe mango powders stored in flexible packaging material, Journal of Food Composition and Analysis 18 (2005) 181–192. [14] E.F.G. Ardito, L.F.C. Madi, S.A. Ortiz, R.M. Solar, J.L. Farah, E.E.M. Mori, D.D. Alvin, I. Delazari, I. Shirose, Stability of dried skim milk, Boletin do Instituto de Techlogia de Alimentos (Brazil) (17) (1980) 205. [15] N. Mrithyunjaya, J.L. Bhanumurthi, Shelf life of laminate and tin packed whole milk powder, Indian Journal of Dairy Sciences 40 (1987) 78–85. [16] N. Furukava, Yamamanaka, Changes in dried milk during storage. Study of protein denaturation of sephadex G-150 gel filtration, Journal of Agricultural Sciences Japan 16 (3/4) (1972) 218–225. [17] N.R. Driscoll, C.P. Brennad, D.G. Hendricks, Sensory quality of non-fat milk after long term storage, Journal of Dairy Science 68 (1985) 7931–7942. [18] E. Pijanowski, S. Zmarlicki, D. Nowak, T. Zoladek, Wettability of dried whole milk and its content of free fat, Nahrung 18 (1974) 753–761. [19] V.P. Kuznetsov, Study of the characteristics of rapid solubility of dried milk during storage, Trudy Vseoyuznyi Nauchno-issledovated Skill Insitute Molochnoi promyshlennosti (49) (1979) 27–28. [20] R. Labztily, T.T. Tran, T. Bekes, F. Rekakasi, Change in the free fat content of dried milks and other milk based products during storage, Elemiszervizsgalati kozlemenyek 26 (4/5) (1980) 123, (cited: Dairy Science Abstract (43) (1980) 8648–8649). [21] M. Ranganadham, Process innovation in the manufacture of Khoa Powder, Journal Agricultural Issues 1 (1) (1988) 45–54. [22] H.M. Jayaprakasha, Membrane processing application for production of whey protein concentrates, PhD Thesis NDRI Karnal India (1992). [23] K. Khamrui, Development of technology for concentrated and dried whey based fruit juice mixes, PhD Thesis NDRI Karnal India (2000). [24] N. King, The physical structure of dried milk—review, Dairy Science Abstract 14 (1965) 151–159. [25] Sat Prakash, Some recent views on reconstitutability and keeping quality of milk powder, Journal Milk and Food Technology 32 (1969) 183–192. [26] Z. Segena Colos, Industrial manufacture of low lactose dried milk, Anales de la Faculted de Ciencias Quimicas Y Farma Chile, 1979. [27] G.K. Jensen, P.S. Hanson, The influencing of packaging and storage temperature on the reconstitutability of infant whole milk powder, 20th International Dairy Congress, 8, 1978, pp. 730–731. [28] F.G. Kieseker, P.T. Clarke, The effect storage on the properties of non fat milk powders, Australian Journal of Dairy Technology 39 (1984) 74–83. [29] D. Kerekreti, Regulation of moisture, bulk density, particle size and wettability of dried milk, Prumysl Potravin 31 (1980) 327–334. [30] M. Peleg, Effect of conditions on the flow properties of powdered sucrose, powder technology, in: M. Peleg, E.B. Bagley (Eds.), Physical Properties of Foods, 7, The AVI Publishing Co Inc., Westport Connecticut USA, 1977, p. 45. [31] R.C.D. Lara, S.E. Gilliland, Growth inhibition of microorganisms in refrigerated milk by added Maillard reaction product, Journal of Food Protection (48) (1980) 138–147. [32] D.D. Muir, M.W. Griffiths, J.D. Phillips, A.W.M. Sweetsur, I.G. West, Effect of bacterial quality and some properties of low heat and high heat dried milk, Journal Society Dairy technology 39 (1986) 115. [33] R.K. Robinson, Modern dairy technology, Advances in Milk Processing, vol. 2, Elsevier Applied Science Publishers, London, 1986. [34] I.A. Radayevam, L.S. Dmitrieva, E.A. Bekhova, The effect of added antioxidants on keeping quality and on phospholipids functions of whole milk powder, 19th International Dairy Congress IE, 1974, pp. 618–627.
Contents lists available at SciVerse ScienceDirect
Powder Technology journal homepage: www.elsevier.com/locate/powtec
Effect of packaging material on storage ability of mango milk powder and the quality of reconstituted mango milk drink Anil Kumar Chauhan ⁎, Vaibhav Patil Centre of Food Science and Technology, Banaras Hindu University, Varanasi-221005, India
a r t i c l e
i n f o
Article history: Received 28 August 2012 Received in revised form 23 January 2013 Accepted 26 January 2013 Available online 1 February 2013 Keywords: Shelf life Mango milk powder Storage Packaging Products
a b s t r a c t Mango milk powder (MMP) was obtained after recirculatory convective drying, conditioning and grinding. The physico-chemical characteristics of fresh canned mango pulp and those of the finished product were estimated. The microbiological quality of the beverage showed the presence of low number of cfu (colony forming unit) as 2.5 × 10 3 and ymc (yeast and mold count) as 3 per gram. The product was free from coliform bacteria. MMP was packaged in pouches of high density polystyrene, tin can, metalized polyesters and four ply laminates polythene aluminum foil–polythene–paper. The shelf life of mango milk powder was predicted on the basis of free flowability of product under controlled storage condition and was found to be maximum in tin containers (10 and 11 months, respectively) at 30 ± 1 °C and 5 ± 1 °C. © 2013 Elsevier B.V. All rights reserved.
