Study On Physical And Chemical Properties Of Highland Barley-wheat Mixed Flour And Quality Of Crackers

Highland barley(Hordeum vulgare L.var.nudum Hook.f.)is a very important plateau cereal crop with characteristics of high protein,vitamins and fiber content,with low fat and carbohydrate content.Highland barley is rich in bioactive compound such as β-glucan,polyphenols,flavonoids.Replacement of part of cake flour by highland barley flour increased the nutritional value and antioxidant properties of crackers,but also improved the taste of highland barley flour products.Mixing highland barley flour and cake flour as ingredients,the physical and chemical properties of mixed flour were studied,and the effects of different highland barley additional proportion on crackers’ quality were studied.After determining the optimal additional ratio of highland barley flour,the formulation of crackers was optimized.Then,a kind of low GI highland barley crackers with good taste and flavor,which has been acceptable to consumers,was developed.Additionally,it provides theoretical basis for the application of highland barley in baked snack and low GI food.The followings were the main results:(1)The content of anthocyanins,polyphenols and β-glucan in highland barley flour were 3.59 mg/g、6.92 mg/g and 5.63 g/100 g respectively.Meanwhile,the content of anthocyanins and polyphenols in cack flour were 0.36 mg/g and 2.11 mg/g.The additional proportion of highland barley flour had significant effects on the color,water holding capacity,oil holding capacity,thermodynamic property and pasting properties of the mixed flour(p<0.05).After addition of highland barley flour,the hardness of dough using mixed flour increased,while malleability and processing performance decreased.(2)Highland barley flour could improve the nutritional value and antioxidant capacity of crackers,while inhibit the formation of acrylamide and reduce starch digestion effectively.With the augment of the additional ratio of highland barley flour,the hardness and the content of acrylamide in crackers were significantly cut down(p<0.05),while the contents of anthocyanins,polyphenols,β-glucan and RS in crackers were significantly aggrandized(p<0.05),as well as the acrylamide inhibition rate.At the same time,antioxidant capacity of DPPH free radical scavenging ability and ABTS free radical scavenging ability in crackers showed an increasing trend,though the starch digestibility was in reverse,and e GI was significantly lessened(p<0.05)which was under 55.(3)The structure of crackers was characterized by scanning electron microscopy,fourier transformation infrared spectroscopy and X-ray diffraction analysis(SEM,FTIR and XRD).The results demenstrated that the additional ratio of highland barley flour could affect the structure and relative crystallinity of starch in crackers.The tight structure of crackers presented loosen with the increase of the additional ratio of highland barley flour,meanwhile,the relative crystalline of crackers increased firstly,then had a lessened tendency for a while which turned into an incremental one after that.Moreover,V-type starch crystal appeared in crackers.(4)Through correlation analysis,it was found that the content of β-glucan had an extremely significant negative correlation with the hardness,SDS and e GI of crackers(p<0.01),whereas with RS of crackers,the correlation was in reverse,and that with RDS of crackers was significantly negative correlation(p<0.05).In the meantime,The contents of flavonoids and polyphenols in crackers were extremely significant negative correlated with DPPH free radical scavenging ability and ABTS free radical scavenging ability together with acrylamide inhibition rate in crackers(p<0.01).(5)The optimal formula was obtained by single factor test and orthogonal test.Taking the mixed flour as benchmark which had highland barley flour and cake flour in each half,the optimal formula included egg、milk powder、plant oil、salt、baking powder and sugar for40%、30%、10%、0.6%、1.0% and 16% respectively.And crackers made with this formula had a hardness of 969.05 g,an alkalinity of 88.57 mg/100 g,and a sensory evaluation of85.56.