Zahid, Maria / M.Z.
(2019)
Factors affecting the shelf life stability of low salt papad.
MRes thesis, University of Nottingham.
Abstract
Papad is an Indian dehydrated snack made from a dough consisting of black gram flour (Phaseolus mungo L.), sodium chloride (NaCl) salt, water, and papadkhar, a raising agent formulation that differs in its composition based on the origin of papad production. Traditional (handmade) papad dough includes small quantities of vegetable oil and papadkhar that helps in dough expansion during frying and creates the characteristic colour and texture of the papads. In contrast, the industrialized papad production at ABWF does not incorporate any oil into or around the papad dough, and a customised papadkhar formulation is used to provide the same functionality as the traditional version. In addition, the mechanisms of papad production are different: traditional method heavily relies on manual processing which can introduce a lot of inconsistency on the final papad, whereas the industrialised version make use of vacuum mixers, cold forming single-screw extruder, rotary cutters, batch dryers and batch fryers to achieve the same final product. The papad dough is extruded as 3G (third-generation) pellet product and stored in high density polyethylene (HDPE) plastic wraps or tubs for short- and longer-term storage, respectively. Finally, the ABWF papad has also been customised for a low salt version; however, quality deterioration of the low salt papads during storage has been observed which affects the stability of the dried papad before and after frying. This study has investigated the quality defects in relation to changing storage relative humidity (RH) and storage temperature through: C-Cell Image analysis, three-point bending test, moisture sorption isotherm, candling, GC-MS chromatography, and sensory analysis to measure the water content (%) and water activity (aw) of the dried low salt papads and how these factors influence the fried product. Our results show that the porosity of the papad structure increases over storage time which is not directly dependent on the storage RH. It is hypothesized that this increase in porosity is due to the increased uptake of carbon dioxide (CO2) by the dried papad from the storage environment which reacts with the calcium hydroxide (Ca(OH)2) from the ABWF papadkhar, generating calcium carbonate (CaCO3) crystals that compete for space in the papad microstructure, thus resulting in increased cracks over storage time. The uptake of CO2 is highest in storage RH < 75% indicating increased quality deterioration with low storage RH. This finding is in correlation with the tests measuring papad breaking strength, crack formation, frying quality and consumeracceptance where the papads stored at 75% and 100% storage RH performed well. 43% and 11% storage RH did not perform well possible due to a reduction in the water content and water activity of the papads, resulting in a rigid, inflexible product with low expansion and a harder texture after frying. To limit the water activity within 0. —0.6 aw, normal cold storage followed by 24-hour rehydration at 75% RH is adequate for a good quality fried low salt papad. To date no previous literature has studied the effect of CO2 on papads in relation to storage RH and temperature, and therefore further research is required to prove the CO2 uptake observed in our study. Additional suggestions test other physiochemical properties of the low salt papads have also been proposed including: starch gelatinization, influence of salt on the whole process line, papadkhar reformulation, and accelerated shelf life testing.
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