1. Introduction Packaging means placing a commodity into a protective wrapper or container for transport or storage. Package has three fold functions of containing, protecting and merchandising. It provides protection to the product against contamination or loss and damage or degradation due to microbial action, exposure to heat, light, moisture and oxygen, evaporation, etc. It also helps in selling the products. It constitutes an important link between the manufacturer and ultimate consumer for the safe delivery of the product through different stages of production, storage, transport, distribution and marketing. Mango pulp is the most utilized part for human consumption. This portion constitutes about 58 to 77% of the total fruit weight depending upon the variety. Prevention of cancer and heart diseases is possible by antioxidants (β-carotene and vitamin C) rich mango. Bioflavonoid present in mango help in building human immune system. The insoluble dietary fiber found abundantly in mango helps in the elimination of waste from the colon and prevents constipation. Mango milk shake is reported to be helpful in body weight gain especially in low weight persons. Mangoes may be used in a variety of preparations with milk forming as the base, viz., mango milk beverages, puddings, custards, ice creams etc. The availability of fresh milk and canned mango is abundant. Manufacture of mango milk powder will provide an alternate pathway for utilization of surplus milk solids. The specialty product, so manufactured, is likely to prove highly remunerative for industry and nutritious for all classes of consumers.
⁎ Corresponding author. Tel.: +91 9450658188; fax: +91 542 2368993. E-mail address: [email protected] (A.K. Chauhan). 0032-5910/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.powtec.2013.01.055
Standardization of manufacturing technology of mango milk powder (MMP) and type of packing material may affect the quality and safety of reconstituted drink. Therefore, evaluation of packaging materials for MMP and its reconstituted drink at different storage condition had undertaken mainly the fulfillment of the consumer demand for nutritional products with assurance of quality and safety. New methods of processing and packaging being developed to meet the growing demand of ready to eat convenience food products with long shelf stability, nutritional integrity and safety assurance. There is an increasing demand in the world for instant powder which could be reconstitute into variety of products. The present investigation has been planned with the objective to evaluate the suitability of certain packaging material and methods of packaging material on shelf of mango milk powder. The packages were pasteurized, dried and filled with inert gases, keeping in view the Metal can, 4-ply laminates (polyethylene-aluminium foil–polyethylene– paper), metalized polyester, polystyrene packages were used. 2. Materials and methods 2.1. Mango milk powder The mango milk powder (MMP) (Fig. 1) prepared was used for the present study. Standardization of spray drying process for mango milk powder was done with reference to optimum total solid concentration, inlet and outlet air temperature and speed atomization keeping the flow rate of the feed constant [1]. The ratio of mango (Totapari) pulp, pasteurized toned milk (Vita brand, 3% fat and 8.5% SNF) and refined cane sugar (ISI Mark) was kept constant at 30, 62 and 8%, respectively. Concentrated toned milk and one third of total
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87
70 Packaging Material
60
Storage Period (months) 50 Flowability (q) 40
Wettability (sec) Solubiliy (ml)
30
Bulk Density (g/ml) 20
Sinkability 2 min Sinkability 4 min
10
Sinkability 6 min 0 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Fig. 1. Effect of different packaging materials on physical properties of mango milk powder stored at 30 ± 1 °C. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)
sugar were preheated to 70–75 °C and double stage homogenized at 1000/500 psi. The homogenized mix was pasteurized followed by cooling to 20 °C and mixing of canned mango pulp with pasteurized formulation. This mixture was spray dried with operating conditions of 185 °C inlet air temperature and an outlet temperature objective of about 85 °C. The resulting product moisture content was about 2.15%. The atomizer speed of 15000 rpm was used to maintain a constant flow rate with droplet size of about 250 μm. Spray dried product was collected and dry blended with the remaining two thirds of powdered cane sugar. The resultant mango milk powder (MMP) blend was collected in polyethylene lined powder bags. The bags were closed and sealed with a minimum headspace, then allowed to cool at room temperature before refilling into the different packaging material used in the study. Samples of MMP were tested at regular intervals of every 2 months up to 8 months and thereafter at monthly intervals up to 12 months. Fresh samples of MMP and those stored in different packages were reconstituted with 4.5 times its weight of potable water in a mixer. Chemical analysis of MMB was carried out by the methods described [2] for total solids, crude fiber content, total sugar and vitamin C. Total soluble solids of MMB were detected by hand refractometer at 20± 0.5 °C and viscosity was determined by a programmable coaxid cylinder viscometer with digital display (Controvac Rheomat 108 E/R Mettle Tolebo, Switzerland) with measuring system 1, 1 for MMB. Flow curve was obtained for shear at range of 100 to 1000 s−1 at 20 °C. MMP was analyzed. Moisture by ISI [3] methods, titratable acidity by AOAC [4], total protein by micro-Kjeldahl methods by AOAC [5] and total ash and fat contents as per ISI methods were described [6]. Fully ripe mangoes of the three selected varieties viz. Baneshan (BE), Suvarnarekha (SR), Totapuri (TT) were washed thoroughly, peeled and cut into pieces and stones were removed manually. The cut pieces were fed into the pulper with a sieve size of 1/1600. The extracted pulp was heated at 60 °C in steam jacketed kettle for 3 min, cooled and potassium metabisulphate was added at the rate of 0.2%. The pulp was then transferred to white high density polyethylene (HDPE) cans and kept in cold storage until use (less than a month) as per the procedure described [7]. Conventional types of mango products have been developed to a considerable extent but the mango industry is eager to develop new processed products [8].
