Procedures to determine the appropriate classification of blanched peanuts (raw or processed) comparing with raw and roasted peanuts.

QUIROGA PATRICIA RAQUEL; RIVEROS CECILIA; GROSSO NELSON R.; LARRAURI MARIANA; ASENSIO CLAUDIA M.; LAMBIR JUDIHT; MARTIN MARIA PAULA; PRIETO MARIA CECILIA

2017-04-03/2017-04-27

Química

Servicios agropecuarios

OBJECTIVEThe goals of this study are to compare the physic-chemical, microbiological, and sensory properties of raw, blanched and roasted peanuts in order to determine if blanched peanuts area raw or processed food product.MATERIALSThe following samples were included in the study: 16 lots of raw peanuts provided by different peanut industries from Argentina: 4 lots from Lorenzati, Ruetsch y CIA SA; 4 lots from Aceitera General Deheza SA; 4 lotsfrom PRODEMAN SA, and 4 lots from Maniagro Argentina SA. 12 lots of blanched peanuts provided by different peanut industries from Argentina:3 lots from Lorenzati, Ruetsch y CIA SA; 3 lots from Aceitera General Deheza SA;3 lots from PRODEMAN SA, and 3 lots from Maniagro Argentina SA. 9 lots of roasted peanuts provided by different peanut industries from Argentina: 3 lots from Lorenzati, Ruetsch y CIA SA; 3 lots from Aceitera General Deheza SA, and3 lots from PRODEMAN SA.METHODSBlanching and roasting processesBlanching and roasting processes were also performed in the Biochemistry Lab (AgronomyCollege, National University of Cordoba). One lot of raw peanuts was selected from each Company (4 lots in total), which were blanched and roasted, separately.The blanching process was performed heating raw peanuts during 15 minutes in a convection oven at 90 °C, the skins were removed manually.The roasting process was performed heating raw peanuts during 25 minutes in a convection oven at 160 °C.In total, 4 more samples of blanched and 4 more samples of roasted peanuts were prepared.Experimental design (ED)Treatments. Total = 3. The treatments are raw peanuts, blanched peanuts, and roastedpeanuts.Repetitions. 16 samples of raw peanuts, 16 samples of blanched peanuts, and 13 samples of roasted peanuts. 16 lots of raw peanuts (4 lots x 4 companies); 16 lots of blanched peanuts (3 lots x 4 companies + 4 lots produced in the lab); 13 lots of roasted peanuts (3 lots x 3 companies + 4 lots produced in the lab). Each lot is considered a repetition.Variables. Total = 15.Physical variables: color L*, a*, b* values. Total = 3 variables.Chemical variables: humidity, peroxide value, enzymatic activity (peroxidase and catalase), nitrogen solubility index, tetrazolium test. Total = 6 variables.Microbiological variables: total aerobic mesophilic plate count and total yeast and moldcount. Total = 2 variables.Sensory evaluation: duo-trio discriminative test for color and flavor, descriptive test for raw and roasted flavor intensities. Total = 4 variables.ED: (Raw treatment x 16 repetitions x 15 variables) + (blanched treatment x 16repetitions x 15 variables) + (roasted treatment x 13 repetitions x 15 variables): 675 analyses.Physical assaysGrains color were determined using a Minolta colorimeter (CR-410). Peanuts were grindedbefore to measure the color (McDaniel et al., 2012). Results were expressed as L*, a*, and b* color values.Chemical assaysMoisture. The moisture content was determined following AOAC (2010) method. Theresults were expressed as percentage g/100 g sample.Peroxide value (PV). This parameter was determined following the procedure described by AOAC (2010). The peroxide value was expressed as meqO2/kg. A storage stability study was performed to determine the increase of this parameter. All samples were stored in plastic bags at 40 °C in an oven during 25 days. The increase of the PV was calculated according to the following equation:Peroxide Value Increase (PVI) = Final PV (storage day 25) - starting PV (storage day 0)Enzymatic activityPeroxidase activity. It was determined according to the method described by AACC (1999).Catalase activity. It was determined according to the method described by Povolotskaya and Sedenka (1956).Protein solubility index (PSI). The percentage of nitrogen (proteins) in peanuts and in their aqueous extracts were determined (AOAC, 2010). The aqueous fraction was performed grinding peanuts and mixing them with DI water at 20 °C. The extract was shaken for 20 min in an orbital shaker. To transform the nitrogen into protein content, the factor 5.46 was used(AOAC, 2010). The results were expressed according to the following formula:NSI = (% protein in aqueous extract/ % protein of peanuts samples) x 100Tetrazolium staining test. The procedure described by Perez and Argüello (1997) wasfollowed. The results were expressed as percentage of grains that presented more than 50% positive staining.Microbiological assaysTotal aerobic mesophilic plate count: the FDA/BAM 8th Ed. Ch. 3 method wasfollowed (FDA, 2001).Total yeast and mold count: The method ISO 21527-2:2008 was followed (ISO, 2008).Sensory analysisDiscriminative tests. Duo-trio discriminative tests were performed to determine if panelists distinguish between the color and the flavor of raw and blanched peanuts and between roasted and blanched peanuts (Meilgaard et al., 2006).Descriptive test. The intensity ratings of raw and roasted flavors were evaluated using a 100-point non-structured scale (Meilgaard et al., 2006).