Physicochemical and sensory characteristics of biscuits from corn flour ( Zea mays ) with orange sweet potato flour ( Ipomoea batatas L.)

. This study was carried out to investigate the physicochemical and sensory characteristics of biscuits as affected by the ratio of corn flour (CF) and orange sweet potato flour (OSPF). Six samples of biscuits were made from CF and OSPF in various ratio namely P 1 (100% corn flour), P 2 (80:20), P 3 (60:40), P 4 (40:60), P 5 (20:80), P 6 (100% OSP flour), and one sample as control namely P 7 (100% wheat flour). The results showed that the ratio of CF and OSPF had a very significant effect (P < 0.01) specific volume, hardness, water absorption , ash content, protein content, fat content, carbohydrate content, and crude fiber content of biscuits. The biscuits most acceptable by consumers were produced from 80% CF with 20% OSPF.


Introduction
Biscuit is one of the snacks processed using wheat flour (WF) and added other food ingredients. Biscuits are a popular food in the community and very practical because they can be consumed anywhere and anytime. Many types of biscuits have been reproduced to produce biscuits that are not only delicious, but also healthy for consumption [1].
Hibrida variety corn is used for food only around 30%, the rest is used for animal feed, industry, and seeds. This can be used as an opportunity to develop this material into processed foods. In addition, this Hibrida variety corn is no less superior to wheat; this corn contains elements of Fe, dietary fiber, and beta-carotene (pro-vitamin A) so that it can be used as processed food. Corn will be more durable and practical if corn is in the form of flour and can be fortified or enriched with nutrients [2]. Corn flour (CF) is suitable for manufacturing foods that do not require ingredients with high gluten content, such as pastries so that CF can be used because it has less than 1% gluten. Biscuits are a type of snack that many people like, so they can be an opportunity to replace WF [3]. *Corresponding author: sentosa.ginting@usu.ac.id Sweet potatoes contain high carbohydrates, so they play a vital role in overcoming malnutrition. Orange sweet potatoes (OSP) are among the most commonly known. (OSP) has a high sugar content, the flesh of the tuber is solid after cooking and has a good texture. OSP has B vitamins and vitamin C and has high beta-carotene [4]. Like tubers in general, OSP also has a relatively short shelf life and spoil quickly because of their high water content. Therefore, it is necessary to process OSP into specific products, for example, processing into flour. One of the products that can utilize orange sweet potato flour (OSPF) is biscuits.

Preparation of CF
Corn that has been harvested is cleaned or separated from the skin and dried in the sun to dry with a maximum moisture content of 14%. After that, the corn kernels are separated from the corn cobs and mashed using a corn grinding machine, then the resulting flour is sifted through a 60 mesh sieve.

Quality of CF and OSPF
CF and orange OSPF that have been researched including water absorption, iprotein icontent, ifat icontent, icarbohydrate icontent, iand icrude ifiber icontent ias ishown iin iTable i2. The quality of corn flour and orange sweet potato flour needs to be known to see the processing and treatment that is determined on the quality of the biscuits produced.