the procedure. Color of reconstituted MMB was estimated by LAB mode lightness for white (L), greenness and redness (a) and yellowness and blueness (b). 2.3. Physical analysis of MMP Bulk density and flowability [9], solubility index [3], wettability [10], and sinkability [11] were determined as per prescribed methods. 2.3.1. Bulk density A 100 ml graduated cylinder of tarred weight was taken. The mouth of cylinder and the powder was allowed to flow freely to 100 ml mark. The net weight was obtained and results expressed as g/ml (loose density). The packed bulk density was determined by tapping the cylinder till the volume attained a constant level. The volume occupied was noted and result expressed as g/ml. 2.3.2. Flowability A plastic funnel with a narrow stem, cut at right angles, was mounted exactly 2 cm above a piece of butter paper positioned on a horizontal table. A sieve with 16-mesh size was fixed to a shaker (100 shakings per minute). Powder sample was placed on the sieve and allowed to go through the funnel in a fine stream at a controlled speed, so as to form a conical heap. When the top of the powder heap touched the end of funnel stem, the powder stream was stopped by switching off the shaker. The base of the powder heap was outlined with a pencil and powder was removed. After removing the powder, the outlined paper circle was cut and weighed. The radius was calculated and the angle of repose was estimated. 1 Tan θ ¼ h= r− =2 a Where, θ h r a
angle of repose, height of stem base (2 mm), radius of the base of powder heap, and diameter of funnel stem.
2.2. Microbiological analysis Total viable count and yeast and mold count were done following the ISI methods mentioned [6] whereas spore count was done as per
2.3.3. Solubility index Fourteen grams of the powder was reconstituted in a 100 ml of distilled water. The sediment obtained from 50 ml by centrifugation
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Table 1 Effect of different packaging materials on physical properties of mango milk powder stored at 30 ± 1 °C. Packaging material
Tin can
Metalized polyester
4-Ply laminates
Polystyrene
Storage period (months)
Flowability (θ)
Wettability (s)
Solubility (ml)
Bulk density (g/ml)
Sinkability 2 min
4 min
6 min
Initial 2 4 6 8 2 4 6 8 2 4 6 8 2 4 6 8
58.50 58.50 60.20 61.40 62.10 58.90 60.00 61.20 63.90 59.10 60.60 61.30 63.95 59.40 62.80 64.10 65.6 0.10 0.29
31.20 31.90 33.10 35.10 35.50 31.60 34.50 36.90 39.10 31.80 34.30 36.40 39.00 31.70 35.20 39.30 42.2 0.10 0.29
0.97 0.97 1.05 1.25 1.40 0.97 1.20 1.42 1.62 0.97 1.20 1.41 1.65 0.99 1.67 1.80 1.90 0.03 0.08
0.70 0.70 0.72 0.73 0.75 0.71 0.73 0.75 0.77 0.72 0.73 0.73 0.77 0.78 0.82 0.86 0.89 0.01 0.03
24.33 24.77 25.27 26.87 28.79 24.50 26.43 28.33 30.93 24.63 26.87 28.67 30.30 25.37 28.87 30.00 32.00 0.10 0.29
18.33 18.57 18.90 19.00 21.30 18.60 20.57 22.50 24.63 18.80 20.37 22.50 24.30 19.43 23.50 24.17 25.00 0.10 0.29
14.23 14.50 15.33 15.83 17.20 14.67 17.80 18.77 20.87 14.83 17.20 18.43 20.53 15.40 18.63 20.50 21.50 0.10 0.29
SEM CD (5%) Number of replicates = 3. CD = critical difference. SEM = standard error mean.
of reconstituted product was measured and results expressed in milliliters.
2.3.4. Wettability A piece of satin-fabric measuring 10 × 10 cm was stretched over one end of the metallic can (open at both ends with 6.5 cm dia and 4.5 cm height) and fastened in position by a rubber band. Another one end can (5 cm dia and 7 cm height) was placed centrally on the cloth. The tray was filled with distilled water at 40 ± 1 °C to a height of 2.5 cm. A triangle made out of 0.4 cm thick glass rod with sides measuring 8 cm long was placed in the dish and served to prevent close contact of the cloth with the bottom of the dish. With the two cans assembled, and cloth resting on outer can, 1 g of powder was transferred to the inner can and spread over the 6 cm circle
of the cloth as evenly as possible with a soft sable hair brush. The inner can was then removed and the outer can lowered into the tray onto the glass triangle and held in place, until the water level in the can ceased to rise. A stopwatch was clicked as soon as the cloth touched the water and stopped when the powder got completely wet. The time taken for complete wetting of powder was recorded in seconds.
