In food packaging, smart indicator films based on natural resources have greatly attracted researchers to minimize the environmental issues as well as to satisfy consumer preferences for food safety. In this research, pH-sensitive films were prepared using purple-fleshed sweet potato starch (SPS) and sweet potato peel (SPP). Two categories of the film (i) SPS and (ii) SPS/SPP, were fabricated via solvent casting technique, incorporating different concentrations of commercial purple sweet potato anthocyanin (CA) at 0%, 1%, 1.5%, and 2% (w/v) and the physicochemical, mechanical, thermal, and morphological properties of the films were investigated. The thickness, water solubility, and swelling degree of the films increased with the increment of CA, whereas there were no significant changes in the water content (WC) of the films. Water vapor permeability (WVP) was decreased for SPS films while statistically similar for SPS/SPP films. The addition of CA reduced the tensile strength (TS) and tensile modulus (TM) yet increased the elongation at break (EaB) of the films as compared to films without CA. The FTIR results confirmed the immobilization of anthocyanin into the film. In SEM images, roughness in the surfaces of the CA-associated films was observed. A reduction of thermal stability was found for the films with anthocyanin except for the SPS/SPP CA 2% film. Furthermore, the CA-associated films showed a remarkable color response when subjected to pH buffers (pH 1 to 12) and successfully monitored chicken freshness. The fastest color migration was observed in acidic conditions when the films were immersed into aqueous, acidic, low fat, and fatty food simulants. The findings of this work demonstrated that the developed pH indicator films have the potential to be implemented as smart packaging to monitor food freshness and quality for safe consumption.
Onion bulbs were stored at five different temperatures to know the storage behavior of onion bulbs. Indian red onion bulbs were kept without wrapping at ambient conditions (25˚C ± 3˚C and 75% RH) and within polyethylene pouch at 2.5˚C, 6˚C, 7˚C and 13˚C for 60 days of storage period. Weight loss, total soluble solids (TSS), number of sprouted and rotten bulbs were measured at an interval of 10 days throughout storage. The greatest decrease (23.25%) in weight was observed throughout storage for onions stored at ambient conditions. TSS was observed to increase in all samples until 40 days of storage and then decreased up to 60 days. Lowest TSS (14.89 ˚Bx) was found in onion stored at ambient conditions at the end of storage. Maximum sprouted (67.25%) and rotten (17.78%) onions were observed for onions stored at 13˚C, whereas minimum sprouted and rotten onions were found at 2.5˚C at 60 days of storage. Results also recommend lowest temperatures (2.5˚C -6˚C) for prolong storage life of onion with no detrimental effects.
An attempt was taken to investigate the effect of drying air temperature and slice thickness
on the drying kinetics and quality of bitter gourd (Momordica charantia) dried in a novel
cabinet dryer (HSTU Fruit and Vegetable Dryer). Fresh bitter gourd was sorted, cleaned,
and sliced at 4 mm, 6 mm, and 8 mm thickness. All the samples were blanched in boiling
water at 100°C for 3 mins. Then the slices with an initial moisture content of 96.47±0.6%
were dried, spreading as a thin layer in the trays of the cabinet dryer using three drying air
temperatures of 60, 70, and 80°C until the desired final moisture content (MC) of
4.66±0.4% was obtained. The results indicated that the shortest drying time (2.08 hrs) was
required by the sample of 4 mm thickness, which was dried at 80°C to reduce moisture
from 96.47±0.6% initial (wet basis, wb) to 4.66±0.4% final moisture (wb). The sample of
8 mm thickness dried at 60°C took the longest drying time (6.67 hrs). The higher drying
rate (34.32 gm H2O/min.cm2
) was noticed at a constant drying rate period in the case of a
6 mm thick slice at 70°C. Whereas a lower drying rate (9.29 gm H2O/min.cm2
) was
observed for drying 8 mm slices using 60°C air temperature. Even though, the effect of
blanching on drying characteristics of bitter gourd was not noticed so much, the drying
rate was found to be increased slightly of pretreated bitter gourd thus drying time was
shorter. A comparison on colour analysis of both fresh and blanched bitter gourd showed
that a 6 mm slice dried at 70°C was found better in retaining green colour than other
samples. The rehydration ratio (6.63±0.62) and the percentage of water uptake
(86.75±0.58) of rehydrated pretreated bitter gourd were also higher in a dried sample of 6
mm. Therefore, pretreated bitter gourd is suggested to dry quickly using 70oC in a cabinet
dryer slicing at 6 mm thickness to obtain a better quality dried product.
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