Comparative effects of pectin and hydrolyzed pectin coating as pre-frying treatments on acrylamide formation in potato chips.

This study aimed to compare the effects of pectin and hydrolyzed pectin coating as pre-frying treatments on acrylamide content and quality characteristics of fried potato chips. The hydrolyzed pectin with molecular weight (Mw) of 8.81 ± 0.49 kDa was obtained through partial degradation of pectin (Mw: 747.57 ± 6.73 kDa) using pectinase. Results showed that both pectin and hydrolyzed pectin coating significantly inhibited acrylamide formation and inhibition rates exceeded 90 %. Hydrolyzed pectin had stronger inhibitory activity against acrylamide formation than pectin, especially when the concentration of hydrolyzed pectin was >2 %, its inhibitory rate exceeded 95 %. Compared to pectin coating, hydrolyzed pectin coating endow fried potato chips with smaller browning, higher crispness, less moisture but higher oil content. Overall, hydrolyzed pectin had better application prospects than pectin in inhibiting acrylamide formation of fried potato chips.

Quantitative study of viable Vibrio parahaemolyticus cells in raw seafood using propidium monoazide in combination with quantitative PCR.

In this study we developed a specific and sensitive quantitative PCR (qPCR) method combined with a propidium monoazide (PMA) sample treatment to quantify tdh-positive viable cells of V. parahaemolyticus in raw seafood (PMA-qPCR). The high selectivity of primers and probes were demonstrated by using purified DNA from 57 strains belonging to 18 species. Using these primers and probes for qPCR and in artificial contamination samples, a good correlation was obtained between Ct values and log CFU/reaction in the range of 12-1.2×10(6)CFU/reaction both from qPCR and PMA-qPCR with R(2) values of 0.9973 and 0.9919, respectively. The optimization of PMA concentration showed that 8 µg/mL was considered optimal to achieve a compromise between minimal impact on intact cells and maximal signal reduction in compromised cells. However, turbidity and cell concentration experiments showed that PMA treatment was not effective in samples where turbidities were ≥10 NTU and OD(600 nm) values were ≥0.8. PMA-qPCR was compared with culture isolation and traditional qPCR in environmental samples (including oyster, scallop, shrimp, and crab). The PMA-qPCR resulted in lower numbers of log CFUg(-1) than qPCR, with values having better agreement with numbers determined by culture isolation. In conclusion, this method is an effective tool for producing reliable quantitative data on viable V. parahaemolyticus in raw seafood.