Desenvolvimento e caracterização de estruturados de goiaba (Psidium guajava L.) utilizando hidrocoloides ágar e goma gelana

Abstract

The structured fruit is a product made with fruit pulp and hydrocolloids, with characteristics similar to in natura fruits, presenting practicality in the consumption, greater shelf life, appearing as an alternative for the reduction of post-harvest losses and fruit reutilization. The objective of the present study was to develop and analyze structured guava (Psidium guajava L.) using the agar and gellan gum hydrocolloids. Four formulations were elaborated: 100% agar ; 100% low acyl gellan (Low Acyl - LA) ; 75% LA gellan and 25% high acyl gellan (High Acyl - HA); 50% LA gellan and 50% HA gellan. In each sample, 0.75% of hydrocolloid per volume of pulp was used. There were conduted chemical and physicochemical analysis for the following parameters: bioactive compounds, antioxidant activity, in vitro simulated bioaccessibility, Scanning Electron Microscopy (SEM), texture profile analysis (TPA), rheology, determination of volatile compounds by solid phase microextraction of headspace and gas chromatography-mass spectrometry (HS-SPME and GC-MS) and sensory evaluation of the guava-structured. The results showed that the most suitable hydrocolloid concentration for the prepared structured guava was 0.75% by weight of pulp, having a hardness of 0.96N and absence of moisture. For the sensorial tests, it was verified that the use of different hydrocolloids (agar and gellan gum) did not influence the average values of the main sensory attributes, except appearance and texture. The Check-All-That-Apply (CATA) analysis indicated that the agar, LA100 / HA0 and LA75 / HA25 samples presented similar characteristics, with higher frequencies of the same atributes. The structured guava showed color characteristics, soluble solids and acidity near to the in natura pulp, so the use of different hydrocolloids did not influence the physical and chemical characteristics of the final product. For the bioaccessibility analysis, it was found that the content of vitamin C, phenolic compounds and antioxidant capacity were directly influenced by the type of hydrocolloid used in the formulation. The TPA of the formulations exhibited similar parameters on elasticity and cohesiveness, regardless of the type of polysaccharide, however, samples LA100 / HA0 and LA50 / HA50 showed higher values for hardness. The HS-SPME and GC-MS of the structured and pulp allowed the identification of forty flavor compounds, Hexanal, (E)-2-Hexanal, 2-Hexanal, 1-Hexanol and β-Caryophyllene the main identified volatile compounds and, thus, much of the volatile composition of the pulp was preserved in guava. SEM of LA100 / HA0 showed gels with firm and compact structures, with the appearance of strong gels. On the other hand, the microscopy of the LA75 / HA25 sample exhibited a more homogeneous and dense network. In the rheological and sensory tests, gels with agar presented with aspects of a weak gel and with lower stress of fracture, however, with greater sweet and acid flavors and sweet aroma in comparison with those structured with aspects of strong gels. Based on the results, it can be inferred that it is possible to formulate a guava structure with characteristics similar to the fruit pulp, with a pleasant taste, without nutritional components, color or aromatic compounds losses, besides it’s strong gel texture.In that way, the product may be produced and marketed as it may be an alternative fruit consumption between harvest periods.