2.3.5. Sinkability In this test, 3.5 ml of distilled water at 20 °C was taken in the spectrophotometer cuvette and 10 mg sample of powder was then dusted on the surface of water and the percentage transmittance was measured at 760 nm in a spectrophotometer. The readings were recorded after 2, 4 and 6 min intervals. The mean of three replicate values was taken as the percentage transmittance.
Table 2 Effect of different packaging materials on physical properties of mango milk powder stored at 5 ± 1 °C. Packaging material
Tin can
Metalized polyester
4-Ply laminates
Polystyrene
SEM CD (5%) Number of replicates = 3. CD = critical difference. SEM = standard error mean.
Storage period (months)
Flowability (θ)
Wettability (s)
Solubility (ml)
Bulk density (g/ml)
Sinkability 2 min
4 min
6 min
Initial 2 4 6 8 2 4 6 8 2 4 6 8 2 4 6 8
58.50 58.90 60.10 61.00 62.10 58.80 62.80 63.70 62.90 59.00 60.30 62.00 62.95 59.30 61.60 63.90 65.00 0.10 0.29
31.20 31.40 32.80 34.70 36.10 32.40 33.10 36.60 37.90 31.70 33.00 36.40 37.90 33.50 35.00 38.80 41.00 0.10 0.29
0.97 0.97 1.03 1.20 1.40 0.97 1.30 1.40 1.52 0.97 1.20 1.38 1.48 0.98 1.21 1.69 1.80 0.01 0.03
0.70 0.70 0.72 0.72 0.73 0.71 0.73 0.74 0.74 0.71 0.73 0.73 0.74 0.77 0.79 0.82 0.86 0.01 0.03
24.27 24.23 24.64 25.09 26.66 24.41 25.35 26.11 27.79 24.43 25.38 26.15 27.82 25.22 28.79 29.75 30.50 0.10 0.29
18.33 18.11 18.76 18.93 21.05 18.55 19.45 20.39 22.51 18.59 19.47 20.41 22.56 19.23 23.15 23.98 24.5 0.10 0.29
14.23 14.25 15.06 15.59 17.02 14.59 16.72 17.69 18.68 14.61 16.74 17.68 18.69 15.16 18.23 19.97 24.55 0.10 0.29
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89
70
60 Packaging Material 50
Storage Period (months) Flowability (q)
40 Wettability (sec) 30
Solubility (ml) Bulk Density (g/ml)
20 Sinkability 2 min Sinkability 4 min
10
Sinkability 6 min 0 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
-10 Fig. 2. Effect of different packaging materials on physical properties of mango milk powder stored at 5 ± 1 °C. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)
Sediment in reconstituted MMB was measured by filling reconstituted MMB in 100 ml cylinder and level was brought up to 100 ml mark. The sediment at the bottom was measured in milliliters after keeping overnights in refrigerator. A digital pH meter (LAB India Instruments Pvt. Ltd., Mumbai) was used for measuring pH of the reconstituted MMP at 30 °C. A panel comprising seven trained judges did sensory evaluation of fresh MMB and reconstituted MMB by using 9-points hedonic scale scorecard.
and 5 ± 1 °C for storage studies. The mango pulps were stored with higher levels of sulfur dioxide [12]. With additional packing such as bag-in-box (a polyethylene pouch placed in a cardboard box) or the aluminium laminated high-density polyethylene, the loss of b-carotene can be further reduced. Baneshan, Suvarnarekha varieties showed that the results of mango powders can be safely stored in metalized polyester/polyester poly packaging for a period of up to 6 months. For storage beyond 6 months additional packaging may be required [13].
2.4. Storage of powder
2.5. Statistical analysis
The samples of MMP were separately packaged in tin, 4-ply laminates, polystyrene and metalized polystyrene and stored at 30 ± 1 °C
Statistical analysis was done by using factorial randomized design of ANOVA. The one factor with four levels that is tin containers,
Table 3 Effect of different packaging materials on microbiology of mango milk powder stored at 30 ± 1 °C and at 5 ± 1 °C. 30 ± 1 °C
5 ± 1 °C cfu × 103
YMC × 101
Spore count × 101
cfu × 103
YMC × 101
Spore count × 101
Packaging material
Storage period (months) Initial
16.0
6.0
12.0
Initial
16.0
6.0
12.0
Tin can
2 4 6 8 2 4 6 8 2 4 6 8 2 4 6 8
12.2 9.5 8.1 7.3 12.0 9.2 7.8 6.0 12.0 9.1 8.0 6.9 11.0 9.2 7.0 6.7 0.10 0.29
4.9 3.0 2.5 1.1 5.1 4.0 2.1 1.2 5.0 3.9 2.1 1.0 5.1 4.0 2.0 0.7 0.10 0.28
11.6 9.5 9.2 7.1 11.2 9.8 7.8 5.0 11.6 9.4 8.6 6.6 11.8 11.2 9.2 10.4 0.10 0.29
2 4 6 8 4 6 8 2 6 8 2 4 2 4 6 8
12.4 9.8 8.4 7.6 9.3 7.9 6.9 12.0 8.2 7.0 11.2 9.4 11.2 9.4 8.0 6.8 0.10 0.29
5.0 3.1 2.8 1.2 4.2 2.4 1.3 5.1 2.2 1.1 5.1 4.0 5.1 4.0 2.2 0.9 0.10 0.28
11.8 11.1 9.8 8.2 11.3 10.1 8.4 11.6 8.6 6.7 11.8 11.3 11.8 11.3 10.1 9.40 0.10 0.29
Metalized polyester
4-Ply laminates
Polystyrene
SEM CD (5%) Number of replicates = 3. CD = critical difference. SEM = standard error mean.
