The CA used in this study are red and yellow in color and have no injury. From the morphological analysis, it appears that the length varies from (54.25±0.5; 73.90±0.43) mm, the width and thickness are identical and vary from (38.79±1.53; 48.52±0.52) mm. The morphological characteristics in particular, the length and width of the present study corroborate those of Gbohaïda et al., (2015)
which range from 60 to 69.9 mm and from 33.55 to 43.42 mm, respectively. However, these values are higher than those found by Marc et al., (2012)
which vary from 31 to 49 mm. In view of these results, cashew apples from the Kara region seem to be elongated compared to those from Côte d’Ivoire, which are rounded.
The Brix degree (soluble sugar content) of the CA used to produce the powder ranged from 12 to 14 for red apples and from 13 to 15 for yellow apples. The Brix degree depends on the color of the fruit. These values are higher than those found by Hêdiblè et al., (2017)
whose values varying between 8.2 and 10.2 °Brix. The difference in Brix from fruit juices could be explained by several factors. In particular, the differences between climatic conditions, pedological, the degree of ripeness of the fruits and also by the variety of the fruits. However, the high moisture content of this raw material which is 88.6% is the major constraint for his preservation and could influence the production yield of his powder.
Cashew apple powder obtained
Photo 2 shows the appearance of the different formulations of powder obtained.
Depending on the drying conditions, the powders obtained under solar drying conditions differ from those obtained by drying in an oven at 45°C, as well as those obtained in an oven at 50°C. Apples that have undergone bleaching gave slightly lighter powders than those that have not been bleached except for those steamed at 45°C. The colour changes observed in the case of powders from bleached apples may be due to Maillard reactions (non-enzymatic browning) that take place in the products during technological treatments Noguchi et al., (1983).
Both reactions (enzymatic browning and non-enzymatic) are sources of color change in the case of unbleached apples. The effect of temperature would also be a source of color changes.
Photo 2: Appearance of CA powders.
The drying temperature 45°C has an impact (slowing effect) on enzymatic and non-enzymatic browning reactions. The powders obtained from apples dried at this temperature have retained much more a color that pulls towards the starting color of fresh apples. The SSASB and SSAAS formulations have a slightly darker color. This could be due to temperature variations during drying especially during the night.
Physico-chemical characteristics of powders
Table 1 presents the results of physico-chemical and compositional analyses obtained from CA powders. It summarizes the contents of water, ash, protein, carbohydrates, fiber, vitamin C, density and hydrogen potential. These values are the two-year average.
Table 1: Physicochemical characteristics of CA powder.
The moisture content of the different types of powder formulations ranged from 10 to 11. According to the Network Bulletin, May 1998, in the case of infant flours, a humidity of less than 8% is recommended. This humidity level is high compared to this standard and cannot promote long-term preservation. This humidity level could be related to the drying temperature and the efficiency of the dryer or climatic conditions. The work of Dos et al., (2012)
gave a humidity of 9.29% in the context of CA bagasse powders. A low humidity such as that of Uchoa et al., (2009)
which is 6.52% is in the value range that guarantees long-term storage.
The pH values of the different powders were less than 4.5; therefore, the fake fruit from which the powder is derived was considered an acidic food product Costa et al., (2009)
. The acidity values found offer great stability, which can make it difficult for microorganisms to grow. However, these pH values are lower than the one found by Ogunjobi et al., (2010)
which was 4.72.
The determination of ash in practice provides information on the solid mineral part of a sample as opposed to its organic part. It is commonly used for food quality control. The standard recommends an ash content of less than 3. Thus, the analysis of Table 1 shows that the ash content of the powders varied from 2.19 to 2.33. This meets the standard. A higher ash content than our study 2.70 was obtained by Ogunjobi et al., (2010)
. a lower value than our study 1.42 was obtained by Costa et al., (2009)
. The ash contents observed testify upstream to a richness of flours in mineral salts essential for nutrition. This testifies that CA powder would improve the mineral content of composite flours or the composition of dietary supplement foods.
