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The study investigated the feasibility of enzymatic extraction for guava juice and evaluated the effects of various preservatives on its shelf life. The crushed guava puree was undergone different pectinase enzyme concentrations over three incubation periods. The findings revealed that pectinase concentrations of 0.1 % and 0.2 %, when incubated for 1 and 2 h, were the most effective. Juice yields ranged from 65.24 % to 78.64 %, with Total Soluble Solids (TSS) varying from 9.12°Brix to 11.56°Brix. The physicochemical properties of the guava juice resulted 84.2 % moisture, 2.16 % protein, 0.77 % fat, 3.27 % fiber, 0.65 % acidity, 2.25 % reducing sugars, 8.27 % non-reducing sugars, 79.53 % antioxidant activity, 173.2 mg/100g of ascorbic acid, 10.52 TSS, 109.7 mg/100g of phenolic content, and a pH of 3.2. Eight juice samples were prepared as per formulation with sodium benzoate and potassium metabisulfite (KMS) at concentrations of 150 ppm, 200 ppm, and 250 ppm, in addition to one refrigerated sample and one control. The stability of these guava juice samples was monitored every 15 days over a 90-day period. Results showed that acidity, TSS, pH, reducing sugars, and non-reducing sugars changed over time. Samples with preservatives exhibited slower changes compared to the control. Phenolic compounds diminished more quickly at ambient temperature than in refrigerated or preservative-treated samples. Initially, phenolic content and antioxidant capacity were 44 mg GAE/100g and 44 %, respectively, but declined to 10–15 mg and 15–17 % by the end of the storage period. Color changes were more noticeable in samples stored at room temperature, whereas preservatives effectively reduced color degradation caused by enzymatic browning. Moreover, ascorbic acid retention was better in samples with preservatives and those stored under refrigeration. The ascorbic acid degradation rate was highest at room temperature (0.023 day^-1) and lowest with 250 ppm KMS (0.016 day^-1). Microbiological tests indicated that the juice remained safe for 40 days at room temperature, 90 days under refrigeration, and approximately 85 days with preservatives.

Abstract In the present research, the impact of fermentation with two strains of Lactiplantibacillus plantarum subsp. plantarum (PTCC 1896 and PTCC 1745) on physicochemical properties, antioxidant bioactive compounds, and some health‐promoting features of guava juice was investigated. Results showed a significant (p

The present work explores different conditions of thermosonication (TS) processing that would ensure microbiological and enzymatic safety for guava juice while simultaneously maximizing the preservation of its quality attributes. The guava juice was subjected to TS treatment (frequency: 40 kHz; power: 200 W; Temperature: 40, 60, and 80 °C; Time: 2, 6 and 10 min) and was compared with fresh and pasteurized (90 °C/60 s) juice samples. The objectives of the research work were to determine the effect of thermosonication on the quality attributes such as total soluble solids (TSS), pH, titratable acidity, cloud value, color attributes, total phenolic contents, total flavonoid contents, antioxidant activity, ascorbic acid levels, enzymatic, microbiological, and sensory properties. The thermosonicated and pasteurized samples showed no significant (p > 0.05) changes in pH, total soluble solids, and titratable acidity. TS improved the cloud value and color attributes. Furthermore, TS enhanced total phenols (10 to17%), flavonoids (5 to 25%), antioxidant activity (10.45% to 14.55%) and retention of ascorbic acid (61.98–83.32%) relative to control. Thermosonicated sample at 80 °C/10 min gives the maximum inactivation of Pectin methyl esterase (PME), Peroxidase (POD) and Polyphenol oxidase (PPO) enzymes. While both thermosonication and pasteurization drastically decreased the microbial count to undetectable levels, only TS exhibited modest improvement in sensory qualities. The results demonstrated that TS can enhance the overall safety, quality, and commercial viability of guava juice as a practical substitute to pasteurization.