Storage period (months)
90
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metalized polyester, 4-ply laminates and polystyrene containers also second factor with 4 levels that is 2, 4, 6 and 8 months. Critical difference (CD) is the least significance difference, greater than which all the differences are significant. The data for each parameter were collected in three replicates. The statistical analysis shows that the effect of different packaging materials and the effect of storage period on physical properties of mango milk powder were stored at 30 ± 1 °C and at 5 ± 1 °C.
3. Results and discussion 3.1. Comparative assessment of packaging materials for mango milk powder The packaging material and storage temperature are known to influence the physical, chemical, microbiological and sensory properties of dried milk products. The selection criteria of a suitable packaging material for mango milk powder was essentially based on the shelf life. The suitability of the packaging materials on quality of mango milk powder during storage are presented and discussed below.
3.2. Chemical properties Moisture, acidity, fat, protein and ash content in MMP stored at 30 ± 1 °C and 5± 1 °C have been presented in Tables 1 and 2 respectively. Comparative value of constituents during storage showed about 0.41% increase in moisture content over a period of six-month storage at 30 °C in the sample of mango milk powder packaged in polystyrene. Samples packed in 4-ply laminates showed an increase of moisture to about 0.21% in 6 months. These results are consistent with those reported by Ardito et al. and Mrithyunjaya and Bhanumurthi [14,15]. It is difficult to ascertain whether the slight increase in moisture percentage in the samples was due to ingress of moisture or the chemical changes occurring during storage. However, there is a gradual increase in moisture content in dried whole milk during storage. Titratable acidity showed a minor increase during the storage irrespective of packaging used, suggesting the interplay of various constituents and resulting chemical changes. A gradual decrease in pH value was noted during storage. Increasing moisture levels caused a slight reduction in total protein content in the sample during storage. There was no change in protein content during storage on dry
(a) 18 16 14 12
30 ± 1°C
10
cfu
8
YMC
6
Spore 4
Count
2 0
Packaging Material Tin can -2
Metallized polyester
4-Ply Laminates
Polystyrene
(b) 14
12
10
5 ± 1°C Storage Period (months)
8
5 ± 1°C cfu 6
5 ± 1°C YMC 5 ± 1°C Spore Count
4
2
0
Tin can
Metallized polyester 4-Ply Laminates
Polystyrene
-2 Fig. 3. (a) Effect of different packaging materials on microbiology of mango milk powder stored at 30 ± 1 °C. (b) Effect of different packaging materials on microbiology of mango milk powder stored at 5 ± 1 °C. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)
A.K. Chauhan, V. Patil / Powder Technology 239 (2013) 86–93
matter basis. These results are consistent with those reported by Furukava and Yamamanaka [16], in kulfi mix powder titratable acidity increased over a period of 8 months storage at 30 °C when packed in the different kinds of packaging materials. Irrespective of type of packaging material, chemical changes occurred faster at 30 °C than those at 5 °C. These results are consistent with those reported by Driscoll [17], chemical deterioration in milk powders was faster at 21 °C at temperature of storage than at 10 °C. Increase in fat content with storage periods with corresponding increase in moisture may be due to liberation of fat from lipo-protein complexes in MMP. Ash content is nearly constant. However, slight decrease in protein content may be owing to its degradation with corresponding changes in moisture. Mango pulp carbohydrates and lactose content in MMP have not been estimated and their contribution to acidity during storage may be the contributing factors. 3.3. Physical properties The effect of packaging materials on physical properties of mango milk powder is presented in Tables 1 and 2 and Figs. 1 and 2. It can be noted that there was a gradual loss of solubility, flowability, wettability, whereas, bulk density and sinkability increased during storage at 30 °C. The losses in flowability, wettability and solubility were faster in samples packed in polystyrene than those in metalized polyester, 4-ply laminates and tin cans. These results are consistent with those reported by Pijanowski [18], an increase in amount of free fat might be responsible for the loss in wettability and flowability and inverse relation between free fat and wettability. The increase in wetting time of MMP samples during storage may be attributed partly to increase in free fat content and native quality of proteins. Considerable increase in wetting time of dried milks attributed this to increased liberation of free fat during storage [19,20]. Loss in wettability in pre-term infant formula, khoa powder and kulfi mix powder after storage at 30 °C has been reported [21]. Besides, similar observations have also been reported in cheddar cheese, whey powder, whey based mushroom soup powder and whey kinnow juice powder, respectively [22,23]. A progressive increase in solubility index of MMP may be attributed to the formation of water insoluble compounds caused by increased casein micelles size due to hydrogen bonding [24] consequent to protein–protein interactions or sugar–protein interaction [25]. The changes in protein structure due to Maillard reaction and protein– protein interaction during storage could be responsible for the loss of solubility [26]. Gradual increase in solubility index from 1.07 to 1.80 ml in WMP after storage for 6 months at 30 °C is reported by Mrithyunjaya and Bhanumurthi [15]. Solubility index of khoa powder [21] and kulfi mix powder also increased