The protein contents of the different powder formulations according to Table 1 vary from 12.83 to 15.33%. This content is higher than the protein content of wheat flour and sweet potato which are respectively 11.9 and 3.2% according to the work of Ndangui, (2015)
. The work of Costa et al., (2009)
and Ogunjobi et al., (2010)
gave a lower protein content of 7.63 and 12.75% respectively in CA powders. The protein content of CA powder could make it possible to compensate for the protein deficit of sweet potato flour or any other flour for the purpose of combining flours in the realization of a dietary supplement.
Dietary fiber, although naturally occurring, is predominantly derived from plants and carbohydrate in nature and can play a major role in the body’s metabolism as a potential source of energy metabolites Zeanandin et al., (2011).
The fiber content in accordance with Table 1 varies from 7.48 % to 7.83%. These values are significantly higher than that found by Ogunjobi et al., (2010)
and Offia et al., (2015)
4.08 and 6.25 respectively in Nigeria. The type of soil, climate and study period could also significantly influence the results obtained. Dietary fiber facilitates bowel movements and prevents many gastrointestinal diseases Offia et al., (2015)
The carbohydrate content of powders varies between 61.15 and 63.59% (Table 1). These contents are high compared to the results of Duarte et al., (2017)
which is 44.5% and slightly low compared to those of Offia et al., (2015)
which is 77.95%. Indeed, the higher the protein, lipid and ash content, the less carbohydrate there is. However, the values found in our study corroborate those found by Ogunjobi et al., (2010)
and Dos et al., (2012)
which were 68.60% and 69.4% respectively.
The lipid content shown in Table 1 ranges from 3.14% to 3.54%. These levels are higher than that found by Duarte et al., (2017)
which is 2.15. However, those in our study are very close to 3.70 found by Costa et al., (2009).
The bulk density ranged from 0.62 to 0.66. A density of 0.63 was found by Offia et al., (2015)
. It is low compared to the result of the same author in the case of wheat flour (0.88). According to this author, 0.63 is the best density in breakfast food preparation and infant food formulation.
Energy and vitamin C characteristics
Table 2 summarizes the vitamin C content, energy value and production yield of CA powders.
Table 2: Characteristics energy value of vitamin C and production yield of PC powder.
Fruit is an excellent source of vitamin C. The different types of formulation reveal a significant amount of vitamin C according to Table 2. The formulations PE50SB, PE50AB, PE45AB, PE45SB, SSASB, SSAAB powder have in descending order amounts of vitamin C respectively (924.5, 894.2; 860.5; 838.4; 694.4; 688.7 mg/100 g). Whitening has a significant effect on vitamin C loss. Low levels of 52.60 and 42.82 mg/100 g were observed respectively in the work of Ogunjobi et al., (2010)
and Offia et al., (2015)
. This could be explained by the effect of temperature during bleaching or the volatility of vitamin C during drying.
The energy value of CA powders ranges from 331.91 to 337.92 Kcal/100 g. This richness in energy value can be explained by a significant part of carbohydrates. These energy values are slightly close to those of infant flours studied in the work of Sanou et al., (2017)
and which varied from 381.1 to 411.3 Kcal/100 g. The consumption of CA powder alone or as a substitute for other flours would be very beneficial in calorie.
The low production yield of powders 22.5-27.32% (w/w) (Table 2) is the consequence of a high humidity of the cashew apple 88.6% which is one of the difficulties in transport. The moisture content of the powders does not correlate with the production yield. Normally, the wetter the powder, the higher the yield. This is not the case in our study because SSASB and PE45AB with humidity 10.23 and 11.34 respectively have yields of 27.32 and 24.18. This is explained by losses during grinding (residues) and sieving.
Fig 1 shows the nutritional value in mineral salts of the powders produced. From the analysis of the results, it appears that the powders analyzed are rich in mineral salts, including potassium 6866 mg/kg, magnesium 680.62 mg/kg, sodium 339.16 mg/kg, calcium 342 mg/kg and iron 20.5 mg/kg. The high ash content (Table 1) confirms the presence of large quantities of mineral salts. A higher calcium and iron content than that of our work respectively 8000 and 40 mg/kg was found by Offia et al., (2015
). But this very high calcium value would probably be due to the treatment of apples with calcium chloride. This same author found a sodium content 60 mg/kg lower than that of our study. This difference can be explained either by the nature of the soils. Since the powder is rich in Ca, Mg and K, it can be used in human food.
Fig 1: Mineral salt composition of CA powder.