The two objectives of this paper were to determine the effect of centrifugation parameters on guava juice physicochemical characteristics and to identify operational characteristics of continuous disc-stack centrifuges based on the performance of a laboratory centrifuge. Effects of g-force (149 g–3731 g) and centrifugation time (10–40 min) on juice physicochemical characteristics (protein, pectin, galacturonic acid, dry matter, total soluble sugars contents; pH; electrical conductivity, clarity and particle size distribution) were assessed. Laboratory centrifuge performance was evaluated for 1343 g, 2388 g and 3731 g. At 1343 g, separation limits (xmax), feed flow-rates of disc-stack centrifuges and cut-off sizes (x50) were determined for corresponding laboratory centrifuge operation times. Significant decrease in average particle size, protein and pectin contents was observed, contrary to juice clarity. Similar clarification efficiency was obtained for g-forces ≥ 1343 g. xmax were 2669 nm, 2200 nm and 1783 nm, with corresponding x50 for continuous centrifuges, 1887 nm, 1556 nm, 1261 nm, for 20 min, 30 min and 40 min, respectively.

In this study, the physicochemical properties, antioxidant capacity, and volatile compounds of the juices of different guava cultivars before and after pectinase treatment were evaluated. The results showed that the guava juice of the small fragrant (SF) cultivar exhibited the highest ascorbic acid concentration (1761.09 mg/L), and the highest contents of total phenolics (329.52 mg GAE/L) and total flavonoids (411.13 mg RE/L) were both found in the juice of the watermelon red (WR) cultivar. After pectinase treatment, the juice yield and the titratable acid, sugar components, total phenolics and total flavonoids, and antioxidant capacity levels of the guava juices were all higher than those of the non-pectinase group. However, lower sensory evaluation scores were obtained in the pectinase-treated guava juices. Aldehydes and terpenoids were the main flavor components in the guava juices, which were responsible for the aroma of the juice, while their relative contents were different in the four cultivar guava juices. Furthermore, pectinase treatment could change the amounts and relative contents of volatile compounds in the guava juice. During the pectinase treatment process, the relative contents of the main aroma constituents in the guava juices were significantly decreased. The findings of this research provide valuable information for the processing of guava juice.

This paper deals with PHL management of Guava fruit through small-scale juice processing in rural areas that have no access of modern energy. Guava trees cover large areas in Tigray region of Ethiopia, however, during the harvest period the consumption and yield of the fruit is not in balance. Consequently, considerable amount of the fruit spoiled in the field. In addition, during this period the market price of the fruit is very low and discourage farmers to collect the fruit as its market price could not cover the labor cost. On the other hand, the fruit is not available out of the yield season. This study has demonstrated fruit processing using locally developed solar energy technologies to improve PHL management of fruits and vegetables. The technology has sized in view of smallholding farmer’s production capacity with an average power of 6kW at an average solar insulation of 800 W/m2 that boils 5 l of water in 5 min. During the experiment, uniformly sliced fruits were boiled using the solar boiler for half an hour to make it sterilized and soft. The boiled fruit was mixed with preservatives, homogenized, filtered and hot-filled into a glass bottle to avoid air traps. The juice examined regularly in 30, 60 and 90 days for its PH, TSS and total microbial load. The results have shown the average total bacteria counts of the juices is below the maximum allowable limit in foods for consumption. Accordingly, the technology would enable smallholding farmers to start equitable agroprocessing.

An experimental investigation on retentivity of major guava juice volatile compounds during ultrafiltration is presented in this paper. Simulated guava juice solutions were used throughout the study and the ultrafiltration was carried out in a batch stirred cell system. Polyethersulfone membranes with MWCO of 100,000 and 500,000 were used. The effects of important process operating parameters such as pressure and pectin concentration were studied. It was found that hydrophobic interactions with the membrane are the major factors, which control the flavor retention. A qualitative correlation between component polarity and retentivity was also observed.