from 1.2 to 2.0 ml over a period of 8 months storage at 30 °C; in similar studies on dried milks [16,27,28] an increase in solubility index with the progress of storage time is also observed. Bulk density of mango milk powder increased with the storage period irrespective of packaging materials used. Increase in bulk density with increased moisture content was also observed [29] in dried milk powder and ice-cream mix powder, respectively. An increase in bulk density may be attributed to increased cohesiveness caused by absorption of moisture during storage. Sinkability of mango milk powder increased with the storage period. Changes occurred faster at 30 °C than those at 5 °C. Flowability decreased with increasing storage period more so at higher temperatures. Irrespective of storage temperatures, samples packed in polystyrene registered a high loss of flowability during storage. Angle of repose (tan θ) increased from 62.93 to 66.16 in spray dried malted milk food on storage at 30 °C for 12 months. A gradual loss of flowability in lactose hydrolyzed infant formula on storage at 30 °C for 12 months. These results are consistent with those reported by Peleg [30]; increase in free fat content and changes
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Table 4 Effect of different packaging materials on physico-chemical properties of reconstituted mango milk powder stored at 30 ± 1 °C. Packaging material
Tin can
Metalized polyester
4-Ply laminates
Polystyrene
Storage period (months)
Total solids (%)
pH
Initial 2 4 6 8 2 4 6 8 2 4 6 8 2 4 6 8
19.78 19.76 19.78 19.74 19.75 19.75 19.77 19.79 19.78 19.76 19.78 19.77 19.77 19.79 19.77 19.78 19.8 0.10 0.29
6.05 6.01 5.97 5.82 5.75 5.99 5.86 5.63 5.59 5.98 5.87 5.65 5.60 5.92 5.68 5.45 5.32 0.11 0.30
SEM CD (5%)
Color L
a
b
70.10 70.12 70.25 70.25 70.28 70.27 70.28 70.36 70.41 70.28 70.28 70.36 70.42 70.32 70.37 70.45 70.52 0.10 0.29
8.01 8.01 8.02 8.02 8.04 8.03 8.04 8.07 8.08 8.04 8.04 8.07 8.08 8.06 8.07 8.09 8.11 0.11 0.30
42.23 42.17 42.14 42.07 41.99 42.10 42.05 41.95 41.86 42.11 42.06 41.95 41.87 42.08 41.98 41.88 41.88 0.11 0.31
Sediments (ml) 5.08 5.10 5.16 5.30 5.42 5.11 5.20 5.41 5.72 5.11 5.20 5.42 5.75 5.14 5.67 5.80 5.96 0.10 0.29
Number of replicates = 3. CD = critical difference. SEM = standard error mean.
in particle structure due to moisture absorption during storage could increase cohesiveness of powder leading to reduction in flowability. Moist powder exhibited higher angle of repose (mainly due to cohesion), despite the fact that the angle of internal friction usually decreases with increase in moisture level. 3.4. Microbiological quality The microbial counts in fresh mango milk powder were SPC 16.0 × 10 3, YMC 6.0 × 10 1 and spore count 12.0 × 10 1 per gram of product. The microbial counts largely depend upon the quality of raw materials used in the product preparation and the methods of processing. The type of package and temperature of storage showed significant influence on the growth and survival of microorganisms
Table 5 Effect of different packaging materials on physico-chemical properties of reconstituted mango milk powder stored at 5 ± 1 °C. Packaging Material
Storage Period Total solids pH (months) (%)
Initial 2 4 6 8 Metalized 2 polyester 4 6 8 4-Ply 2 laminates 4 6 8 Polystyrene 2 4 6 8 SEM CD (5%) Tin can
Number of replicates = 3. CD = critical difference. SEM = standard error mean.
19.78 19.79 19.78 19.76 19.77 19.77 19.78 19.78 19.76 19.78 19.79 19.76 19.77 19.77 19.77 19.78 19.78 0.10 0.29
6.05 6.03 5.99 5.87 5.81 6.01 5.93 5.87 5.76 6.02 5.92 5.88 5.77 5.95 5.71 5.52 5.37 9.90 28.51
Color L
a
b
70.10 70.20 70.21 70.24 70.29 70.23 70.25 70.31 70.35 70.22 70.25 70.30 70.35 70.29 70.34 70.42 70.45 0.10 0.29
8.01 8.01 8.02 8.03 8.04 8.02 8.03 8.05 8.07 8.02 8.02 8.04 8.06 8.04 8.05 8.07 8.09 0.10 0.29
42.23 42.19 42.18 42.15 42.11 42.14 42.11 42.07 42.01 42.13 42.12 42.07 42.02 42.05 42.01 41.93 41.82 0.10 0.29
Sediments (mg) 5.08 5.08 5.11 5.20 5.40 5.09 5.30 5.40 5.52 5.09 5.20 5.38 5.48 5.11 5.31 5.70 4.92 0.10 0.29
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80 70 60
Packaging Material 50
Storage Period (months)
40
Total Solids (%)
30
pH Colour
20
Sediments (mg) 10 0 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
-10 Fig. 4. Effect of different packaging materials on physico-chemical properties of reconstituted mango milk powder stored at 30 ± 1 °C. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)
in mango milk powder (Table 3 and Fig. 3). While yeast and mold counts decreased rapidly during storage, spores exhibited a great resistance. The death rate of bacteria was slower at 5 °C than at 30 °C. Low water activity in the product coupled with antibacterial nature of some of the chemical compounds released in various degradation reactions may have caused rapid destruction of microbial cells during storage [31]. As the rate of chemical reactions is slow at lower temperatures of storage, the decline in microbial number was found to be slow. A decrease in microbial counts from initial numbers of 4.1 × 10 3 to 2.2 × 10 3 was also reported [32] in SMP after storage for 6 months at 30 °C. The spore counts in MMP showed insignificant decrease during storage at 30 °C and 5 °C. Spores survive even in most adverse conditions [33]. An insignificant reduction in spore count from an initial number of 4.5 × 10 2 to 4.0 × 10 2 in high heat SMP after storage for 6 months at 30 °C is observed by Muir et al. [32]. The YMC also showed a declining trend during the entire storage period, becoming almost negligible at the end of storage study both at 30 °C and 5 °C. Yeast and mold grow at aw above 0.6. Lower aw
should be one reason for the accelerated death of yeast and mold during storage. These results are consistent with those reported by Ranganadham [21].