Effect of blending ratio of CF and OSPF on physical quality of biscuits
The iresults ishowed ithat iratio iof iCF iand iOSPF ihad ieffect ito iphysical iquality iof biscuits ias ishown iin iTable i3.  Table 3 shows the comparison of CF biscuits with OSPF in each treatment P1 to P6 which was very significantly different from P7. This is because P7 biscuits are made from 100% WF, WF contains gluten which can absorb a little water so that it forms a structure to trap air in order to increase the volume of dough in food making [10]. Biscuits with treatments P1 to P6 were not significantly different and had the lowest specific volume value in treatments P1 and P3, namely 1.51 ml/g. iThis iis ibecause ithere iis ino iaddition iof iWF iso ithat ithere iis ino igluten iin iit iand icauses ithe iproduct ito inot iexpand ior iincrease iin ivolume.
The relationship between flour ratio with biscuit spesific volume can be seen in Figure 1. The comparison of CF with OSPF in table 3 is very significantly different where the lowest hardness value is 3.22 kg/cm 2 in treatment P7 (100% WF) which means the texture of P7 biscuits is less hard than other treatments. WF that contains gluten is able to form a cell wall structure that produces crumb products. This specific property is not processed by CF and OSPF so that the resulting biscuit product has a higher hardness value as in the treatment P1 (100% CF) and P6 (100% OSPF) which has a hardness value of 3 .73 kg/cm 2 and 4.75 kg/cm 2 . It can be seen that CF has higher amylose content (33.10%) when compared to OSPF (22.9%) [11]. The relationship between flour ratio with biscuit hardness can be seen in Figure 2.  Table 3 shows the comparison of CF with OSPF has a very significant effect on the water absorption of biscuits. The highest water absorption in treatment P4 (40% CF: 60% OSPF) was 1.55 g and the lowest water absorption in treatment P7. This result was due to the higher amylose content of CF (33.10%) and OSPF (22.9%) than WF (20%). %). iThis iis iin iaccordance iwith ithe iliterature iof iKusnandar i [12], iwhich istates ithat ithe ihigher ithe iamount iof amylose in flour, the water absorption of flour will also be higher, besides that the presence of protein also increases water absorption because it is easy to absorb water. The relationship between flour ratio with biscuit water absorption can be seen in Figure 3.

Figures in table mean of 3 replicates±standard ideviation. iNumbers ifollowed iby idifferent iletters iin ithe
isame icolumn ishow isignificantly idifferent ieffects iat ithe i5% ilevel i(lowercase iletter) iand ivery significant differences at the 1% level (capital letter) with the LSR test. Table 4 shows that the comparison of CF with OSPF on the moisture content of biscuits gave an insignificant different effect so that it was not continued to the LSR test. Table 4 shows the comparison of CF with orange OSPF has a very significant effect (P < 0.01) on the ash content of biscuits, where the highest ash content in treatment P6 (100% OSPF) is 1.57% and The lowest ash content in the P1 treatment (100% CF) was 1.26%. This result is because in testing the quality of CF and OSPF, it is found that the ash content of OSPF is higher than CF so that it has an effect on the ash content of biscuit products. The relationship between flour ratio with biscuit ash content can be seen in Figure  4.  Table 4 shows the comparison of CF with OSPF ihas ia ivery isignificant ieffect i(P i< i0.01) ion ithe iprotein icontent iof ibiscuits, where the highest protein content in P7 biscuits (100% WF) is 11.32% and the protein content is 11.32%. the lowest was in P6 biscuit (100% OSPF) which was 4.39% [13]. The relationship between flour ratio with biscuit protein content can be seen in Figure 5.  Table 4 shows the comparison of CF with OSPF ihas ia ivery isignificant ieffect i(P<0.01) ion ithe ifat icontent iof ibiscuits. This is because the fat content of CF and OSPF is different and there is the addition of 50 g of shortening in the manufacture of biscuit products [14][15][16]. The relationship between flour ratio with biscuit water absorption can be seen in Figure  6.  Table 4 shows the comparison of CF with orange OSPF has a very significant effect (P<0.01) on the carbohydrate content of biscuits. From the results of the study, the highest carbohydrate content in P6 biscuit (100% OSPF) was 63.46% and the lowest was in P2 biscuit (80% CF: 20% OSPF) which was 54.4% [17]. The relationship between flour ratio with biscuit carbohydrate content can be seen in Figure 7.  Table 4 shows that the ratio of CF and OSPF ihas ia ivery isignificant ieffect i(P<0.01) ion ithe icrude ifiber icontent iof ithe ibiscuits. iFrom ithe iresults iof ithe ibiscuit iresearch, it was found that the highest crude fiber content in P5 biscuits was 4.12%. This result is because the results of the analysis of raw materials, namely CF has a lower fiber content (3.58%) than the fiber content of OSPF (4.22%), meaning the greater the addition of OSPF the higher the crude fiber content in biscuits. The relationship between flour ratio with biscuit crude fiber content can be seen in Figure 8.