3.5. Sensory quality Packaging material and temperature of storage had marked influence on the sensory quality of mango milk powder. Mango milk samples packed in polystyrene were acceptable up to 150 days of storage at 30 °C and 5 °C. The 4-ply laminates containers and metalized polyester offered almost equal storage quality to the product. Samples were acceptable up to 8 months of storage at 30 °C and for 9 months at 5 °C. Among the four packaging materials studied. Tin cans offered the highest protection against loss in sensory scores of mango milk powder. The samples packed in tin cans were acceptable up to 8 months of storage at 30 °C and for 8 months at 5 °C. On the basis of above results, it could be recommended that tin cans are most useful for long storage of MMP.
80 70 60
Packaging Material Storage Period (months)
50
Total Solids (%) 40
pH Colour
30
Colour 20
Colour Sediments (mg)
10 0 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
-10 Fig. 5. Effect of different packaging materials on physico-chemical properties of reconstituted mango milk powder stored at 5 ± 1 °C. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)
A.K. Chauhan, V. Patil / Powder Technology 239 (2013) 86–93
3.6. Physico-chemical properties of reconstituted mango milk drink Fresh samples of MMP and those stored in different package were reconstituted with of 4.5 times its weights potable water in mixer. The stored dried mango milk powder samples were reconstituted after every 2 months of storage up to 8 months. The physico-chemical properties of reconstituted mango milk drink (RMMD) are presented in Tables 4 and 5 and Figs. 4 and 5. The pH of mango milk drink reconstituted from mango milk powder decreased with advancing storage period. The change in pH was faster in samples packed in polystyrene containers than those in metalized polyester, 4-ply laminates and tins. These results are consistent with those reported by Ranganadham [21]; amino groups of protein get blocked in the Maillard reaction leading to decreased pH. There was an increase in l and a value and decrease in b value for color in reconstituted mango milk drink. Change in color occurred faster at 30 °C than that a 5 °C. 3.7. Sensory quality of reconstituted mango milk beverage The sensory score of mango milk drink prepared from stored reconstituted MMP was significantly different from those of the samples prepared from fresh MMP. These results are consistent with those reported by Radayevam et al. [34]; the flavor scores of reconstituted mango milk drink decreased steadily with the progress of storage period. The rate of deterioration was faster at 30 °C than at 5 °C. The rate of deterioration was slightly faster in samples packed in polystyrene than those packed in metalized polyester, 4-ply laminates and tins. The rapid decline in flavor scores after 5 months storage could be expected due to oxidative changes. The body and texture score also decreased with increased storage period. There was a steady reduction in color and appearance scores of mango milk prepared from progressively stored MMP. Reduction in color and appearance may be due to oxidation of pigments. The statistical analysis has shown that tin can has significant difference as compared to other packaging material because the difference between the mean value of tin can and other treatment is more than the critical difference (CD) value. 4. Conclusion It is concluded that mango milk powder packed in tin containers, metalized polyester, 4-ply laminates and polystyrene containers can be preserved for 2, 4, 6 and 8 months at 30 °C and at 5 °C respectively. Therefore, the most suitable packaging material for long storage of MMP is tin can, whereas the least suitable materials is polystyrene under both the temperature conditions studied. This shelf life was achieved without addition of any preservative or antioxidant. References [1] C.G. Hill, An Introduction to Chemical Engineering Kinetics and Reactor Design, John Wiley and Sons Publication, New York, 1977. [2] S. Ranganna, Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2nd ed. Tata McGraw Hill Publications Co Ltd. Replika Press Pvt Ltd., Delhi, 2001. [3] ISI, Handbook of Food Analysis, Dairy Products Part-XI Indian Standards Institution Manak Bhavan New Delhi India, 1981. [4] AOAC, Official Methods of Analysis, Association of Official Analytical Chemist, Washington DC, 1995.