iEffect iof iblending iratio iof iCF iand iOSPF ion isensory icharacteristics iof ibiscuits
The iresults ishowed ithat iratio iof iCF iand iOSPF ihad ieffect ito isensory icharacteristics iof ibiscuits ias ishown iin iTable i5.    table mean of 3 replicates, ±standard deviation. Numbers followed by different letters in the same column show significantly different effects at the 5% level (lowercase letter) and very significant differences at the 1% level (capital letter) with the LSR test. * Commercial product From the data above, it can be seen that the highest color hedonic value is in P2 biscuits with a score of 5.76. Although the panelists gave a lower score than commercial biscuits, P2 biscuits had the highest score than P7 biscuits (100% wheat flour). This is because the P2 biscuit (80% corn flour: 20% orange sweet potato flour) has a golden yellow color obtained from the beta-carotene pigment found in corn flour and orange sweet potato flour. While the color hedonic value with the lowest score is P7 biscuit (100% wheat flour), this is because the color on P7 biscuit is much different from other biscuits because it only uses wheat flour so that the resulting color is pale white, therefore the panelists gave lower score. The relationship between flour ratio with the hedonic value of biscuit color can be seen in Figure 9. The data below shows that the highest hedonic aroma value is P2 biscuit (80% corn flour: 20% orange sweet potato flour) with a score of 5.84. P2 biscuits were still lower than commercial biscuit scores, although P2 biscuits were not commercial products, panelists gave an assessment of the aroma of liking. This is because the panelists like the smell of corn mixed with a slight aroma of orange sweet potato (80% corn flour: 20% orange sweet potato flour) when compared to P1 biscuits (100% corn flour) which has the lowest score of 5.65. The relationship between flour ratio with the hedonic value of biscuit aroma can be seen in Figure 10. Based on the data below, it can be seen that the panelists gave an unsignificantly different score on the taste of the biscuits from corn flour with orange sweet potato flour, this is because the biscuits are made from raw materials of corn and orange sweet potato which are processed in the same way, resulting in biscuits. with a similar taste. According to Winarno [16], chemical compounds, temperature, and interactions with other flavor components can affect the taste of a food ingredient. The relationship between flour ratio with the hedonic value of biscuit aroma can be seen in Figure 11. From the data below, it can be seen that the panelists gave a non-significantly different score on the texture of the biscuits from corn flour with orange sweet potato flour, this was because the biscuit texture of all biscuit treatments was crunchy, so the texture was quite liked by the panelists. According to Kusnandar [12], the crispness of a product is caused by the retrogradation process (amylose molecules bind to each other and bind to amylopectin molecules on the outside of the granule) during the baking of cooled biscuits. The relationship between flour ratio with the hedonic value of biscuit taste can be seen in Figure  12.  Table 5 can be seen that the average of all hedonic values is 5 which means somewhat like so that the general acceptance hedonic value for biscuits from CF and OSPF is also somewhat like. The relationship between the effect of the comparison of CF with OSPF on overall acceptability of biscuit can be seen in Figure 13.
General acceptance relates to the hedonic values of color, aroma, taste, and texture. From the data above, it can be seen that the highest general acceptance value is in commercial products, but for each treatment P1 to P7, the general acceptance value is almost the same, namely 5 (slightly like) and the resulting notation also gives an insignificant difference.

Conclusions
The blending ratio of CF and OSPF has a very significant effect on the specific volume, hardness, water absorption, ash content, protein content, fat content, carbohydrate content, crude fiber content and hedonic value of biscuits. The results of the study concluded that the biscuits with the best physicochemical and sensory characteristics were P2 biscuits which were produced from 80% CF and 20% OSPF.