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[5] AOAC, Official Methods of Analysis, 16th ed., Association of Official Analytical Chemist, Washington DC, 1970. [6] SP:18 (Part-XI), ISI Handbook of Food Analysis, Dairy Products Indian Standards Institution Manak Bhavan New Delhi India, 1981. [7] D. Amba, P.G. Adsule, Bulk Preservation of Mango Pulp in High Density Polyethylene (HDPE) Containers, Indian Food Packer, Nov–Dec 1979, pp. 34–37. [8] M. Hassan, J. Ahmed, Physico-chemical and Sensory Characteristics of Mango-Milk Beverage, Indian Food Packer, March–April 1998, pp. 32–36. [9] A. Sjollema, Some investigations on the free flowing properties and porosity of milk powders, Neth Milk and Dairy Journal 17 (1963) 245–253. [10] M.M. Muers, M.A. House, A simple method for comparing the wettability of instant spray dried separated milk powders, XVI International Dairy Congress B, 1962, pp. 923–930. [11] E. Sammhammer, A method for measuring instant properties of milk powder, Milchwissenschaft 21 (1966) 413. [12] D.V. Sudhakar, S.B. Maini, Stability of carotenoids during storage of mango pulp, Journal of Food Science and Technology 31 (1994) 228–230. [13] T.V. Hymavathi, V. Khader, Carotene, ascorbic acid and sugar content of vacuum dehydrated ripe mango powders stored in flexible packaging material, Journal of Food Composition and Analysis 18 (2005) 181–192. [14] E.F.G. Ardito, L.F.C. Madi, S.A. Ortiz, R.M. Solar, J.L. Farah, E.E.M. Mori, D.D. Alvin, I. Delazari, I. Shirose, Stability of dried skim milk, Boletin do Instituto de Techlogia de Alimentos (Brazil) (17) (1980) 205. [15] N. Mrithyunjaya, J.L. Bhanumurthi, Shelf life of laminate and tin packed whole milk powder, Indian Journal of Dairy Sciences 40 (1987) 78–85. [16] N. Furukava, Yamamanaka, Changes in dried milk during storage. Study of protein denaturation of sephadex G-150 gel filtration, Journal of Agricultural Sciences Japan 16 (3/4) (1972) 218–225. [17] N.R. Driscoll, C.P. Brennad, D.G. Hendricks, Sensory quality of non-fat milk after long term storage, Journal of Dairy Science 68 (1985) 7931–7942. [18] E. Pijanowski, S. Zmarlicki, D. Nowak, T. Zoladek, Wettability of dried whole milk and its content of free fat, Nahrung 18 (1974) 753–761. [19] V.P. Kuznetsov, Study of the characteristics of rapid solubility of dried milk during storage, Trudy Vseoyuznyi Nauchno-issledovated Skill Insitute Molochnoi promyshlennosti (49) (1979) 27–28. [20] R. Labztily, T.T. Tran, T. Bekes, F. Rekakasi, Change in the free fat content of dried milks and other milk based products during storage, Elemiszervizsgalati kozlemenyek 26 (4/5) (1980) 123, (cited: Dairy Science Abstract (43) (1980) 8648–8649). [21] M. Ranganadham, Process innovation in the manufacture of Khoa Powder, Journal Agricultural Issues 1 (1) (1988) 45–54. [22] H.M. Jayaprakasha, Membrane processing application for production of whey protein concentrates, PhD Thesis NDRI Karnal India (1992). [23] K. Khamrui, Development of technology for concentrated and dried whey based fruit juice mixes, PhD Thesis NDRI Karnal India (2000). [24] N. King, The physical structure of dried milk—review, Dairy Science Abstract 14 (1965) 151–159. [25] Sat Prakash, Some recent views on reconstitutability and keeping quality of milk powder, Journal Milk and Food Technology 32 (1969) 183–192. [26] Z. Segena Colos, Industrial manufacture of low lactose dried milk, Anales de la Faculted de Ciencias Quimicas Y Farma Chile, 1979. [27] G.K. Jensen, P.S. Hanson, The influencing of packaging and storage temperature on the reconstitutability of infant whole milk powder, 20th International Dairy Congress, 8, 1978, pp. 730–731. [28] F.G. Kieseker, P.T. Clarke, The effect storage on the properties of non fat milk powders, Australian Journal of Dairy Technology 39 (1984) 74–83. [29] D. Kerekreti, Regulation of moisture, bulk density, particle size and wettability of dried milk, Prumysl Potravin 31 (1980) 327–334. [30] M. Peleg, Effect of conditions on the flow properties of powdered sucrose, powder technology, in: M. Peleg, E.B. Bagley (Eds.), Physical Properties of Foods, 7, The AVI Publishing Co Inc., Westport Connecticut USA, 1977, p. 45. [31] R.C.D. Lara, S.E. Gilliland, Growth inhibition of microorganisms in refrigerated milk by added Maillard reaction product, Journal of Food Protection (48) (1980) 138–147. [32] D.D. Muir, M.W. Griffiths, J.D. Phillips, A.W.M. Sweetsur, I.G. West, Effect of bacterial quality and some properties of low heat and high heat dried milk, Journal Society Dairy technology 39 (1986) 115. [33] R.K. Robinson, Modern dairy technology, Advances in Milk Processing, vol. 2, Elsevier Applied Science Publishers, London, 1986. [34] I.A. Radayevam, L.S. Dmitrieva, E.A. Bekhova, The effect of added antioxidants on keeping quality and on phospholipids functions of whole milk powder, 19th International Dairy Congress IE, 1974, pp. 618–627.